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GCC(1)                               GNU                              GCC(1)

NAME         top

       gcc - GNU project C and C++ compiler

SYNOPSIS         top

       gcc [-c|-S|-E] [-std=standard]
           [-g] [-pg] [-Olevel]
           [-Wwarn...] [-Wpedantic]
           [-Idir...] [-Ldir...]
           [-Dmacro[=defn]...] [-Umacro]
           [-foption...] [-mmachine-option...]
           [-o outfile] [@file] infile...

       Only the most useful options are listed here; see below for the
       remainder.  g++ accepts mostly the same options as gcc.

DESCRIPTION         top

       When you invoke GCC, it normally does preprocessing, compilation,
       assembly and linking.  The "overall options" allow you to stop this
       process at an intermediate stage.  For example, the -c option says
       not to run the linker.  Then the output consists of object files
       output by the assembler.

       Other options are passed on to one or more stages of processing.
       Some options control the preprocessor and others the compiler itself.
       Yet other options control the assembler and linker; most of these are
       not documented here, since you rarely need to use any of them.

       Most of the command-line options that you can use with GCC are useful
       for C programs; when an option is only useful with another language
       (usually C++), the explanation says so explicitly.  If the
       description for a particular option does not mention a source
       language, you can use that option with all supported languages.

       The usual way to run GCC is to run the executable called gcc, or
       machine-gcc when cross-compiling, or machine-gcc-version to run a
       specific version of GCC.  When you compile C++ programs, you should
       invoke GCC as g++ instead.

       The gcc program accepts options and file names as operands.  Many
       options have multi-letter names; therefore multiple single-letter
       options may not be grouped: -dv is very different from -d -v.

       You can mix options and other arguments.  For the most part, the
       order you use doesn't matter.  Order does matter when you use several
       options of the same kind; for example, if you specify -L more than
       once, the directories are searched in the order specified.  Also, the
       placement of the -l option is significant.

       Many options have long names starting with -f or with -W---for
       example, -fmove-loop-invariants, -Wformat and so on.  Most of these
       have both positive and negative forms; the negative form of -ffoo is
       -fno-foo.  This manual documents only one of these two forms,
       whichever one is not the default.

OPTIONS         top

       Option Summary

       Here is a summary of all the options, grouped by type.  Explanations
       are in the following sections.

       Overall Options
           -c  -S  -E  -o file  -x language -v  -###  --help[=class[,...]]
           --target-help  --version -pass-exit-codes  -pipe  -specs=file
           -wrapper @file -fplugin=file -fplugin-arg-name=arg
           -fdump-ada-spec[-slim] -fada-spec-parent=unit -fdump-go-spec=file

       C Language Options
           -ansi  -std=standard  -fgnu89-inline -aux-info filename
           -fallow-parameterless-variadic-functions -fno-asm  -fno-builtin
           -fno-builtin-function -fhosted  -ffreestanding -fopenacc -fopenmp
           -fopenmp-simd -fms-extensions -fplan9-extensions
           -fsso-struct=endianness -fallow-single-precision  -fcond-mismatch
           -flax-vector-conversions -fsigned-bitfields  -fsigned-char
           -funsigned-bitfields  -funsigned-char -trigraphs -traditional
           -traditional-cpp

       C++ Language Options
           -fabi-version=n  -fno-access-control  -fcheck-new
           -fconstexpr-depth=n  -ffriend-injection -fno-elide-constructors
           -fno-enforce-eh-specs -ffor-scope  -fno-for-scope
           -fno-gnu-keywords -fno-implicit-templates
           -fno-implicit-inline-templates -fno-implement-inlines
           -fms-extensions -fno-nonansi-builtins  -fnothrow-opt
           -fno-operator-names -fno-optional-diags  -fpermissive
           -fno-pretty-templates -frepo  -fno-rtti -fsized-deallocation
           -ftemplate-backtrace-limit=n -ftemplate-depth=n
           -fno-threadsafe-statics  -fuse-cxa-atexit -fno-weak  -nostdinc++
           -fvisibility-inlines-hidden -fvisibility-ms-compat
           -fext-numeric-literals -Wabi=n  -Wabi-tag  -Wconversion-null
           -Wctor-dtor-privacy -Wdelete-non-virtual-dtor -Wliteral-suffix
           -Wmultiple-inheritance -Wnamespaces -Wnarrowing -Wnoexcept
           -Wnon-virtual-dtor  -Wreorder -Weffc++  -Wstrict-null-sentinel
           -Wtemplates -Wno-non-template-friend  -Wold-style-cast
           -Woverloaded-virtual  -Wno-pmf-conversions -Wsign-promo
           -Wvirtual-inheritance

       Objective-C and Objective-C++ Language Options
           -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime
           -fno-nil-receivers -fobjc-abi-version=n -fobjc-call-cxx-cdtors
           -fobjc-direct-dispatch -fobjc-exceptions -fobjc-gc
           -fobjc-nilcheck -fobjc-std=objc1 -fno-local-ivars
           -fivar-visibility=[public|protected|private|package]
           -freplace-objc-classes -fzero-link -gen-decls -Wassign-intercept
           -Wno-protocol  -Wselector -Wstrict-selector-match
           -Wundeclared-selector

       Diagnostic Message Formatting Options
           -fmessage-length=n -fdiagnostics-show-location=[once|every-line]
           -fdiagnostics-color=[auto|never|always]
           -fno-diagnostics-show-option -fno-diagnostics-show-caret

       Warning Options
           -fsyntax-only  -fmax-errors=n  -Wpedantic -pedantic-errors -w
           -Wextra  -Wall  -Waddress  -Waggregate-return
           -Wno-aggressive-loop-optimizations -Warray-bounds
           -Warray-bounds=n -Wno-attributes -Wbool-compare
           -Wno-builtin-macro-redefined -Wc90-c99-compat -Wc99-c11-compat
           -Wc++-compat -Wc++11-compat -Wc++14-compat -Wcast-align
           -Wcast-qual -Wchar-subscripts -Wclobbered  -Wcomment
           -Wconditionally-supported -Wconversion -Wcoverage-mismatch
           -Wno-cpp -Wdate-time -Wdelete-incomplete -Wno-deprecated
           -Wno-deprecated-declarations -Wno-designated-init
           -Wdisabled-optimization -Wno-discarded-qualifiers
           -Wno-discarded-array-qualifiers -Wno-div-by-zero
           -Wdouble-promotion -Wduplicated-cond -Wempty-body  -Wenum-compare
           -Wno-endif-labels -Werror  -Werror=* -Wfatal-errors -Wfloat-equal
           -Wformat  -Wformat=2 -Wno-format-contains-nul
           -Wno-format-extra-args -Wformat-nonliteral -Wformat-security
           -Wformat-signedness  -Wformat-y2k -Wframe-address
           -Wframe-larger-than=len -Wno-free-nonheap-object
           -Wjump-misses-init -Wignored-qualifiers  -Wignored-attributes
           -Wincompatible-pointer-types -Wimplicit
           -Wimplicit-function-declaration  -Wimplicit-int -Winit-self
           -Winline  -Wno-int-conversion -Wno-int-to-pointer-cast
           -Winvalid-memory-model -Wno-invalid-offsetof -Winvalid-pch
           -Wlarger-than=len -Wlogical-op -Wlogical-not-parentheses
           -Wlong-long -Wmain -Wmaybe-uninitialized -Wmemset-transposed-args
           -Wmisleading-indentation -Wmissing-braces
           -Wmissing-field-initializers -Wmissing-include-dirs
           -Wno-multichar -Wnonnull -Wnonnull-compare
           -Wnormalized=[none|id|nfc|nfkc] -Wnull-dereference -Wodr
           -Wno-overflow  -Wopenmp-simd -Woverride-init-side-effects
           -Woverlength-strings -Wpacked  -Wpacked-bitfield-compat  -Wpadded
           -Wparentheses -Wno-pedantic-ms-format -Wplacement-new
           -Wplacement-new=n -Wpointer-arith  -Wno-pointer-to-int-cast
           -Wno-pragmas -Wredundant-decls  -Wno-return-local-addr
           -Wreturn-type  -Wsequence-point  -Wshadow  -Wno-shadow-ivar
           -Wshift-overflow -Wshift-overflow=n -Wshift-count-negative
           -Wshift-count-overflow -Wshift-negative-value -Wsign-compare
           -Wsign-conversion -Wfloat-conversion -Wno-scalar-storage-order
           -Wsizeof-pointer-memaccess  -Wsizeof-array-argument
           -Wstack-protector -Wstack-usage=len -Wstrict-aliasing
           -Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=n
           -Wsuggest-attribute=[pure|const|noreturn|format]
           -Wsuggest-final-types  -Wsuggest-final-methods -Wsuggest-override
           -Wmissing-format-attribute -Wsubobject-linkage -Wswitch
           -Wswitch-default  -Wswitch-enum -Wswitch-bool -Wsync-nand
           -Wsystem-headers  -Wtautological-compare  -Wtrampolines
           -Wtrigraphs -Wtype-limits  -Wundef -Wuninitialized
           -Wunknown-pragmas  -Wunsafe-loop-optimizations
           -Wunsuffixed-float-constants  -Wunused  -Wunused-function
           -Wunused-label  -Wunused-local-typedefs -Wunused-parameter
           -Wno-unused-result -Wunused-value  -Wunused-variable
           -Wunused-const-variable -Wunused-const-variable=n
           -Wunused-but-set-parameter -Wunused-but-set-variable
           -Wuseless-cast -Wvariadic-macros -Wvector-operation-performance
           -Wvla -Wvolatile-register-var  -Wwrite-strings
           -Wzero-as-null-pointer-constant -Whsa

       C and Objective-C-only Warning Options
           -Wbad-function-cast  -Wmissing-declarations
           -Wmissing-parameter-type  -Wmissing-prototypes  -Wnested-externs
           -Wold-style-declaration  -Wold-style-definition
           -Wstrict-prototypes  -Wtraditional  -Wtraditional-conversion
           -Wdeclaration-after-statement -Wpointer-sign

       Debugging Options
           -g  -glevel  -gcoff  -gdwarf -gdwarf-version -ggdb
           -grecord-gcc-switches  -gno-record-gcc-switches -gstabs  -gstabs+
           -gstrict-dwarf  -gno-strict-dwarf -gvms  -gxcoff  -gxcoff+
           -gz[=type] -fdebug-prefix-map=old=new -fdebug-types-section
           -feliminate-dwarf2-dups -fno-eliminate-unused-debug-types
           -femit-struct-debug-baseonly -femit-struct-debug-reduced
           -femit-struct-debug-detailed[=spec-list]
           -feliminate-unused-debug-symbols -femit-class-debug-always
           -fno-merge-debug-strings -fno-dwarf2-cfi-asm -fvar-tracking
           -fvar-tracking-assignments

       Optimization Options
           -faggressive-loop-optimizations -falign-functions[=n]
           -falign-jumps[=n] -falign-labels[=n] -falign-loops[=n]
           -fassociative-math -fauto-profile -fauto-profile[=path]
           -fauto-inc-dec -fbranch-probabilities
           -fbranch-target-load-optimize -fbranch-target-load-optimize2
           -fbtr-bb-exclusive -fcaller-saves -fcombine-stack-adjustments
           -fconserve-stack -fcompare-elim -fcprop-registers -fcrossjumping
           -fcse-follow-jumps -fcse-skip-blocks -fcx-fortran-rules
           -fcx-limited-range -fdata-sections -fdce -fdelayed-branch
           -fdelete-null-pointer-checks -fdevirtualize
           -fdevirtualize-speculatively -fdevirtualize-at-ltrans -fdse
           -fearly-inlining -fipa-sra -fexpensive-optimizations
           -ffat-lto-objects -ffast-math -ffinite-math-only -ffloat-store
           -fexcess-precision=style -fforward-propagate -ffp-contract=style
           -ffunction-sections -fgcse -fgcse-after-reload -fgcse-las
           -fgcse-lm -fgraphite-identity -fgcse-sm -fhoist-adjacent-loads
           -fif-conversion -fif-conversion2 -findirect-inlining
           -finline-functions -finline-functions-called-once
           -finline-limit=n -finline-small-functions -fipa-cp -fipa-cp-clone
           -fipa-cp-alignment -fipa-pta -fipa-profile -fipa-pure-const
           -fipa-reference -fipa-icf -fira-algorithm=algorithm
           -fira-region=region -fira-hoist-pressure -fira-loop-pressure
           -fno-ira-share-save-slots -fno-ira-share-spill-slots
           -fisolate-erroneous-paths-dereference
           -fisolate-erroneous-paths-attribute -fivopts
           -fkeep-inline-functions -fkeep-static-functions
           -fkeep-static-consts -flive-range-shrinkage -floop-block
           -floop-interchange -floop-strip-mine -floop-unroll-and-jam
           -floop-nest-optimize -floop-parallelize-all -flra-remat -flto
           -flto-compression-level -flto-partition=alg -fmerge-all-constants
           -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves
           -fmove-loop-invariants -fno-branch-count-reg -fno-defer-pop
           -fno-function-cse -fno-guess-branch-probability -fno-inline
           -fno-math-errno -fno-peephole -fno-peephole2
           -fno-sched-interblock -fno-sched-spec -fno-signed-zeros
           -fno-toplevel-reorder -fno-trapping-math
           -fno-zero-initialized-in-bss -fomit-frame-pointer
           -foptimize-sibling-calls -fpartial-inlining -fpeel-loops
           -fpredictive-commoning -fprefetch-loop-arrays
           -fprofile-correction -fprofile-use -fprofile-use=path
           -fprofile-values -fprofile-reorder-functions -freciprocal-math
           -free -frename-registers -freorder-blocks
           -freorder-blocks-algorithm=algorithm
           -freorder-blocks-and-partition -freorder-functions
           -frerun-cse-after-loop -freschedule-modulo-scheduled-loops
           -frounding-math -fsched2-use-superblocks -fsched-pressure
           -fsched-spec-load -fsched-spec-load-dangerous
           -fsched-stalled-insns-dep[=n] -fsched-stalled-insns[=n]
           -fsched-group-heuristic -fsched-critical-path-heuristic
           -fsched-spec-insn-heuristic -fsched-rank-heuristic
           -fsched-last-insn-heuristic -fsched-dep-count-heuristic
           -fschedule-fusion -fschedule-insns -fschedule-insns2
           -fsection-anchors -fselective-scheduling -fselective-scheduling2
           -fsel-sched-pipelining -fsel-sched-pipelining-outer-loops
           -fsemantic-interposition -fshrink-wrap -fsignaling-nans
           -fsingle-precision-constant -fsplit-ivs-in-unroller -fsplit-paths
           -fsplit-wide-types -fssa-backprop -fssa-phiopt -fstdarg-opt
           -fstrict-aliasing -fstrict-overflow -fthread-jumps -ftracer
           -ftree-bit-ccp -ftree-builtin-call-dce -ftree-ccp -ftree-ch
           -ftree-coalesce-vars -ftree-copy-prop -ftree-dce
           -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre
           -ftree-loop-if-convert -ftree-loop-if-convert-stores
           -ftree-loop-im -ftree-phiprop -ftree-loop-distribution
           -ftree-loop-distribute-patterns -ftree-loop-ivcanon
           -ftree-loop-linear -ftree-loop-optimize -ftree-loop-vectorize
           -ftree-parallelize-loops=n -ftree-pre -ftree-partial-pre
           -ftree-pta -ftree-reassoc -ftree-sink -ftree-slsr -ftree-sra
           -ftree-switch-conversion -ftree-tail-merge -ftree-ter
           -ftree-vectorize -ftree-vrp -funconstrained-commons
           -funit-at-a-time -funroll-all-loops -funroll-loops
           -funsafe-loop-optimizations -funsafe-math-optimizations
           -funswitch-loops -fipa-ra -fvariable-expansion-in-unroller
           -fvect-cost-model -fvpt -fweb -fwhole-program -fwpa
           -fuse-linker-plugin --param name=value -O  -O0  -O1  -O2  -O3
           -Os -Ofast -Og

       Program Instrumentation Options
           -p  -pg  -fprofile-arcs --coverage -ftest-coverage
           -fprofile-dir=path -fprofile-generate -fprofile-generate=path
           -fsanitize=style -fsanitize-recover -fsanitize-recover=style
           -fasan-shadow-offset=number -fsanitize-sections=s1,s2,...
           -fsanitize-undefined-trap-on-error -fbounds-check
           -fcheck-pointer-bounds -fchkp-check-incomplete-type
           -fchkp-first-field-has-own-bounds -fchkp-narrow-bounds
           -fchkp-narrow-to-innermost-array -fchkp-optimize
           -fchkp-use-fast-string-functions
           -fchkp-use-nochk-string-functions -fchkp-use-static-bounds
           -fchkp-use-static-const-bounds
           -fchkp-treat-zero-dynamic-size-as-infinite -fchkp-check-read
           -fchkp-check-read -fchkp-check-write -fchkp-store-bounds
           -fchkp-instrument-calls -fchkp-instrument-marked-only
           -fchkp-use-wrappers -fstack-protector -fstack-protector-all
           -fstack-protector-strong -fstack-protector-explicit -fstack-check
           -fstack-limit-register=reg  -fstack-limit-symbol=sym
           -fno-stack-limit -fsplit-stack -fvtable-verify=[std|preinit|none]
           -fvtv-counts -fvtv-debug -finstrument-functions
           -finstrument-functions-exclude-function-list=sym,sym,...
           -finstrument-functions-exclude-file-list=file,file,...

       Preprocessor Options
           -Aquestion=answer -A-question[=answer] -C  -dD  -dI  -dM  -dN
           -Dmacro[=defn]  -E  -H -idirafter dir -include file  -imacros
           file -iprefix file  -iwithprefix dir -iwithprefixbefore dir
           -isystem dir -imultilib dir -isysroot dir -M  -MM  -MF  -MG  -MP
           -MQ  -MT  -nostdinc -P  -fdebug-cpp -ftrack-macro-expansion
           -fworking-directory -remap -trigraphs  -undef  -Umacro -Wp,option
           -Xpreprocessor option -no-integrated-cpp

       Assembler Option
           -Wa,option  -Xassembler option

       Linker Options
           object-file-name  -fuse-ld=linker -llibrary -nostartfiles
           -nodefaultlibs  -nostdlib -pie -rdynamic -s  -static
           -static-libgcc -static-libstdc++ -static-libasan -static-libtsan
           -static-liblsan -static-libubsan -static-libmpx
           -static-libmpxwrappers -shared -shared-libgcc  -symbolic -T
           script  -Wl,option  -Xlinker option -u symbol -z keyword

       Directory Options
           -Bprefix -Idir -iplugindir=dir -iquotedir -Ldir
           -no-canonical-prefixes -I- --sysroot=dir --no-sysroot-suffix

       Code Generation Options
           -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions
           -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables
           -fasynchronous-unwind-tables -fno-gnu-unique
           -finhibit-size-directive  -fno-common  -fno-ident
           -fpcc-struct-return  -fpic  -fPIC -fpie -fPIE -fno-plt
           -fno-jump-tables -frecord-gcc-switches -freg-struct-return
           -fshort-enums  -fshort-wchar -fverbose-asm  -fpack-struct[=n]
           -fleading-underscore  -ftls-model=model -fstack-reuse=reuse_level
           -ftrapv  -fwrapv -fvisibility=[default|internal|hidden|protected]
           -fstrict-volatile-bitfields -fsync-libcalls

       Developer Options
           -dletters  -dumpspecs  -dumpmachine  -dumpversion -fchecking
           -fdbg-cnt-list -fdbg-cnt=counter-value-list
           -fdisable-ipa-pass_name -fdisable-rtl-pass_name
           -fdisable-rtl-pass-name=range-list -fdisable-tree-pass_name
           -fdisable-tree-pass-name=range-list -fdump-noaddr
           -fdump-unnumbered -fdump-unnumbered-links
           -fdump-translation-unit[-n] -fdump-class-hierarchy[-n]
           -fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline -fdump-passes
           -fdump-rtl-pass -fdump-rtl-pass=filename -fdump-statistics
           -fdump-tree-all -fdump-tree-original[-n]
           -fdump-tree-optimized[-n] -fdump-tree-cfg -fdump-tree-alias
           -fdump-tree-ch -fdump-tree-ssa[-n] -fdump-tree-pre[-n]
           -fdump-tree-ccp[-n] -fdump-tree-dce[-n] -fdump-tree-gimple[-raw]
           -fdump-tree-dom[-n] -fdump-tree-dse[-n] -fdump-tree-phiprop[-n]
           -fdump-tree-phiopt[-n] -fdump-tree-backprop[-n]
           -fdump-tree-forwprop[-n] -fdump-tree-nrv -fdump-tree-vect
           -fdump-tree-sink -fdump-tree-sra[-n] -fdump-tree-forwprop[-n]
           -fdump-tree-fre[-n] -fdump-tree-vtable-verify -fdump-tree-vrp[-n]
           -fdump-tree-split-paths[-n] -fdump-tree-storeccp[-n]
           -fdump-final-insns=file -fcompare-debug[=opts]
           -fcompare-debug-second -fenable-kind-pass
           -fenable-kind-pass=range-list -fira-verbose=n -flto-report
           -flto-report-wpa -fmem-report-wpa -fmem-report
           -fpre-ipa-mem-report -fpost-ipa-mem-report -fopt-info
           -fopt-info-options[=file] -fprofile-report -frandom-seed=string
           -fsched-verbose=n -fsel-sched-verbose -fsel-sched-dump-cfg
           -fsel-sched-pipelining-verbose -fstats  -fstack-usage
           -ftime-report -fvar-tracking-assignments-toggle -gtoggle
           -print-file-name=library  -print-libgcc-file-name
           -print-multi-directory  -print-multi-lib
           -print-multi-os-directory -print-prog-name=program
           -print-search-dirs  -Q -print-sysroot
           -print-sysroot-headers-suffix -save-temps -save-temps=cwd
           -save-temps=obj -time[=file]

       Machine-Dependent Options
           AArch64 Options -mabi=name  -mbig-endian  -mlittle-endian
           -mgeneral-regs-only -mcmodel=tiny  -mcmodel=small  -mcmodel=large
           -mstrict-align -momit-leaf-frame-pointer
           -mno-omit-leaf-frame-pointer -mtls-dialect=desc
           -mtls-dialect=traditional -mtls-size=size -mfix-cortex-a53-835769
           -mno-fix-cortex-a53-835769 -mfix-cortex-a53-843419
           -mno-fix-cortex-a53-843419 -mlow-precision-recip-sqrt
           -mno-low-precision-recip-sqrt -march=name  -mcpu=name
           -mtune=name

           Adapteva Epiphany Options -mhalf-reg-file
           -mprefer-short-insn-regs -mbranch-cost=num -mcmove -mnops=num
           -msoft-cmpsf -msplit-lohi -mpost-inc -mpost-modify
           -mstack-offset=num -mround-nearest -mlong-calls -mshort-calls
           -msmall16 -mfp-mode=mode -mvect-double -max-vect-align=num
           -msplit-vecmove-early -m1reg-reg

           ARC Options -mbarrel-shifter -mcpu=cpu -mA6 -mARC600 -mA7
           -mARC700 -mdpfp -mdpfp-compact -mdpfp-fast -mno-dpfp-lrsr -mea
           -mno-mpy -mmul32x16 -mmul64 -matomic -mnorm -mspfp -mspfp-compact
           -mspfp-fast -msimd -msoft-float -mswap -mcrc -mdsp-packa -mdvbf
           -mlock -mmac-d16 -mmac-24 -mrtsc -mswape -mtelephony -mxy -misize
           -mannotate-align -marclinux -marclinux_prof -mlong-calls
           -mmedium-calls -msdata -mucb-mcount -mvolatile-cache -malign-call
           -mauto-modify-reg -mbbit-peephole -mno-brcc -mcase-vector-pcrel
           -mcompact-casesi -mno-cond-exec -mearly-cbranchsi -mexpand-adddi
           -mindexed-loads -mlra -mlra-priority-none -mlra-priority-compact
           mlra-priority-noncompact -mno-millicode -mmixed-code -mq-class
           -mRcq -mRcw -msize-level=level -mtune=cpu -mmultcost=num
           -munalign-prob-threshold=probability -mmpy-option=multo -mdiv-rem
           -mcode-density -mll64 -mfpu=fpu

           ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name
           -mapcs-stack-check  -mno-apcs-stack-check -mapcs-float
           -mno-apcs-float -mapcs-reentrant  -mno-apcs-reentrant
           -msched-prolog  -mno-sched-prolog -mlittle-endian  -mbig-endian
           -mfloat-abi=name -mfp16-format=name -mthumb-interwork
           -mno-thumb-interwork -mcpu=name  -march=name  -mfpu=name
           -mtune=name -mprint-tune-info -mstructure-size-boundary=n
           -mabort-on-noreturn -mlong-calls  -mno-long-calls
           -msingle-pic-base  -mno-single-pic-base -mpic-register=reg
           -mnop-fun-dllimport -mpoke-function-name -mthumb  -marm
           -mtpcs-frame  -mtpcs-leaf-frame -mcaller-super-interworking
           -mcallee-super-interworking -mtp=name -mtls-dialect=dialect
           -mword-relocations -mfix-cortex-m3-ldrd -munaligned-access
           -mneon-for-64bits -mslow-flash-data -masm-syntax-unified
           -mrestrict-it

           AVR Options -mmcu=mcu -maccumulate-args -mbranch-cost=cost
           -mcall-prologues -mint8 -mn_flash=size -mno-interrupts -mrelax
           -mrmw -mstrict-X -mtiny-stack -nodevicelib -Waddr-space-convert

           Blackfin Options -mcpu=cpu[-sirevision] -msim
           -momit-leaf-frame-pointer  -mno-omit-leaf-frame-pointer
           -mspecld-anomaly  -mno-specld-anomaly  -mcsync-anomaly
           -mno-csync-anomaly -mlow-64k -mno-low64k  -mstack-check-l1
           -mid-shared-library -mno-id-shared-library  -mshared-library-id=n
           -mleaf-id-shared-library  -mno-leaf-id-shared-library -msep-data
           -mno-sep-data  -mlong-calls  -mno-long-calls -mfast-fp
           -minline-plt -mmulticore  -mcorea  -mcoreb  -msdram -micplb

           C6X Options -mbig-endian  -mlittle-endian -march=cpu -msim
           -msdata=sdata-type

           CRIS Options -mcpu=cpu  -march=cpu  -mtune=cpu
           -mmax-stack-frame=n  -melinux-stacksize=n -metrax4  -metrax100
           -mpdebug  -mcc-init  -mno-side-effects -mstack-align
           -mdata-align  -mconst-align -m32-bit  -m16-bit  -m8-bit
           -mno-prologue-epilogue  -mno-gotplt -melf  -maout  -melinux
           -mlinux  -sim  -sim2 -mmul-bug-workaround
           -mno-mul-bug-workaround

           CR16 Options -mmac -mcr16cplus -mcr16c -msim -mint32 -mbit-ops
           -mdata-model=model

           Darwin Options -all_load  -allowable_client  -arch
           -arch_errors_fatal -arch_only  -bind_at_load  -bundle
           -bundle_loader -client_name  -compatibility_version
           -current_version -dead_strip -dependency-file  -dylib_file
           -dylinker_install_name -dynamic  -dynamiclib
           -exported_symbols_list -filelist  -flat_namespace
           -force_cpusubtype_ALL -force_flat_namespace
           -headerpad_max_install_names -iframework -image_base  -init
           -install_name  -keep_private_externs -multi_module
           -multiply_defined  -multiply_defined_unused -noall_load
           -no_dead_strip_inits_and_terms -nofixprebinding -nomultidefs
           -noprebind  -noseglinkedit -pagezero_size  -prebind
           -prebind_all_twolevel_modules -private_bundle  -read_only_relocs
           -sectalign -sectobjectsymbols  -whyload  -seg1addr -sectcreate
           -sectobjectsymbols  -sectorder -segaddr -segs_read_only_addr
           -segs_read_write_addr -seg_addr_table  -seg_addr_table_filename
           -seglinkedit -segprot  -segs_read_only_addr
           -segs_read_write_addr -single_module  -static  -sub_library
           -sub_umbrella -twolevel_namespace  -umbrella  -undefined
           -unexported_symbols_list  -weak_reference_mismatches -whatsloaded
           -F -gused -gfull -mmacosx-version-min=version -mkernel
           -mone-byte-bool

           DEC Alpha Options -mno-fp-regs  -msoft-float -mieee
           -mieee-with-inexact  -mieee-conformant -mfp-trap-mode=mode
           -mfp-rounding-mode=mode -mtrap-precision=mode  -mbuild-constants
           -mcpu=cpu-type  -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix
           -mfloat-vax  -mfloat-ieee -mexplicit-relocs  -msmall-data
           -mlarge-data -msmall-text  -mlarge-text -mmemory-latency=time

           FR30 Options -msmall-model -mno-lsim

           FT32 Options -msim -mlra -mnodiv

           FRV Options -mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float
           -msoft-float -malloc-cc  -mfixed-cc  -mdword  -mno-dword -mdouble
           -mno-double -mmedia  -mno-media  -mmuladd  -mno-muladd -mfdpic
           -minline-plt -mgprel-ro  -multilib-library-pic -mlinked-fp
           -mlong-calls  -malign-labels -mlibrary-pic  -macc-4  -macc-8
           -mpack  -mno-pack  -mno-eflags  -mcond-move  -mno-cond-move
           -moptimize-membar -mno-optimize-membar -mscc  -mno-scc
           -mcond-exec  -mno-cond-exec -mvliw-branch  -mno-vliw-branch
           -mmulti-cond-exec  -mno-multi-cond-exec  -mnested-cond-exec
           -mno-nested-cond-exec  -mtomcat-stats -mTLS -mtls -mcpu=cpu

           GNU/Linux Options -mglibc -muclibc -mmusl -mbionic -mandroid
           -tno-android-cc -tno-android-ld

           H8/300 Options -mrelax  -mh  -ms  -mn  -mexr -mno-exr  -mint32
           -malign-300

           HPPA Options -march=architecture-type -mdisable-fpregs
           -mdisable-indexing -mfast-indirect-calls  -mgas  -mgnu-ld
           -mhp-ld -mfixed-range=register-range -mjump-in-delay -mlinker-opt
           -mlong-calls -mlong-load-store  -mno-disable-fpregs
           -mno-disable-indexing  -mno-fast-indirect-calls  -mno-gas
           -mno-jump-in-delay  -mno-long-load-store -mno-portable-runtime
           -mno-soft-float -mno-space-regs  -msoft-float  -mpa-risc-1-0
           -mpa-risc-1-1  -mpa-risc-2-0  -mportable-runtime -mschedule=cpu-
           type  -mspace-regs  -msio  -mwsio -munix=unix-std  -nolibdld
           -static  -threads

           IA-64 Options -mbig-endian  -mlittle-endian  -mgnu-as  -mgnu-ld
           -mno-pic -mvolatile-asm-stop  -mregister-names  -msdata
           -mno-sdata -mconstant-gp  -mauto-pic  -mfused-madd
           -minline-float-divide-min-latency
           -minline-float-divide-max-throughput -mno-inline-float-divide
           -minline-int-divide-min-latency
           -minline-int-divide-max-throughput -mno-inline-int-divide
           -minline-sqrt-min-latency -minline-sqrt-max-throughput
           -mno-inline-sqrt -mdwarf2-asm -mearly-stop-bits
           -mfixed-range=register-range -mtls-size=tls-size -mtune=cpu-type
           -milp32 -mlp64 -msched-br-data-spec -msched-ar-data-spec
           -msched-control-spec -msched-br-in-data-spec
           -msched-ar-in-data-spec -msched-in-control-spec -msched-spec-ldc
           -msched-spec-control-ldc -msched-prefer-non-data-spec-insns
           -msched-prefer-non-control-spec-insns
           -msched-stop-bits-after-every-cycle
           -msched-count-spec-in-critical-path
           -msel-sched-dont-check-control-spec -msched-fp-mem-deps-zero-cost
           -msched-max-memory-insns-hard-limit -msched-max-memory-insns=max-
           insns

           LM32 Options -mbarrel-shift-enabled -mdivide-enabled
           -mmultiply-enabled -msign-extend-enabled -muser-enabled

           M32R/D Options -m32r2 -m32rx -m32r -mdebug -malign-loops
           -mno-align-loops -missue-rate=number -mbranch-cost=number
           -mmodel=code-size-model-type -msdata=sdata-type -mno-flush-func
           -mflush-func=name -mno-flush-trap -mflush-trap=number -G num

           M32C Options -mcpu=cpu -msim -memregs=number

           M680x0 Options -march=arch  -mcpu=cpu  -mtune=tune -m68000
           -m68020  -m68020-40  -m68020-60  -m68030  -m68040 -m68060
           -mcpu32  -m5200  -m5206e  -m528x  -m5307  -m5407 -mcfv4e
           -mbitfield  -mno-bitfield  -mc68000  -mc68020 -mnobitfield  -mrtd
           -mno-rtd  -mdiv  -mno-div  -mshort -mno-short  -mhard-float
           -m68881  -msoft-float  -mpcrel -malign-int  -mstrict-align
           -msep-data  -mno-sep-data -mshared-library-id=n
           -mid-shared-library  -mno-id-shared-library -mxgot -mno-xgot

           MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div
           -mrelax-immediates -mno-relax-immediates  -mwide-bitfields
           -mno-wide-bitfields -m4byte-functions  -mno-4byte-functions
           -mcallgraph-data -mno-callgraph-data  -mslow-bytes
           -mno-slow-bytes  -mno-lsim -mlittle-endian  -mbig-endian  -m210
           -m340  -mstack-increment

           MeP Options -mabsdiff -mall-opts -maverage -mbased=n -mbitops
           -mc=n -mclip -mconfig=name -mcop -mcop32 -mcop64 -mivc2 -mdc
           -mdiv -meb -mel -mio-volatile -ml -mleadz -mm -mminmax -mmult
           -mno-opts -mrepeat -ms -msatur -msdram -msim -msimnovec -mtf
           -mtiny=n

           MicroBlaze Options -msoft-float -mhard-float -msmall-divides
           -mcpu=cpu -mmemcpy -mxl-soft-mul -mxl-soft-div -mxl-barrel-shift
           -mxl-pattern-compare -mxl-stack-check -mxl-gp-opt -mno-clearbss
           -mxl-multiply-high -mxl-float-convert -mxl-float-sqrt
           -mbig-endian -mlittle-endian -mxl-reorder -mxl-mode-app-model

           MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2
           -mips3  -mips4  -mips32  -mips32r2  -mips32r3  -mips32r5
           -mips32r6  -mips64  -mips64r2  -mips64r3  -mips64r5  -mips64r6
           -mips16  -mno-mips16  -mflip-mips16 -minterlink-compressed
           -mno-interlink-compressed -minterlink-mips16
           -mno-interlink-mips16 -mabi=abi  -mabicalls  -mno-abicalls
           -mshared  -mno-shared  -mplt  -mno-plt  -mxgot  -mno-xgot -mgp32
           -mgp64  -mfp32  -mfpxx  -mfp64  -mhard-float  -msoft-float
           -mno-float  -msingle-float  -mdouble-float -modd-spreg
           -mno-odd-spreg -mabs=mode  -mnan=encoding -mdsp  -mno-dsp
           -mdspr2  -mno-dspr2 -mmcu -mmno-mcu -meva -mno-eva -mvirt
           -mno-virt -mxpa -mno-xpa -mmicromips -mno-micromips -mfpu=fpu-
           type -msmartmips  -mno-smartmips -mpaired-single
           -mno-paired-single  -mdmx  -mno-mdmx -mips3d  -mno-mips3d  -mmt
           -mno-mt  -mllsc  -mno-llsc -mlong64  -mlong32  -msym32
           -mno-sym32 -Gnum  -mlocal-sdata  -mno-local-sdata -mextern-sdata
           -mno-extern-sdata  -mgpopt  -mno-gopt -membedded-data
           -mno-embedded-data -muninit-const-in-rodata
           -mno-uninit-const-in-rodata -mcode-readable=setting
           -msplit-addresses  -mno-split-addresses -mexplicit-relocs
           -mno-explicit-relocs -mcheck-zero-division
           -mno-check-zero-division -mdivide-traps  -mdivide-breaks -mmemcpy
           -mno-memcpy  -mlong-calls  -mno-long-calls -mmad -mno-mad -mimadd
           -mno-imadd -mfused-madd  -mno-fused-madd  -nocpp -mfix-24k
           -mno-fix-24k -mfix-r4000  -mno-fix-r4000  -mfix-r4400
           -mno-fix-r4400 -mfix-r10000 -mno-fix-r10000  -mfix-rm7000
           -mno-fix-rm7000 -mfix-vr4120  -mno-fix-vr4120 -mfix-vr4130
           -mno-fix-vr4130  -mfix-sb1  -mno-fix-sb1 -mflush-func=func
           -mno-flush-func -mbranch-cost=num  -mbranch-likely
           -mno-branch-likely -mcompact-branches=policy -mfp-exceptions
           -mno-fp-exceptions -mvr4130-align -mno-vr4130-align -msynci
           -mno-synci -mrelax-pic-calls -mno-relax-pic-calls
           -mmcount-ra-address -mframe-header-opt -mno-frame-header-opt

           MMIX Options -mlibfuncs  -mno-libfuncs  -mepsilon  -mno-epsilon
           -mabi=gnu -mabi=mmixware  -mzero-extend  -mknuthdiv
           -mtoplevel-symbols -melf  -mbranch-predict  -mno-branch-predict
           -mbase-addresses -mno-base-addresses  -msingle-exit
           -mno-single-exit

           MN10300 Options -mmult-bug  -mno-mult-bug -mno-am33 -mam33
           -mam33-2 -mam34 -mtune=cpu-type -mreturn-pointer-on-d0 -mno-crt0
           -mrelax -mliw -msetlb

           Moxie Options -meb -mel -mmul.x -mno-crt0

           MSP430 Options -msim -masm-hex -mmcu= -mcpu= -mlarge -msmall
           -mrelax -mwarn-mcu -mcode-region= -mdata-region=
           -msilicon-errata= -msilicon-errata-warn= -mhwmult= -minrt

           NDS32 Options -mbig-endian -mlittle-endian -mreduced-regs
           -mfull-regs -mcmov -mno-cmov -mperf-ext -mno-perf-ext -mv3push
           -mno-v3push -m16bit -mno-16bit -misr-vector-size=num
           -mcache-block-size=num -march=arch -mcmodel=code-model
           -mctor-dtor -mrelax

           Nios II Options -G num -mgpopt=option -mgpopt -mno-gpopt -mel
           -meb -mno-bypass-cache -mbypass-cache -mno-cache-volatile
           -mcache-volatile -mno-fast-sw-div -mfast-sw-div -mhw-mul
           -mno-hw-mul -mhw-mulx -mno-hw-mulx -mno-hw-div -mhw-div
           -mcustom-insn=N -mno-custom-insn -mcustom-fpu-cfg=name -mhal
           -msmallc -msys-crt0=name -msys-lib=name -march=arch -mbmx
           -mno-bmx -mcdx -mno-cdx

           Nvidia PTX Options -m32 -m64 -mmainkernel -moptimize

           PDP-11 Options -mfpu  -msoft-float  -mac0  -mno-ac0  -m40  -m45
           -m10 -mbcopy  -mbcopy-builtin  -mint32  -mno-int16 -mint16
           -mno-int32  -mfloat32  -mno-float64 -mfloat64  -mno-float32
           -mabshi  -mno-abshi -mbranch-expensive  -mbranch-cheap -munix-asm
           -mdec-asm

           picoChip Options -mae=ae_type -mvliw-lookahead=N
           -msymbol-as-address -mno-inefficient-warnings

           PowerPC Options See RS/6000 and PowerPC Options.

           RL78 Options -msim -mmul=none -mmul=g13 -mmul=g14 -mallregs
           -mcpu=g10 -mcpu=g13 -mcpu=g14 -mg10 -mg13 -mg14 -m64bit-doubles
           -m32bit-doubles

           RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type
           -mcmodel=code-model -mpowerpc64 -maltivec  -mno-altivec
           -mpowerpc-gpopt  -mno-powerpc-gpopt -mpowerpc-gfxopt
           -mno-powerpc-gfxopt -mmfcrf  -mno-mfcrf  -mpopcntb  -mno-popcntb
           -mpopcntd -mno-popcntd -mfprnd  -mno-fprnd -mcmpb -mno-cmpb
           -mmfpgpr -mno-mfpgpr -mhard-dfp -mno-hard-dfp -mfull-toc
           -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-toc -m64  -m32
           -mxl-compat  -mno-xl-compat  -mpe -malign-power  -malign-natural
           -msoft-float  -mhard-float  -mmultiple  -mno-multiple
           -msingle-float -mdouble-float -msimple-fpu -mstring  -mno-string
           -mupdate  -mno-update -mavoid-indexed-addresses
           -mno-avoid-indexed-addresses -mfused-madd  -mno-fused-madd
           -mbit-align  -mno-bit-align -mstrict-align  -mno-strict-align
           -mrelocatable -mno-relocatable  -mrelocatable-lib
           -mno-relocatable-lib -mtoc  -mno-toc  -mlittle  -mlittle-endian
           -mbig  -mbig-endian -mdynamic-no-pic  -maltivec -mswdiv
           -msingle-pic-base -mprioritize-restricted-insns=priority
           -msched-costly-dep=dependence_type -minsert-sched-nops=scheme
           -mcall-sysv  -mcall-netbsd -maix-struct-return
           -msvr4-struct-return -mabi=abi-type -msecure-plt -mbss-plt
           -mblock-move-inline-limit=num -misel -mno-isel -misel=yes
           -misel=no -mspe -mno-spe -mspe=yes  -mspe=no -mpaired
           -mgen-cell-microcode -mwarn-cell-microcode -mvrsave -mno-vrsave
           -mmulhw -mno-mulhw -mdlmzb -mno-dlmzb -mfloat-gprs=yes
           -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double
           -mprototype  -mno-prototype -msim  -mmvme  -mads  -myellowknife
           -memb  -msdata -msdata=opt  -mvxworks  -G num  -pthread -mrecip
           -mrecip=opt -mno-recip -mrecip-precision -mno-recip-precision
           -mveclibabi=type -mfriz -mno-friz -mpointers-to-nested-functions
           -mno-pointers-to-nested-functions -msave-toc-indirect
           -mno-save-toc-indirect -mpower8-fusion -mno-mpower8-fusion
           -mpower8-vector -mno-power8-vector -mcrypto -mno-crypto -mhtm
           -mno-htm -mdirect-move -mno-direct-move -mquad-memory
           -mno-quad-memory -mquad-memory-atomic -mno-quad-memory-atomic
           -mcompat-align-parm -mno-compat-align-parm -mupper-regs-df
           -mno-upper-regs-df -mupper-regs-sf -mno-upper-regs-sf
           -mupper-regs -mno-upper-regs -mmodulo -mno-modulo -mfloat128
           -mno-float128 -mfloat128-hardware -mno-float128-hardware
           -mpower9-fusion -mno-mpower9-fusion -mpower9-vector
           -mno-power9-vector -mpower9-dform -mno-power9-dform -mlra
           -mno-lra

           RX Options -m64bit-doubles  -m32bit-doubles  -fpu  -nofpu -mcpu=
           -mbig-endian-data -mlittle-endian-data -msmall-data -msim
           -mno-sim -mas100-syntax -mno-as100-syntax -mrelax
           -mmax-constant-size= -mint-register= -mpid -mallow-string-insns
           -mno-allow-string-insns -mjsr -mno-warn-multiple-fast-interrupts
           -msave-acc-in-interrupts

           S/390 and zSeries Options -mtune=cpu-type  -march=cpu-type
           -mhard-float  -msoft-float  -mhard-dfp -mno-hard-dfp
           -mlong-double-64 -mlong-double-128 -mbackchain  -mno-backchain
           -mpacked-stack  -mno-packed-stack -msmall-exec  -mno-small-exec
           -mmvcle -mno-mvcle -m64  -m31  -mdebug  -mno-debug  -mesa
           -mzarch -mhtm -mvx -mzvector -mtpf-trace -mno-tpf-trace
           -mfused-madd  -mno-fused-madd -mwarn-framesize
           -mwarn-dynamicstack  -mstack-size -mstack-guard
           -mhotpatch=halfwords,halfwords

           Score Options -meb -mel -mnhwloop -muls -mmac -mscore5 -mscore5u
           -mscore7 -mscore7d

           SH Options -m1  -m2  -m2e -m2a-nofpu -m2a-single-only -m2a-single
           -m2a -m3  -m3e -m4-nofpu  -m4-single-only  -m4-single  -m4
           -m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al -mb  -ml
           -mdalign  -mrelax -mbigtable -mfmovd -mrenesas -mno-renesas
           -mnomacsave -mieee -mno-ieee -mbitops  -misize
           -minline-ic_invalidate -mpadstruct -mspace -mprefergot
           -musermode -multcost=number -mdiv=strategy -mdivsi3_libfunc=name
           -mfixed-range=register-range -maccumulate-outgoing-args
           -matomic-model=atomic-model -mbranch-cost=num -mzdcbranch
           -mno-zdcbranch -mcbranch-force-delay-slot -mfused-madd
           -mno-fused-madd -mfsca -mno-fsca -mfsrra -mno-fsrra
           -mpretend-cmove -mtas

           Solaris 2 Options -mclear-hwcap -mno-clear-hwcap -mimpure-text
           -mno-impure-text -pthreads -pthread

           SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model
           -mmemory-model=mem-model -m32  -m64  -mapp-regs  -mno-app-regs
           -mfaster-structs  -mno-faster-structs  -mflat  -mno-flat -mfpu
           -mno-fpu  -mhard-float  -msoft-float -mhard-quad-float
           -msoft-quad-float -mstack-bias  -mno-stack-bias
           -mstd-struct-return  -mno-std-struct-return -munaligned-doubles
           -mno-unaligned-doubles -muser-mode  -mno-user-mode -mv8plus
           -mno-v8plus  -mvis  -mno-vis -mvis2  -mno-vis2  -mvis3  -mno-vis3
           -mcbcond -mno-cbcond -mfmaf  -mno-fmaf  -mpopc  -mno-popc
           -mfix-at697f -mfix-ut699

           SPU Options -mwarn-reloc -merror-reloc -msafe-dma -munsafe-dma
           -mbranch-hints -msmall-mem -mlarge-mem -mstdmain
           -mfixed-range=register-range -mea32 -mea64
           -maddress-space-conversion -mno-address-space-conversion
           -mcache-size=cache-size -matomic-updates -mno-atomic-updates

           System V Options -Qy  -Qn  -YP,paths  -Ym,dir

           TILE-Gx Options -mcpu=CPU -m32 -m64 -mbig-endian -mlittle-endian
           -mcmodel=code-model

           TILEPro Options -mcpu=cpu -m32

           V850 Options -mlong-calls  -mno-long-calls  -mep  -mno-ep
           -mprolog-function  -mno-prolog-function  -mspace -mtda=n  -msda=n
           -mzda=n -mapp-regs  -mno-app-regs -mdisable-callt
           -mno-disable-callt -mv850e2v3 -mv850e2 -mv850e1 -mv850es -mv850e
           -mv850 -mv850e3v5 -mloop -mrelax -mlong-jumps -msoft-float
           -mhard-float -mgcc-abi -mrh850-abi -mbig-switch

           VAX Options -mg  -mgnu  -munix

           Visium Options -mdebug -msim -mfpu -mno-fpu -mhard-float
           -msoft-float -mcpu=cpu-type -mtune=cpu-type -msv-mode -muser-mode

           VMS Options -mvms-return-codes -mdebug-main=prefix -mmalloc64
           -mpointer-size=size

           VxWorks Options -mrtp  -non-static  -Bstatic  -Bdynamic
           -Xbind-lazy  -Xbind-now

           x86 Options -mtune=cpu-type  -march=cpu-type -mtune-ctrl=feature-
           list -mdump-tune-features -mno-default -mfpmath=unit
           -masm=dialect  -mno-fancy-math-387 -mno-fp-ret-in-387
           -msoft-float -mno-wide-multiply  -mrtd  -malign-double
           -mpreferred-stack-boundary=num -mincoming-stack-boundary=num
           -mcld -mcx16 -msahf -mmovbe -mcrc32 -mrecip -mrecip=opt
           -mvzeroupper -mprefer-avx128 -mmmx  -msse  -msse2 -msse3 -mssse3
           -msse4.1 -msse4.2 -msse4 -mavx -mavx2 -mavx512f -mavx512pf
           -mavx512er -mavx512cd -mavx512vl -mavx512bw -mavx512dq
           -mavx512ifma -mavx512vbmi -msha -maes -mpclmul -mfsgsbase -mrdrnd
           -mf16c -mfma -mprefetchwt1 -mclflushopt -mxsavec -mxsaves -msse4a
           -m3dnow -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop -mlzcnt -mbmi2
           -mfxsr -mxsave -mxsaveopt -mrtm -mlwp -mmpx -mmwaitx -mclzero
           -mpku -mthreads -mms-bitfields -mno-align-stringops
           -minline-all-stringops -minline-stringops-dynamically
           -mstringop-strategy=alg -mmemcpy-strategy=strategy
           -mmemset-strategy=strategy -mpush-args
           -maccumulate-outgoing-args  -m128bit-long-double
           -m96bit-long-double -mlong-double-64 -mlong-double-80
           -mlong-double-128 -mregparm=num  -msseregparm -mveclibabi=type
           -mvect8-ret-in-mem -mpc32 -mpc64 -mpc80 -mstackrealign
           -momit-leaf-frame-pointer  -mno-red-zone -mno-tls-direct-seg-refs
           -mcmodel=code-model -mabi=name -maddress-mode=mode -m32 -m64
           -mx32 -m16 -miamcu -mlarge-data-threshold=num -msse2avx -mfentry
           -mrecord-mcount -mnop-mcount -m8bit-idiv
           -mavx256-split-unaligned-load -mavx256-split-unaligned-store
           -malign-data=type -mstack-protector-guard=guard -mmitigate-rop

           x86 Windows Options -mconsole -mcygwin -mno-cygwin -mdll
           -mnop-fun-dllimport -mthread -municode -mwin32 -mwindows
           -fno-set-stack-executable

           Xstormy16 Options -msim

           Xtensa Options -mconst16 -mno-const16 -mfused-madd
           -mno-fused-madd -mforce-no-pic -mserialize-volatile
           -mno-serialize-volatile -mtext-section-literals
           -mno-text-section-literals -mauto-litpools  -mno-auto-litpools
           -mtarget-align  -mno-target-align -mlongcalls  -mno-longcalls

           zSeries Options See S/390 and zSeries Options.

       Options Controlling the Kind of Output

       Compilation can involve up to four stages: preprocessing, compilation
       proper, assembly and linking, always in that order.  GCC is capable
       of preprocessing and compiling several files either into several
       assembler input files, or into one assembler input file; then each
       assembler input file produces an object file, and linking combines
       all the object files (those newly compiled, and those specified as
       input) into an executable file.

       For any given input file, the file name suffix determines what kind
       of compilation is done:

       file.c
           C source code that must be preprocessed.

       file.i
           C source code that should not be preprocessed.

       file.ii
           C++ source code that should not be preprocessed.

       file.m
           Objective-C source code.  Note that you must link with the
           libobjc library to make an Objective-C program work.

       file.mi
           Objective-C source code that should not be preprocessed.

       file.mm
       file.M
           Objective-C++ source code.  Note that you must link with the
           libobjc library to make an Objective-C++ program work.  Note that
           .M refers to a literal capital M.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.h
           C, C++, Objective-C or Objective-C++ header file to be turned
           into a precompiled header (default), or C, C++ header file to be
           turned into an Ada spec (via the -fdump-ada-spec switch).

       file.cc
       file.cp
       file.cxx
       file.cpp
       file.CPP
       file.c++
       file.C
           C++ source code that must be preprocessed.  Note that in .cxx,
           the last two letters must both be literally x.  Likewise, .C
           refers to a literal capital C.

       file.mm
       file.M
           Objective-C++ source code that must be preprocessed.

       file.mii
           Objective-C++ source code that should not be preprocessed.

       file.hh
       file.H
       file.hp
       file.hxx
       file.hpp
       file.HPP
       file.h++
       file.tcc
           C++ header file to be turned into a precompiled header or Ada
           spec.

       file.f
       file.for
       file.ftn
           Fixed form Fortran source code that should not be preprocessed.

       file.F
       file.FOR
       file.fpp
       file.FPP
       file.FTN
           Fixed form Fortran source code that must be preprocessed (with
           the traditional preprocessor).

       file.f90
       file.f95
       file.f03
       file.f08
           Free form Fortran source code that should not be preprocessed.

       file.F90
       file.F95
       file.F03
       file.F08
           Free form Fortran source code that must be preprocessed (with the
           traditional preprocessor).

       file.go
           Go source code.

       file.ads
           Ada source code file that contains a library unit declaration (a
           declaration of a package, subprogram, or generic, or a generic
           instantiation), or a library unit renaming declaration (a
           package, generic, or subprogram renaming declaration).  Such
           files are also called specs.

       file.adb
           Ada source code file containing a library unit body (a subprogram
           or package body).  Such files are also called bodies.

       file.s
           Assembler code.

       file.S
       file.sx
           Assembler code that must be preprocessed.

       other
           An object file to be fed straight into linking.  Any file name
           with no recognized suffix is treated this way.

       You can specify the input language explicitly with the -x option:

       -x language
           Specify explicitly the language for the following input files
           (rather than letting the compiler choose a default based on the
           file name suffix).  This option applies to all following input
           files until the next -x option.  Possible values for language
           are:

                   c  c-header  cpp-output
                   c++  c++-header  c++-cpp-output
                   objective-c  objective-c-header  objective-c-cpp-output
                   objective-c++ objective-c++-header objective-c++-cpp-output
                   assembler  assembler-with-cpp
                   ada
                   f77  f77-cpp-input f95  f95-cpp-input
                   go
                   java

       -x none
           Turn off any specification of a language, so that subsequent
           files are handled according to their file name suffixes (as they
           are if -x has not been used at all).

       If you only want some of the stages of compilation, you can use -x
       (or filename suffixes) to tell gcc where to start, and one of the
       options -c, -S, or -E to say where gcc is to stop.  Note that some
       combinations (for example, -x cpp-output -E) instruct gcc to do
       nothing at all.

       -c  Compile or assemble the source files, but do not link.  The
           linking stage simply is not done.  The ultimate output is in the
           form of an object file for each source file.

           By default, the object file name for a source file is made by
           replacing the suffix .c, .i, .s, etc., with .o.

           Unrecognized input files, not requiring compilation or assembly,
           are ignored.

       -S  Stop after the stage of compilation proper; do not assemble.  The
           output is in the form of an assembler code file for each non-
           assembler input file specified.

           By default, the assembler file name for a source file is made by
           replacing the suffix .c, .i, etc., with .s.

           Input files that don't require compilation are ignored.

       -E  Stop after the preprocessing stage; do not run the compiler
           proper.  The output is in the form of preprocessed source code,
           which is sent to the standard output.

           Input files that don't require preprocessing are ignored.

       -o file
           Place output in file file.  This applies to whatever sort of
           output is being produced, whether it be an executable file, an
           object file, an assembler file or preprocessed C code.

           If -o is not specified, the default is to put an executable file
           in a.out, the object file for source.suffix in source.o, its
           assembler file in source.s, a precompiled header file in
           source.suffix.gch, and all preprocessed C source on standard
           output.

       -v  Print (on standard error output) the commands executed to run the
           stages of compilation.  Also print the version number of the
           compiler driver program and of the preprocessor and the compiler
           proper.

       -###
           Like -v except the commands are not executed and arguments are
           quoted unless they contain only alphanumeric characters or
           "./-_".  This is useful for shell scripts to capture the driver-
           generated command lines.

       --help
           Print (on the standard output) a description of the command-line
           options understood by gcc.  If the -v option is also specified
           then --help is also passed on to the various processes invoked by
           gcc, so that they can display the command-line options they
           accept.  If the -Wextra option has also been specified (prior to
           the --help option), then command-line options that have no
           documentation associated with them are also displayed.

       --target-help
           Print (on the standard output) a description of target-specific
           command-line options for each tool.  For some targets extra
           target-specific information may also be printed.

       --help={class|[^]qualifier}[,...]
           Print (on the standard output) a description of the command-line
           options understood by the compiler that fit into all specified
           classes and qualifiers.  These are the supported classes:

           optimizers
               Display all of the optimization options supported by the
               compiler.

           warnings
               Display all of the options controlling warning messages
               produced by the compiler.

           target
               Display target-specific options.  Unlike the --target-help
               option however, target-specific options of the linker and
               assembler are not displayed.  This is because those tools do
               not currently support the extended --help= syntax.

           params
               Display the values recognized by the --param option.

           language
               Display the options supported for language, where language is
               the name of one of the languages supported in this version of
               GCC.

           common
               Display the options that are common to all languages.

           These are the supported qualifiers:

           undocumented
               Display only those options that are undocumented.

           joined
               Display options taking an argument that appears after an
               equal sign in the same continuous piece of text, such as:
               --help=target.

           separate
               Display options taking an argument that appears as a separate
               word following the original option, such as: -o output-file.

           Thus for example to display all the undocumented target-specific
           switches supported by the compiler, use:

                   --help=target,undocumented

           The sense of a qualifier can be inverted by prefixing it with the
           ^ character, so for example to display all binary warning options
           (i.e., ones that are either on or off and that do not take an
           argument) that have a description, use:

                   --help=warnings,^joined,^undocumented

           The argument to --help= should not consist solely of inverted
           qualifiers.

           Combining several classes is possible, although this usually
           restricts the output so much that there is nothing to display.
           One case where it does work, however, is when one of the classes
           is target.  For example, to display all the target-specific
           optimization options, use:

                   --help=target,optimizers

           The --help= option can be repeated on the command line.  Each
           successive use displays its requested class of options, skipping
           those that have already been displayed.

           If the -Q option appears on the command line before the --help=
           option, then the descriptive text displayed by --help= is
           changed.  Instead of describing the displayed options, an
           indication is given as to whether the option is enabled, disabled
           or set to a specific value (assuming that the compiler knows this
           at the point where the --help= option is used).

           Here is a truncated example from the ARM port of gcc:

                     % gcc -Q -mabi=2 --help=target -c
                     The following options are target specific:
                     -mabi=                                2
                     -mabort-on-noreturn                   [disabled]
                     -mapcs                                [disabled]

           The output is sensitive to the effects of previous command-line
           options, so for example it is possible to find out which
           optimizations are enabled at -O2 by using:

                   -Q -O2 --help=optimizers

           Alternatively you can discover which binary optimizations are
           enabled by -O3 by using:

                   gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
                   gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
                   diff /tmp/O2-opts /tmp/O3-opts | grep enabled

       --version
           Display the version number and copyrights of the invoked GCC.

       -pass-exit-codes
           Normally the gcc program exits with the code of 1 if any phase of
           the compiler returns a non-success return code.  If you specify
           -pass-exit-codes, the gcc program instead returns with the
           numerically highest error produced by any phase returning an
           error indication.  The C, C++, and Fortran front ends return 4 if
           an internal compiler error is encountered.

       -pipe
           Use pipes rather than temporary files for communication between
           the various stages of compilation.  This fails to work on some
           systems where the assembler is unable to read from a pipe; but
           the GNU assembler has no trouble.

       -specs=file
           Process file after the compiler reads in the standard specs file,
           in order to override the defaults which the gcc driver program
           uses when determining what switches to pass to cc1, cc1plus, as,
           ld, etc.  More than one -specs=file can be specified on the
           command line, and they are processed in order, from left to
           right.

       -wrapper
           Invoke all subcommands under a wrapper program.  The name of the
           wrapper program and its parameters are passed as a comma
           separated list.

                   gcc -c t.c -wrapper gdb,--args

           This invokes all subprograms of gcc under gdb --args, thus the
           invocation of cc1 is gdb --args cc1 ....

       -fplugin=name.so
           Load the plugin code in file name.so, assumed to be a shared
           object to be dlopen'd by the compiler.  The base name of the
           shared object file is used to identify the plugin for the
           purposes of argument parsing (See -fplugin-arg-name-key=value
           below).  Each plugin should define the callback functions
           specified in the Plugins API.

       -fplugin-arg-name-key=value
           Define an argument called key with a value of value for the
           plugin called name.

       -fdump-ada-spec[-slim]
           For C and C++ source and include files, generate corresponding
           Ada specs.

       -fada-spec-parent=unit
           In conjunction with -fdump-ada-spec[-slim] above, generate Ada
           specs as child units of parent unit.

       -fdump-go-spec=file
           For input files in any language, generate corresponding Go
           declarations in file.  This generates Go "const", "type", "var",
           and "func" declarations which may be a useful way to start
           writing a Go interface to code written in some other language.

       @file
           Read command-line options from file.  The options read are
           inserted in place of the original @file option.  If file does not
           exist, or cannot be read, then the option will be treated
           literally, and not removed.

           Options in file are separated by whitespace.  A whitespace
           character may be included in an option by surrounding the entire
           option in either single or double quotes.  Any character
           (including a backslash) may be included by prefixing the
           character to be included with a backslash.  The file may itself
           contain additional @file options; any such options will be
           processed recursively.

       Compiling C++ Programs

       C++ source files conventionally use one of the suffixes .C, .cc,
       .cpp, .CPP, .c++, .cp, or .cxx; C++ header files often use .hh, .hpp,
       .H, or (for shared template code) .tcc; and preprocessed C++ files
       use the suffix .ii.  GCC recognizes files with these names and
       compiles them as C++ programs even if you call the compiler the same
       way as for compiling C programs (usually with the name gcc).

       However, the use of gcc does not add the C++ library.  g++ is a
       program that calls GCC and automatically specifies linking against
       the C++ library.  It treats .c, .h and .i files as C++ source files
       instead of C source files unless -x is used.  This program is also
       useful when precompiling a C header file with a .h extension for use
       in C++ compilations.  On many systems, g++ is also installed with the
       name c++.

       When you compile C++ programs, you may specify many of the same
       command-line options that you use for compiling programs in any
       language; or command-line options meaningful for C and related
       languages; or options that are meaningful only for C++ programs.

       Options Controlling C Dialect

       The following options control the dialect of C (or languages derived
       from C, such as C++, Objective-C and Objective-C++) that the compiler
       accepts:

       -ansi
           In C mode, this is equivalent to -std=c90. In C++ mode, it is
           equivalent to -std=c++98.

           This turns off certain features of GCC that are incompatible with
           ISO C90 (when compiling C code), or of standard C++ (when
           compiling C++ code), such as the "asm" and "typeof" keywords, and
           predefined macros such as "unix" and "vax" that identify the type
           of system you are using.  It also enables the undesirable and
           rarely used ISO trigraph feature.  For the C compiler, it
           disables recognition of C++ style // comments as well as the
           "inline" keyword.

           The alternate keywords "__asm__", "__extension__", "__inline__"
           and "__typeof__" continue to work despite -ansi.  You would not
           want to use them in an ISO C program, of course, but it is useful
           to put them in header files that might be included in
           compilations done with -ansi.  Alternate predefined macros such
           as "__unix__" and "__vax__" are also available, with or without
           -ansi.

           The -ansi option does not cause non-ISO programs to be rejected
           gratuitously.  For that, -Wpedantic is required in addition to
           -ansi.

           The macro "__STRICT_ANSI__" is predefined when the -ansi option
           is used.  Some header files may notice this macro and refrain
           from declaring certain functions or defining certain macros that
           the ISO standard doesn't call for; this is to avoid interfering
           with any programs that might use these names for other things.

           Functions that are normally built in but do not have semantics
           defined by ISO C (such as "alloca" and "ffs") are not built-in
           functions when -ansi is used.

       -std=
           Determine the language standard.   This option is currently only
           supported when compiling C or C++.

           The compiler can accept several base standards, such as c90 or
           c++98, and GNU dialects of those standards, such as gnu90 or
           gnu++98.  When a base standard is specified, the compiler accepts
           all programs following that standard plus those using GNU
           extensions that do not contradict it.  For example, -std=c90
           turns off certain features of GCC that are incompatible with ISO
           C90, such as the "asm" and "typeof" keywords, but not other GNU
           extensions that do not have a meaning in ISO C90, such as
           omitting the middle term of a "?:" expression. On the other hand,
           when a GNU dialect of a standard is specified, all features
           supported by the compiler are enabled, even when those features
           change the meaning of the base standard.  As a result, some
           strict-conforming programs may be rejected.  The particular
           standard is used by -Wpedantic to identify which features are GNU
           extensions given that version of the standard. For example
           -std=gnu90 -Wpedantic warns about C++ style // comments, while
           -std=gnu99 -Wpedantic does not.

           A value for this option must be provided; possible values are

           c90
           c89
           iso9899:1990
               Support all ISO C90 programs (certain GNU extensions that
               conflict with ISO C90 are disabled). Same as -ansi for C
               code.

           iso9899:199409
               ISO C90 as modified in amendment 1.

           c99
           c9x
           iso9899:1999
           iso9899:199x
               ISO C99.  This standard is substantially completely
               supported, modulo bugs and floating-point issues (mainly but
               not entirely relating to optional C99 features from Annexes F
               and G).  See <http://gcc.gnu.org/c99status.html > for more
               information.  The names c9x and iso9899:199x are deprecated.

           c11
           c1x
           iso9899:2011
               ISO C11, the 2011 revision of the ISO C standard.  This
               standard is substantially completely supported, modulo bugs,
               floating-point issues (mainly but not entirely relating to
               optional C11 features from Annexes F and G) and the optional
               Annexes K (Bounds-checking interfaces) and L (Analyzability).
               The name c1x is deprecated.

           gnu90
           gnu89
               GNU dialect of ISO C90 (including some C99 features).

           gnu99
           gnu9x
               GNU dialect of ISO C99.  The name gnu9x is deprecated.

           gnu11
           gnu1x
               GNU dialect of ISO C11.  This is the default for C code.  The
               name gnu1x is deprecated.

           c++98
           c++03
               The 1998 ISO C++ standard plus the 2003 technical corrigendum
               and some additional defect reports. Same as -ansi for C++
               code.

           gnu++98
           gnu++03
               GNU dialect of -std=c++98.

           c++11
           c++0x
               The 2011 ISO C++ standard plus amendments.  The name c++0x is
               deprecated.

           gnu++11
           gnu++0x
               GNU dialect of -std=c++11.  The name gnu++0x is deprecated.

           c++14
           c++1y
               The 2014 ISO C++ standard plus amendments.  The name c++1y is
               deprecated.

           gnu++14
           gnu++1y
               GNU dialect of -std=c++14.  This is the default for C++ code.
               The name gnu++1y is deprecated.

           c++1z
               The next revision of the ISO C++ standard, tentatively
               planned for 2017.  Support is highly experimental, and will
               almost certainly change in incompatible ways in future
               releases.

           gnu++1z
               GNU dialect of -std=c++1z.  Support is highly experimental,
               and will almost certainly change in incompatible ways in
               future releases.

       -fgnu89-inline
           The option -fgnu89-inline tells GCC to use the traditional GNU
           semantics for "inline" functions when in C99 mode.

           Using this option is roughly equivalent to adding the
           "gnu_inline" function attribute to all inline functions.

           The option -fno-gnu89-inline explicitly tells GCC to use the C99
           semantics for "inline" when in C99 or gnu99 mode (i.e., it
           specifies the default behavior).  This option is not supported in
           -std=c90 or -std=gnu90 mode.

           The preprocessor macros "__GNUC_GNU_INLINE__" and
           "__GNUC_STDC_INLINE__" may be used to check which semantics are
           in effect for "inline" functions.

       -aux-info filename
           Output to the given filename prototyped declarations for all
           functions declared and/or defined in a translation unit,
           including those in header files.  This option is silently ignored
           in any language other than C.

           Besides declarations, the file indicates, in comments, the origin
           of each declaration (source file and line), whether the
           declaration was implicit, prototyped or unprototyped (I, N for
           new or O for old, respectively, in the first character after the
           line number and the colon), and whether it came from a
           declaration or a definition (C or F, respectively, in the
           following character).  In the case of function definitions, a
           K&R-style list of arguments followed by their declarations is
           also provided, inside comments, after the declaration.

       -fallow-parameterless-variadic-functions
           Accept variadic functions without named parameters.

           Although it is possible to define such a function, this is not
           very useful as it is not possible to read the arguments.  This is
           only supported for C as this construct is allowed by C++.

       -fno-asm
           Do not recognize "asm", "inline" or "typeof" as a keyword, so
           that code can use these words as identifiers.  You can use the
           keywords "__asm__", "__inline__" and "__typeof__" instead.  -ansi
           implies -fno-asm.

           In C++, this switch only affects the "typeof" keyword, since
           "asm" and "inline" are standard keywords.  You may want to use
           the -fno-gnu-keywords flag instead, which has the same effect.
           In C99 mode (-std=c99 or -std=gnu99), this switch only affects
           the "asm" and "typeof" keywords, since "inline" is a standard
           keyword in ISO C99.

       -fno-builtin
       -fno-builtin-function
           Don't recognize built-in functions that do not begin with
           __builtin_ as prefix.

           GCC normally generates special code to handle certain built-in
           functions more efficiently; for instance, calls to "alloca" may
           become single instructions which adjust the stack directly, and
           calls to "memcpy" may become inline copy loops.  The resulting
           code is often both smaller and faster, but since the function
           calls no longer appear as such, you cannot set a breakpoint on
           those calls, nor can you change the behavior of the functions by
           linking with a different library.  In addition, when a function
           is recognized as a built-in function, GCC may use information
           about that function to warn about problems with calls to that
           function, or to generate more efficient code, even if the
           resulting code still contains calls to that function.  For
           example, warnings are given with -Wformat for bad calls to
           "printf" when "printf" is built in and "strlen" is known not to
           modify global memory.

           With the -fno-builtin-function option only the built-in function
           function is disabled.  function must not begin with __builtin_.
           If a function is named that is not built-in in this version of
           GCC, this option is ignored.  There is no corresponding
           -fbuiltin-function option; if you wish to enable built-in
           functions selectively when using -fno-builtin or -ffreestanding,
           you may define macros such as:

                   #define abs(n)          __builtin_abs ((n))
                   #define strcpy(d, s)    __builtin_strcpy ((d), (s))

       -fhosted
           Assert that compilation targets a hosted environment.  This
           implies -fbuiltin.  A hosted environment is one in which the
           entire standard library is available, and in which "main" has a
           return type of "int".  Examples are nearly everything except a
           kernel.  This is equivalent to -fno-freestanding.

       -ffreestanding
           Assert that compilation targets a freestanding environment.  This
           implies -fno-builtin.  A freestanding environment is one in which
           the standard library may not exist, and program startup may not
           necessarily be at "main".  The most obvious example is an OS
           kernel.  This is equivalent to -fno-hosted.

       -fopenacc
           Enable handling of OpenACC directives "#pragma acc" in C/C++ and
           "!$acc" in Fortran.  When -fopenacc is specified, the compiler
           generates accelerated code according to the OpenACC Application
           Programming Interface v2.0 <http://www.openacc.org/ >.  This
           option implies -pthread, and thus is only supported on targets
           that have support for -pthread.

       -fopenacc-dim=geom
           Specify default compute dimensions for parallel offload regions
           that do not explicitly specify.  The geom value is a triple of
           ':'-separated sizes, in order 'gang', 'worker' and, 'vector'.  A
           size can be omitted, to use a target-specific default value.

       -fopenmp
           Enable handling of OpenMP directives "#pragma omp" in C/C++ and
           "!$omp" in Fortran.  When -fopenmp is specified, the compiler
           generates parallel code according to the OpenMP Application
           Program Interface v4.0 <http://www.openmp.org/ >.  This option
           implies -pthread, and thus is only supported on targets that have
           support for -pthread. -fopenmp implies -fopenmp-simd.

       -fopenmp-simd
           Enable handling of OpenMP's SIMD directives with "#pragma omp" in
           C/C++ and "!$omp" in Fortran. Other OpenMP directives are
           ignored.

       -fcilkplus
           Enable the usage of Cilk Plus language extension features for
           C/C++.  When the option -fcilkplus is specified, enable the usage
           of the Cilk Plus Language extension features for C/C++.  The
           present implementation follows ABI version 1.2.  This is an
           experimental feature that is only partially complete, and whose
           interface may change in future versions of GCC as the official
           specification changes.  Currently, all features but "_Cilk_for"
           have been implemented.

       -fgnu-tm
           When the option -fgnu-tm is specified, the compiler generates
           code for the Linux variant of Intel's current Transactional
           Memory ABI specification document (Revision 1.1, May 6 2009).
           This is an experimental feature whose interface may change in
           future versions of GCC, as the official specification changes.
           Please note that not all architectures are supported for this
           feature.

           For more information on GCC's support for transactional memory,

           Note that the transactional memory feature is not supported with
           non-call exceptions (-fnon-call-exceptions).

       -fms-extensions
           Accept some non-standard constructs used in Microsoft header
           files.

           In C++ code, this allows member names in structures to be similar
           to previous types declarations.

                   typedef int UOW;
                   struct ABC {
                     UOW UOW;
                   };

           Some cases of unnamed fields in structures and unions are only
           accepted with this option.

           Note that this option is off for all targets but x86 targets
           using ms-abi.

       -fplan9-extensions
           Accept some non-standard constructs used in Plan 9 code.

           This enables -fms-extensions, permits passing pointers to
           structures with anonymous fields to functions that expect
           pointers to elements of the type of the field, and permits
           referring to anonymous fields declared using a typedef.    This
           is only supported for C, not C++.

       -trigraphs
           Support ISO C trigraphs.  The -ansi option (and -std options for
           strict ISO C conformance) implies -trigraphs.

       -traditional
       -traditional-cpp
           Formerly, these options caused GCC to attempt to emulate a pre-
           standard C compiler.  They are now only supported with the -E
           switch.  The preprocessor continues to support a pre-standard
           mode.  See the GNU CPP manual for details.

       -fcond-mismatch
           Allow conditional expressions with mismatched types in the second
           and third arguments.  The value of such an expression is void.
           This option is not supported for C++.

       -flax-vector-conversions
           Allow implicit conversions between vectors with differing numbers
           of elements and/or incompatible element types.  This option
           should not be used for new code.

       -funsigned-char
           Let the type "char" be unsigned, like "unsigned char".

           Each kind of machine has a default for what "char" should be.  It
           is either like "unsigned char" by default or like "signed char"
           by default.

           Ideally, a portable program should always use "signed char" or
           "unsigned char" when it depends on the signedness of an object.
           But many programs have been written to use plain "char" and
           expect it to be signed, or expect it to be unsigned, depending on
           the machines they were written for.  This option, and its
           inverse, let you make such a program work with the opposite
           default.

           The type "char" is always a distinct type from each of "signed
           char" or "unsigned char", even though its behavior is always just
           like one of those two.

       -fsigned-char
           Let the type "char" be signed, like "signed char".

           Note that this is equivalent to -fno-unsigned-char, which is the
           negative form of -funsigned-char.  Likewise, the option
           -fno-signed-char is equivalent to -funsigned-char.

       -fsigned-bitfields
       -funsigned-bitfields
       -fno-signed-bitfields
       -fno-unsigned-bitfields
           These options control whether a bit-field is signed or unsigned,
           when the declaration does not use either "signed" or "unsigned".
           By default, such a bit-field is signed, because this is
           consistent: the basic integer types such as "int" are signed
           types.

       -fsso-struct=endianness
           Set the default scalar storage order of structures and unions to
           the specified endianness.  The accepted values are big-endian and
           little-endian.  If the option is not passed, the compiler uses
           the native endianness of the target.  This option is not
           supported for C++.

           Warning: the -fsso-struct switch causes GCC to generate code that
           is not binary compatible with code generated without it if the
           specified endianness is not the native endianness of the target.

       Options Controlling C++ Dialect

       This section describes the command-line options that are only
       meaningful for C++ programs.  You can also use most of the GNU
       compiler options regardless of what language your program is in.  For
       example, you might compile a file firstClass.C like this:

               g++ -g -fstrict-enums -O -c firstClass.C

       In this example, only -fstrict-enums is an option meant only for C++
       programs; you can use the other options with any language supported
       by GCC.

       Some options for compiling C programs, such as -std, are also
       relevant for C++ programs.

       Here is a list of options that are only for compiling C++ programs:

       -fabi-version=n
           Use version n of the C++ ABI.  The default is version 0.

           Version 0 refers to the version conforming most closely to the
           C++ ABI specification.  Therefore, the ABI obtained using version
           0 will change in different versions of G++ as ABI bugs are fixed.

           Version 1 is the version of the C++ ABI that first appeared in
           G++ 3.2.

           Version 2 is the version of the C++ ABI that first appeared in
           G++ 3.4, and was the default through G++ 4.9.

           Version 3 corrects an error in mangling a constant address as a
           template argument.

           Version 4, which first appeared in G++ 4.5, implements a standard
           mangling for vector types.

           Version 5, which first appeared in G++ 4.6, corrects the mangling
           of attribute const/volatile on function pointer types, decltype
           of a plain decl, and use of a function parameter in the
           declaration of another parameter.

           Version 6, which first appeared in G++ 4.7, corrects the
           promotion behavior of C++11 scoped enums and the mangling of
           template argument packs, const/static_cast, prefix ++ and --, and
           a class scope function used as a template argument.

           Version 7, which first appeared in G++ 4.8, that treats nullptr_t
           as a builtin type and corrects the mangling of lambdas in default
           argument scope.

           Version 8, which first appeared in G++ 4.9, corrects the
           substitution behavior of function types with function-cv-
           qualifiers.

           Version 9, which first appeared in G++ 5.2, corrects the
           alignment of "nullptr_t".

           Version 10, which first appeared in G++ 6.1, adds mangling of
           attributes that affect type identity, such as ia32 calling
           convention attributes (e.g. stdcall).

           See also -Wabi.

       -fabi-compat-version=n
           On targets that support strong aliases, G++ works around mangling
           changes by creating an alias with the correct mangled name when
           defining a symbol with an incorrect mangled name.  This switch
           specifies which ABI version to use for the alias.

           With -fabi-version=0 (the default), this defaults to 8 (GCC 5
           compatibility).  If another ABI version is explicitly selected,
           this defaults to 0.  For compatibility with GCC versions 3.2
           through 4.9, use -fabi-compat-version=2.

           If this option is not provided but -Wabi=n is, that version is
           used for compatibility aliases.  If this option is provided along
           with -Wabi (without the version), the version from this option is
           used for the warning.

       -fno-access-control
           Turn off all access checking.  This switch is mainly useful for
           working around bugs in the access control code.

       -fcheck-new
           Check that the pointer returned by "operator new" is non-null
           before attempting to modify the storage allocated.  This check is
           normally unnecessary because the C++ standard specifies that
           "operator new" only returns 0 if it is declared "throw()", in
           which case the compiler always checks the return value even
           without this option.  In all other cases, when "operator new" has
           a non-empty exception specification, memory exhaustion is
           signalled by throwing "std::bad_alloc".  See also new (nothrow).

       -fconcepts
           Enable support for the C++ Extensions for Concepts Technical
           Specification, ISO 19217 (2015), which allows code like

                   template <class T> concept bool Addable = requires (T t) { t + t; };
                   template <Addable T> T add (T a, T b) { return a + b; }

       -fconstexpr-depth=n
           Set the maximum nested evaluation depth for C++11 constexpr
           functions to n.  A limit is needed to detect endless recursion
           during constant expression evaluation.  The minimum specified by
           the standard is 512.

       -fdeduce-init-list
           Enable deduction of a template type parameter as
           "std::initializer_list" from a brace-enclosed initializer list,
           i.e.

                   template <class T> auto forward(T t) -> decltype (realfn (t))
                   {
                     return realfn (t);
                   }

                   void f()
                   {
                     forward({1,2}); // call forward<std::initializer_list<int>>
                   }

           This deduction was implemented as a possible extension to the
           originally proposed semantics for the C++11 standard, but was not
           part of the final standard, so it is disabled by default.  This
           option is deprecated, and may be removed in a future version of
           G++.

       -ffriend-injection
           Inject friend functions into the enclosing namespace, so that
           they are visible outside the scope of the class in which they are
           declared.  Friend functions were documented to work this way in
           the old Annotated C++ Reference Manual.  However, in ISO C++ a
           friend function that is not declared in an enclosing scope can
           only be found using argument dependent lookup.  GCC defaults to
           the standard behavior.

           This option is for compatibility, and may be removed in a future
           release of G++.

       -fno-elide-constructors
           The C++ standard allows an implementation to omit creating a
           temporary that is only used to initialize another object of the
           same type.  Specifying this option disables that optimization,
           and forces G++ to call the copy constructor in all cases.

       -fno-enforce-eh-specs
           Don't generate code to check for violation of exception
           specifications at run time.  This option violates the C++
           standard, but may be useful for reducing code size in production
           builds, much like defining "NDEBUG".  This does not give user
           code permission to throw exceptions in violation of the exception
           specifications; the compiler still optimizes based on the
           specifications, so throwing an unexpected exception results in
           undefined behavior at run time.

       -fextern-tls-init
       -fno-extern-tls-init
           The C++11 and OpenMP standards allow "thread_local" and
           "threadprivate" variables to have dynamic (runtime)
           initialization.  To support this, any use of such a variable goes
           through a wrapper function that performs any necessary
           initialization.  When the use and definition of the variable are
           in the same translation unit, this overhead can be optimized
           away, but when the use is in a different translation unit there
           is significant overhead even if the variable doesn't actually
           need dynamic initialization.  If the programmer can be sure that
           no use of the variable in a non-defining TU needs to trigger
           dynamic initialization (either because the variable is statically
           initialized, or a use of the variable in the defining TU will be
           executed before any uses in another TU), they can avoid this
           overhead with the -fno-extern-tls-init option.

           On targets that support symbol aliases, the default is
           -fextern-tls-init.  On targets that do not support symbol
           aliases, the default is -fno-extern-tls-init.

       -ffor-scope
       -fno-for-scope
           If -ffor-scope is specified, the scope of variables declared in a
           for-init-statement is limited to the "for" loop itself, as
           specified by the C++ standard.  If -fno-for-scope is specified,
           the scope of variables declared in a for-init-statement extends
           to the end of the enclosing scope, as was the case in old
           versions of G++, and other (traditional) implementations of C++.

           If neither flag is given, the default is to follow the standard,
           but to allow and give a warning for old-style code that would
           otherwise be invalid, or have different behavior.

       -fno-gnu-keywords
           Do not recognize "typeof" as a keyword, so that code can use this
           word as an identifier.  You can use the keyword "__typeof__"
           instead.  This option is implied by the strict ISO C++ dialects:
           -ansi, -std=c++98, -std=c++11, etc.

       -fno-implicit-templates
           Never emit code for non-inline templates that are instantiated
           implicitly (i.e. by use); only emit code for explicit
           instantiations.

       -fno-implicit-inline-templates
           Don't emit code for implicit instantiations of inline templates,
           either.  The default is to handle inlines differently so that
           compiles with and without optimization need the same set of
           explicit instantiations.

       -fno-implement-inlines
           To save space, do not emit out-of-line copies of inline functions
           controlled by "#pragma implementation".  This causes linker
           errors if these functions are not inlined everywhere they are
           called.

       -fms-extensions
           Disable Wpedantic warnings about constructs used in MFC, such as
           implicit int and getting a pointer to member function via non-
           standard syntax.

       -fno-nonansi-builtins
           Disable built-in declarations of functions that are not mandated
           by ANSI/ISO C.  These include "ffs", "alloca", "_exit", "index",
           "bzero", "conjf", and other related functions.

       -fnothrow-opt
           Treat a "throw()" exception specification as if it were a
           "noexcept" specification to reduce or eliminate the text size
           overhead relative to a function with no exception specification.
           If the function has local variables of types with non-trivial
           destructors, the exception specification actually makes the
           function smaller because the EH cleanups for those variables can
           be optimized away.  The semantic effect is that an exception
           thrown out of a function with such an exception specification
           results in a call to "terminate" rather than "unexpected".

       -fno-operator-names
           Do not treat the operator name keywords "and", "bitand", "bitor",
           "compl", "not", "or" and "xor" as synonyms as keywords.

       -fno-optional-diags
           Disable diagnostics that the standard says a compiler does not
           need to issue.  Currently, the only such diagnostic issued by G++
           is the one for a name having multiple meanings within a class.

       -fpermissive
           Downgrade some diagnostics about nonconformant code from errors
           to warnings.  Thus, using -fpermissive allows some nonconforming
           code to compile.

       -fno-pretty-templates
           When an error message refers to a specialization of a function
           template, the compiler normally prints the signature of the
           template followed by the template arguments and any typedefs or
           typenames in the signature (e.g. "void f(T) [with T = int]"
           rather than "void f(int)") so that it's clear which template is
           involved.  When an error message refers to a specialization of a
           class template, the compiler omits any template arguments that
           match the default template arguments for that template.  If
           either of these behaviors make it harder to understand the error
           message rather than easier, you can use -fno-pretty-templates to
           disable them.

       -frepo
           Enable automatic template instantiation at link time.  This
           option also implies -fno-implicit-templates.

       -fno-rtti
           Disable generation of information about every class with virtual
           functions for use by the C++ run-time type identification
           features ("dynamic_cast" and "typeid").  If you don't use those
           parts of the language, you can save some space by using this
           flag.  Note that exception handling uses the same information,
           but G++ generates it as needed. The "dynamic_cast" operator can
           still be used for casts that do not require run-time type
           information, i.e. casts to "void *" or to unambiguous base
           classes.

       -fsized-deallocation
           Enable the built-in global declarations

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           as introduced in C++14.  This is useful for user-defined
           replacement deallocation functions that, for example, use the
           size of the object to make deallocation faster.  Enabled by
           default under -std=c++14 and above.  The flag
           -Wsized-deallocation warns about places that might want to add a
           definition.

       -fstrict-enums
           Allow the compiler to optimize using the assumption that a value
           of enumerated type can only be one of the values of the
           enumeration (as defined in the C++ standard; basically, a value
           that can be represented in the minimum number of bits needed to
           represent all the enumerators).  This assumption may not be valid
           if the program uses a cast to convert an arbitrary integer value
           to the enumerated type.

       -ftemplate-backtrace-limit=n
           Set the maximum number of template instantiation notes for a
           single warning or error to n.  The default value is 10.

       -ftemplate-depth=n
           Set the maximum instantiation depth for template classes to n.  A
           limit on the template instantiation depth is needed to detect
           endless recursions during template class instantiation.  ANSI/ISO
           C++ conforming programs must not rely on a maximum depth greater
           than 17 (changed to 1024 in C++11).  The default value is 900, as
           the compiler can run out of stack space before hitting 1024 in
           some situations.

       -fno-threadsafe-statics
           Do not emit the extra code to use the routines specified in the
           C++ ABI for thread-safe initialization of local statics.  You can
           use this option to reduce code size slightly in code that doesn't
           need to be thread-safe.

       -fuse-cxa-atexit
           Register destructors for objects with static storage duration
           with the "__cxa_atexit" function rather than the "atexit"
           function.  This option is required for fully standards-compliant
           handling of static destructors, but only works if your C library
           supports "__cxa_atexit".

       -fno-use-cxa-get-exception-ptr
           Don't use the "__cxa_get_exception_ptr" runtime routine.  This
           causes "std::uncaught_exception" to be incorrect, but is
           necessary if the runtime routine is not available.

       -fvisibility-inlines-hidden
           This switch declares that the user does not attempt to compare
           pointers to inline functions or methods where the addresses of
           the two functions are taken in different shared objects.

           The effect of this is that GCC may, effectively, mark inline
           methods with "__attribute__ ((visibility ("hidden")))" so that
           they do not appear in the export table of a DSO and do not
           require a PLT indirection when used within the DSO.  Enabling
           this option can have a dramatic effect on load and link times of
           a DSO as it massively reduces the size of the dynamic export
           table when the library makes heavy use of templates.

           The behavior of this switch is not quite the same as marking the
           methods as hidden directly, because it does not affect static
           variables local to the function or cause the compiler to deduce
           that the function is defined in only one shared object.

           You may mark a method as having a visibility explicitly to negate
           the effect of the switch for that method.  For example, if you do
           want to compare pointers to a particular inline method, you might
           mark it as having default visibility.  Marking the enclosing
           class with explicit visibility has no effect.

           Explicitly instantiated inline methods are unaffected by this
           option as their linkage might otherwise cross a shared library
           boundary.

       -fvisibility-ms-compat
           This flag attempts to use visibility settings to make GCC's C++
           linkage model compatible with that of Microsoft Visual Studio.

           The flag makes these changes to GCC's linkage model:

           1.  It sets the default visibility to "hidden", like
               -fvisibility=hidden.

           2.  Types, but not their members, are not hidden by default.

           3.  The One Definition Rule is relaxed for types without explicit
               visibility specifications that are defined in more than one
               shared object: those declarations are permitted if they are
               permitted when this option is not used.

           In new code it is better to use -fvisibility=hidden and export
           those classes that are intended to be externally visible.
           Unfortunately it is possible for code to rely, perhaps
           accidentally, on the Visual Studio behavior.

           Among the consequences of these changes are that static data
           members of the same type with the same name but defined in
           different shared objects are different, so changing one does not
           change the other; and that pointers to function members defined
           in different shared objects may not compare equal.  When this
           flag is given, it is a violation of the ODR to define types with
           the same name differently.

       -fno-weak
           Do not use weak symbol support, even if it is provided by the
           linker.  By default, G++ uses weak symbols if they are available.
           This option exists only for testing, and should not be used by
           end-users; it results in inferior code and has no benefits.  This
           option may be removed in a future release of G++.

       -nostdinc++
           Do not search for header files in the standard directories
           specific to C++, but do still search the other standard
           directories.  (This option is used when building the C++
           library.)

       In addition, these optimization, warning, and code generation options
       have meanings only for C++ programs:

       -Wabi (C, Objective-C, C++ and Objective-C++ only)
           Warn when G++ it generates code that is probably not compatible
           with the vendor-neutral C++ ABI.  Since G++ now defaults to
           updating the ABI with each major release, normally -Wabi will
           warn only if there is a check added later in a release series for
           an ABI issue discovered since the initial release.  -Wabi will
           warn about more things if an older ABI version is selected (with
           -fabi-version=n).

           -Wabi can also be used with an explicit version number to warn
           about compatibility with a particular -fabi-version level, e.g.
           -Wabi=2 to warn about changes relative to -fabi-version=2.

           If an explicit version number is provided and
           -fabi-compat-version is not specified, the version number from
           this option is used for compatibility aliases.  If no explicit
           version number is provided with this option, but
           -fabi-compat-version is specified, that version number is used
           for ABI warnings.

           Although an effort has been made to warn about all such cases,
           there are probably some cases that are not warned about, even
           though G++ is generating incompatible code.  There may also be
           cases where warnings are emitted even though the code that is
           generated is compatible.

           You should rewrite your code to avoid these warnings if you are
           concerned about the fact that code generated by G++ may not be
           binary compatible with code generated by other compilers.

           Known incompatibilities in -fabi-version=2 (which was the default
           from GCC 3.4 to 4.9) include:

           *   A template with a non-type template parameter of reference
               type was mangled incorrectly:

                       extern int N;
                       template <int &> struct S {};
                       void n (S<N>) {2}

               This was fixed in -fabi-version=3.

           *   SIMD vector types declared using "__attribute
               ((vector_size))" were mangled in a non-standard way that does
               not allow for overloading of functions taking vectors of
               different sizes.

               The mangling was changed in -fabi-version=4.

           *   "__attribute ((const))" and "noreturn" were mangled as type
               qualifiers, and "decltype" of a plain declaration was folded
               away.

               These mangling issues were fixed in -fabi-version=5.

           *   Scoped enumerators passed as arguments to a variadic function
               are promoted like unscoped enumerators, causing "va_arg" to
               complain.  On most targets this does not actually affect the
               parameter passing ABI, as there is no way to pass an argument
               smaller than "int".

               Also, the ABI changed the mangling of template argument
               packs, "const_cast", "static_cast", prefix
               increment/decrement, and a class scope function used as a
               template argument.

               These issues were corrected in -fabi-version=6.

           *   Lambdas in default argument scope were mangled incorrectly,
               and the ABI changed the mangling of "nullptr_t".

               These issues were corrected in -fabi-version=7.

           *   When mangling a function type with function-cv-qualifiers,
               the un-qualified function type was incorrectly treated as a
               substitution candidate.

               This was fixed in -fabi-version=8, the default for GCC 5.1.

           *   "decltype(nullptr)" incorrectly had an alignment of 1,
               leading to unaligned accesses.  Note that this did not affect
               the ABI of a function with a "nullptr_t" parameter, as
               parameters have a minimum alignment.

               This was fixed in -fabi-version=9, the default for GCC 5.2.

           *   Target-specific attributes that affect the identity of a
               type, such as ia32 calling conventions on a function type
               (stdcall, regparm, etc.), did not affect the mangled name,
               leading to name collisions when function pointers were used
               as template arguments.

               This was fixed in -fabi-version=10, the default for GCC 6.1.

           It also warns about psABI-related changes.  The known psABI
           changes at this point include:

           *   For SysV/x86-64, unions with "long double" members are passed
               in memory as specified in psABI.  For example:

                       union U {
                         long double ld;
                         int i;
                       };

               "union U" is always passed in memory.

       -Wabi-tag (C++ and Objective-C++ only)
           Warn when a type with an ABI tag is used in a context that does
           not have that ABI tag.  See C++ Attributes for more information
           about ABI tags.

       -Wctor-dtor-privacy (C++ and Objective-C++ only)
           Warn when a class seems unusable because all the constructors or
           destructors in that class are private, and it has neither friends
           nor public static member functions.  Also warn if there are no
           non-private methods, and there's at least one private member
           function that isn't a constructor or destructor.

       -Wdelete-non-virtual-dtor (C++ and Objective-C++ only)
           Warn when "delete" is used to destroy an instance of a class that
           has virtual functions and non-virtual destructor. It is unsafe to
           delete an instance of a derived class through a pointer to a base
           class if the base class does not have a virtual destructor.  This
           warning is enabled by -Wall.

       -Wliteral-suffix (C++ and Objective-C++ only)
           Warn when a string or character literal is followed by a ud-
           suffix which does not begin with an underscore.  As a conforming
           extension, GCC treats such suffixes as separate preprocessing
           tokens in order to maintain backwards compatibility with code
           that uses formatting macros from "<inttypes.h>".  For example:

                   #define __STDC_FORMAT_MACROS
                   #include <inttypes.h>
                   #include <stdio.h>

                   int main() {
                     int64_t i64 = 123;
                     printf("My int64: %" PRId64"\n", i64);
                   }

           In this case, "PRId64" is treated as a separate preprocessing
           token.

           This warning is enabled by default.

       -Wlto-type-mismatch
           During the link-time optimization warn about type mismatches in
           global declarations from different compilation units.  Requires
           -flto to be enabled.  Enabled by default.

       -Wnarrowing (C++ and Objective-C++ only)
           With -std=gnu++98 or -std=c++98, warn when a narrowing conversion
           prohibited by C++11 occurs within { }, e.g.

                   int i = { 2.2 }; // error: narrowing from double to int

           This flag is included in -Wall and -Wc++11-compat.

           When a later standard is in effect, e.g. when using -std=c++11,
           narrowing conversions are diagnosed by default, as required by
           the standard.  A narrowing conversion from a constant produces an
           error, and a narrowing conversion from a non-constant produces a
           warning, but -Wno-narrowing suppresses the diagnostic.  Note that
           this does not affect the meaning of well-formed code; narrowing
           conversions are still considered ill-formed in SFINAE contexts.

       -Wnoexcept (C++ and Objective-C++ only)
           Warn when a noexcept-expression evaluates to false because of a
           call to a function that does not have a non-throwing exception
           specification (i.e. "throw()" or "noexcept") but is known by the
           compiler to never throw an exception.

       -Wnon-virtual-dtor (C++ and Objective-C++ only)
           Warn when a class has virtual functions and an accessible non-
           virtual destructor itself or in an accessible polymorphic base
           class, in which case it is possible but unsafe to delete an
           instance of a derived class through a pointer to the class itself
           or base class.  This warning is automatically enabled if -Weffc++
           is specified.

       -Wreorder (C++ and Objective-C++ only)
           Warn when the order of member initializers given in the code does
           not match the order in which they must be executed.  For
           instance:

                   struct A {
                     int i;
                     int j;
                     A(): j (0), i (1) { }
                   };

           The compiler rearranges the member initializers for "i" and "j"
           to match the declaration order of the members, emitting a warning
           to that effect.  This warning is enabled by -Wall.

       -fext-numeric-literals (C++ and Objective-C++ only)
           Accept imaginary, fixed-point, or machine-defined literal number
           suffixes as GNU extensions.  When this option is turned off these
           suffixes are treated as C++11 user-defined literal numeric
           suffixes.  This is on by default for all pre-C++11 dialects and
           all GNU dialects: -std=c++98, -std=gnu++98, -std=gnu++11,
           -std=gnu++14.  This option is off by default for ISO C++11
           onwards (-std=c++11, ...).

       The following -W... options are not affected by -Wall.

       -Weffc++ (C++ and Objective-C++ only)
           Warn about violations of the following style guidelines from
           Scott Meyers' Effective C++ series of books:

           *   Define a copy constructor and an assignment operator for
               classes with dynamically-allocated memory.

           *   Prefer initialization to assignment in constructors.

           *   Have "operator=" return a reference to *this.

           *   Don't try to return a reference when you must return an
               object.

           *   Distinguish between prefix and postfix forms of increment and
               decrement operators.

           *   Never overload "&&", "||", or ",".

           This option also enables -Wnon-virtual-dtor, which is also one of
           the effective C++ recommendations.  However, the check is
           extended to warn about the lack of virtual destructor in
           accessible non-polymorphic bases classes too.

           When selecting this option, be aware that the standard library
           headers do not obey all of these guidelines; use grep -v to
           filter out those warnings.

       -Wstrict-null-sentinel (C++ and Objective-C++ only)
           Warn about the use of an uncasted "NULL" as sentinel.  When
           compiling only with GCC this is a valid sentinel, as "NULL" is
           defined to "__null".  Although it is a null pointer constant
           rather than a null pointer, it is guaranteed to be of the same
           size as a pointer.  But this use is not portable across different
           compilers.

       -Wno-non-template-friend (C++ and Objective-C++ only)
           Disable warnings when non-templatized friend functions are
           declared within a template.  Since the advent of explicit
           template specification support in G++, if the name of the friend
           is an unqualified-id (i.e., friend foo(int)), the C++ language
           specification demands that the friend declare or define an
           ordinary, nontemplate function.  (Section 14.5.3).  Before G++
           implemented explicit specification, unqualified-ids could be
           interpreted as a particular specialization of a templatized
           function.  Because this non-conforming behavior is no longer the
           default behavior for G++, -Wnon-template-friend allows the
           compiler to check existing code for potential trouble spots and
           is on by default.  This new compiler behavior can be turned off
           with -Wno-non-template-friend, which keeps the conformant
           compiler code but disables the helpful warning.

       -Wold-style-cast (C++ and Objective-C++ only)
           Warn if an old-style (C-style) cast to a non-void type is used
           within a C++ program.  The new-style casts ("dynamic_cast",
           "static_cast", "reinterpret_cast", and "const_cast") are less
           vulnerable to unintended effects and much easier to search for.

       -Woverloaded-virtual (C++ and Objective-C++ only)
           Warn when a function declaration hides virtual functions from a
           base class.  For example, in:

                   struct A {
                     virtual void f();
                   };

                   struct B: public A {
                     void f(int);
                   };

           the "A" class version of "f" is hidden in "B", and code like:

                   B* b;
                   b->f();

           fails to compile.

       -Wno-pmf-conversions (C++ and Objective-C++ only)
           Disable the diagnostic for converting a bound pointer to member
           function to a plain pointer.

       -Wsign-promo (C++ and Objective-C++ only)
           Warn when overload resolution chooses a promotion from unsigned
           or enumerated type to a signed type, over a conversion to an
           unsigned type of the same size.  Previous versions of G++ tried
           to preserve unsignedness, but the standard mandates the current
           behavior.

       -Wtemplates (C++ and Objective-C++ only)
           Warn when a primary template declaration is encountered.  Some
           coding rules disallow templates, and this may be used to enforce
           that rule.  The warning is inactive inside a system header file,
           such as the STL, so one can still use the STL.  One may also
           instantiate or specialize templates.

       -Wmultiple-inheritance (C++ and Objective-C++ only)
           Warn when a class is defined with multiple direct base classes.
           Some coding rules disallow multiple inheritance, and this may be
           used to enforce that rule.  The warning is inactive inside a
           system header file, such as the STL, so one can still use the
           STL.  One may also define classes that indirectly use multiple
           inheritance.

       -Wvirtual-inheritance
           Warn when a class is defined with a virtual direct base classe.
           Some coding rules disallow multiple inheritance, and this may be
           used to enforce that rule.  The warning is inactive inside a
           system header file, such as the STL, so one can still use the
           STL.  One may also define classes that indirectly use virtual
           inheritance.

       -Wnamespaces
           Warn when a namespace definition is opened.  Some coding rules
           disallow namespaces, and this may be used to enforce that rule.
           The warning is inactive inside a system header file, such as the
           STL, so one can still use the STL.  One may also use using
           directives and qualified names.

       -Wno-terminate (C++ and Objective-C++ only)
           Disable the warning about a throw-expression that will
           immediately result in a call to "terminate".

       Options Controlling Objective-C and Objective-C++ Dialects

       (NOTE: This manual does not describe the Objective-C and
       Objective-C++ languages themselves.

       This section describes the command-line options that are only
       meaningful for Objective-C and Objective-C++ programs.  You can also
       use most of the language-independent GNU compiler options.  For
       example, you might compile a file some_class.m like this:

               gcc -g -fgnu-runtime -O -c some_class.m

       In this example, -fgnu-runtime is an option meant only for Objective-
       C and Objective-C++ programs; you can use the other options with any
       language supported by GCC.

       Note that since Objective-C is an extension of the C language,
       Objective-C compilations may also use options specific to the C
       front-end (e.g., -Wtraditional).  Similarly, Objective-C++
       compilations may use C++-specific options (e.g., -Wabi).

       Here is a list of options that are only for compiling Objective-C and
       Objective-C++ programs:

       -fconstant-string-class=class-name
           Use class-name as the name of the class to instantiate for each
           literal string specified with the syntax "@"..."".  The default
           class name is "NXConstantString" if the GNU runtime is being
           used, and "NSConstantString" if the NeXT runtime is being used
           (see below).  The -fconstant-cfstrings option, if also present,
           overrides the -fconstant-string-class setting and cause "@"...""
           literals to be laid out as constant CoreFoundation strings.

       -fgnu-runtime
           Generate object code compatible with the standard GNU Objective-C
           runtime.  This is the default for most types of systems.

       -fnext-runtime
           Generate output compatible with the NeXT runtime.  This is the
           default for NeXT-based systems, including Darwin and Mac OS X.
           The macro "__NEXT_RUNTIME__" is predefined if (and only if) this
           option is used.

       -fno-nil-receivers
           Assume that all Objective-C message dispatches ("[receiver
           message:arg]") in this translation unit ensure that the receiver
           is not "nil".  This allows for more efficient entry points in the
           runtime to be used.  This option is only available in conjunction
           with the NeXT runtime and ABI version 0 or 1.

       -fobjc-abi-version=n
           Use version n of the Objective-C ABI for the selected runtime.
           This option is currently supported only for the NeXT runtime.  In
           that case, Version 0 is the traditional (32-bit) ABI without
           support for properties and other Objective-C 2.0 additions.
           Version 1 is the traditional (32-bit) ABI with support for
           properties and other Objective-C 2.0 additions.  Version 2 is the
           modern (64-bit) ABI.  If nothing is specified, the default is
           Version 0 on 32-bit target machines, and Version 2 on 64-bit
           target machines.

       -fobjc-call-cxx-cdtors
           For each Objective-C class, check if any of its instance
           variables is a C++ object with a non-trivial default constructor.
           If so, synthesize a special "- (id) .cxx_construct" instance
           method which runs non-trivial default constructors on any such
           instance variables, in order, and then return "self".  Similarly,
           check if any instance variable is a C++ object with a non-trivial
           destructor, and if so, synthesize a special "- (void)
           .cxx_destruct" method which runs all such default destructors, in
           reverse order.

           The "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods
           thusly generated only operate on instance variables declared in
           the current Objective-C class, and not those inherited from
           superclasses.  It is the responsibility of the Objective-C
           runtime to invoke all such methods in an object's inheritance
           hierarchy.  The "- (id) .cxx_construct" methods are invoked by
           the runtime immediately after a new object instance is allocated;
           the "- (void) .cxx_destruct" methods are invoked immediately
           before the runtime deallocates an object instance.

           As of this writing, only the NeXT runtime on Mac OS X 10.4 and
           later has support for invoking the "- (id) .cxx_construct" and "-
           (void) .cxx_destruct" methods.

       -fobjc-direct-dispatch
           Allow fast jumps to the message dispatcher.  On Darwin this is
           accomplished via the comm page.

       -fobjc-exceptions
           Enable syntactic support for structured exception handling in
           Objective-C, similar to what is offered by C++ and Java.  This
           option is required to use the Objective-C keywords @try, @throw,
           @catch, @finally and @synchronized.  This option is available
           with both the GNU runtime and the NeXT runtime (but not available
           in conjunction with the NeXT runtime on Mac OS X 10.2 and
           earlier).

       -fobjc-gc
           Enable garbage collection (GC) in Objective-C and Objective-C++
           programs.  This option is only available with the NeXT runtime;
           the GNU runtime has a different garbage collection implementation
           that does not require special compiler flags.

       -fobjc-nilcheck
           For the NeXT runtime with version 2 of the ABI, check for a nil
           receiver in method invocations before doing the actual method
           call.  This is the default and can be disabled using
           -fno-objc-nilcheck.  Class methods and super calls are never
           checked for nil in this way no matter what this flag is set to.
           Currently this flag does nothing when the GNU runtime, or an
           older version of the NeXT runtime ABI, is used.

       -fobjc-std=objc1
           Conform to the language syntax of Objective-C 1.0, the language
           recognized by GCC 4.0.  This only affects the Objective-C
           additions to the C/C++ language; it does not affect conformance
           to C/C++ standards, which is controlled by the separate C/C++
           dialect option flags.  When this option is used with the
           Objective-C or Objective-C++ compiler, any Objective-C syntax
           that is not recognized by GCC 4.0 is rejected.  This is useful if
           you need to make sure that your Objective-C code can be compiled
           with older versions of GCC.

       -freplace-objc-classes
           Emit a special marker instructing ld(1) not to statically link in
           the resulting object file, and allow dyld(1) to load it in at run
           time instead.  This is used in conjunction with the Fix-and-
           Continue debugging mode, where the object file in question may be
           recompiled and dynamically reloaded in the course of program
           execution, without the need to restart the program itself.
           Currently, Fix-and-Continue functionality is only available in
           conjunction with the NeXT runtime on Mac OS X 10.3 and later.

       -fzero-link
           When compiling for the NeXT runtime, the compiler ordinarily
           replaces calls to "objc_getClass("...")" (when the name of the
           class is known at compile time) with static class references that
           get initialized at load time, which improves run-time
           performance.  Specifying the -fzero-link flag suppresses this
           behavior and causes calls to "objc_getClass("...")"  to be
           retained.  This is useful in Zero-Link debugging mode, since it
           allows for individual class implementations to be modified during
           program execution.  The GNU runtime currently always retains
           calls to "objc_get_class("...")"  regardless of command-line
           options.

       -fno-local-ivars
           By default instance variables in Objective-C can be accessed as
           if they were local variables from within the methods of the class
           they're declared in.  This can lead to shadowing between instance
           variables and other variables declared either locally inside a
           class method or globally with the same name.  Specifying the
           -fno-local-ivars flag disables this behavior thus avoiding
           variable shadowing issues.

       -fivar-visibility=[public|protected|private|package]
           Set the default instance variable visibility to the specified
           option so that instance variables declared outside the scope of
           any access modifier directives default to the specified
           visibility.

       -gen-decls
           Dump interface declarations for all classes seen in the source
           file to a file named sourcename.decl.

       -Wassign-intercept (Objective-C and Objective-C++ only)
           Warn whenever an Objective-C assignment is being intercepted by
           the garbage collector.

       -Wno-protocol (Objective-C and Objective-C++ only)
           If a class is declared to implement a protocol, a warning is
           issued for every method in the protocol that is not implemented
           by the class.  The default behavior is to issue a warning for
           every method not explicitly implemented in the class, even if a
           method implementation is inherited from the superclass.  If you
           use the -Wno-protocol option, then methods inherited from the
           superclass are considered to be implemented, and no warning is
           issued for them.

       -Wselector (Objective-C and Objective-C++ only)
           Warn if multiple methods of different types for the same selector
           are found during compilation.  The check is performed on the list
           of methods in the final stage of compilation.  Additionally, a
           check is performed for each selector appearing in a
           "@selector(...)"  expression, and a corresponding method for that
           selector has been found during compilation.  Because these checks
           scan the method table only at the end of compilation, these
           warnings are not produced if the final stage of compilation is
           not reached, for example because an error is found during
           compilation, or because the -fsyntax-only option is being used.

       -Wstrict-selector-match (Objective-C and Objective-C++ only)
           Warn if multiple methods with differing argument and/or return
           types are found for a given selector when attempting to send a
           message using this selector to a receiver of type "id" or
           "Class".  When this flag is off (which is the default behavior),
           the compiler omits such warnings if any differences found are
           confined to types that share the same size and alignment.

       -Wundeclared-selector (Objective-C and Objective-C++ only)
           Warn if a "@selector(...)" expression referring to an undeclared
           selector is found.  A selector is considered undeclared if no
           method with that name has been declared before the
           "@selector(...)" expression, either explicitly in an @interface
           or @protocol declaration, or implicitly in an @implementation
           section.  This option always performs its checks as soon as a
           "@selector(...)" expression is found, while -Wselector only
           performs its checks in the final stage of compilation.  This also
           enforces the coding style convention that methods and selectors
           must be declared before being used.

       -print-objc-runtime-info
           Generate C header describing the largest structure that is passed
           by value, if any.

       Options to Control Diagnostic Messages Formatting

       Traditionally, diagnostic messages have been formatted irrespective
       of the output device's aspect (e.g. its width, ...).  You can use the
       options described below to control the formatting algorithm for
       diagnostic messages, e.g. how many characters per line, how often
       source location information should be reported.  Note that some
       language front ends may not honor these options.

       -fmessage-length=n
           Try to format error messages so that they fit on lines of about n
           characters.  If n is zero, then no line-wrapping is done; each
           error message appears on a single line.  This is the default for
           all front ends.

       -fdiagnostics-show-location=once
           Only meaningful in line-wrapping mode.  Instructs the diagnostic
           messages reporter to emit source location information once; that
           is, in case the message is too long to fit on a single physical
           line and has to be wrapped, the source location won't be emitted
           (as prefix) again, over and over, in subsequent continuation
           lines.  This is the default behavior.

       -fdiagnostics-show-location=every-line
           Only meaningful in line-wrapping mode.  Instructs the diagnostic
           messages reporter to emit the same source location information
           (as prefix) for physical lines that result from the process of
           breaking a message which is too long to fit on a single line.

       -fdiagnostics-color[=WHEN]
       -fno-diagnostics-color
           Use color in diagnostics.  WHEN is never, always, or auto.  The
           default depends on how the compiler has been configured, it can
           be any of the above WHEN options or also never if GCC_COLORS
           environment variable isn't present in the environment, and auto
           otherwise.  auto means to use color only when the standard error
           is a terminal.  The forms -fdiagnostics-color and
           -fno-diagnostics-color are aliases for -fdiagnostics-color=always
           and -fdiagnostics-color=never, respectively.

           The colors are defined by the environment variable GCC_COLORS.
           Its value is a colon-separated list of capabilities and Select
           Graphic Rendition (SGR) substrings. SGR commands are interpreted
           by the terminal or terminal emulator.  (See the section in the
           documentation of your text terminal for permitted values and
           their meanings as character attributes.)  These substring values
           are integers in decimal representation and can be concatenated
           with semicolons.  Common values to concatenate include 1 for
           bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default
           foreground color, 30 to 37 for foreground colors, 90 to 97 for
           16-color mode foreground colors, 38;5;0 to 38;5;255 for 88-color
           and 256-color modes foreground colors, 49 for default background
           color, 40 to 47 for background colors, 100 to 107 for 16-color
           mode background colors, and 48;5;0 to 48;5;255 for 88-color and
           256-color modes background colors.

           The default GCC_COLORS is

                   error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01

           where 01;31 is bold red, 01;35 is bold magenta, 01;36 is bold
           cyan, 01;32 is bold green and 01 is bold. Setting GCC_COLORS to
           the empty string disables colors.  Supported capabilities are as
           follows.

           "error="
               SGR substring for error: markers.

           "warning="
               SGR substring for warning: markers.

           "note="
               SGR substring for note: markers.

           "caret="
               SGR substring for caret line.

           "locus="
               SGR substring for location information, file:line or
               file:line:column etc.

           "quote="
               SGR substring for information printed within quotes.

       -fno-diagnostics-show-option
           By default, each diagnostic emitted includes text indicating the
           command-line option that directly controls the diagnostic (if
           such an option is known to the diagnostic machinery).  Specifying
           the -fno-diagnostics-show-option flag suppresses that behavior.

       -fno-diagnostics-show-caret
           By default, each diagnostic emitted includes the original source
           line and a caret ^ indicating the column.  This option suppresses
           this information.  The source line is truncated to n characters,
           if the -fmessage-length=n option is given.  When the output is
           done to the terminal, the width is limited to the width given by
           the COLUMNS environment variable or, if not set, to the terminal
           width.

       Options to Request or Suppress Warnings

       Warnings are diagnostic messages that report constructions that are
       not inherently erroneous but that are risky or suggest there may have
       been an error.

       The following language-independent options do not enable specific
       warnings but control the kinds of diagnostics produced by GCC.

       -fsyntax-only
           Check the code for syntax errors, but don't do anything beyond
           that.

       -fmax-errors=n
           Limits the maximum number of error messages to n, at which point
           GCC bails out rather than attempting to continue processing the
           source code.  If n is 0 (the default), there is no limit on the
           number of error messages produced.  If -Wfatal-errors is also
           specified, then -Wfatal-errors takes precedence over this option.

       -w  Inhibit all warning messages.

       -Werror
           Make all warnings into errors.

       -Werror=
           Make the specified warning into an error.  The specifier for a
           warning is appended; for example -Werror=switch turns the
           warnings controlled by -Wswitch into errors.  This switch takes a
           negative form, to be used to negate -Werror for specific
           warnings; for example -Wno-error=switch makes -Wswitch warnings
           not be errors, even when -Werror is in effect.

           The warning message for each controllable warning includes the
           option that controls the warning.  That option can then be used
           with -Werror= and -Wno-error= as described above.  (Printing of
           the option in the warning message can be disabled using the
           -fno-diagnostics-show-option flag.)

           Note that specifying -Werror=foo automatically implies -Wfoo.
           However, -Wno-error=foo does not imply anything.

       -Wfatal-errors
           This option causes the compiler to abort compilation on the first
           error occurred rather than trying to keep going and printing
           further error messages.

       You can request many specific warnings with options beginning with
       -W, for example -Wimplicit to request warnings on implicit
       declarations.  Each of these specific warning options also has a
       negative form beginning -Wno- to turn off warnings; for example,
       -Wno-implicit.  This manual lists only one of the two forms,
       whichever is not the default.  For further language-specific options
       also refer to C++ Dialect Options and Objective-C and Objective-C++
       Dialect Options.

       Some options, such as -Wall and -Wextra, turn on other options, such
       as -Wunused, which may turn on further options, such as
       -Wunused-value. The combined effect of positive and negative forms is
       that more specific options have priority over less specific ones,
       independently of their position in the command-line. For options of
       the same specificity, the last one takes effect. Options enabled or
       disabled via pragmas take effect as if they appeared at the end of
       the command-line.

       When an unrecognized warning option is requested (e.g.,
       -Wunknown-warning), GCC emits a diagnostic stating that the option is
       not recognized.  However, if the -Wno- form is used, the behavior is
       slightly different: no diagnostic is produced for
       -Wno-unknown-warning unless other diagnostics are being produced.
       This allows the use of new -Wno- options with old compilers, but if
       something goes wrong, the compiler warns that an unrecognized option
       is present.

       -Wpedantic
       -pedantic
           Issue all the warnings demanded by strict ISO C and ISO C++;
           reject all programs that use forbidden extensions, and some other
           programs that do not follow ISO C and ISO C++.  For ISO C,
           follows the version of the ISO C standard specified by any -std
           option used.

           Valid ISO C and ISO C++ programs should compile properly with or
           without this option (though a rare few require -ansi or a -std
           option specifying the required version of ISO C).  However,
           without this option, certain GNU extensions and traditional C and
           C++ features are supported as well.  With this option, they are
           rejected.

           -Wpedantic does not cause warning messages for use of the
           alternate keywords whose names begin and end with __.  Pedantic
           warnings are also disabled in the expression that follows
           "__extension__".  However, only system header files should use
           these escape routes; application programs should avoid them.

           Some users try to use -Wpedantic to check programs for strict ISO
           C conformance.  They soon find that it does not do quite what
           they want: it finds some non-ISO practices, but not all---only
           those for which ISO C requires a diagnostic, and some others for
           which diagnostics have been added.

           A feature to report any failure to conform to ISO C might be
           useful in some instances, but would require considerable
           additional work and would be quite different from -Wpedantic.  We
           don't have plans to support such a feature in the near future.

           Where the standard specified with -std represents a GNU extended
           dialect of C, such as gnu90 or gnu99, there is a corresponding
           base standard, the version of ISO C on which the GNU extended
           dialect is based.  Warnings from -Wpedantic are given where they
           are required by the base standard.  (It does not make sense for
           such warnings to be given only for features not in the specified
           GNU C dialect, since by definition the GNU dialects of C include
           all features the compiler supports with the given option, and
           there would be nothing to warn about.)

       -pedantic-errors
           Give an error whenever the base standard (see -Wpedantic)
           requires a diagnostic, in some cases where there is undefined
           behavior at compile-time and in some other cases that do not
           prevent compilation of programs that are valid according to the
           standard. This is not equivalent to -Werror=pedantic, since there
           are errors enabled by this option and not enabled by the latter
           and vice versa.

       -Wall
           This enables all the warnings about constructions that some users
           consider questionable, and that are easy to avoid (or modify to
           prevent the warning), even in conjunction with macros.  This also
           enables some language-specific warnings described in C++ Dialect
           Options and Objective-C and Objective-C++ Dialect Options.

           -Wall turns on the following warning flags:

           -Waddress -Warray-bounds=1 (only with -O2) -Wbool-compare
           -Wc++11-compat  -Wc++14-compat -Wchar-subscripts -Wcomment
           -Wenum-compare (in C/ObjC; this is on by default in C++) -Wformat
           -Wimplicit (C and Objective-C only) -Wimplicit-int (C and
           Objective-C only) -Wimplicit-function-declaration (C and
           Objective-C only) -Winit-self (only for C++)
           -Wlogical-not-parentheses -Wmain (only for C/ObjC and unless
           -ffreestanding) -Wmaybe-uninitialized -Wmemset-transposed-args
           -Wmisleading-indentation (only for C/C++) -Wmissing-braces (only
           for C/ObjC) -Wnarrowing (only for C++) -Wnonnull
           -Wnonnull-compare -Wopenmp-simd -Wparentheses -Wpointer-sign
           -Wreorder -Wreturn-type -Wsequence-point -Wsign-compare (only in
           C++) -Wsizeof-pointer-memaccess -Wstrict-aliasing
           -Wstrict-overflow=1 -Wswitch -Wtautological-compare -Wtrigraphs
           -Wuninitialized -Wunknown-pragmas -Wunused-function
           -Wunused-label -Wunused-value -Wunused-variable
           -Wvolatile-register-var

           Note that some warning flags are not implied by -Wall.  Some of
           them warn about constructions that users generally do not
           consider questionable, but which occasionally you might wish to
           check for; others warn about constructions that are necessary or
           hard to avoid in some cases, and there is no simple way to modify
           the code to suppress the warning. Some of them are enabled by
           -Wextra but many of them must be enabled individually.

       -Wextra
           This enables some extra warning flags that are not enabled by
           -Wall. (This option used to be called -W.  The older name is
           still supported, but the newer name is more descriptive.)

           -Wclobbered -Wempty-body -Wignored-qualifiers
           -Wmissing-field-initializers -Wmissing-parameter-type (C only)
           -Wold-style-declaration (C only) -Woverride-init -Wsign-compare
           (C only) -Wtype-limits -Wuninitialized -Wshift-negative-value (in
           C++03 and in C99 and newer) -Wunused-parameter (only with
           -Wunused or -Wall) -Wunused-but-set-parameter (only with -Wunused
           or -Wall)

           The option -Wextra also prints warning messages for the following
           cases:

           *   A pointer is compared against integer zero with "<", "<=",
               ">", or ">=".

           *   (C++ only) An enumerator and a non-enumerator both appear in
               a conditional expression.

           *   (C++ only) Ambiguous virtual bases.

           *   (C++ only) Subscripting an array that has been declared
               "register".

           *   (C++ only) Taking the address of a variable that has been
               declared "register".

           *   (C++ only) A base class is not initialized in a derived
               class's copy constructor.

       -Wchar-subscripts
           Warn if an array subscript has type "char".  This is a common
           cause of error, as programmers often forget that this type is
           signed on some machines.  This warning is enabled by -Wall.

       -Wcomment
           Warn whenever a comment-start sequence /* appears in a /*
           comment, or whenever a Backslash-Newline appears in a // comment.
           This warning is enabled by -Wall.

       -Wno-coverage-mismatch
           Warn if feedback profiles do not match when using the
           -fprofile-use option.  If a source file is changed between
           compiling with -fprofile-gen and with -fprofile-use, the files
           with the profile feedback can fail to match the source file and
           GCC cannot use the profile feedback information.  By default,
           this warning is enabled and is treated as an error.
           -Wno-coverage-mismatch can be used to disable the warning or
           -Wno-error=coverage-mismatch can be used to disable the error.
           Disabling the error for this warning can result in poorly
           optimized code and is useful only in the case of very minor
           changes such as bug fixes to an existing code-base.  Completely
           disabling the warning is not recommended.

       -Wno-cpp
           (C, Objective-C, C++, Objective-C++ and Fortran only)

           Suppress warning messages emitted by "#warning" directives.

       -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only)
           Give a warning when a value of type "float" is implicitly
           promoted to "double".  CPUs with a 32-bit "single-precision"
           floating-point unit implement "float" in hardware, but emulate
           "double" in software.  On such a machine, doing computations
           using "double" values is much more expensive because of the
           overhead required for software emulation.

           It is easy to accidentally do computations with "double" because
           floating-point literals are implicitly of type "double".  For
           example, in:

                   float area(float radius)
                   {
                      return 3.14159 * radius * radius;
                   }

           the compiler performs the entire computation with "double"
           because the floating-point literal is a "double".

       -Wformat
       -Wformat=n
           Check calls to "printf" and "scanf", etc., to make sure that the
           arguments supplied have types appropriate to the format string
           specified, and that the conversions specified in the format
           string make sense.  This includes standard functions, and others
           specified by format attributes, in the "printf", "scanf",
           "strftime" and "strfmon" (an X/Open extension, not in the C
           standard) families (or other target-specific families).  Which
           functions are checked without format attributes having been
           specified depends on the standard version selected, and such
           checks of functions without the attribute specified are disabled
           by -ffreestanding or -fno-builtin.

           The formats are checked against the format features supported by
           GNU libc version 2.2.  These include all ISO C90 and C99
           features, as well as features from the Single Unix Specification
           and some BSD and GNU extensions.  Other library implementations
           may not support all these features; GCC does not support warning
           about features that go beyond a particular library's limitations.
           However, if -Wpedantic is used with -Wformat, warnings are given
           about format features not in the selected standard version (but
           not for "strfmon" formats, since those are not in any version of
           the C standard).

           -Wformat=1
           -Wformat
               Option -Wformat is equivalent to -Wformat=1, and -Wno-format
               is equivalent to -Wformat=0.  Since -Wformat also checks for
               null format arguments for several functions, -Wformat also
               implies -Wnonnull.  Some aspects of this level of format
               checking can be disabled by the options:
               -Wno-format-contains-nul, -Wno-format-extra-args, and
               -Wno-format-zero-length.  -Wformat is enabled by -Wall.

           -Wno-format-contains-nul
               If -Wformat is specified, do not warn about format strings
               that contain NUL bytes.

           -Wno-format-extra-args
               If -Wformat is specified, do not warn about excess arguments
               to a "printf" or "scanf" format function.  The C standard
               specifies that such arguments are ignored.

               Where the unused arguments lie between used arguments that
               are specified with $ operand number specifications, normally
               warnings are still given, since the implementation could not
               know what type to pass to "va_arg" to skip the unused
               arguments.  However, in the case of "scanf" formats, this
               option suppresses the warning if the unused arguments are all
               pointers, since the Single Unix Specification says that such
               unused arguments are allowed.

           -Wno-format-zero-length
               If -Wformat is specified, do not warn about zero-length
               formats.  The C standard specifies that zero-length formats
               are allowed.

           -Wformat=2
               Enable -Wformat plus additional format checks.  Currently
               equivalent to -Wformat -Wformat-nonliteral -Wformat-security
               -Wformat-y2k.

           -Wformat-nonliteral
               If -Wformat is specified, also warn if the format string is
               not a string literal and so cannot be checked, unless the
               format function takes its format arguments as a "va_list".

           -Wformat-security
               If -Wformat is specified, also warn about uses of format
               functions that represent possible security problems.  At
               present, this warns about calls to "printf" and "scanf"
               functions where the format string is not a string literal and
               there are no format arguments, as in "printf (foo);".  This
               may be a security hole if the format string came from
               untrusted input and contains %n.  (This is currently a subset
               of what -Wformat-nonliteral warns about, but in future
               warnings may be added to -Wformat-security that are not
               included in -Wformat-nonliteral.)

           -Wformat-signedness
               If -Wformat is specified, also warn if the format string
               requires an unsigned argument and the argument is signed and
               vice versa.

           -Wformat-y2k
               If -Wformat is specified, also warn about "strftime" formats
               that may yield only a two-digit year.

       -Wnonnull
           Warn about passing a null pointer for arguments marked as
           requiring a non-null value by the "nonnull" function attribute.

           -Wnonnull is included in -Wall and -Wformat.  It can be disabled
           with the -Wno-nonnull option.

       -Wnonnull-compare
           Warn when comparing an argument marked with the "nonnull"
           function attribute against null inside the function.

           -Wnonnull-compare is included in -Wall.  It can be disabled with
           the -Wno-nonnull-compare option.

       -Wnull-dereference
           Warn if the compiler detects paths that trigger erroneous or
           undefined behavior due to dereferencing a null pointer.  This
           option is only active when -fdelete-null-pointer-checks is
           active, which is enabled by optimizations in most targets.  The
           precision of the warnings depends on the optimization options
           used.

       -Winit-self (C, C++, Objective-C and Objective-C++ only)
           Warn about uninitialized variables that are initialized with
           themselves.  Note this option can only be used with the
           -Wuninitialized option.

           For example, GCC warns about "i" being uninitialized in the
           following snippet only when -Winit-self has been specified:

                   int f()
                   {
                     int i = i;
                     return i;
                   }

           This warning is enabled by -Wall in C++.

       -Wimplicit-int (C and Objective-C only)
           Warn when a declaration does not specify a type.  This warning is
           enabled by -Wall.

       -Wimplicit-function-declaration (C and Objective-C only)
           Give a warning whenever a function is used before being declared.
           In C99 mode (-std=c99 or -std=gnu99), this warning is enabled by
           default and it is made into an error by -pedantic-errors. This
           warning is also enabled by -Wall.

       -Wimplicit (C and Objective-C only)
           Same as -Wimplicit-int and -Wimplicit-function-declaration.  This
           warning is enabled by -Wall.

       -Wignored-qualifiers (C and C++ only)
           Warn if the return type of a function has a type qualifier such
           as "const".  For ISO C such a type qualifier has no effect, since
           the value returned by a function is not an lvalue.  For C++, the
           warning is only emitted for scalar types or "void".  ISO C
           prohibits qualified "void" return types on function definitions,
           so such return types always receive a warning even without this
           option.

           This warning is also enabled by -Wextra.

       -Wignored-attributes (C and C++ only)
           Warn when an attribute is ignored.  This is different from the
           -Wattributes option in that it warns whenever the compiler
           decides to drop an attribute, not that the attribute is either
           unknown, used in a wrong place, etc.  This warning is enabled by
           default.

       -Wmain
           Warn if the type of "main" is suspicious.  "main" should be a
           function with external linkage, returning int, taking either zero
           arguments, two, or three arguments of appropriate types.  This
           warning is enabled by default in C++ and is enabled by either
           -Wall or -Wpedantic.

       -Wmisleading-indentation (C and C++ only)
           Warn when the indentation of the code does not reflect the block
           structure.  Specifically, a warning is issued for "if", "else",
           "while", and "for" clauses with a guarded statement that does not
           use braces, followed by an unguarded statement with the same
           indentation.

           In the following example, the call to "bar" is misleadingly
           indented as if it were guarded by the "if" conditional.

                     if (some_condition ())
                       foo ();
                       bar ();  /* Gotcha: this is not guarded by the "if".  */

           In the case of mixed tabs and spaces, the warning uses the
           -ftabstop= option to determine if the statements line up
           (defaulting to 8).

           The warning is not issued for code involving multiline
           preprocessor logic such as the following example.

                     if (flagA)
                       foo (0);
                   #if SOME_CONDITION_THAT_DOES_NOT_HOLD
                     if (flagB)
                   #endif
                       foo (1);

           The warning is not issued after a "#line" directive, since this
           typically indicates autogenerated code, and no assumptions can be
           made about the layout of the file that the directive references.

           This warning is enabled by -Wall in C and C++.

       -Wmissing-braces
           Warn if an aggregate or union initializer is not fully bracketed.
           In the following example, the initializer for "a" is not fully
           bracketed, but that for "b" is fully bracketed.  This warning is
           enabled by -Wall in C.

                   int a[2][2] = { 0, 1, 2, 3 };
                   int b[2][2] = { { 0, 1 }, { 2, 3 } };

           This warning is enabled by -Wall.

       -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
           Warn if a user-supplied include directory does not exist.

       -Wparentheses
           Warn if parentheses are omitted in certain contexts, such as when
           there is an assignment in a context where a truth value is
           expected, or when operators are nested whose precedence people
           often get confused about.

           Also warn if a comparison like "x<=y<=z" appears; this is
           equivalent to "(x<=y ? 1 : 0) <= z", which is a different
           interpretation from that of ordinary mathematical notation.

           Also warn about constructions where there may be confusion to
           which "if" statement an "else" branch belongs.  Here is an
           example of such a case:

                   {
                     if (a)
                       if (b)
                         foo ();
                     else
                       bar ();
                   }

           In C/C++, every "else" branch belongs to the innermost possible
           "if" statement, which in this example is "if (b)".  This is often
           not what the programmer expected, as illustrated in the above
           example by indentation the programmer chose.  When there is the
           potential for this confusion, GCC issues a warning when this flag
           is specified.  To eliminate the warning, add explicit braces
           around the innermost "if" statement so there is no way the "else"
           can belong to the enclosing "if".  The resulting code looks like
           this:

                   {
                     if (a)
                       {
                         if (b)
                           foo ();
                         else
                           bar ();
                       }
                   }

           Also warn for dangerous uses of the GNU extension to "?:" with
           omitted middle operand. When the condition in the "?": operator
           is a boolean expression, the omitted value is always 1.  Often
           programmers expect it to be a value computed inside the
           conditional expression instead.

           This warning is enabled by -Wall.

       -Wsequence-point
           Warn about code that may have undefined semantics because of
           violations of sequence point rules in the C and C++ standards.

           The C and C++ standards define the order in which expressions in
           a C/C++ program are evaluated in terms of sequence points, which
           represent a partial ordering between the execution of parts of
           the program: those executed before the sequence point, and those
           executed after it.  These occur after the evaluation of a full
           expression (one which is not part of a larger expression), after
           the evaluation of the first operand of a "&&", "||", "? :" or ","
           (comma) operator, before a function is called (but after the
           evaluation of its arguments and the expression denoting the
           called function), and in certain other places.  Other than as
           expressed by the sequence point rules, the order of evaluation of
           subexpressions of an expression is not specified.  All these
           rules describe only a partial order rather than a total order,
           since, for example, if two functions are called within one
           expression with no sequence point between them, the order in
           which the functions are called is not specified.  However, the
           standards committee have ruled that function calls do not
           overlap.

           It is not specified when between sequence points modifications to
           the values of objects take effect.  Programs whose behavior
           depends on this have undefined behavior; the C and C++ standards
           specify that "Between the previous and next sequence point an
           object shall have its stored value modified at most once by the
           evaluation of an expression.  Furthermore, the prior value shall
           be read only to determine the value to be stored.".  If a program
           breaks these rules, the results on any particular implementation
           are entirely unpredictable.

           Examples of code with undefined behavior are "a = a++;", "a[n] =
           b[n++]" and "a[i++] = i;".  Some more complicated cases are not
           diagnosed by this option, and it may give an occasional false
           positive result, but in general it has been found fairly
           effective at detecting this sort of problem in programs.

           The standard is worded confusingly, therefore there is some
           debate over the precise meaning of the sequence point rules in
           subtle cases.  Links to discussions of the problem, including
           proposed formal definitions, may be found on the GCC readings
           page, at <http://gcc.gnu.org/readings.html >.

           This warning is enabled by -Wall for C and C++.

       -Wno-return-local-addr
           Do not warn about returning a pointer (or in C++, a reference) to
           a variable that goes out of scope after the function returns.

       -Wreturn-type
           Warn whenever a function is defined with a return type that
           defaults to "int".  Also warn about any "return" statement with
           no return value in a function whose return type is not "void"
           (falling off the end of the function body is considered returning
           without a value), and about a "return" statement with an
           expression in a function whose return type is "void".

           For C++, a function without return type always produces a
           diagnostic message, even when -Wno-return-type is specified.  The
           only exceptions are "main" and functions defined in system
           headers.

           This warning is enabled by -Wall.

       -Wshift-count-negative
           Warn if shift count is negative. This warning is enabled by
           default.

       -Wshift-count-overflow
           Warn if shift count >= width of type. This warning is enabled by
           default.

       -Wshift-negative-value
           Warn if left shifting a negative value.  This warning is enabled
           by -Wextra in C99 and C++11 modes (and newer).

       -Wshift-overflow
       -Wshift-overflow=n
           Warn about left shift overflows.  This warning is enabled by
           default in C99 and C++11 modes (and newer).

           -Wshift-overflow=1
               This is the warning level of -Wshift-overflow and is enabled
               by default in C99 and C++11 modes (and newer).  This warning
               level does not warn about left-shifting 1 into the sign bit.
               (However, in C, such an overflow is still rejected in
               contexts where an integer constant expression is required.)

           -Wshift-overflow=2
               This warning level also warns about left-shifting 1 into the
               sign bit, unless C++14 mode is active.

       -Wswitch
           Warn whenever a "switch" statement has an index of enumerated
           type and lacks a "case" for one or more of the named codes of
           that enumeration.  (The presence of a "default" label prevents
           this warning.)  "case" labels outside the enumeration range also
           provoke warnings when this option is used (even if there is a
           "default" label).  This warning is enabled by -Wall.

       -Wswitch-default
           Warn whenever a "switch" statement does not have a "default"
           case.

       -Wswitch-enum
           Warn whenever a "switch" statement has an index of enumerated
           type and lacks a "case" for one or more of the named codes of
           that enumeration.  "case" labels outside the enumeration range
           also provoke warnings when this option is used.  The only
           difference between -Wswitch and this option is that this option
           gives a warning about an omitted enumeration code even if there
           is a "default" label.

       -Wswitch-bool
           Warn whenever a "switch" statement has an index of boolean type
           and the case values are outside the range of a boolean type.  It
           is possible to suppress this warning by casting the controlling
           expression to a type other than "bool".  For example:

                   switch ((int) (a == 4))
                     {
                     ...
                     }

           This warning is enabled by default for C and C++ programs.

       -Wsync-nand (C and C++ only)
           Warn when "__sync_fetch_and_nand" and "__sync_nand_and_fetch"
           built-in functions are used.  These functions changed semantics
           in GCC 4.4.

       -Wtrigraphs
           Warn if any trigraphs are encountered that might change the
           meaning of the program (trigraphs within comments are not warned
           about).  This warning is enabled by -Wall.

       -Wunused-but-set-parameter
           Warn whenever a function parameter is assigned to, but otherwise
           unused (aside from its declaration).

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused together with -Wextra.

       -Wunused-but-set-variable
           Warn whenever a local variable is assigned to, but otherwise
           unused (aside from its declaration).  This warning is enabled by
           -Wall.

           To suppress this warning use the "unused" attribute.

           This warning is also enabled by -Wunused, which is enabled by
           -Wall.

       -Wunused-function
           Warn whenever a static function is declared but not defined or a
           non-inline static function is unused.  This warning is enabled by
           -Wall.

       -Wunused-label
           Warn whenever a label is declared but not used.  This warning is
           enabled by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only)
           Warn when a typedef locally defined in a function is not used.
           This warning is enabled by -Wall.

       -Wunused-parameter
           Warn whenever a function parameter is unused aside from its
           declaration.

           To suppress this warning use the "unused" attribute.

       -Wno-unused-result
           Do not warn if a caller of a function marked with attribute
           "warn_unused_result" does not use its return value. The default
           is -Wunused-result.

       -Wunused-variable
           Warn whenever a local or static variable is unused aside from its
           declaration. This option implies -Wunused-const-variable=1 for C,
           but not for C++. This warning is enabled by -Wall.

           To suppress this warning use the "unused" attribute.

       -Wunused-const-variable
       -Wunused-const-variable=n
           Warn whenever a constant static variable is unused aside from its
           declaration.  -Wunused-const-variable=1 is enabled by
           -Wunused-variable for C, but not for C++. In C this declares
           variable storage, but in C++ this is not an error since const
           variables take the place of "#define"s.

           To suppress this warning use the "unused" attribute.

           -Wunused-const-variable=1
               This is the warning level that is enabled by
               -Wunused-variable for C.  It warns only about unused static
               const variables defined in the main compilation unit, but not
               about static const variables declared in any header included.

           -Wunused-const-variable=2
               This warning level also warns for unused constant static
               variables in headers (excluding system headers).  This is the
               warning level of -Wunused-const-variable and must be
               explicitly requested since in C++ this isn't an error and in
               C it might be harder to clean up all headers included.

       -Wunused-value
           Warn whenever a statement computes a result that is explicitly
           not used. To suppress this warning cast the unused expression to
           "void". This includes an expression-statement or the left-hand
           side of a comma expression that contains no side effects. For
           example, an expression such as "x[i,j]" causes a warning, while
           "x[(void)i,j]" does not.

           This warning is enabled by -Wall.

       -Wunused
           All the above -Wunused options combined.

           In order to get a warning about an unused function parameter, you
           must either specify -Wextra -Wunused (note that -Wall implies
           -Wunused), or separately specify -Wunused-parameter.

       -Wuninitialized
           Warn if an automatic variable is used without first being
           initialized or if a variable may be clobbered by a "setjmp" call.
           In C++, warn if a non-static reference or non-static "const"
           member appears in a class without constructors.

           If you want to warn about code that uses the uninitialized value
           of the variable in its own initializer, use the -Winit-self
           option.

           These warnings occur for individual uninitialized or clobbered
           elements of structure, union or array variables as well as for
           variables that are uninitialized or clobbered as a whole.  They
           do not occur for variables or elements declared "volatile".
           Because these warnings depend on optimization, the exact
           variables or elements for which there are warnings depends on the
           precise optimization options and version of GCC used.

           Note that there may be no warning about a variable that is used
           only to compute a value that itself is never used, because such
           computations may be deleted by data flow analysis before the
           warnings are printed.

       -Winvalid-memory-model
           Warn for invocations of __atomic Builtins, __sync Builtins, and
           the C11 atomic generic functions with a memory consistency
           argument that is either invalid for the operation or outside the
           range of values of the "memory_order" enumeration.  For example,
           since the "__atomic_store" and "__atomic_store_n" built-ins are
           only defined for the relaxed, release, and sequentially
           consistent memory orders the following code is diagnosed:

                   void store (int *i)
                   {
                     __atomic_store_n (i, 0, memory_order_consume);
                   }

           -Winvalid-memory-model is enabled by default.

       -Wmaybe-uninitialized
           For an automatic variable, if there exists a path from the
           function entry to a use of the variable that is initialized, but
           there exist some other paths for which the variable is not
           initialized, the compiler emits a warning if it cannot prove the
           uninitialized paths are not executed at run time. These warnings
           are made optional because GCC is not smart enough to see all the
           reasons why the code might be correct in spite of appearing to
           have an error.  Here is one example of how this can happen:

                   {
                     int x;
                     switch (y)
                       {
                       case 1: x = 1;
                         break;
                       case 2: x = 4;
                         break;
                       case 3: x = 5;
                       }
                     foo (x);
                   }

           If the value of "y" is always 1, 2 or 3, then "x" is always
           initialized, but GCC doesn't know this. To suppress the warning,
           you need to provide a default case with assert(0) or similar
           code.

           This option also warns when a non-volatile automatic variable
           might be changed by a call to "longjmp".  These warnings as well
           are possible only in optimizing compilation.

           The compiler sees only the calls to "setjmp".  It cannot know
           where "longjmp" will be called; in fact, a signal handler could
           call it at any point in the code.  As a result, you may get a
           warning even when there is in fact no problem because "longjmp"
           cannot in fact be called at the place that would cause a problem.

           Some spurious warnings can be avoided if you declare all the
           functions you use that never return as "noreturn".

           This warning is enabled by -Wall or -Wextra.

       -Wunknown-pragmas
           Warn when a "#pragma" directive is encountered that is not
           understood by GCC.  If this command-line option is used, warnings
           are even issued for unknown pragmas in system header files.  This
           is not the case if the warnings are only enabled by the -Wall
           command-line option.

       -Wno-pragmas
           Do not warn about misuses of pragmas, such as incorrect
           parameters, invalid syntax, or conflicts between pragmas.  See
           also -Wunknown-pragmas.

       -Wstrict-aliasing
           This option is only active when -fstrict-aliasing is active.  It
           warns about code that might break the strict aliasing rules that
           the compiler is using for optimization.  The warning does not
           catch all cases, but does attempt to catch the more common
           pitfalls.  It is included in -Wall.  It is equivalent to
           -Wstrict-aliasing=3

       -Wstrict-aliasing=n
           This option is only active when -fstrict-aliasing is active.  It
           warns about code that might break the strict aliasing rules that
           the compiler is using for optimization.  Higher levels correspond
           to higher accuracy (fewer false positives).  Higher levels also
           correspond to more effort, similar to the way -O works.
           -Wstrict-aliasing is equivalent to -Wstrict-aliasing=3.

           Level 1: Most aggressive, quick, least accurate.  Possibly useful
           when higher levels do not warn but -fstrict-aliasing still breaks
           the code, as it has very few false negatives.  However, it has
           many false positives.  Warns for all pointer conversions between
           possibly incompatible types, even if never dereferenced.  Runs in
           the front end only.

           Level 2: Aggressive, quick, not too precise.  May still have many
           false positives (not as many as level 1 though), and few false
           negatives (but possibly more than level 1).  Unlike level 1, it
           only warns when an address is taken.  Warns about incomplete
           types.  Runs in the front end only.

           Level 3 (default for -Wstrict-aliasing): Should have very few
           false positives and few false negatives.  Slightly slower than
           levels 1 or 2 when optimization is enabled.  Takes care of the
           common pun+dereference pattern in the front end:
           "*(int*)&some_float".  If optimization is enabled, it also runs
           in the back end, where it deals with multiple statement cases
           using flow-sensitive points-to information.  Only warns when the
           converted pointer is dereferenced.  Does not warn about
           incomplete types.

       -Wstrict-overflow
       -Wstrict-overflow=n
           This option is only active when -fstrict-overflow is active.  It
           warns about cases where the compiler optimizes based on the
           assumption that signed overflow does not occur.  Note that it
           does not warn about all cases where the code might overflow: it
           only warns about cases where the compiler implements some
           optimization.  Thus this warning depends on the optimization
           level.

           An optimization that assumes that signed overflow does not occur
           is perfectly safe if the values of the variables involved are
           such that overflow never does, in fact, occur.  Therefore this
           warning can easily give a false positive: a warning about code
           that is not actually a problem.  To help focus on important
           issues, several warning levels are defined.  No warnings are
           issued for the use of undefined signed overflow when estimating
           how many iterations a loop requires, in particular when
           determining whether a loop will be executed at all.

           -Wstrict-overflow=1
               Warn about cases that are both questionable and easy to
               avoid.  For example,  with -fstrict-overflow, the compiler
               simplifies "x + 1 > x" to 1.  This level of -Wstrict-overflow
               is enabled by -Wall; higher levels are not, and must be
               explicitly requested.

           -Wstrict-overflow=2
               Also warn about other cases where a comparison is simplified
               to a constant.  For example: "abs (x) >= 0".  This can only
               be simplified when -fstrict-overflow is in effect, because
               "abs (INT_MIN)" overflows to "INT_MIN", which is less than
               zero.  -Wstrict-overflow (with no level) is the same as
               -Wstrict-overflow=2.

           -Wstrict-overflow=3
               Also warn about other cases where a comparison is simplified.
               For example: "x + 1 > 1" is simplified to "x > 0".

           -Wstrict-overflow=4
               Also warn about other simplifications not covered by the
               above cases.  For example: "(x * 10) / 5" is simplified to "x
               * 2".

           -Wstrict-overflow=5
               Also warn about cases where the compiler reduces the
               magnitude of a constant involved in a comparison.  For
               example: "x + 2 > y" is simplified to "x + 1 >= y".  This is
               reported only at the highest warning level because this
               simplification applies to many comparisons, so this warning
               level gives a very large number of false positives.

       -Wsuggest-attribute=[pure|const|noreturn|format]
           Warn for cases where adding an attribute may be beneficial. The
           attributes currently supported are listed below.

           -Wsuggest-attribute=pure
           -Wsuggest-attribute=const
           -Wsuggest-attribute=noreturn
               Warn about functions that might be candidates for attributes
               "pure", "const" or "noreturn".  The compiler only warns for
               functions visible in other compilation units or (in the case
               of "pure" and "const") if it cannot prove that the function
               returns normally. A function returns normally if it doesn't
               contain an infinite loop or return abnormally by throwing,
               calling "abort" or trapping.  This analysis requires option
               -fipa-pure-const, which is enabled by default at -O and
               higher.  Higher optimization levels improve the accuracy of
               the analysis.

           -Wsuggest-attribute=format
           -Wmissing-format-attribute
               Warn about function pointers that might be candidates for
               "format" attributes.  Note these are only possible
               candidates, not absolute ones.  GCC guesses that function
               pointers with "format" attributes that are used in
               assignment, initialization, parameter passing or return
               statements should have a corresponding "format" attribute in
               the resulting type.  I.e. the left-hand side of the
               assignment or initialization, the type of the parameter
               variable, or the return type of the containing function
               respectively should also have a "format" attribute to avoid
               the warning.

               GCC also warns about function definitions that might be
               candidates for "format" attributes.  Again, these are only
               possible candidates.  GCC guesses that "format" attributes
               might be appropriate for any function that calls a function
               like "vprintf" or "vscanf", but this might not always be the
               case, and some functions for which "format" attributes are
               appropriate may not be detected.

       -Wsuggest-final-types
           Warn about types with virtual methods where code quality would be
           improved if the type were declared with the C++11 "final"
           specifier, or, if possible, declared in an anonymous namespace.
           This allows GCC to more aggressively devirtualize the polymorphic
           calls. This warning is more effective with link time
           optimization, where the information about the class hierarchy
           graph is more complete.

       -Wsuggest-final-methods
           Warn about virtual methods where code quality would be improved
           if the method were declared with the C++11 "final" specifier, or,
           if possible, its type were declared in an anonymous namespace or
           with the "final" specifier.  This warning is more effective with
           link time optimization, where the information about the class
           hierarchy graph is more complete. It is recommended to first
           consider suggestions of -Wsuggest-final-types and then rebuild
           with new annotations.

       -Wsuggest-override
           Warn about overriding virtual functions that are not marked with
           the override keyword.

       -Warray-bounds
       -Warray-bounds=n
           This option is only active when -ftree-vrp is active (default for
           -O2 and above). It warns about subscripts to arrays that are
           always out of bounds. This warning is enabled by -Wall.

           -Warray-bounds=1
               This is the warning level of -Warray-bounds and is enabled by
               -Wall; higher levels are not, and must be explicitly
               requested.

           -Warray-bounds=2
               This warning level also warns about out of bounds access for
               arrays at the end of a struct and for arrays accessed through
               pointers. This warning level may give a larger number of
               false positives and is deactivated by default.

       -Wbool-compare
           Warn about boolean expression compared with an integer value
           different from "true"/"false".  For instance, the following
           comparison is always false:

                   int n = 5;
                   ...
                   if ((n > 1) == 2) { ... }

           This warning is enabled by -Wall.

       -Wduplicated-cond
           Warn about duplicated conditions in an if-else-if chain.  For
           instance, warn for the following code:

                   if (p->q != NULL) { ... }
                   else if (p->q != NULL) { ... }

       -Wframe-address
           Warn when the __builtin_frame_address or __builtin_return_address
           is called with an argument greater than 0.  Such calls may return
           indeterminate values or crash the program.  The warning is
           included in -Wall.

       -Wno-discarded-qualifiers (C and Objective-C only)
           Do not warn if type qualifiers on pointers are being discarded.
           Typically, the compiler warns if a "const char *" variable is
           passed to a function that takes a "char *" parameter.  This
           option can be used to suppress such a warning.

       -Wno-discarded-array-qualifiers (C and Objective-C only)
           Do not warn if type qualifiers on arrays which are pointer
           targets are being discarded. Typically, the compiler warns if a
           "const int (*)[]" variable is passed to a function that takes a
           "int (*)[]" parameter.  This option can be used to suppress such
           a warning.

       -Wno-incompatible-pointer-types (C and Objective-C only)
           Do not warn when there is a conversion between pointers that have
           incompatible types.  This warning is for cases not covered by
           -Wno-pointer-sign, which warns for pointer argument passing or
           assignment with different signedness.

       -Wno-int-conversion (C and Objective-C only)
           Do not warn about incompatible integer to pointer and pointer to
           integer conversions.  This warning is about implicit conversions;
           for explicit conversions the warnings -Wno-int-to-pointer-cast
           and -Wno-pointer-to-int-cast may be used.

       -Wno-div-by-zero
           Do not warn about compile-time integer division by zero.
           Floating-point division by zero is not warned about, as it can be
           a legitimate way of obtaining infinities and NaNs.

       -Wsystem-headers
           Print warning messages for constructs found in system header
           files.  Warnings from system headers are normally suppressed, on
           the assumption that they usually do not indicate real problems
           and would only make the compiler output harder to read.  Using
           this command-line option tells GCC to emit warnings from system
           headers as if they occurred in user code.  However, note that
           using -Wall in conjunction with this option does not warn about
           unknown pragmas in system headers---for that, -Wunknown-pragmas
           must also be used.

       -Wtautological-compare
           Warn if a self-comparison always evaluates to true or false.
           This warning detects various mistakes such as:

                   int i = 1;
                   ...
                   if (i > i) { ... }

           This warning is enabled by -Wall.

       -Wtrampolines
           Warn about trampolines generated for pointers to nested
           functions.  A trampoline is a small piece of data or code that is
           created at run time on the stack when the address of a nested
           function is taken, and is used to call the nested function
           indirectly.  For some targets, it is made up of data only and
           thus requires no special treatment.  But, for most targets, it is
           made up of code and thus requires the stack to be made executable
           in order for the program to work properly.

       -Wfloat-equal
           Warn if floating-point values are used in equality comparisons.

           The idea behind this is that sometimes it is convenient (for the
           programmer) to consider floating-point values as approximations
           to infinitely precise real numbers.  If you are doing this, then
           you need to compute (by analyzing the code, or in some other way)
           the maximum or likely maximum error that the computation
           introduces, and allow for it when performing comparisons (and
           when producing output, but that's a different problem).  In
           particular, instead of testing for equality, you should check to
           see whether the two values have ranges that overlap; and this is
           done with the relational operators, so equality comparisons are
           probably mistaken.

       -Wtraditional (C and Objective-C only)
           Warn about certain constructs that behave differently in
           traditional and ISO C.  Also warn about ISO C constructs that
           have no traditional C equivalent, and/or problematic constructs
           that should be avoided.

           *   Macro parameters that appear within string literals in the
               macro body.  In traditional C macro replacement takes place
               within string literals, but in ISO C it does not.

           *   In traditional C, some preprocessor directives did not exist.
               Traditional preprocessors only considered a line to be a
               directive if the # appeared in column 1 on the line.
               Therefore -Wtraditional warns about directives that
               traditional C understands but ignores because the # does not
               appear as the first character on the line.  It also suggests
               you hide directives like "#pragma" not understood by
               traditional C by indenting them.  Some traditional
               implementations do not recognize "#elif", so this option
               suggests avoiding it altogether.

           *   A function-like macro that appears without arguments.

           *   The unary plus operator.

           *   The U integer constant suffix, or the F or L floating-point
               constant suffixes.  (Traditional C does support the L suffix
               on integer constants.)  Note, these suffixes appear in macros
               defined in the system headers of most modern systems, e.g.
               the _MIN/_MAX macros in "<limits.h>".  Use of these macros in
               user code might normally lead to spurious warnings, however
               GCC's integrated preprocessor has enough context to avoid
               warning in these cases.

           *   A function declared external in one block and then used after
               the end of the block.

           *   A "switch" statement has an operand of type "long".

           *   A non-"static" function declaration follows a "static" one.
               This construct is not accepted by some traditional C
               compilers.

           *   The ISO type of an integer constant has a different width or
               signedness from its traditional type.  This warning is only
               issued if the base of the constant is ten.  I.e. hexadecimal
               or octal values, which typically represent bit patterns, are
               not warned about.

           *   Usage of ISO string concatenation is detected.

           *   Initialization of automatic aggregates.

           *   Identifier conflicts with labels.  Traditional C lacks a
               separate namespace for labels.

           *   Initialization of unions.  If the initializer is zero, the
               warning is omitted.  This is done under the assumption that
               the zero initializer in user code appears conditioned on e.g.
               "__STDC__" to avoid missing initializer warnings and relies
               on default initialization to zero in the traditional C case.

           *   Conversions by prototypes between fixed/floating-point values
               and vice versa.  The absence of these prototypes when
               compiling with traditional C causes serious problems.  This
               is a subset of the possible conversion warnings; for the full
               set use -Wtraditional-conversion.

           *   Use of ISO C style function definitions.  This warning
               intentionally is not issued for prototype declarations or
               variadic functions because these ISO C features appear in
               your code when using libiberty's traditional C compatibility
               macros, "PARAMS" and "VPARAMS".  This warning is also
               bypassed for nested functions because that feature is already
               a GCC extension and thus not relevant to traditional C
               compatibility.

       -Wtraditional-conversion (C and Objective-C only)
           Warn if a prototype causes a type conversion that is different
           from what would happen to the same argument in the absence of a
           prototype.  This includes conversions of fixed point to floating
           and vice versa, and conversions changing the width or signedness
           of a fixed-point argument except when the same as the default
           promotion.

       -Wdeclaration-after-statement (C and Objective-C only)
           Warn when a declaration is found after a statement in a block.
           This construct, known from C++, was introduced with ISO C99 and
           is by default allowed in GCC.  It is not supported by ISO C90.

       -Wundef
           Warn if an undefined identifier is evaluated in an "#if"
           directive.

       -Wno-endif-labels
           Do not warn whenever an "#else" or an "#endif" are followed by
           text.

       -Wshadow
           Warn whenever a local variable or type declaration shadows
           another variable, parameter, type, class member (in C++), or
           instance variable (in Objective-C) or whenever a built-in
           function is shadowed. Note that in C++, the compiler warns if a
           local variable shadows an explicit typedef, but not if it shadows
           a struct/class/enum.

       -Wno-shadow-ivar (Objective-C only)
           Do not warn whenever a local variable shadows an instance
           variable in an Objective-C method.

       -Wlarger-than=len
           Warn whenever an object of larger than len bytes is defined.

       -Wframe-larger-than=len
           Warn if the size of a function frame is larger than len bytes.
           The computation done to determine the stack frame size is
           approximate and not conservative.  The actual requirements may be
           somewhat greater than len even if you do not get a warning.  In
           addition, any space allocated via "alloca", variable-length
           arrays, or related constructs is not included by the compiler
           when determining whether or not to issue a warning.

       -Wno-free-nonheap-object
           Do not warn when attempting to free an object that was not
           allocated on the heap.

       -Wstack-usage=len
           Warn if the stack usage of a function might be larger than len
           bytes.  The computation done to determine the stack usage is
           conservative.  Any space allocated via "alloca", variable-length
           arrays, or related constructs is included by the compiler when
           determining whether or not to issue a warning.

           The message is in keeping with the output of -fstack-usage.

           *   If the stack usage is fully static but exceeds the specified
               amount, it's:

                         warning: stack usage is 1120 bytes

           *   If the stack usage is (partly) dynamic but bounded, it's:

                         warning: stack usage might be 1648 bytes

           *   If the stack usage is (partly) dynamic and not bounded, it's:

                         warning: stack usage might be unbounded

       -Wunsafe-loop-optimizations
           Warn if the loop cannot be optimized because the compiler cannot
           assume anything on the bounds of the loop indices.  With
           -funsafe-loop-optimizations warn if the compiler makes such
           assumptions.

       -Wno-pedantic-ms-format (MinGW targets only)
           When used in combination with -Wformat and -pedantic without GNU
           extensions, this option disables the warnings about non-ISO
           "printf" / "scanf" format width specifiers "I32", "I64", and "I"
           used on Windows targets, which depend on the MS runtime.

       -Wplacement-new
       -Wplacement-new=n
           Warn about placement new expressions with undefined behavior,
           such as constructing an object in a buffer that is smaller than
           the type of the object.  For example, the placement new
           expression below is diagnosed because it attempts to construct an
           array of 64 integers in a buffer only 64 bytes large.

                   char buf [64];
                   new (buf) int[64];

           This warning is enabled by default.

           -Wplacement-new=1
               This is the default warning level of -Wplacement-new.  At
               this level the warning is not issued for some strictly
               undefined constructs that GCC allows as extensions for
               compatibility with legacy code.  For example, the following
               "new" expression is not diagnosed at this level even though
               it has undefined behavior according to the C++ standard
               because it writes past the end of the one-element array.

                       struct S { int n, a[1]; };
                       S *s = (S *)malloc (sizeof *s + 31 * sizeof s->a[0]);
                       new (s->a)int [32]();

           -Wplacement-new=2
               At this level, in addition to diagnosing all the same
               constructs as at level 1, a diagnostic is also issued for
               placement new expressions that construct an object in the
               last member of structure whose type is an array of a single
               element and whose size is less than the size of the object
               being constructed.  While the previous example would be
               diagnosed, the following construct makes use of the flexible
               member array extension to avoid the warning at level 2.

                       struct S { int n, a[]; };
                       S *s = (S *)malloc (sizeof *s + 32 * sizeof s->a[0]);
                       new (s->a)int [32]();

       -Wpointer-arith
           Warn about anything that depends on the "size of" a function type
           or of "void".  GNU C assigns these types a size of 1, for
           convenience in calculations with "void *" pointers and pointers
           to functions.  In C++, warn also when an arithmetic operation
           involves "NULL".  This warning is also enabled by -Wpedantic.

       -Wtype-limits
           Warn if a comparison is always true or always false due to the
           limited range of the data type, but do not warn for constant
           expressions.  For example, warn if an unsigned variable is
           compared against zero with "<" or ">=".  This warning is also
           enabled by -Wextra.

       -Wbad-function-cast (C and Objective-C only)
           Warn when a function call is cast to a non-matching type.  For
           example, warn if a call to a function returning an integer type
           is cast to a pointer type.

       -Wc90-c99-compat (C and Objective-C only)
           Warn about features not present in ISO C90, but present in ISO
           C99.  For instance, warn about use of variable length arrays,
           "long long" type, "bool" type, compound literals, designated
           initializers, and so on.  This option is independent of the
           standards mode.  Warnings are disabled in the expression that
           follows "__extension__".

       -Wc99-c11-compat (C and Objective-C only)
           Warn about features not present in ISO C99, but present in ISO
           C11.  For instance, warn about use of anonymous structures and
           unions, "_Atomic" type qualifier, "_Thread_local" storage-class
           specifier, "_Alignas" specifier, "Alignof" operator, "_Generic"
           keyword, and so on.  This option is independent of the standards
           mode.  Warnings are disabled in the expression that follows
           "__extension__".

       -Wc++-compat (C and Objective-C only)
           Warn about ISO C constructs that are outside of the common subset
           of ISO C and ISO C++, e.g. request for implicit conversion from
           "void *" to a pointer to non-"void" type.

       -Wc++11-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++
           1998 and ISO C++ 2011, e.g., identifiers in ISO C++ 1998 that are
           keywords in ISO C++ 2011.  This warning turns on -Wnarrowing and
           is enabled by -Wall.

       -Wc++14-compat (C++ and Objective-C++ only)
           Warn about C++ constructs whose meaning differs between ISO C++
           2011 and ISO C++ 2014.  This warning is enabled by -Wall.

       -Wcast-qual
           Warn whenever a pointer is cast so as to remove a type qualifier
           from the target type.  For example, warn if a "const char *" is
           cast to an ordinary "char *".

           Also warn when making a cast that introduces a type qualifier in
           an unsafe way.  For example, casting "char **" to "const char **"
           is unsafe, as in this example:

                     /* p is char ** value.  */
                     const char **q = (const char **) p;
                     /* Assignment of readonly string to const char * is OK.  */
                     *q = "string";
                     /* Now char** pointer points to read-only memory.  */
                     **p = 'b';

       -Wcast-align
           Warn whenever a pointer is cast such that the required alignment
           of the target is increased.  For example, warn if a "char *" is
           cast to an "int *" on machines where integers can only be
           accessed at two- or four-byte boundaries.

       -Wwrite-strings
           When compiling C, give string constants the type "const
           char[length]" so that copying the address of one into a
           non-"const" "char *" pointer produces a warning.  These warnings
           help you find at compile time code that can try to write into a
           string constant, but only if you have been very careful about
           using "const" in declarations and prototypes.  Otherwise, it is
           just a nuisance. This is why we did not make -Wall request these
           warnings.

           When compiling C++, warn about the deprecated conversion from
           string literals to "char *".  This warning is enabled by default
           for C++ programs.

       -Wclobbered
           Warn for variables that might be changed by "longjmp" or "vfork".
           This warning is also enabled by -Wextra.

       -Wconditionally-supported (C++ and Objective-C++ only)
           Warn for conditionally-supported (C++11 [intro.defs]) constructs.

       -Wconversion
           Warn for implicit conversions that may alter a value. This
           includes conversions between real and integer, like "abs (x)"
           when "x" is "double"; conversions between signed and unsigned,
           like "unsigned ui = -1"; and conversions to smaller types, like
           "sqrtf (M_PI)". Do not warn for explicit casts like "abs ((int)
           x)" and "ui = (unsigned) -1", or if the value is not changed by
           the conversion like in "abs (2.0)".  Warnings about conversions
           between signed and unsigned integers can be disabled by using
           -Wno-sign-conversion.

           For C++, also warn for confusing overload resolution for user-
           defined conversions; and conversions that never use a type
           conversion operator: conversions to "void", the same type, a base
           class or a reference to them. Warnings about conversions between
           signed and unsigned integers are disabled by default in C++
           unless -Wsign-conversion is explicitly enabled.

       -Wno-conversion-null (C++ and Objective-C++ only)
           Do not warn for conversions between "NULL" and non-pointer types.
           -Wconversion-null is enabled by default.

       -Wzero-as-null-pointer-constant (C++ and Objective-C++ only)
           Warn when a literal 0 is used as null pointer constant.  This can
           be useful to facilitate the conversion to "nullptr" in C++11.

       -Wsubobject-linkage (C++ and Objective-C++ only)
           Warn if a class type has a base or a field whose type uses the
           anonymous namespace or depends on a type with no linkage.  If a
           type A depends on a type B with no or internal linkage, defining
           it in multiple translation units would be an ODR violation
           because the meaning of B is different in each translation unit.
           If A only appears in a single translation unit, the best way to
           silence the warning is to give it internal linkage by putting it
           in an anonymous namespace as well.  The compiler doesn't give
           this warning for types defined in the main .C file, as those are
           unlikely to have multiple definitions.  -Wsubobject-linkage is
           enabled by default.

       -Wdate-time
           Warn when macros "__TIME__", "__DATE__" or "__TIMESTAMP__" are
           encountered as they might prevent bit-wise-identical reproducible
           compilations.

       -Wdelete-incomplete (C++ and Objective-C++ only)
           Warn when deleting a pointer to incomplete type, which may cause
           undefined behavior at runtime.  This warning is enabled by
           default.

       -Wuseless-cast (C++ and Objective-C++ only)
           Warn when an expression is casted to its own type.

       -Wempty-body
           Warn if an empty body occurs in an "if", "else" or "do while"
           statement.  This warning is also enabled by -Wextra.

       -Wenum-compare
           Warn about a comparison between values of different enumerated
           types.  In C++ enumeral mismatches in conditional expressions are
           also diagnosed and the warning is enabled by default.  In C this
           warning is enabled by -Wall.

       -Wjump-misses-init (C, Objective-C only)
           Warn if a "goto" statement or a "switch" statement jumps forward
           across the initialization of a variable, or jumps backward to a
           label after the variable has been initialized.  This only warns
           about variables that are initialized when they are declared.
           This warning is only supported for C and Objective-C; in C++ this
           sort of branch is an error in any case.

           -Wjump-misses-init is included in -Wc++-compat.  It can be
           disabled with the -Wno-jump-misses-init option.

       -Wsign-compare
           Warn when a comparison between signed and unsigned values could
           produce an incorrect result when the signed value is converted to
           unsigned.  In C++, this warning is also enabled by -Wall.  In C,
           it is also enabled by -Wextra.

       -Wsign-conversion
           Warn for implicit conversions that may change the sign of an
           integer value, like assigning a signed integer expression to an
           unsigned integer variable. An explicit cast silences the warning.
           In C, this option is enabled also by -Wconversion.

       -Wfloat-conversion
           Warn for implicit conversions that reduce the precision of a real
           value.  This includes conversions from real to integer, and from
           higher precision real to lower precision real values.  This
           option is also enabled by -Wconversion.

       -Wno-scalar-storage-order
           Do not warn on suspicious constructs involving reverse scalar
           storage order.

       -Wsized-deallocation (C++ and Objective-C++ only)
           Warn about a definition of an unsized deallocation function

                   void operator delete (void *) noexcept;
                   void operator delete[] (void *) noexcept;

           without a definition of the corresponding sized deallocation
           function

                   void operator delete (void *, std::size_t) noexcept;
                   void operator delete[] (void *, std::size_t) noexcept;

           or vice versa.  Enabled by -Wextra along with
           -fsized-deallocation.

       -Wsizeof-pointer-memaccess
           Warn for suspicious length parameters to certain string and
           memory built-in functions if the argument uses "sizeof".  This
           warning warns e.g.  about "memset (ptr, 0, sizeof (ptr));" if
           "ptr" is not an array, but a pointer, and suggests a possible
           fix, or about "memcpy (&foo, ptr, sizeof (&foo));".  This warning
           is enabled by -Wall.

       -Wsizeof-array-argument
           Warn when the "sizeof" operator is applied to a parameter that is
           declared as an array in a function definition.  This warning is
           enabled by default for C and C++ programs.

       -Wmemset-transposed-args
           Warn for suspicious calls to the "memset" built-in function, if
           the second argument is not zero and the third argument is zero.
           This warns e.g.@ about "memset (buf, sizeof buf, 0)" where most
           probably "memset (buf, 0, sizeof buf)" was meant instead.  The
           diagnostics is only emitted if the third argument is literal
           zero.  If it is some expression that is folded to zero, a cast of
           zero to some type, etc., it is far less likely that the user has
           mistakenly exchanged the arguments and no warning is emitted.
           This warning is enabled by -Wall.

       -Waddress
           Warn about suspicious uses of memory addresses. These include
           using the address of a function in a conditional expression, such
           as "void func(void); if (func)", and comparisons against the
           memory address of a string literal, such as "if (x == "abc")".
           Such uses typically indicate a programmer error: the address of a
           function always evaluates to true, so their use in a conditional
           usually indicate that the programmer forgot the parentheses in a
           function call; and comparisons against string literals result in
           unspecified behavior and are not portable in C, so they usually
           indicate that the programmer intended to use "strcmp".  This
           warning is enabled by -Wall.

       -Wlogical-op
           Warn about suspicious uses of logical operators in expressions.
           This includes using logical operators in contexts where a bit-
           wise operator is likely to be expected.  Also warns when the
           operands of a logical operator are the same:

                   extern int a;
                   if (a < 0 && a < 0) { ... }

       -Wlogical-not-parentheses
           Warn about logical not used on the left hand side operand of a
           comparison.  This option does not warn if the RHS operand is of a
           boolean type.  Its purpose is to detect suspicious code like the
           following:

                   int a;
                   ...
                   if (!a > 1) { ... }

           It is possible to suppress the warning by wrapping the LHS into
           parentheses:

                   if ((!a) > 1) { ... }

           This warning is enabled by -Wall.

       -Waggregate-return
           Warn if any functions that return structures or unions are
           defined or called.  (In languages where you can return an array,
           this also elicits a warning.)

       -Wno-aggressive-loop-optimizations
           Warn if in a loop with constant number of iterations the compiler
           detects undefined behavior in some statement during one or more
           of the iterations.

       -Wno-attributes
           Do not warn if an unexpected "__attribute__" is used, such as
           unrecognized attributes, function attributes applied to
           variables, etc.  This does not stop errors for incorrect use of
           supported attributes.

       -Wno-builtin-macro-redefined
           Do not warn if certain built-in macros are redefined.  This
           suppresses warnings for redefinition of "__TIMESTAMP__",
           "__TIME__", "__DATE__", "__FILE__", and "__BASE_FILE__".

       -Wstrict-prototypes (C and Objective-C only)
           Warn if a function is declared or defined without specifying the
           argument types.  (An old-style function definition is permitted
           without a warning if preceded by a declaration that specifies the
           argument types.)

       -Wold-style-declaration (C and Objective-C only)
           Warn for obsolescent usages, according to the C Standard, in a
           declaration. For example, warn if storage-class specifiers like
           "static" are not the first things in a declaration.  This warning
           is also enabled by -Wextra.

       -Wold-style-definition (C and Objective-C only)
           Warn if an old-style function definition is used.  A warning is
           given even if there is a previous prototype.

       -Wmissing-parameter-type (C and Objective-C only)
           A function parameter is declared without a type specifier in
           K&R-style functions:

                   void foo(bar) { }

           This warning is also enabled by -Wextra.

       -Wmissing-prototypes (C and Objective-C only)
           Warn if a global function is defined without a previous prototype
           declaration.  This warning is issued even if the definition
           itself provides a prototype.  Use this option to detect global
           functions that do not have a matching prototype declaration in a
           header file.  This option is not valid for C++ because all
           function declarations provide prototypes and a non-matching
           declaration declares an overload rather than conflict with an
           earlier declaration.  Use -Wmissing-declarations to detect
           missing declarations in C++.

       -Wmissing-declarations
           Warn if a global function is defined without a previous
           declaration.  Do so even if the definition itself provides a
           prototype.  Use this option to detect global functions that are
           not declared in header files.  In C, no warnings are issued for
           functions with previous non-prototype declarations; use
           -Wmissing-prototypes to detect missing prototypes.  In C++, no
           warnings are issued for function templates, or for inline
           functions, or for functions in anonymous namespaces.

       -Wmissing-field-initializers
           Warn if a structure's initializer has some fields missing.  For
           example, the following code causes such a warning, because "x.h"
           is implicitly zero:

                   struct s { int f, g, h; };
                   struct s x = { 3, 4 };

           This option does not warn about designated initializers, so the
           following modification does not trigger a warning:

                   struct s { int f, g, h; };
                   struct s x = { .f = 3, .g = 4 };

           In C++ this option does not warn either about the empty { }
           initializer, for example:

                   struct s { int f, g, h; };
                   s x = { };

           This warning is included in -Wextra.  To get other -Wextra
           warnings without this one, use -Wextra
           -Wno-missing-field-initializers.

       -Wno-multichar
           Do not warn if a multicharacter constant ('FOOF') is used.
           Usually they indicate a typo in the user's code, as they have
           implementation-defined values, and should not be used in portable
           code.

       -Wnormalized[=<none|id|nfc|nfkc>]
           In ISO C and ISO C++, two identifiers are different if they are
           different sequences of characters.  However, sometimes when
           characters outside the basic ASCII character set are used, you
           can have two different character sequences that look the same.
           To avoid confusion, the ISO 10646 standard sets out some
           normalization rules which when applied ensure that two sequences
           that look the same are turned into the same sequence.  GCC can
           warn you if you are using identifiers that have not been
           normalized; this option controls that warning.

           There are four levels of warning supported by GCC.  The default
           is -Wnormalized=nfc, which warns about any identifier that is not
           in the ISO 10646 "C" normalized form, NFC.  NFC is the
           recommended form for most uses.  It is equivalent to
           -Wnormalized.

           Unfortunately, there are some characters allowed in identifiers
           by ISO C and ISO C++ that, when turned into NFC, are not allowed
           in identifiers.  That is, there's no way to use these symbols in
           portable ISO C or C++ and have all your identifiers in NFC.
           -Wnormalized=id suppresses the warning for these characters.  It
           is hoped that future versions of the standards involved will
           correct this, which is why this option is not the default.

           You can switch the warning off for all characters by writing
           -Wnormalized=none or -Wno-normalized.  You should only do this if
           you are using some other normalization scheme (like "D"), because
           otherwise you can easily create bugs that are literally
           impossible to see.

           Some characters in ISO 10646 have distinct meanings but look
           identical in some fonts or display methodologies, especially once
           formatting has been applied.  For instance "\u207F", "SUPERSCRIPT
           LATIN SMALL LETTER N", displays just like a regular "n" that has
           been placed in a superscript.  ISO 10646 defines the NFKC
           normalization scheme to convert all these into a standard form as
           well, and GCC warns if your code is not in NFKC if you use
           -Wnormalized=nfkc.  This warning is comparable to warning about
           every identifier that contains the letter O because it might be
           confused with the digit 0, and so is not the default, but may be
           useful as a local coding convention if the programming
           environment cannot be fixed to display these characters
           distinctly.

       -Wno-deprecated
           Do not warn about usage of deprecated features.

       -Wno-deprecated-declarations
           Do not warn about uses of functions, variables, and types marked
           as deprecated by using the "deprecated" attribute.

       -Wno-overflow
           Do not warn about compile-time overflow in constant expressions.

       -Wno-odr
           Warn about One Definition Rule violations during link-time
           optimization.  Requires -flto-odr-type-merging to be enabled.
           Enabled by default.

       -Wopenmp-simd
           Warn if the vectorizer cost model overrides the OpenMP or the
           Cilk Plus simd directive set by user.  The
           -fsimd-cost-model=unlimited option can be used to relax the cost
           model.

       -Woverride-init (C and Objective-C only)
           Warn if an initialized field without side effects is overridden
           when using designated initializers.

           This warning is included in -Wextra.  To get other -Wextra
           warnings without this one, use -Wextra -Wno-override-init.

       -Woverride-init-side-effects (C and Objective-C only)
           Warn if an initialized field with side effects is overridden when
           using designated initializers.  This warning is enabled by
           default.

       -Wpacked
           Warn if a structure is given the packed attribute, but the packed
           attribute has no effect on the layout or size of the structure.
           Such structures may be mis-aligned for little benefit.  For
           instance, in this code, the variable "f.x" in "struct bar" is
           misaligned even though "struct bar" does not itself have the
           packed attribute:

                   struct foo {
                     int x;
                     char a, b, c, d;
                   } __attribute__((packed));
                   struct bar {
                     char z;
                     struct foo f;
                   };

       -Wpacked-bitfield-compat
           The 4.1, 4.2 and 4.3 series of GCC ignore the "packed" attribute
           on bit-fields of type "char".  This has been fixed in GCC 4.4 but
           the change can lead to differences in the structure layout.  GCC
           informs you when the offset of such a field has changed in GCC
           4.4.  For example there is no longer a 4-bit padding between
           field "a" and "b" in this structure:

                   struct foo
                   {
                     char a:4;
                     char b:8;
                   } __attribute__ ((packed));

           This warning is enabled by default.  Use
           -Wno-packed-bitfield-compat to disable this warning.

       -Wpadded
           Warn if padding is included in a structure, either to align an
           element of the structure or to align the whole structure.
           Sometimes when this happens it is possible to rearrange the
           fields of the structure to reduce the padding and so make the
           structure smaller.

       -Wredundant-decls
           Warn if anything is declared more than once in the same scope,
           even in cases where multiple declaration is valid and changes
           nothing.

       -Wnested-externs (C and Objective-C only)
           Warn if an "extern" declaration is encountered within a function.

       -Wno-inherited-variadic-ctor
           Suppress warnings about use of C++11 inheriting constructors when
           the base class inherited from has a C variadic constructor; the
           warning is on by default because the ellipsis is not inherited.

       -Winline
           Warn if a function that is declared as inline cannot be inlined.
           Even with this option, the compiler does not warn about failures
           to inline functions declared in system headers.

           The compiler uses a variety of heuristics to determine whether or
           not to inline a function.  For example, the compiler takes into
           account the size of the function being inlined and the amount of
           inlining that has already been done in the current function.
           Therefore, seemingly insignificant changes in the source program
           can cause the warnings produced by -Winline to appear or
           disappear.

       -Wno-invalid-offsetof (C++ and Objective-C++ only)
           Suppress warnings from applying the "offsetof" macro to a non-POD
           type.  According to the 2014 ISO C++ standard, applying
           "offsetof" to a non-standard-layout type is undefined.  In
           existing C++ implementations, however, "offsetof" typically gives
           meaningful results.  This flag is for users who are aware that
           they are writing nonportable code and who have deliberately
           chosen to ignore the warning about it.

           The restrictions on "offsetof" may be relaxed in a future version
           of the C++ standard.

       -Wno-int-to-pointer-cast
           Suppress warnings from casts to pointer type of an integer of a
           different size. In C++, casting to a pointer type of smaller size
           is an error. Wint-to-pointer-cast is enabled by default.

       -Wno-pointer-to-int-cast (C and Objective-C only)
           Suppress warnings from casts from a pointer to an integer type of
           a different size.

       -Winvalid-pch
           Warn if a precompiled header is found in the search path but
           can't be used.

       -Wlong-long
           Warn if "long long" type is used.  This is enabled by either
           -Wpedantic or -Wtraditional in ISO C90 and C++98 modes.  To
           inhibit the warning messages, use -Wno-long-long.

       -Wvariadic-macros
           Warn if variadic macros are used in ISO C90 mode, or if the GNU
           alternate syntax is used in ISO C99 mode.  This is enabled by
           either -Wpedantic or -Wtraditional.  To inhibit the warning
           messages, use -Wno-variadic-macros.

       -Wvarargs
           Warn upon questionable usage of the macros used to handle
           variable arguments like "va_start".  This is default.  To inhibit
           the warning messages, use -Wno-varargs.

       -Wvector-operation-performance
           Warn if vector operation is not implemented via SIMD capabilities
           of the architecture.  Mainly useful for the performance tuning.
           Vector operation can be implemented "piecewise", which means that
           the scalar operation is performed on every vector element; "in
           parallel", which means that the vector operation is implemented
           using scalars of wider type, which normally is more performance
           efficient; and "as a single scalar", which means that vector fits
           into a scalar type.

       -Wno-virtual-move-assign
           Suppress warnings about inheriting from a virtual base with a
           non-trivial C++11 move assignment operator.  This is dangerous
           because if the virtual base is reachable along more than one
           path, it is moved multiple times, which can mean both objects end
           up in the moved-from state.  If the move assignment operator is
           written to avoid moving from a moved-from object, this warning
           can be disabled.

       -Wvla
           Warn if variable length array is used in the code.  -Wno-vla
           prevents the -Wpedantic warning of the variable length array.

       -Wvolatile-register-var
           Warn if a register variable is declared volatile.  The volatile
           modifier does not inhibit all optimizations that may eliminate
           reads and/or writes to register variables.  This warning is
           enabled by -Wall.

       -Wdisabled-optimization
           Warn if a requested optimization pass is disabled.  This warning
           does not generally indicate that there is anything wrong with
           your code; it merely indicates that GCC's optimizers are unable
           to handle the code effectively.  Often, the problem is that your
           code is too big or too complex; GCC refuses to optimize programs
           when the optimization itself is likely to take inordinate amounts
           of time.

       -Wpointer-sign (C and Objective-C only)
           Warn for pointer argument passing or assignment with different
           signedness.  This option is only supported for C and Objective-C.
           It is implied by -Wall and by -Wpedantic, which can be disabled
           with -Wno-pointer-sign.

       -Wstack-protector
           This option is only active when -fstack-protector is active.  It
           warns about functions that are not protected against stack
           smashing.

       -Woverlength-strings
           Warn about string constants that are longer than the "minimum
           maximum" length specified in the C standard.  Modern compilers
           generally allow string constants that are much longer than the
           standard's minimum limit, but very portable programs should avoid
           using longer strings.

           The limit applies after string constant concatenation, and does
           not count the trailing NUL.  In C90, the limit was 509
           characters; in C99, it was raised to 4095.  C++98 does not
           specify a normative minimum maximum, so we do not diagnose
           overlength strings in C++.

           This option is implied by -Wpedantic, and can be disabled with
           -Wno-overlength-strings.

       -Wunsuffixed-float-constants (C and Objective-C only)
           Issue a warning for any floating constant that does not have a
           suffix.  When used together with -Wsystem-headers it warns about
           such constants in system header files.  This can be useful when
           preparing code to use with the "FLOAT_CONST_DECIMAL64" pragma
           from the decimal floating-point extension to C99.

       -Wno-designated-init (C and Objective-C only)
           Suppress warnings when a positional initializer is used to
           initialize a structure that has been marked with the
           "designated_init" attribute.

       -Whsa
           Issue a warning when HSAIL cannot be emitted for the compiled
           function or OpenMP construct.

       Options for Debugging Your Program

       To tell GCC to emit extra information for use by a debugger, in
       almost all cases you need only to add -g to your other options.

       GCC allows you to use -g with -O.  The shortcuts taken by optimized
       code may occasionally be surprising: some variables you declared may
       not exist at all; flow of control may briefly move where you did not
       expect it; some statements may not be executed because they compute
       constant results or their values are already at hand; some statements
       may execute in different places because they have been moved out of
       loops.  Nevertheless it is possible to debug optimized output.  This
       makes it reasonable to use the optimizer for programs that might have
       bugs.

       If you are not using some other optimization option, consider using
       -Og with -g.  With no -O option at all, some compiler passes that
       collect information useful for debugging do not run at all, so that
       -Og may result in a better debugging experience.

       -g  Produce debugging information in the operating system's native
           format (stabs, COFF, XCOFF, or DWARF).  GDB can work with this
           debugging information.

           On most systems that use stabs format, -g enables use of extra
           debugging information that only GDB can use; this extra
           information makes debugging work better in GDB but probably makes
           other debuggers crash or refuse to read the program.  If you want
           to control for certain whether to generate the extra information,
           use -gstabs+, -gstabs, -gxcoff+, -gxcoff, or -gvms (see below).

       -ggdb
           Produce debugging information for use by GDB.  This means to use
           the most expressive format available (DWARF, stabs, or the native
           format if neither of those are supported), including GDB
           extensions if at all possible.

       -gdwarf
       -gdwarf-version
           Produce debugging information in DWARF format (if that is
           supported).  The value of version may be either 2, 3, 4 or 5; the
           default version for most targets is 4.  DWARF Version 5 is only
           experimental.

           Note that with DWARF Version 2, some ports require and always use
           some non-conflicting DWARF 3 extensions in the unwind tables.

           Version 4 may require GDB 7.0 and -fvar-tracking-assignments for
           maximum benefit.

           GCC no longer supports DWARF Version 1, which is substantially
           different than Version 2 and later.  For historical reasons, some
           other DWARF-related options (including -feliminate-dwarf2-dups
           and -fno-dwarf2-cfi-asm) retain a reference to DWARF Version 2 in
           their names, but apply to all currently-supported versions of
           DWARF.

       -gstabs
           Produce debugging information in stabs format (if that is
           supported), without GDB extensions.  This is the format used by
           DBX on most BSD systems.  On MIPS, Alpha and System V Release 4
           systems this option produces stabs debugging output that is not
           understood by DBX or SDB.  On System V Release 4 systems this
           option requires the GNU assembler.

       -gstabs+
           Produce debugging information in stabs format (if that is
           supported), using GNU extensions understood only by the GNU
           debugger (GDB).  The use of these extensions is likely to make
           other debuggers crash or refuse to read the program.

       -gcoff
           Produce debugging information in COFF format (if that is
           supported).  This is the format used by SDB on most System V
           systems prior to System V Release 4.

       -gxcoff
           Produce debugging information in XCOFF format (if that is
           supported).  This is the format used by the DBX debugger on IBM
           RS/6000 systems.

       -gxcoff+
           Produce debugging information in XCOFF format (if that is
           supported), using GNU extensions understood only by the GNU
           debugger (GDB).  The use of these extensions is likely to make
           other debuggers crash or refuse to read the program, and may
           cause assemblers other than the GNU assembler (GAS) to fail with
           an error.

       -gvms
           Produce debugging information in Alpha/VMS debug format (if that
           is supported).  This is the format used by DEBUG on Alpha/VMS
           systems.

       -glevel
       -ggdblevel
       -gstabslevel
       -gcofflevel
       -gxcofflevel
       -gvmslevel
           Request debugging information and also use level to specify how
           much information.  The default level is 2.

           Level 0 produces no debug information at all.  Thus, -g0 negates
           -g.

           Level 1 produces minimal information, enough for making
           backtraces in parts of the program that you don't plan to debug.
           This includes descriptions of functions and external variables,
           and line number tables, but no information about local variables.

           Level 3 includes extra information, such as all the macro
           definitions present in the program.  Some debuggers support macro
           expansion when you use -g3.

           -gdwarf does not accept a concatenated debug level, to avoid
           confusion with -gdwarf-level.  Instead use an additional -glevel
           option to change the debug level for DWARF.

       -feliminate-unused-debug-symbols
           Produce debugging information in stabs format (if that is
           supported), for only symbols that are actually used.

       -femit-class-debug-always
           Instead of emitting debugging information for a C++ class in only
           one object file, emit it in all object files using the class.
           This option should be used only with debuggers that are unable to
           handle the way GCC normally emits debugging information for
           classes because using this option increases the size of debugging
           information by as much as a factor of two.

       -fno-merge-debug-strings
           Direct the linker to not merge together strings in the debugging
           information that are identical in different object files.
           Merging is not supported by all assemblers or linkers.  Merging
           decreases the size of the debug information in the output file at
           the cost of increasing link processing time.  Merging is enabled
           by default.

       -fdebug-prefix-map=old=new
           When compiling files in directory old, record debugging
           information describing them as in new instead.

       -fvar-tracking
           Run variable tracking pass.  It computes where variables are
           stored at each position in code.  Better debugging information is
           then generated (if the debugging information format supports this
           information).

           It is enabled by default when compiling with optimization (-Os,
           -O, -O2, ...), debugging information (-g) and the debug info
           format supports it.

       -fvar-tracking-assignments
           Annotate assignments to user variables early in the compilation
           and attempt to carry the annotations over throughout the
           compilation all the way to the end, in an attempt to improve
           debug information while optimizing.  Use of -gdwarf-4 is
           recommended along with it.

           It can be enabled even if var-tracking is disabled, in which case
           annotations are created and maintained, but discarded at the end.
           By default, this flag is enabled together with -fvar-tracking,
           except when selective scheduling is enabled.

       -gsplit-dwarf
           Separate as much DWARF debugging information as possible into a
           separate output file with the extension .dwo.  This option allows
           the build system to avoid linking files with debug information.
           To be useful, this option requires a debugger capable of reading
           .dwo files.

       -gpubnames
           Generate DWARF ".debug_pubnames" and ".debug_pubtypes" sections.

       -ggnu-pubnames
           Generate ".debug_pubnames" and ".debug_pubtypes" sections in a
           format suitable for conversion into a GDB index.  This option is
           only useful with a linker that can produce GDB index version 7.

       -fdebug-types-section
           When using DWARF Version 4 or higher, type DIEs can be put into
           their own ".debug_types" section instead of making them part of
           the ".debug_info" section.  It is more efficient to put them in a
           separate comdat sections since the linker can then remove
           duplicates.  But not all DWARF consumers support ".debug_types"
           sections yet and on some objects ".debug_types" produces larger
           instead of smaller debugging information.

       -grecord-gcc-switches
       -gno-record-gcc-switches
           This switch causes the command-line options used to invoke the
           compiler that may affect code generation to be appended to the
           DW_AT_producer attribute in DWARF debugging information.  The
           options are concatenated with spaces separating them from each
           other and from the compiler version.  It is enabled by default.
           See also -frecord-gcc-switches for another way of storing
           compiler options into the object file.

       -gstrict-dwarf
           Disallow using extensions of later DWARF standard version than
           selected with -gdwarf-version.  On most targets using non-
           conflicting DWARF extensions from later standard versions is
           allowed.

       -gno-strict-dwarf
           Allow using extensions of later DWARF standard version than
           selected with -gdwarf-version.

       -gz[=type]
           Produce compressed debug sections in DWARF format, if that is
           supported.  If type is not given, the default type depends on the
           capabilities of the assembler and linker used.  type may be one
           of none (don't compress debug sections), zlib (use zlib
           compression in ELF gABI format), or zlib-gnu (use zlib
           compression in traditional GNU format).  If the linker doesn't
           support writing compressed debug sections, the option is
           rejected.  Otherwise, if the assembler does not support them, -gz
           is silently ignored when producing object files.

       -feliminate-dwarf2-dups
           Compress DWARF debugging information by eliminating duplicated
           information about each symbol.  This option only makes sense when
           generating DWARF debugging information.

       -femit-struct-debug-baseonly
           Emit debug information for struct-like types only when the base
           name of the compilation source file matches the base name of file
           in which the struct is defined.

           This option substantially reduces the size of debugging
           information, but at significant potential loss in type
           information to the debugger.  See -femit-struct-debug-reduced for
           a less aggressive option.  See -femit-struct-debug-detailed for
           more detailed control.

           This option works only with DWARF debug output.

       -femit-struct-debug-reduced
           Emit debug information for struct-like types only when the base
           name of the compilation source file matches the base name of file
           in which the type is defined, unless the struct is a template or
           defined in a system header.

           This option significantly reduces the size of debugging
           information, with some potential loss in type information to the
           debugger.  See -femit-struct-debug-baseonly for a more aggressive
           option.  See -femit-struct-debug-detailed for more detailed
           control.

           This option works only with DWARF debug output.

       -femit-struct-debug-detailed[=spec-list]
           Specify the struct-like types for which the compiler generates
           debug information.  The intent is to reduce duplicate struct
           debug information between different object files within the same
           program.

           This option is a detailed version of -femit-struct-debug-reduced
           and -femit-struct-debug-baseonly, which serves for most needs.

           A specification has the
           syntax[dir:|ind:][ord:|gen:](any|sys|base|none)

           The optional first word limits the specification to structs that
           are used directly (dir:) or used indirectly (ind:).  A struct
           type is used directly when it is the type of a variable, member.
           Indirect uses arise through pointers to structs.  That is, when
           use of an incomplete struct is valid, the use is indirect.  An
           example is struct one direct; struct two * indirect;.

           The optional second word limits the specification to ordinary
           structs (ord:) or generic structs (gen:).  Generic structs are a
           bit complicated to explain.  For C++, these are non-explicit
           specializations of template classes, or non-template classes
           within the above.  Other programming languages have generics, but
           -femit-struct-debug-detailed does not yet implement them.

           The third word specifies the source files for those structs for
           which the compiler should emit debug information.  The values
           none and any have the normal meaning.  The value base means that
           the base of name of the file in which the type declaration
           appears must match the base of the name of the main compilation
           file.  In practice, this means that when compiling foo.c, debug
           information is generated for types declared in that file and
           foo.h, but not other header files.  The value sys means those
           types satisfying base or declared in system or compiler headers.

           You may need to experiment to determine the best settings for
           your application.

           The default is -femit-struct-debug-detailed=all.

           This option works only with DWARF debug output.

       -fno-dwarf2-cfi-asm
           Emit DWARF unwind info as compiler generated ".eh_frame" section
           instead of using GAS ".cfi_*" directives.

       -fno-eliminate-unused-debug-types
           Normally, when producing DWARF output, GCC avoids producing debug
           symbol output for types that are nowhere used in the source file
           being compiled.  Sometimes it is useful to have GCC emit
           debugging information for all types declared in a compilation
           unit, regardless of whether or not they are actually used in that
           compilation unit, for example if, in the debugger, you want to
           cast a value to a type that is not actually used in your program
           (but is declared).  More often, however, this results in a
           significant amount of wasted space.

       Options That Control Optimization

       These options control various sorts of optimizations.

       Without any optimization option, the compiler's goal is to reduce the
       cost of compilation and to make debugging produce the expected
       results.  Statements are independent: if you stop the program with a
       breakpoint between statements, you can then assign a new value to any
       variable or change the program counter to any other statement in the
       function and get exactly the results you expect from the source code.

       Turning on optimization flags makes the compiler attempt to improve
       the performance and/or code size at the expense of compilation time
       and possibly the ability to debug the program.

       The compiler performs optimization based on the knowledge it has of
       the program.  Compiling multiple files at once to a single output
       file mode allows the compiler to use information gained from all of
       the files when compiling each of them.

       Not all optimizations are controlled directly by a flag.  Only
       optimizations that have a flag are listed in this section.

       Most optimizations are only enabled if an -O level is set on the
       command line.  Otherwise they are disabled, even if individual
       optimization flags are specified.

       Depending on the target and how GCC was configured, a slightly
       different set of optimizations may be enabled at each -O level than
       those listed here.  You can invoke GCC with -Q --help=optimizers to
       find out the exact set of optimizations that are enabled at each
       level.

       -O
       -O1 Optimize.  Optimizing compilation takes somewhat more time, and a
           lot more memory for a large function.

           With -O, the compiler tries to reduce code size and execution
           time, without performing any optimizations that take a great deal
           of compilation time.

           -O turns on the following optimization flags:

           -fauto-inc-dec -fbranch-count-reg -fcombine-stack-adjustments
           -fcompare-elim -fcprop-registers -fdce -fdefer-pop
           -fdelayed-branch -fdse -fforward-propagate
           -fguess-branch-probability -fif-conversion2 -fif-conversion
           -finline-functions-called-once -fipa-pure-const -fipa-profile
           -fipa-reference -fmerge-constants -fmove-loop-invariants
           -freorder-blocks -fshrink-wrap -fsplit-wide-types -fssa-backprop
           -fssa-phiopt -ftree-bit-ccp -ftree-ccp -ftree-ch
           -ftree-coalesce-vars -ftree-copy-prop -ftree-dce
           -ftree-dominator-opts -ftree-dse -ftree-forwprop -ftree-fre
           -ftree-phiprop -ftree-sink -ftree-slsr -ftree-sra -ftree-pta
           -ftree-ter -funit-at-a-time

           -O also turns on -fomit-frame-pointer on machines where doing so
           does not interfere with debugging.

       -O2 Optimize even more.  GCC performs nearly all supported
           optimizations that do not involve a space-speed tradeoff.  As
           compared to -O, this option increases both compilation time and
           the performance of the generated code.

           -O2 turns on all optimization flags specified by -O.  It also
           turns on the following optimization flags: -fthread-jumps
           -falign-functions  -falign-jumps -falign-loops  -falign-labels
           -fcaller-saves -fcrossjumping -fcse-follow-jumps
           -fcse-skip-blocks -fdelete-null-pointer-checks -fdevirtualize
           -fdevirtualize-speculatively -fexpensive-optimizations -fgcse
           -fgcse-lm -fhoist-adjacent-loads -finline-small-functions
           -findirect-inlining -fipa-cp -fipa-cp-alignment -fipa-sra
           -fipa-icf -fisolate-erroneous-paths-dereference -flra-remat
           -foptimize-sibling-calls -foptimize-strlen -fpartial-inlining
           -fpeephole2 -freorder-blocks-algorithm=stc
           -freorder-blocks-and-partition -freorder-functions
           -frerun-cse-after-loop -fsched-interblock  -fsched-spec
           -fschedule-insns  -fschedule-insns2 -fstrict-aliasing
           -fstrict-overflow -ftree-builtin-call-dce
           -ftree-switch-conversion -ftree-tail-merge -ftree-pre -ftree-vrp
           -fipa-ra

           Please note the warning under -fgcse about invoking -O2 on
           programs that use computed gotos.

       -O3 Optimize yet more.  -O3 turns on all optimizations specified by
           -O2 and also turns on the -finline-functions, -funswitch-loops,
           -fpredictive-commoning, -fgcse-after-reload,
           -ftree-loop-vectorize, -ftree-loop-distribute-patterns,
           -fsplit-paths -ftree-slp-vectorize, -fvect-cost-model,
           -ftree-partial-pre and -fipa-cp-clone options.

       -O0 Reduce compilation time and make debugging produce the expected
           results.  This is the default.

       -Os Optimize for size.  -Os enables all -O2 optimizations that do not
           typically increase code size.  It also performs further
           optimizations designed to reduce code size.

           -Os disables the following optimization flags: -falign-functions
           -falign-jumps  -falign-loops -falign-labels  -freorder-blocks
           -freorder-blocks-algorithm=stc -freorder-blocks-and-partition
           -fprefetch-loop-arrays

       -Ofast
           Disregard strict standards compliance.  -Ofast enables all -O3
           optimizations.  It also enables optimizations that are not valid
           for all standard-compliant programs.  It turns on -ffast-math and
           the Fortran-specific -fno-protect-parens and -fstack-arrays.

       -Og Optimize debugging experience.  -Og enables optimizations that do
           not interfere with debugging. It should be the optimization level
           of choice for the standard edit-compile-debug cycle, offering a
           reasonable level of optimization while maintaining fast
           compilation and a good debugging experience.

       If you use multiple -O options, with or without level numbers, the
       last such option is the one that is effective.

       Options of the form -fflag specify machine-independent flags.  Most
       flags have both positive and negative forms; the negative form of
       -ffoo is -fno-foo.  In the table below, only one of the forms is
       listed---the one you typically use.  You can figure out the other
       form by either removing no- or adding it.

       The following options control specific optimizations.  They are
       either activated by -O options or are related to ones that are.  You
       can use the following flags in the rare cases when "fine-tuning" of
       optimizations to be performed is desired.

       -fno-defer-pop
           Always pop the arguments to each function call as soon as that
           function returns.  For machines that must pop arguments after a
           function call, the compiler normally lets arguments accumulate on
           the stack for several function calls and pops them all at once.

           Disabled at levels -O, -O2, -O3, -Os.

       -fforward-propagate
           Perform a forward propagation pass on RTL.  The pass tries to
           combine two instructions and checks if the result can be
           simplified.  If loop unrolling is active, two passes are
           performed and the second is scheduled after loop unrolling.

           This option is enabled by default at optimization levels -O, -O2,
           -O3, -Os.

       -ffp-contract=style
           -ffp-contract=off disables floating-point expression contraction.
           -ffp-contract=fast enables floating-point expression contraction
           such as forming of fused multiply-add operations if the target
           has native support for them.  -ffp-contract=on enables floating-
           point expression contraction if allowed by the language standard.
           This is currently not implemented and treated equal to
           -ffp-contract=off.

           The default is -ffp-contract=fast.

       -fomit-frame-pointer
           Don't keep the frame pointer in a register for functions that
           don't need one.  This avoids the instructions to save, set up and
           restore frame pointers; it also makes an extra register available
           in many functions.  It also makes debugging impossible on some
           machines.

           On some machines, such as the VAX, this flag has no effect,
           because the standard calling sequence automatically handles the
           frame pointer and nothing is saved by pretending it doesn't
           exist.  The machine-description macro "FRAME_POINTER_REQUIRED"
           controls whether a target machine supports this flag.

           The default setting (when not optimizing for size) for 32-bit
           GNU/Linux x86 and 32-bit Darwin x86 targets is
           -fomit-frame-pointer.  You can configure GCC with the
           --enable-frame-pointer configure option to change the default.

           Enabled at levels -O, -O2, -O3, -Os.

       -foptimize-sibling-calls
           Optimize sibling and tail recursive calls.

           Enabled at levels -O2, -O3, -Os.

       -foptimize-strlen
           Optimize various standard C string functions (e.g. "strlen",
           "strchr" or "strcpy") and their "_FORTIFY_SOURCE" counterparts
           into faster alternatives.

           Enabled at levels -O2, -O3.

       -fno-inline
           Do not expand any functions inline apart from those marked with
           the "always_inline" attribute.  This is the default when not
           optimizing.

           Single functions can be exempted from inlining by marking them
           with the "noinline" attribute.

       -finline-small-functions
           Integrate functions into their callers when their body is smaller
           than expected function call code (so overall size of program gets
           smaller).  The compiler heuristically decides which functions are
           simple enough to be worth integrating in this way.  This inlining
           applies to all functions, even those not declared inline.

           Enabled at level -O2.

       -findirect-inlining
           Inline also indirect calls that are discovered to be known at
           compile time thanks to previous inlining.  This option has any
           effect only when inlining itself is turned on by the
           -finline-functions or -finline-small-functions options.

           Enabled at level -O2.

       -finline-functions
           Consider all functions for inlining, even if they are not
           declared inline.  The compiler heuristically decides which
           functions are worth integrating in this way.

           If all calls to a given function are integrated, and the function
           is declared "static", then the function is normally not output as
           assembler code in its own right.

           Enabled at level -O3.

       -finline-functions-called-once
           Consider all "static" functions called once for inlining into
           their caller even if they are not marked "inline".  If a call to
           a given function is integrated, then the function is not output
           as assembler code in its own right.

           Enabled at levels -O1, -O2, -O3 and -Os.

       -fearly-inlining
           Inline functions marked by "always_inline" and functions whose
           body seems smaller than the function call overhead early before
           doing -fprofile-generate instrumentation and real inlining pass.
           Doing so makes profiling significantly cheaper and usually
           inlining faster on programs having large chains of nested wrapper
           functions.

           Enabled by default.

       -fipa-sra
           Perform interprocedural scalar replacement of aggregates, removal
           of unused parameters and replacement of parameters passed by
           reference by parameters passed by value.

           Enabled at levels -O2, -O3 and -Os.

       -finline-limit=n
           By default, GCC limits the size of functions that can be inlined.
           This flag allows coarse control of this limit.  n is the size of
           functions that can be inlined in number of pseudo instructions.

           Inlining is actually controlled by a number of parameters, which
           may be specified individually by using --param name=value.  The
           -finline-limit=n option sets some of these parameters as follows:

           max-inline-insns-single
               is set to n/2.

           max-inline-insns-auto
               is set to n/2.

           See below for a documentation of the individual parameters
           controlling inlining and for the defaults of these parameters.

           Note: there may be no value to -finline-limit that results in
           default behavior.

           Note: pseudo instruction represents, in this particular context,
           an abstract measurement of function's size.  In no way does it
           represent a count of assembly instructions and as such its exact
           meaning might change from one release to an another.

       -fno-keep-inline-dllexport
           This is a more fine-grained version of -fkeep-inline-functions,
           which applies only to functions that are declared using the
           "dllexport" attribute or declspec

       -fkeep-inline-functions
           In C, emit "static" functions that are declared "inline" into the
           object file, even if the function has been inlined into all of
           its callers.  This switch does not affect functions using the
           "extern inline" extension in GNU C90.  In C++, emit any and all
           inline functions into the object file.

       -fkeep-static-functions
           Emit "static" functions into the object file, even if the
           function is never used.

       -fkeep-static-consts
           Emit variables declared "static const" when optimization isn't
           turned on, even if the variables aren't referenced.

           GCC enables this option by default.  If you want to force the
           compiler to check if a variable is referenced, regardless of
           whether or not optimization is turned on, use the
           -fno-keep-static-consts option.

       -fmerge-constants
           Attempt to merge identical constants (string constants and
           floating-point constants) across compilation units.

           This option is the default for optimized compilation if the
           assembler and linker support it.  Use -fno-merge-constants to
           inhibit this behavior.

           Enabled at levels -O, -O2, -O3, -Os.

       -fmerge-all-constants
           Attempt to merge identical constants and identical variables.

           This option implies -fmerge-constants.  In addition to
           -fmerge-constants this considers e.g. even constant initialized
           arrays or initialized constant variables with integral or
           floating-point types.  Languages like C or C++ require each
           variable, including multiple instances of the same variable in
           recursive calls, to have distinct locations, so using this option
           results in non-conforming behavior.

       -fmodulo-sched
           Perform swing modulo scheduling immediately before the first
           scheduling pass.  This pass looks at innermost loops and reorders
           their instructions by overlapping different iterations.

       -fmodulo-sched-allow-regmoves
           Perform more aggressive SMS-based modulo scheduling with register
           moves allowed.  By setting this flag certain anti-dependences
           edges are deleted, which triggers the generation of reg-moves
           based on the life-range analysis.  This option is effective only
           with -fmodulo-sched enabled.

       -fno-branch-count-reg
           Avoid running a pass scanning for opportunities to use "decrement
           and branch" instructions on a count register instead of
           generating sequences of instructions that decrement a register,
           compare it against zero, and then branch based upon the result.
           This option is only meaningful on architectures that support such
           instructions, which include x86, PowerPC, IA-64 and S/390.  Note
           that the -fno-branch-count-reg option doesn't remove the
           decrement and branch instructions from the generated instruction
           stream introduced by other optimization passes.

           Enabled by default at -O1 and higher.

           The default is -fbranch-count-reg.

       -fno-function-cse
           Do not put function addresses in registers; make each instruction
           that calls a constant function contain the function's address
           explicitly.

           This option results in less efficient code, but some strange
           hacks that alter the assembler output may be confused by the
           optimizations performed when this option is not used.

           The default is -ffunction-cse

       -fno-zero-initialized-in-bss
           If the target supports a BSS section, GCC by default puts
           variables that are initialized to zero into BSS.  This can save
           space in the resulting code.

           This option turns off this behavior because some programs
           explicitly rely on variables going to the data section---e.g., so
           that the resulting executable can find the beginning of that
           section and/or make assumptions based on that.

           The default is -fzero-initialized-in-bss.

       -fthread-jumps
           Perform optimizations that check to see if a jump branches to a
           location where another comparison subsumed by the first is found.
           If so, the first branch is redirected to either the destination
           of the second branch or a point immediately following it,
           depending on whether the condition is known to be true or false.

           Enabled at levels -O2, -O3, -Os.

       -fsplit-wide-types
           When using a type that occupies multiple registers, such as "long
           long" on a 32-bit system, split the registers apart and allocate
           them independently.  This normally generates better code for
           those types, but may make debugging more difficult.

           Enabled at levels -O, -O2, -O3, -Os.

       -fcse-follow-jumps
           In common subexpression elimination (CSE), scan through jump
           instructions when the target of the jump is not reached by any
           other path.  For example, when CSE encounters an "if" statement
           with an "else" clause, CSE follows the jump when the condition
           tested is false.

           Enabled at levels -O2, -O3, -Os.

       -fcse-skip-blocks
           This is similar to -fcse-follow-jumps, but causes CSE to follow
           jumps that conditionally skip over blocks.  When CSE encounters a
           simple "if" statement with no else clause, -fcse-skip-blocks
           causes CSE to follow the jump around the body of the "if".

           Enabled at levels -O2, -O3, -Os.

       -frerun-cse-after-loop
           Re-run common subexpression elimination after loop optimizations
           are performed.

           Enabled at levels -O2, -O3, -Os.

       -fgcse
           Perform a global common subexpression elimination pass.  This
           pass also performs global constant and copy propagation.

           Note: When compiling a program using computed gotos, a GCC
           extension, you may get better run-time performance if you disable
           the global common subexpression elimination pass by adding
           -fno-gcse to the command line.

           Enabled at levels -O2, -O3, -Os.

       -fgcse-lm
           When -fgcse-lm is enabled, global common subexpression
           elimination attempts to move loads that are only killed by stores
           into themselves.  This allows a loop containing a load/store
           sequence to be changed to a load outside the loop, and a
           copy/store within the loop.

           Enabled by default when -fgcse is enabled.

       -fgcse-sm
           When -fgcse-sm is enabled, a store motion pass is run after
           global common subexpression elimination.  This pass attempts to
           move stores out of loops.  When used in conjunction with
           -fgcse-lm, loops containing a load/store sequence can be changed
           to a load before the loop and a store after the loop.

           Not enabled at any optimization level.

       -fgcse-las
           When -fgcse-las is enabled, the global common subexpression
           elimination pass eliminates redundant loads that come after
           stores to the same memory location (both partial and full
           redundancies).

           Not enabled at any optimization level.

       -fgcse-after-reload
           When -fgcse-after-reload is enabled, a redundant load elimination
           pass is performed after reload.  The purpose of this pass is to
           clean up redundant spilling.

       -faggressive-loop-optimizations
           This option tells the loop optimizer to use language constraints
           to derive bounds for the number of iterations of a loop.  This
           assumes that loop code does not invoke undefined behavior by for
           example causing signed integer overflows or out-of-bound array
           accesses.  The bounds for the number of iterations of a loop are
           used to guide loop unrolling and peeling and loop exit test
           optimizations.  This option is enabled by default.

       -funsafe-loop-optimizations
           This option tells the loop optimizer to assume that loop indices
           do not overflow, and that loops with nontrivial exit condition
           are not infinite.  This enables a wider range of loop
           optimizations even if the loop optimizer itself cannot prove that
           these assumptions are valid.  If you use
           -Wunsafe-loop-optimizations, the compiler warns you if it finds
           this kind of loop.

       -funconstrained-commons
           This option tells the compiler that variables declared in common
           blocks (e.g. Fortran) may later be overridden with longer
           trailing arrays. This prevents certain optimizations that depend
           on knowing the array bounds.

       -fcrossjumping
           Perform cross-jumping transformation.  This transformation
           unifies equivalent code and saves code size.  The resulting code
           may or may not perform better than without cross-jumping.

           Enabled at levels -O2, -O3, -Os.

       -fauto-inc-dec
           Combine increments or decrements of addresses with memory
           accesses.  This pass is always skipped on architectures that do
           not have instructions to support this.  Enabled by default at -O
           and higher on architectures that support this.

       -fdce
           Perform dead code elimination (DCE) on RTL.  Enabled by default
           at -O and higher.

       -fdse
           Perform dead store elimination (DSE) on RTL.  Enabled by default
           at -O and higher.

       -fif-conversion
           Attempt to transform conditional jumps into branch-less
           equivalents.  This includes use of conditional moves, min, max,
           set flags and abs instructions, and some tricks doable by
           standard arithmetics.  The use of conditional execution on chips
           where it is available is controlled by -fif-conversion2.

           Enabled at levels -O, -O2, -O3, -Os.

       -fif-conversion2
           Use conditional execution (where available) to transform
           conditional jumps into branch-less equivalents.

           Enabled at levels -O, -O2, -O3, -Os.

       -fdeclone-ctor-dtor
           The C++ ABI requires multiple entry points for constructors and
           destructors: one for a base subobject, one for a complete object,
           and one for a virtual destructor that calls operator delete
           afterwards.  For a hierarchy with virtual bases, the base and
           complete variants are clones, which means two copies of the
           function.  With this option, the base and complete variants are
           changed to be thunks that call a common implementation.

           Enabled by -Os.

       -fdelete-null-pointer-checks
           Assume that programs cannot safely dereference null pointers, and
           that no code or data element resides at address zero.  This
           option enables simple constant folding optimizations at all
           optimization levels.  In addition, other optimization passes in
           GCC use this flag to control global dataflow analyses that
           eliminate useless checks for null pointers; these assume that a
           memory access to address zero always results in a trap, so that
           if a pointer is checked after it has already been dereferenced,
           it cannot be null.

           Note however that in some environments this assumption is not
           true.  Use -fno-delete-null-pointer-checks to disable this
           optimization for programs that depend on that behavior.

           This option is enabled by default on most targets.  On Nios II
           ELF, it defaults to off.  On AVR and CR16, this option is
           completely disabled.

           Passes that use the dataflow information are enabled
           independently at different optimization levels.

       -fdevirtualize
           Attempt to convert calls to virtual functions to direct calls.
           This is done both within a procedure and interprocedurally as
           part of indirect inlining (-findirect-inlining) and
           interprocedural constant propagation (-fipa-cp).  Enabled at
           levels -O2, -O3, -Os.

       -fdevirtualize-speculatively
           Attempt to convert calls to virtual functions to speculative
           direct calls.  Based on the analysis of the type inheritance
           graph, determine for a given call the set of likely targets. If
           the set is small, preferably of size 1, change the call into a
           conditional deciding between direct and indirect calls.  The
           speculative calls enable more optimizations, such as inlining.
           When they seem useless after further optimization, they are
           converted back into original form.

       -fdevirtualize-at-ltrans
           Stream extra information needed for aggressive devirtualization
           when running the link-time optimizer in local transformation
           mode.  This option enables more devirtualization but
           significantly increases the size of streamed data. For this
           reason it is disabled by default.

       -fexpensive-optimizations
           Perform a number of minor optimizations that are relatively
           expensive.

           Enabled at levels -O2, -O3, -Os.

       -free
           Attempt to remove redundant extension instructions.  This is
           especially helpful for the x86-64 architecture, which implicitly
           zero-extends in 64-bit registers after writing to their lower
           32-bit half.

           Enabled for Alpha, AArch64 and x86 at levels -O2, -O3, -Os.

       -fno-lifetime-dse
           In C++ the value of an object is only affected by changes within
           its lifetime: when the constructor begins, the object has an
           indeterminate value, and any changes during the lifetime of the
           object are dead when the object is destroyed.  Normally dead
           store elimination will take advantage of this; if your code
           relies on the value of the object storage persisting beyond the
           lifetime of the object, you can use this flag to disable this
           optimization.  To preserve stores before the constructor starts
           (e.g. because your operator new clears the object storage) but
           still treat the object as dead after the destructor you, can use
           -flifetime-dse=1.  The default behavior can be explicitly
           selected with -flifetime-dse=2.  -flifetime-dse=0 is equivalent
           to -fno-lifetime-dse.

       -flive-range-shrinkage
           Attempt to decrease register pressure through register live range
           shrinkage.  This is helpful for fast processors with small or
           moderate size register sets.

       -fira-algorithm=algorithm
           Use the specified coloring algorithm for the integrated register
           allocator.  The algorithm argument can be priority, which
           specifies Chow's priority coloring, or CB, which specifies
           Chaitin-Briggs coloring.  Chaitin-Briggs coloring is not
           implemented for all architectures, but for those targets that do
           support it, it is the default because it generates better code.

       -fira-region=region
           Use specified regions for the integrated register allocator.  The
           region argument should be one of the following:

           all Use all loops as register allocation regions.  This can give
               the best results for machines with a small and/or irregular
               register set.

           mixed
               Use all loops except for loops with small register pressure
               as the regions.  This value usually gives the best results in
               most cases and for most architectures, and is enabled by
               default when compiling with optimization for speed (-O, -O2,
               ...).

           one Use all functions as a single region.  This typically results
               in the smallest code size, and is enabled by default for -Os
               or -O0.

       -fira-hoist-pressure
           Use IRA to evaluate register pressure in the code hoisting pass
           for decisions to hoist expressions.  This option usually results
           in smaller code, but it can slow the compiler down.

           This option is enabled at level -Os for all targets.

       -fira-loop-pressure
           Use IRA to evaluate register pressure in loops for decisions to
           move loop invariants.  This option usually results in generation
           of faster and smaller code on machines with large register files
           (>= 32 registers), but it can slow the compiler down.

           This option is enabled at level -O3 for some targets.

       -fno-ira-share-save-slots
           Disable sharing of stack slots used for saving call-used hard
           registers living through a call.  Each hard register gets a
           separate stack slot, and as a result function stack frames are
           larger.

       -fno-ira-share-spill-slots
           Disable sharing of stack slots allocated for pseudo-registers.
           Each pseudo-register that does not get a hard register gets a
           separate stack slot, and as a result function stack frames are
           larger.

       -flra-remat
           Enable CFG-sensitive rematerialization in LRA.  Instead of
           loading values of spilled pseudos, LRA tries to rematerialize
           (recalculate) values if it is profitable.

           Enabled at levels -O2, -O3, -Os.

       -fdelayed-branch
           If supported for the target machine, attempt to reorder
           instructions to exploit instruction slots available after delayed
           branch instructions.

           Enabled at levels -O, -O2, -O3, -Os.

       -fschedule-insns
           If supported for the target machine, attempt to reorder
           instructions to eliminate execution stalls due to required data
           being unavailable.  This helps machines that have slow floating
           point or memory load instructions by allowing other instructions
           to be issued until the result of the load or floating-point
           instruction is required.

           Enabled at levels -O2, -O3.

       -fschedule-insns2
           Similar to -fschedule-insns, but requests an additional pass of
           instruction scheduling after register allocation has been done.
           This is especially useful on machines with a relatively small
           number of registers and where memory load instructions take more
           than one cycle.

           Enabled at levels -O2, -O3, -Os.

       -fno-sched-interblock
           Don't schedule instructions across basic blocks.  This is
           normally enabled by default when scheduling before register
           allocation, i.e.  with -fschedule-insns or at -O2 or higher.

       -fno-sched-spec
           Don't allow speculative motion of non-load instructions.  This is
           normally enabled by default when scheduling before register
           allocation, i.e.  with -fschedule-insns or at -O2 or higher.

       -fsched-pressure
           Enable register pressure sensitive insn scheduling before
           register allocation.  This only makes sense when scheduling
           before register allocation is enabled, i.e. with -fschedule-insns
           or at -O2 or higher.  Usage of this option can improve the
           generated code and decrease its size by preventing register
           pressure increase above the number of available hard registers
           and subsequent spills in register allocation.

       -fsched-spec-load
           Allow speculative motion of some load instructions.  This only
           makes sense when scheduling before register allocation, i.e. with
           -fschedule-insns or at -O2 or higher.

       -fsched-spec-load-dangerous
           Allow speculative motion of more load instructions.  This only
           makes sense when scheduling before register allocation, i.e. with
           -fschedule-insns or at -O2 or higher.

       -fsched-stalled-insns
       -fsched-stalled-insns=n
           Define how many insns (if any) can be moved prematurely from the
           queue of stalled insns into the ready list during the second
           scheduling pass.  -fno-sched-stalled-insns means that no insns
           are moved prematurely, -fsched-stalled-insns=0 means there is no
           limit on how many queued insns can be moved prematurely.
           -fsched-stalled-insns without a value is equivalent to
           -fsched-stalled-insns=1.

       -fsched-stalled-insns-dep
       -fsched-stalled-insns-dep=n
           Define how many insn groups (cycles) are examined for a
           dependency on a stalled insn that is a candidate for premature
           removal from the queue of stalled insns.  This has an effect only
           during the second scheduling pass, and only if
           -fsched-stalled-insns is used.  -fno-sched-stalled-insns-dep is
           equivalent to -fsched-stalled-insns-dep=0.
           -fsched-stalled-insns-dep without a value is equivalent to
           -fsched-stalled-insns-dep=1.

       -fsched2-use-superblocks
           When scheduling after register allocation, use superblock
           scheduling.  This allows motion across basic block boundaries,
           resulting in faster schedules.  This option is experimental, as
           not all machine descriptions used by GCC model the CPU closely
           enough to avoid unreliable results from the algorithm.

           This only makes sense when scheduling after register allocation,
           i.e. with -fschedule-insns2 or at -O2 or higher.

       -fsched-group-heuristic
           Enable the group heuristic in the scheduler.  This heuristic
           favors the instruction that belongs to a schedule group.  This is
           enabled by default when scheduling is enabled, i.e. with
           -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-critical-path-heuristic
           Enable the critical-path heuristic in the scheduler.  This
           heuristic favors instructions on the critical path.  This is
           enabled by default when scheduling is enabled, i.e. with
           -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

       -fsched-spec-insn-heuristic
           Enable the speculative instruction heuristic in the scheduler.
           This heuristic favors speculative instructions with greater
           dependency weakness.  This is enabled by default when scheduling
           is enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or
           at -O2 or higher.

       -fsched-rank-heuristic
           Enable the rank heuristic in the scheduler.  This heuristic
           favors the instruction belonging to a basic block with greater
           size or frequency.  This is enabled by default when scheduling is
           enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at
           -O2 or higher.

       -fsched-last-insn-heuristic
           Enable the last-instruction heuristic in the scheduler.  This
           heuristic favors the instruction that is less dependent on the
           last instruction scheduled.  This is enabled by default when
           scheduling is enabled, i.e. with -fschedule-insns or
           -fschedule-insns2 or at -O2 or higher.

       -fsched-dep-count-heuristic
           Enable the dependent-count heuristic in the scheduler.  This
           heuristic favors the instruction that has more instructions
           depending on it.  This is enabled by default when scheduling is
           enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at
           -O2 or higher.

       -freschedule-modulo-scheduled-loops
           Modulo scheduling is performed before traditional scheduling.  If
           a loop is modulo scheduled, later scheduling passes may change
           its schedule.  Use this option to control that behavior.

       -fselective-scheduling
           Schedule instructions using selective scheduling algorithm.
           Selective scheduling runs instead of the first scheduler pass.

       -fselective-scheduling2
           Schedule instructions using selective scheduling algorithm.
           Selective scheduling runs instead of the second scheduler pass.

       -fsel-sched-pipelining
           Enable software pipelining of innermost loops during selective
           scheduling.  This option has no effect unless one of
           -fselective-scheduling or -fselective-scheduling2 is turned on.

       -fsel-sched-pipelining-outer-loops
           When pipelining loops during selective scheduling, also pipeline
           outer loops.  This option has no effect unless
           -fsel-sched-pipelining is turned on.

       -fsemantic-interposition
           Some object formats, like ELF, allow interposing of symbols by
           the dynamic linker.  This means that for symbols exported from
           the DSO, the compiler cannot perform interprocedural propagation,
           inlining and other optimizations in anticipation that the
           function or variable in question may change. While this feature
           is useful, for example, to rewrite memory allocation functions by
           a debugging implementation, it is expensive in the terms of code
           quality.  With -fno-semantic-interposition the compiler assumes
           that if interposition happens for functions the overwriting
           function will have precisely the same semantics (and side
           effects).  Similarly if interposition happens for variables, the
           constructor of the variable will be the same. The flag has no
           effect for functions explicitly declared inline (where it is
           never allowed for interposition to change semantics) and for
           symbols explicitly declared weak.

       -fshrink-wrap
           Emit function prologues only before parts of the function that
           need it, rather than at the top of the function.  This flag is
           enabled by default at -O and higher.

       -fcaller-saves
           Enable allocation of values to registers that are clobbered by
           function calls, by emitting extra instructions to save and
           restore the registers around such calls.  Such allocation is done
           only when it seems to result in better code.

           This option is always enabled by default on certain machines,
           usually those which have no call-preserved registers to use
           instead.

           Enabled at levels -O2, -O3, -Os.

       -fcombine-stack-adjustments
           Tracks stack adjustments (pushes and pops) and stack memory
           references and then tries to find ways to combine them.

           Enabled by default at -O1 and higher.

       -fipa-ra
           Use caller save registers for allocation if those registers are
           not used by any called function.  In that case it is not
           necessary to save and restore them around calls.  This is only
           possible if called functions are part of same compilation unit as
           current function and they are compiled before it.

           Enabled at levels -O2, -O3, -Os.

       -fconserve-stack
           Attempt to minimize stack usage.  The compiler attempts to use
           less stack space, even if that makes the program slower.  This
           option implies setting the large-stack-frame parameter to 100 and
           the large-stack-frame-growth parameter to 400.

       -ftree-reassoc
           Perform reassociation on trees.  This flag is enabled by default
           at -O and higher.

       -ftree-pre
           Perform partial redundancy elimination (PRE) on trees.  This flag
           is enabled by default at -O2 and -O3.

       -ftree-partial-pre
           Make partial redundancy elimination (PRE) more aggressive.  This
           flag is enabled by default at -O3.

       -ftree-forwprop
           Perform forward propagation on trees.  This flag is enabled by
           default at -O and higher.

       -ftree-fre
           Perform full redundancy elimination (FRE) on trees.  The
           difference between FRE and PRE is that FRE only considers
           expressions that are computed on all paths leading to the
           redundant computation.  This analysis is faster than PRE, though
           it exposes fewer redundancies.  This flag is enabled by default
           at -O and higher.

       -ftree-phiprop
           Perform hoisting of loads from conditional pointers on trees.
           This pass is enabled by default at -O and higher.

       -fhoist-adjacent-loads
           Speculatively hoist loads from both branches of an if-then-else
           if the loads are from adjacent locations in the same structure
           and the target architecture has a conditional move instruction.
           This flag is enabled by default at -O2 and higher.

       -ftree-copy-prop
           Perform copy propagation on trees.  This pass eliminates
           unnecessary copy operations.  This flag is enabled by default at
           -O and higher.

       -fipa-pure-const
           Discover which functions are pure or constant.  Enabled by
           default at -O and higher.

       -fipa-reference
           Discover which static variables do not escape the compilation
           unit.  Enabled by default at -O and higher.

       -fipa-pta
           Perform interprocedural pointer analysis and interprocedural
           modification and reference analysis.  This option can cause
           excessive memory and compile-time usage on large compilation
           units.  It is not enabled by default at any optimization level.

       -fipa-profile
           Perform interprocedural profile propagation.  The functions
           called only from cold functions are marked as cold. Also
           functions executed once (such as "cold", "noreturn", static
           constructors or destructors) are identified. Cold functions and
           loop less parts of functions executed once are then optimized for
           size.  Enabled by default at -O and higher.

       -fipa-cp
           Perform interprocedural constant propagation.  This optimization
           analyzes the program to determine when values passed to functions
           are constants and then optimizes accordingly.  This optimization
           can substantially increase performance if the application has
           constants passed to functions.  This flag is enabled by default
           at -O2, -Os and -O3.

       -fipa-cp-clone
           Perform function cloning to make interprocedural constant
           propagation stronger.  When enabled, interprocedural constant
           propagation performs function cloning when externally visible
           function can be called with constant arguments.  Because this
           optimization can create multiple copies of functions, it may
           significantly increase code size (see --param
           ipcp-unit-growth=value).  This flag is enabled by default at -O3.

       -fipa-cp-alignment
           When enabled, this optimization propagates alignment of function
           parameters to support better vectorization and string operations.

           This flag is enabled by default at -O2 and -Os.  It requires that
           -fipa-cp is enabled.

       -fipa-icf
           Perform Identical Code Folding for functions and read-only
           variables.  The optimization reduces code size and may disturb
           unwind stacks by replacing a function by equivalent one with a
           different name. The optimization works more effectively with link
           time optimization enabled.

           Nevertheless the behavior is similar to Gold Linker ICF
           optimization, GCC ICF works on different levels and thus the
           optimizations are not same - there are equivalences that are
           found only by GCC and equivalences found only by Gold.

           This flag is enabled by default at -O2 and -Os.

       -fisolate-erroneous-paths-dereference
           Detect paths that trigger erroneous or undefined behavior due to
           dereferencing a null pointer.  Isolate those paths from the main
           control flow and turn the statement with erroneous or undefined
           behavior into a trap.  This flag is enabled by default at -O2 and
           higher and depends on -fdelete-null-pointer-checks also being
           enabled.

       -fisolate-erroneous-paths-attribute
           Detect paths that trigger erroneous or undefined behavior due a
           null value being used in a way forbidden by a "returns_nonnull"
           or "nonnull" attribute.  Isolate those paths from the main
           control flow and turn the statement with erroneous or undefined
           behavior into a trap.  This is not currently enabled, but may be
           enabled by -O2 in the future.

       -ftree-sink
           Perform forward store motion on trees.  This flag is enabled by
           default at -O and higher.

       -ftree-bit-ccp
           Perform sparse conditional bit constant propagation on trees and
           propagate pointer alignment information.  This pass only operates
           on local scalar variables and is enabled by default at -O and
           higher.  It requires that -ftree-ccp is enabled.

       -ftree-ccp
           Perform sparse conditional constant propagation (CCP) on trees.
           This pass only operates on local scalar variables and is enabled
           by default at -O and higher.

       -fssa-backprop
           Propagate information about uses of a value up the definition
           chain in order to simplify the definitions.  For example, this
           pass strips sign operations if the sign of a value never matters.
           The flag is enabled by default at -O and higher.

       -fssa-phiopt
           Perform pattern matching on SSA PHI nodes to optimize conditional
           code.  This pass is enabled by default at -O and higher.

       -ftree-switch-conversion
           Perform conversion of simple initializations in a switch to
           initializations from a scalar array.  This flag is enabled by
           default at -O2 and higher.

       -ftree-tail-merge
           Look for identical code sequences.  When found, replace one with
           a jump to the other.  This optimization is known as tail merging
           or cross jumping.  This flag is enabled by default at -O2 and
           higher.  The compilation time in this pass can be limited using
           max-tail-merge-comparisons parameter and max-tail-merge-
           iterations parameter.

       -ftree-dce
           Perform dead code elimination (DCE) on trees.  This flag is
           enabled by default at -O and higher.

       -ftree-builtin-call-dce
           Perform conditional dead code elimination (DCE) for calls to
           built-in functions that may set "errno" but are otherwise side-
           effect free.  This flag is enabled by default at -O2 and higher
           if -Os is not also specified.

       -ftree-dominator-opts
           Perform a variety of simple scalar cleanups (constant/copy
           propagation, redundancy elimination, range propagation and
           expression simplification) based on a dominator tree traversal.
           This also performs jump threading (to reduce jumps to jumps).
           This flag is enabled by default at -O and higher.

       -ftree-dse
           Perform dead store elimination (DSE) on trees.  A dead store is a
           store into a memory location that is later overwritten by another
           store without any intervening loads.  In this case the earlier
           store can be deleted.  This flag is enabled by default at -O and
           higher.

       -ftree-ch
           Perform loop header copying on trees.  This is beneficial since
           it increases effectiveness of code motion optimizations.  It also
           saves one jump.  This flag is enabled by default at -O and
           higher.  It is not enabled for -Os, since it usually increases
           code size.

       -ftree-loop-optimize
           Perform loop optimizations on trees.  This flag is enabled by
           default at -O and higher.

       -ftree-loop-linear
       -floop-interchange
       -floop-strip-mine
       -floop-block
       -floop-unroll-and-jam
           Perform loop nest optimizations.  Same as -floop-nest-optimize.
           To use this code transformation, GCC has to be configured with
           --with-isl to enable the Graphite loop transformation
           infrastructure.

       -fgraphite-identity
           Enable the identity transformation for graphite.  For every SCoP
           we generate the polyhedral representation and transform it back
           to gimple.  Using -fgraphite-identity we can check the costs or
           benefits of the GIMPLE -> GRAPHITE -> GIMPLE transformation.
           Some minimal optimizations are also performed by the code
           generator isl, like index splitting and dead code elimination in
           loops.

       -floop-nest-optimize
           Enable the isl based loop nest optimizer.  This is a generic loop
           nest optimizer based on the Pluto optimization algorithms.  It
           calculates a loop structure optimized for data-locality and
           parallelism.  This option is experimental.

       -floop-parallelize-all
           Use the Graphite data dependence analysis to identify loops that
           can be parallelized.  Parallelize all the loops that can be
           analyzed to not contain loop carried dependences without checking
           that it is profitable to parallelize the loops.

       -ftree-coalesce-vars
           While transforming the program out of the SSA representation,
           attempt to reduce copying by coalescing versions of different
           user-defined variables, instead of just compiler temporaries.
           This may severely limit the ability to debug an optimized program
           compiled with -fno-var-tracking-assignments.  In the negated
           form, this flag prevents SSA coalescing of user variables.  This
           option is enabled by default if optimization is enabled, and it
           does very little otherwise.

       -ftree-loop-if-convert
           Attempt to transform conditional jumps in the innermost loops to
           branch-less equivalents.  The intent is to remove control-flow
           from the innermost loops in order to improve the ability of the
           vectorization pass to handle these loops.  This is enabled by
           default if vectorization is enabled.

       -ftree-loop-if-convert-stores
           Attempt to also if-convert conditional jumps containing memory
           writes.  This transformation can be unsafe for multi-threaded
           programs as it transforms conditional memory writes into
           unconditional memory writes.  For example,

                   for (i = 0; i < N; i++)
                     if (cond)
                       A[i] = expr;

           is transformed to

                   for (i = 0; i < N; i++)
                     A[i] = cond ? expr : A[i];

           potentially producing data races.

       -ftree-loop-distribution
           Perform loop distribution.  This flag can improve cache
           performance on big loop bodies and allow further loop
           optimizations, like parallelization or vectorization, to take
           place.  For example, the loop

                   DO I = 1, N
                     A(I) = B(I) + C
                     D(I) = E(I) * F
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = B(I) + C
                   ENDDO
                   DO I = 1, N
                      D(I) = E(I) * F
                   ENDDO

       -ftree-loop-distribute-patterns
           Perform loop distribution of patterns that can be code generated
           with calls to a library.  This flag is enabled by default at -O3.

           This pass distributes the initialization loops and generates a
           call to memset zero.  For example, the loop

                   DO I = 1, N
                     A(I) = 0
                     B(I) = A(I) + I
                   ENDDO

           is transformed to

                   DO I = 1, N
                      A(I) = 0
                   ENDDO
                   DO I = 1, N
                      B(I) = A(I) + I
                   ENDDO

           and the initialization loop is transformed into a call to memset
           zero.

       -ftree-loop-im
           Perform loop invariant motion on trees.  This pass moves only
           invariants that are hard to handle at RTL level (function calls,
           operations that expand to nontrivial sequences of insns).  With
           -funswitch-loops it also moves operands of conditions that are
           invariant out of the loop, so that we can use just trivial
           invariantness analysis in loop unswitching.  The pass also
           includes store motion.

       -ftree-loop-ivcanon
           Create a canonical counter for number of iterations in loops for
           which determining number of iterations requires complicated
           analysis.  Later optimizations then may determine the number
           easily.  Useful especially in connection with unrolling.

       -fivopts
           Perform induction variable optimizations (strength reduction,
           induction variable merging and induction variable elimination) on
           trees.

       -ftree-parallelize-loops=n
           Parallelize loops, i.e., split their iteration space to run in n
           threads.  This is only possible for loops whose iterations are
           independent and can be arbitrarily reordered.  The optimization
           is only profitable on multiprocessor machines, for loops that are
           CPU-intensive, rather than constrained e.g. by memory bandwidth.
           This option implies -pthread, and thus is only supported on
           targets that have support for -pthread.

       -ftree-pta
           Perform function-local points-to analysis on trees.  This flag is
           enabled by default at -O and higher.

       -ftree-sra
           Perform scalar replacement of aggregates.  This pass replaces
           structure references with scalars to prevent committing
           structures to memory too early.  This flag is enabled by default
           at -O and higher.

       -ftree-ter
           Perform temporary expression replacement during the SSA->normal
           phase.  Single use/single def temporaries are replaced at their
           use location with their defining expression.  This results in
           non-GIMPLE code, but gives the expanders much more complex trees
           to work on resulting in better RTL generation.  This is enabled
           by default at -O and higher.

       -ftree-slsr
           Perform straight-line strength reduction on trees.  This
           recognizes related expressions involving multiplications and
           replaces them by less expensive calculations when possible.  This
           is enabled by default at -O and higher.

       -ftree-vectorize
           Perform vectorization on trees. This flag enables
           -ftree-loop-vectorize and -ftree-slp-vectorize if not explicitly
           specified.

       -ftree-loop-vectorize
           Perform loop vectorization on trees. This flag is enabled by
           default at -O3 and when -ftree-vectorize is enabled.

       -ftree-slp-vectorize
           Perform basic block vectorization on trees. This flag is enabled
           by default at -O3 and when -ftree-vectorize is enabled.

       -fvect-cost-model=model
           Alter the cost model used for vectorization.  The model argument
           should be one of unlimited, dynamic or cheap.  With the unlimited
           model the vectorized code-path is assumed to be profitable while
           with the dynamic model a runtime check guards the vectorized
           code-path to enable it only for iteration counts that will likely
           execute faster than when executing the original scalar loop.  The
           cheap model disables vectorization of loops where doing so would
           be cost prohibitive for example due to required runtime checks
           for data dependence or alignment but otherwise is equal to the
           dynamic model.  The default cost model depends on other
           optimization flags and is either dynamic or cheap.

       -fsimd-cost-model=model
           Alter the cost model used for vectorization of loops marked with
           the OpenMP or Cilk Plus simd directive.  The model argument
           should be one of unlimited, dynamic, cheap.  All values of model
           have the same meaning as described in -fvect-cost-model and by
           default a cost model defined with -fvect-cost-model is used.

       -ftree-vrp
           Perform Value Range Propagation on trees.  This is similar to the
           constant propagation pass, but instead of values, ranges of
           values are propagated.  This allows the optimizers to remove
           unnecessary range checks like array bound checks and null pointer
           checks.  This is enabled by default at -O2 and higher.  Null
           pointer check elimination is only done if
           -fdelete-null-pointer-checks is enabled.

       -fsplit-paths
           Split paths leading to loop backedges.  This can improve dead
           code elimination and common subexpression elimination.  This is
           enabled by default at -O2 and above.

       -fsplit-ivs-in-unroller
           Enables expression of values of induction variables in later
           iterations of the unrolled loop using the value in the first
           iteration.  This breaks long dependency chains, thus improving
           efficiency of the scheduling passes.

           A combination of -fweb and CSE is often sufficient to obtain the
           same effect.  However, that is not reliable in cases where the
           loop body is more complicated than a single basic block.  It also
           does not work at all on some architectures due to restrictions in
           the CSE pass.

           This optimization is enabled by default.

       -fvariable-expansion-in-unroller
           With this option, the compiler creates multiple copies of some
           local variables when unrolling a loop, which can result in
           superior code.

       -fpartial-inlining
           Inline parts of functions.  This option has any effect only when
           inlining itself is turned on by the -finline-functions or
           -finline-small-functions options.

           Enabled at level -O2.

       -fpredictive-commoning
           Perform predictive commoning optimization, i.e., reusing
           computations (especially memory loads and stores) performed in
           previous iterations of loops.

           This option is enabled at level -O3.

       -fprefetch-loop-arrays
           If supported by the target machine, generate instructions to
           prefetch memory to improve the performance of loops that access
           large arrays.

           This option may generate better or worse code; results are highly
           dependent on the structure of loops within the source code.

           Disabled at level -Os.

       -fno-peephole
       -fno-peephole2
           Disable any machine-specific peephole optimizations.  The
           difference between -fno-peephole and -fno-peephole2 is in how
           they are implemented in the compiler; some targets use one, some
           use the other, a few use both.

           -fpeephole is enabled by default.  -fpeephole2 enabled at levels
           -O2, -O3, -Os.

       -fno-guess-branch-probability
           Do not guess branch probabilities using heuristics.

           GCC uses heuristics to guess branch probabilities if they are not
           provided by profiling feedback (-fprofile-arcs).  These
           heuristics are based on the control flow graph.  If some branch
           probabilities are specified by "__builtin_expect", then the
           heuristics are used to guess branch probabilities for the rest of
           the control flow graph, taking the "__builtin_expect" info into
           account.  The interactions between the heuristics and
           "__builtin_expect" can be complex, and in some cases, it may be
           useful to disable the heuristics so that the effects of
           "__builtin_expect" are easier to understand.

           The default is -fguess-branch-probability at levels -O, -O2, -O3,
           -Os.

       -freorder-blocks
           Reorder basic blocks in the compiled function in order to reduce
           number of taken branches and improve code locality.

           Enabled at levels -O, -O2, -O3, -Os.

       -freorder-blocks-algorithm=algorithm
           Use the specified algorithm for basic block reordering.  The
           algorithm argument can be simple, which does not increase code
           size (except sometimes due to secondary effects like alignment),
           or stc, the "software trace cache" algorithm, which tries to put
           all often executed code together, minimizing the number of
           branches executed by making extra copies of code.

           The default is simple at levels -O, -Os, and stc at levels -O2,
           -O3.

       -freorder-blocks-and-partition
           In addition to reordering basic blocks in the compiled function,
           in order to reduce number of taken branches, partitions hot and
           cold basic blocks into separate sections of the assembly and .o
           files, to improve paging and cache locality performance.

           This optimization is automatically turned off in the presence of
           exception handling, for linkonce sections, for functions with a
           user-defined section attribute and on any architecture that does
           not support named sections.

           Enabled for x86 at levels -O2, -O3.

       -freorder-functions
           Reorder functions in the object file in order to improve code
           locality.  This is implemented by using special subsections
           ".text.hot" for most frequently executed functions and
           ".text.unlikely" for unlikely executed functions.  Reordering is
           done by the linker so object file format must support named
           sections and linker must place them in a reasonable way.

           Also profile feedback must be available to make this option
           effective.  See -fprofile-arcs for details.

           Enabled at levels -O2, -O3, -Os.

       -fstrict-aliasing
           Allow the compiler to assume the strictest aliasing rules
           applicable to the language being compiled.  For C (and C++), this
           activates optimizations based on the type of expressions.  In
           particular, an object of one type is assumed never to reside at
           the same address as an object of a different type, unless the
           types are almost the same.  For example, an "unsigned int" can
           alias an "int", but not a "void*" or a "double".  A character
           type may alias any other type.

           Pay special attention to code like this:

                   union a_union {
                     int i;
                     double d;
                   };

                   int f() {
                     union a_union t;
                     t.d = 3.0;
                     return t.i;
                   }

           The practice of reading from a different union member than the
           one most recently written to (called "type-punning") is common.
           Even with -fstrict-aliasing, type-punning is allowed, provided
           the memory is accessed through the union type.  So, the code
           above works as expected.    However, this code might not:

                   int f() {
                     union a_union t;
                     int* ip;
                     t.d = 3.0;
                     ip = &t.i;
                     return *ip;
                   }

           Similarly, access by taking the address, casting the resulting
           pointer and dereferencing the result has undefined behavior, even
           if the cast uses a union type, e.g.:

                   int f() {
                     double d = 3.0;
                     return ((union a_union *) &d)->i;
                   }

           The -fstrict-aliasing option is enabled at levels -O2, -O3, -Os.

       -fstrict-overflow
           Allow the compiler to assume strict signed overflow rules,
           depending on the language being compiled.  For C (and C++) this
           means that overflow when doing arithmetic with signed numbers is
           undefined, which means that the compiler may assume that it does
           not happen.  This permits various optimizations.  For example,
           the compiler assumes that an expression like "i + 10 > i" is
           always true for signed "i".  This assumption is only valid if
           signed overflow is undefined, as the expression is false if "i +
           10" overflows when using twos complement arithmetic.  When this
           option is in effect any attempt to determine whether an operation
           on signed numbers overflows must be written carefully to not
           actually involve overflow.

           This option also allows the compiler to assume strict pointer
           semantics: given a pointer to an object, if adding an offset to
           that pointer does not produce a pointer to the same object, the
           addition is undefined.  This permits the compiler to conclude
           that "p + u > p" is always true for a pointer "p" and unsigned
           integer "u".  This assumption is only valid because pointer
           wraparound is undefined, as the expression is false if "p + u"
           overflows using twos complement arithmetic.

           See also the -fwrapv option.  Using -fwrapv means that integer
           signed overflow is fully defined: it wraps.  When -fwrapv is
           used, there is no difference between -fstrict-overflow and
           -fno-strict-overflow for integers.  With -fwrapv certain types of
           overflow are permitted.  For example, if the compiler gets an
           overflow when doing arithmetic on constants, the overflowed value
           can still be used with -fwrapv, but not otherwise.

           The -fstrict-overflow option is enabled at levels -O2, -O3, -Os.

       -falign-functions
       -falign-functions=n
           Align the start of functions to the next power-of-two greater
           than n, skipping up to n bytes.  For instance,
           -falign-functions=32 aligns functions to the next 32-byte
           boundary, but -falign-functions=24 aligns to the next 32-byte
           boundary only if this can be done by skipping 23 bytes or less.

           -fno-align-functions and -falign-functions=1 are equivalent and
           mean that functions are not aligned.

           Some assemblers only support this flag when n is a power of two;
           in that case, it is rounded up.

           If n is not specified or is zero, use a machine-dependent
           default.

           Enabled at levels -O2, -O3.

       -falign-labels
       -falign-labels=n
           Align all branch targets to a power-of-two boundary, skipping up
           to n bytes like -falign-functions.  This option can easily make
           code slower, because it must insert dummy operations for when the
           branch target is reached in the usual flow of the code.

           -fno-align-labels and -falign-labels=1 are equivalent and mean
           that labels are not aligned.

           If -falign-loops or -falign-jumps are applicable and are greater
           than this value, then their values are used instead.

           If n is not specified or is zero, use a machine-dependent default
           which is very likely to be 1, meaning no alignment.

           Enabled at levels -O2, -O3.

       -falign-loops
       -falign-loops=n
           Align loops to a power-of-two boundary, skipping up to n bytes
           like -falign-functions.  If the loops are executed many times,
           this makes up for any execution of the dummy operations.

           -fno-align-loops and -falign-loops=1 are equivalent and mean that
           loops are not aligned.

           If n is not specified or is zero, use a machine-dependent
           default.

           Enabled at levels -O2, -O3.

       -falign-jumps
       -falign-jumps=n
           Align branch targets to a power-of-two boundary, for branch
           targets where the targets can only be reached by jumping,
           skipping up to n bytes like -falign-functions.  In this case, no
           dummy operations need be executed.

           -fno-align-jumps and -falign-jumps=1 are equivalent and mean that
           loops are not aligned.

           If n is not specified or is zero, use a machine-dependent
           default.

           Enabled at levels -O2, -O3.

       -funit-at-a-time
           This option is left for compatibility reasons. -funit-at-a-time
           has no effect, while -fno-unit-at-a-time implies
           -fno-toplevel-reorder and -fno-section-anchors.

           Enabled by default.

       -fno-toplevel-reorder
           Do not reorder top-level functions, variables, and "asm"
           statements.  Output them in the same order that they appear in
           the input file.  When this option is used, unreferenced static
           variables are not removed.  This option is intended to support
           existing code that relies on a particular ordering.  For new
           code, it is better to use attributes when possible.

           Enabled at level -O0.  When disabled explicitly, it also implies
           -fno-section-anchors, which is otherwise enabled at -O0 on some
           targets.

       -fweb
           Constructs webs as commonly used for register allocation purposes
           and assign each web individual pseudo register.  This allows the
           register allocation pass to operate on pseudos directly, but also
           strengthens several other optimization passes, such as CSE, loop
           optimizer and trivial dead code remover.  It can, however, make
           debugging impossible, since variables no longer stay in a "home
           register".

           Enabled by default with -funroll-loops.

       -fwhole-program
           Assume that the current compilation unit represents the whole
           program being compiled.  All public functions and variables with
           the exception of "main" and those merged by attribute
           "externally_visible" become static functions and in effect are
           optimized more aggressively by interprocedural optimizers.

           This option should not be used in combination with -flto.
           Instead relying on a linker plugin should provide safer and more
           precise information.

       -flto[=n]
           This option runs the standard link-time optimizer.  When invoked
           with source code, it generates GIMPLE (one of GCC's internal
           representations) and writes it to special ELF sections in the
           object file.  When the object files are linked together, all the
           function bodies are read from these ELF sections and instantiated
           as if they had been part of the same translation unit.

           To use the link-time optimizer, -flto and optimization options
           should be specified at compile time and during the final link.
           It is recommended that you compile all the files participating in
           the same link with the same options and also specify those
           options at link time.  For example:

                   gcc -c -O2 -flto foo.c
                   gcc -c -O2 -flto bar.c
                   gcc -o myprog -flto -O2 foo.o bar.o

           The first two invocations to GCC save a bytecode representation
           of GIMPLE into special ELF sections inside foo.o and bar.o.  The
           final invocation reads the GIMPLE bytecode from foo.o and bar.o,
           merges the two files into a single internal image, and compiles
           the result as usual.  Since both foo.o and bar.o are merged into
           a single image, this causes all the interprocedural analyses and
           optimizations in GCC to work across the two files as if they were
           a single one.  This means, for example, that the inliner is able
           to inline functions in bar.o into functions in foo.o and vice-
           versa.

           Another (simpler) way to enable link-time optimization is:

                   gcc -o myprog -flto -O2 foo.c bar.c

           The above generates bytecode for foo.c and bar.c, merges them
           together into a single GIMPLE representation and optimizes them
           as usual to produce myprog.

           The only important thing to keep in mind is that to enable link-
           time optimizations you need to use the GCC driver to perform the
           link step.  GCC then automatically performs link-time
           optimization if any of the objects involved were compiled with
           the -flto command-line option.  You generally should specify the
           optimization options to be used for link-time optimization though
           GCC tries to be clever at guessing an optimization level to use
           from the options used at compile time if you fail to specify one
           at link time.  You can always override the automatic decision to
           do link-time optimization at link time by passing -fno-lto to the
           link command.

           To make whole program optimization effective, it is necessary to
           make certain whole program assumptions.  The compiler needs to
           know what functions and variables can be accessed by libraries
           and runtime outside of the link-time optimized unit.  When
           supported by the linker, the linker plugin (see
           -fuse-linker-plugin) passes information to the compiler about
           used and externally visible symbols.  When the linker plugin is
           not available, -fwhole-program should be used to allow the
           compiler to make these assumptions, which leads to more
           aggressive optimization decisions.

           When -fuse-linker-plugin is not enabled, when a file is compiled
           with -flto, the generated object file is larger than a regular
           object file because it contains GIMPLE bytecodes and the usual
           final code (see -ffat-lto-objects.  This means that object files
           with LTO information can be linked as normal object files; if
           -fno-lto is passed to the linker, no interprocedural
           optimizations are applied.  Note that when -fno-fat-lto-objects
           is enabled the compile stage is faster but you cannot perform a
           regular, non-LTO link on them.

           Additionally, the optimization flags used to compile individual
           files are not necessarily related to those used at link time.
           For instance,

                   gcc -c -O0 -ffat-lto-objects -flto foo.c
                   gcc -c -O0 -ffat-lto-objects -flto bar.c
                   gcc -o myprog -O3 foo.o bar.o

           This produces individual object files with unoptimized assembler
           code, but the resulting binary myprog is optimized at -O3.  If,
           instead, the final binary is generated with -fno-lto, then myprog
           is not optimized.

           When producing the final binary, GCC only applies link-time
           optimizations to those files that contain bytecode.  Therefore,
           you can mix and match object files and libraries with GIMPLE
           bytecodes and final object code.  GCC automatically selects which
           files to optimize in LTO mode and which files to link without
           further processing.

           There are some code generation flags preserved by GCC when
           generating bytecodes, as they need to be used during the final
           link stage.  Generally options specified at link time override
           those specified at compile time.

           If you do not specify an optimization level option -O at link
           time, then GCC uses the highest optimization level used when
           compiling the object files.

           Currently, the following options and their settings are taken
           from the first object file that explicitly specifies them: -fPIC,
           -fpic, -fpie, -fcommon, -fexceptions, -fnon-call-exceptions,
           -fgnu-tm and all the -m target flags.

           Certain ABI-changing flags are required to match in all
           compilation units, and trying to override this at link time with
           a conflicting value is ignored.  This includes options such as
           -freg-struct-return and -fpcc-struct-return.

           Other options such as -ffp-contract, -fno-strict-overflow,
           -fwrapv, -fno-trapv or -fno-strict-aliasing are passed through to
           the link stage and merged conservatively for conflicting
           translation units.  Specifically -fno-strict-overflow, -fwrapv
           and -fno-trapv take precedence; and for example -ffp-contract=off
           takes precedence over -ffp-contract=fast.  You can override them
           at link time.

           If LTO encounters objects with C linkage declared with
           incompatible types in separate translation units to be linked
           together (undefined behavior according to ISO C99 6.2.7), a non-
           fatal diagnostic may be issued.  The behavior is still undefined
           at run time.  Similar diagnostics may be raised for other
           languages.

           Another feature of LTO is that it is possible to apply
           interprocedural optimizations on files written in different
           languages:

                   gcc -c -flto foo.c
                   g++ -c -flto bar.cc
                   gfortran -c -flto baz.f90
                   g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran

           Notice that the final link is done with g++ to get the C++
           runtime libraries and -lgfortran is added to get the Fortran
           runtime libraries.  In general, when mixing languages in LTO
           mode, you should use the same link command options as when mixing
           languages in a regular (non-LTO) compilation.

           If object files containing GIMPLE bytecode are stored in a
           library archive, say libfoo.a, it is possible to extract and use
           them in an LTO link if you are using a linker with plugin
           support.  To create static libraries suitable for LTO, use gcc-ar
           and gcc-ranlib instead of ar and ranlib; to show the symbols of
           object files with GIMPLE bytecode, use gcc-nm.  Those commands
           require that ar, ranlib and nm have been compiled with plugin
           support.  At link time, use the the flag -fuse-linker-plugin to
           ensure that the library participates in the LTO optimization
           process:

                   gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo

           With the linker plugin enabled, the linker extracts the needed
           GIMPLE files from libfoo.a and passes them on to the running GCC
           to make them part of the aggregated GIMPLE image to be optimized.

           If you are not using a linker with plugin support and/or do not
           enable the linker plugin, then the objects inside libfoo.a are
           extracted and linked as usual, but they do not participate in the
           LTO optimization process.  In order to make a static library
           suitable for both LTO optimization and usual linkage, compile its
           object files with -flto -ffat-lto-objects.

           Link-time optimizations do not require the presence of the whole
           program to operate.  If the program does not require any symbols
           to be exported, it is possible to combine -flto and
           -fwhole-program to allow the interprocedural optimizers to use
           more aggressive assumptions which may lead to improved
           optimization opportunities.  Use of -fwhole-program is not needed
           when linker plugin is active (see -fuse-linker-plugin).

           The current implementation of LTO makes no attempt to generate
           bytecode that is portable between different types of hosts.  The
           bytecode files are versioned and there is a strict version check,
           so bytecode files generated in one version of GCC do not work
           with an older or newer version of GCC.

           Link-time optimization does not work well with generation of
           debugging information.  Combining -flto with -g is currently
           experimental and expected to produce unexpected results.

           If you specify the optional n, the optimization and code
           generation done at link time is executed in parallel using n
           parallel jobs by utilizing an installed make program.  The
           environment variable MAKE may be used to override the program
           used.  The default value for n is 1.

           You can also specify -flto=jobserver to use GNU make's job server
           mode to determine the number of parallel jobs. This is useful
           when the Makefile calling GCC is already executing in parallel.
           You must prepend a + to the command recipe in the parent Makefile
           for this to work.  This option likely only works if MAKE is GNU
           make.

       -flto-partition=alg
           Specify the partitioning algorithm used by the link-time
           optimizer.  The value is either 1to1 to specify a partitioning
           mirroring the original source files or balanced to specify
           partitioning into equally sized chunks (whenever possible) or max
           to create new partition for every symbol where possible.
           Specifying none as an algorithm disables partitioning and
           streaming completely.  The default value is balanced. While 1to1
           can be used as an workaround for various code ordering issues,
           the max partitioning is intended for internal testing only.  The
           value one specifies that exactly one partition should be used
           while the value none bypasses partitioning and executes the link-
           time optimization step directly from the WPA phase.

       -flto-odr-type-merging
           Enable streaming of mangled types names of C++ types and their
           unification at link time.  This increases size of LTO object
           files, but enables diagnostics about One Definition Rule
           violations.

       -flto-compression-level=n
           This option specifies the level of compression used for
           intermediate language written to LTO object files, and is only
           meaningful in conjunction with LTO mode (-flto).  Valid values
           are 0 (no compression) to 9 (maximum compression).  Values
           outside this range are clamped to either 0 or 9.  If the option
           is not given, a default balanced compression setting is used.

       -fuse-linker-plugin
           Enables the use of a linker plugin during link-time optimization.
           This option relies on plugin support in the linker, which is
           available in gold or in GNU ld 2.21 or newer.

           This option enables the extraction of object files with GIMPLE
           bytecode out of library archives. This improves the quality of
           optimization by exposing more code to the link-time optimizer.
           This information specifies what symbols can be accessed
           externally (by non-LTO object or during dynamic linking).
           Resulting code quality improvements on binaries (and shared
           libraries that use hidden visibility) are similar to
           -fwhole-program.  See -flto for a description of the effect of
           this flag and how to use it.

           This option is enabled by default when LTO support in GCC is
           enabled and GCC was configured for use with a linker supporting
           plugins (GNU ld 2.21 or newer or gold).

       -ffat-lto-objects
           Fat LTO objects are object files that contain both the
           intermediate language and the object code. This makes them usable
           for both LTO linking and normal linking. This option is effective
           only when compiling with -flto and is ignored at link time.

           -fno-fat-lto-objects improves compilation time over plain LTO,
           but requires the complete toolchain to be aware of LTO. It
           requires a linker with linker plugin support for basic
           functionality.  Additionally, nm, ar and ranlib need to support
           linker plugins to allow a full-featured build environment
           (capable of building static libraries etc).  GCC provides the
           gcc-ar, gcc-nm, gcc-ranlib wrappers to pass the right options to
           these tools. With non fat LTO makefiles need to be modified to
           use them.

           The default is -fno-fat-lto-objects on targets with linker plugin
           support.

       -fcompare-elim
           After register allocation and post-register allocation
           instruction splitting, identify arithmetic instructions that
           compute processor flags similar to a comparison operation based
           on that arithmetic.  If possible, eliminate the explicit
           comparison operation.

           This pass only applies to certain targets that cannot explicitly
           represent the comparison operation before register allocation is
           complete.

           Enabled at levels -O, -O2, -O3, -Os.

       -fcprop-registers
           After register allocation and post-register allocation
           instruction splitting, perform a copy-propagation pass to try to
           reduce scheduling dependencies and occasionally eliminate the
           copy.

           Enabled at levels -O, -O2, -O3, -Os.

       -fprofile-correction
           Profiles collected using an instrumented binary for multi-
           threaded programs may be inconsistent due to missed counter
           updates. When this option is specified, GCC uses heuristics to
           correct or smooth out such inconsistencies. By default, GCC emits
           an error message when an inconsistent profile is detected.

       -fprofile-use
       -fprofile-use=path
           Enable profile feedback-directed optimizations, and the following
           optimizations which are generally profitable only with profile
           feedback available: -fbranch-probabilities, -fvpt,
           -funroll-loops, -fpeel-loops, -ftracer, -ftree-vectorize, and
           ftree-loop-distribute-patterns.

           Before you can use this option, you must first generate profiling
           information.

           By default, GCC emits an error message if the feedback profiles
           do not match the source code.  This error can be turned into a
           warning by using -Wcoverage-mismatch.  Note this may result in
           poorly optimized code.

           If path is specified, GCC looks at the path to find the profile
           feedback data files. See -fprofile-dir.

       -fauto-profile
       -fauto-profile=path
           Enable sampling-based feedback-directed optimizations, and the
           following optimizations which are generally profitable only with
           profile feedback available: -fbranch-probabilities, -fvpt,
           -funroll-loops, -fpeel-loops, -ftracer, -ftree-vectorize,
           -finline-functions, -fipa-cp, -fipa-cp-clone,
           -fpredictive-commoning, -funswitch-loops, -fgcse-after-reload,
           and -ftree-loop-distribute-patterns.

           path is the name of a file containing AutoFDO profile
           information.  If omitted, it defaults to fbdata.afdo in the
           current directory.

           Producing an AutoFDO profile data file requires running your
           program with the perf utility on a supported GNU/Linux target
           system.  For more information, see
           <https://perf.wiki.kernel.org/ >.

           E.g.

                   perf record -e br_inst_retired:near_taken -b -o perf.data \
                       -- your_program

           Then use the create_gcov tool to convert the raw profile data to
           a format that can be used by GCC.  You must also supply the
           unstripped binary for your program to this tool.  See
           <https://github.com/google/autofdo >.

           E.g.

                   create_gcov --binary=your_program.unstripped --profile=perf.data \
                       --gcov=profile.afdo

       The following options control compiler behavior regarding floating-
       point arithmetic.  These options trade off between speed and
       correctness.  All must be specifically enabled.

       -ffloat-store
           Do not store floating-point variables in registers, and inhibit
           other options that might change whether a floating-point value is
           taken from a register or memory.

           This option prevents undesirable excess precision on machines
           such as the 68000 where the floating registers (of the 68881)
           keep more precision than a "double" is supposed to have.
           Similarly for the x86 architecture.  For most programs, the
           excess precision does only good, but a few programs rely on the
           precise definition of IEEE floating point.  Use -ffloat-store for
           such programs, after modifying them to store all pertinent
           intermediate computations into variables.

       -fexcess-precision=style
           This option allows further control over excess precision on
           machines where floating-point registers have more precision than
           the IEEE "float" and "double" types and the processor does not
           support operations rounding to those types.  By default,
           -fexcess-precision=fast is in effect; this means that operations
           are carried out in the precision of the registers and that it is
           unpredictable when rounding to the types specified in the source
           code takes place.  When compiling C, if
           -fexcess-precision=standard is specified then excess precision
           follows the rules specified in ISO C99; in particular, both casts
           and assignments cause values to be rounded to their semantic
           types (whereas -ffloat-store only affects assignments).  This
           option is enabled by default for C if a strict conformance option
           such as -std=c99 is used.

           -fexcess-precision=standard is not implemented for languages
           other than C, and has no effect if -funsafe-math-optimizations or
           -ffast-math is specified.  On the x86, it also has no effect if
           -mfpmath=sse or -mfpmath=sse+387 is specified; in the former
           case, IEEE semantics apply without excess precision, and in the
           latter, rounding is unpredictable.

       -ffast-math
           Sets the options -fno-math-errno, -funsafe-math-optimizations,
           -ffinite-math-only, -fno-rounding-math, -fno-signaling-nans and
           -fcx-limited-range.

           This option causes the preprocessor macro "__FAST_MATH__" to be
           defined.

           This option is not turned on by any -O option besides -Ofast
           since it can result in incorrect output for programs that depend
           on an exact implementation of IEEE or ISO rules/specifications
           for math functions. It may, however, yield faster code for
           programs that do not require the guarantees of these
           specifications.

       -fno-math-errno
           Do not set "errno" after calling math functions that are executed
           with a single instruction, e.g., "sqrt".  A program that relies
           on IEEE exceptions for math error handling may want to use this
           flag for speed while maintaining IEEE arithmetic compatibility.

           This option is not turned on by any -O option since it can result
           in incorrect output for programs that depend on an exact
           implementation of IEEE or ISO rules/specifications for math
           functions. It may, however, yield faster code for programs that
           do not require the guarantees of these specifications.

           The default is -fmath-errno.

           On Darwin systems, the math library never sets "errno".  There is
           therefore no reason for the compiler to consider the possibility
           that it might, and -fno-math-errno is the default.

       -funsafe-math-optimizations
           Allow optimizations for floating-point arithmetic that (a) assume
           that arguments and results are valid and (b) may violate IEEE or
           ANSI standards.  When used at link time, it may include libraries
           or startup files that change the default FPU control word or
           other similar optimizations.

           This option is not turned on by any -O option since it can result
           in incorrect output for programs that depend on an exact
           implementation of IEEE or ISO rules/specifications for math
           functions. It may, however, yield faster code for programs that
           do not require the guarantees of these specifications.  Enables
           -fno-signed-zeros, -fno-trapping-math, -fassociative-math and
           -freciprocal-math.

           The default is -fno-unsafe-math-optimizations.

       -fassociative-math
           Allow re-association of operands in series of floating-point
           operations.  This violates the ISO C and C++ language standard by
           possibly changing computation result.  NOTE: re-ordering may
           change the sign of zero as well as ignore NaNs and inhibit or
           create underflow or overflow (and thus cannot be used on code
           that relies on rounding behavior like "(x + 2**52) - 2**52".  May
           also reorder floating-point comparisons and thus may not be used
           when ordered comparisons are required.  This option requires that
           both -fno-signed-zeros and -fno-trapping-math be in effect.
           Moreover, it doesn't make much sense with -frounding-math. For
           Fortran the option is automatically enabled when both
           -fno-signed-zeros and -fno-trapping-math are in effect.

           The default is -fno-associative-math.

       -freciprocal-math
           Allow the reciprocal of a value to be used instead of dividing by
           the value if this enables optimizations.  For example "x / y" can
           be replaced with "x * (1/y)", which is useful if "(1/y)" is
           subject to common subexpression elimination.  Note that this
           loses precision and increases the number of flops operating on
           the value.

           The default is -fno-reciprocal-math.

       -ffinite-math-only
           Allow optimizations for floating-point arithmetic that assume
           that arguments and results are not NaNs or +-Infs.

           This option is not turned on by any -O option since it can result
           in incorrect output for programs that depend on an exact
           implementation of IEEE or ISO rules/specifications for math
           functions. It may, however, yield faster code for programs that
           do not require the guarantees of these specifications.

           The default is -fno-finite-math-only.

       -fno-signed-zeros
           Allow optimizations for floating-point arithmetic that ignore the
           signedness of zero.  IEEE arithmetic specifies the behavior of
           distinct +0.0 and -0.0 values, which then prohibits
           simplification of expressions such as x+0.0 or 0.0*x (even with
           -ffinite-math-only).  This option implies that the sign of a zero
           result isn't significant.

           The default is -fsigned-zeros.

       -fno-trapping-math
           Compile code assuming that floating-point operations cannot
           generate user-visible traps.  These traps include division by
           zero, overflow, underflow, inexact result and invalid operation.
           This option requires that -fno-signaling-nans be in effect.
           Setting this option may allow faster code if one relies on "non-
           stop" IEEE arithmetic, for example.

           This option should never be turned on by any -O option since it
           can result in incorrect output for programs that depend on an
           exact implementation of IEEE or ISO rules/specifications for math
           functions.

           The default is -ftrapping-math.

       -frounding-math
           Disable transformations and optimizations that assume default
           floating-point rounding behavior.  This is round-to-zero for all
           floating point to integer conversions, and round-to-nearest for
           all other arithmetic truncations.  This option should be
           specified for programs that change the FP rounding mode
           dynamically, or that may be executed with a non-default rounding
           mode.  This option disables constant folding of floating-point
           expressions at compile time (which may be affected by rounding
           mode) and arithmetic transformations that are unsafe in the
           presence of sign-dependent rounding modes.

           The default is -fno-rounding-math.

           This option is experimental and does not currently guarantee to
           disable all GCC optimizations that are affected by rounding mode.
           Future versions of GCC may provide finer control of this setting
           using C99's "FENV_ACCESS" pragma.  This command-line option will
           be used to specify the default state for "FENV_ACCESS".

       -fsignaling-nans
           Compile code assuming that IEEE signaling NaNs may generate user-
           visible traps during floating-point operations.  Setting this
           option disables optimizations that may change the number of
           exceptions visible with signaling NaNs.  This option implies
           -ftrapping-math.

           This option causes the preprocessor macro "__SUPPORT_SNAN__" to
           be defined.

           The default is -fno-signaling-nans.

           This option is experimental and does not currently guarantee to
           disable all GCC optimizations that affect signaling NaN behavior.

       -fsingle-precision-constant
           Treat floating-point constants as single precision instead of
           implicitly converting them to double-precision constants.

       -fcx-limited-range
           When enabled, this option states that a range reduction step is
           not needed when performing complex division.  Also, there is no
           checking whether the result of a complex multiplication or
           division is "NaN + I*NaN", with an attempt to rescue the
           situation in that case.  The default is -fno-cx-limited-range,
           but is enabled by -ffast-math.

           This option controls the default setting of the ISO C99
           "CX_LIMITED_RANGE" pragma.  Nevertheless, the option applies to
           all languages.

       -fcx-fortran-rules
           Complex multiplication and division follow Fortran rules.  Range
           reduction is done as part of complex division, but there is no
           checking whether the result of a complex multiplication or
           division is "NaN + I*NaN", with an attempt to rescue the
           situation in that case.

           The default is -fno-cx-fortran-rules.

       The following options control optimizations that may improve
       performance, but are not enabled by any -O options.  This section
       includes experimental options that may produce broken code.

       -fbranch-probabilities
           After running a program compiled with -fprofile-arcs, you can
           compile it a second time using -fbranch-probabilities, to improve
           optimizations based on the number of times each branch was taken.
           When a program compiled with -fprofile-arcs exits, it saves arc
           execution counts to a file called sourcename.gcda for each source
           file.  The information in this data file is very dependent on the
           structure of the generated code, so you must use the same source
           code and the same optimization options for both compilations.

           With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each
           JUMP_INSN and CALL_INSN.  These can be used to improve
           optimization.  Currently, they are only used in one place: in
           reorg.c, instead of guessing which path a branch is most likely
           to take, the REG_BR_PROB values are used to exactly determine
           which path is taken more often.

       -fprofile-values
           If combined with -fprofile-arcs, it adds code so that some data
           about values of expressions in the program is gathered.

           With -fbranch-probabilities, it reads back the data gathered from
           profiling values of expressions for usage in optimizations.

           Enabled with -fprofile-generate and -fprofile-use.

       -fprofile-reorder-functions
           Function reordering based on profile instrumentation collects
           first time of execution of a function and orders these functions
           in ascending order.

           Enabled with -fprofile-use.

       -fvpt
           If combined with -fprofile-arcs, this option instructs the
           compiler to add code to gather information about values of
           expressions.

           With -fbranch-probabilities, it reads back the data gathered and
           actually performs the optimizations based on them.  Currently the
           optimizations include specialization of division operations using
           the knowledge about the value of the denominator.

       -frename-registers
           Attempt to avoid false dependencies in scheduled code by making
           use of registers left over after register allocation.  This
           optimization most benefits processors with lots of registers.
           Depending on the debug information format adopted by the target,
           however, it can make debugging impossible, since variables no
           longer stay in a "home register".

           Enabled by default with -funroll-loops and -fpeel-loops.

       -fschedule-fusion
           Performs a target dependent pass over the instruction stream to
           schedule instructions of same type together because target
           machine can execute them more efficiently if they are adjacent to
           each other in the instruction flow.

           Enabled at levels -O2, -O3, -Os.

       -ftracer
           Perform tail duplication to enlarge superblock size.  This
           transformation simplifies the control flow of the function
           allowing other optimizations to do a better job.

           Enabled with -fprofile-use.

       -funroll-loops
           Unroll loops whose number of iterations can be determined at
           compile time or upon entry to the loop.  -funroll-loops implies
           -frerun-cse-after-loop, -fweb and -frename-registers.  It also
           turns on complete loop peeling (i.e. complete removal of loops
           with a small constant number of iterations).  This option makes
           code larger, and may or may not make it run faster.

           Enabled with -fprofile-use.

       -funroll-all-loops
           Unroll all loops, even if their number of iterations is uncertain
           when the loop is entered.  This usually makes programs run more
           slowly.  -funroll-all-loops implies the same options as
           -funroll-loops.

       -fpeel-loops
           Peels loops for which there is enough information that they do
           not roll much (from profile feedback).  It also turns on complete
           loop peeling (i.e. complete removal of loops with small constant
           number of iterations).

           Enabled with -fprofile-use.

       -fmove-loop-invariants
           Enables the loop invariant motion pass in the RTL loop optimizer.
           Enabled at level -O1

       -funswitch-loops
           Move branches with loop invariant conditions out of the loop,
           with duplicates of the loop on both branches (modified according
           to result of the condition).

       -ffunction-sections
       -fdata-sections
           Place each function or data item into its own section in the
           output file if the target supports arbitrary sections.  The name
           of the function or the name of the data item determines the
           section's name in the output file.

           Use these options on systems where the linker can perform
           optimizations to improve locality of reference in the instruction
           space.  Most systems using the ELF object format and SPARC
           processors running Solaris 2 have linkers with such
           optimizations.  AIX may have these optimizations in the future.

           Only use these options when there are significant benefits from
           doing so.  When you specify these options, the assembler and
           linker create larger object and executable files and are also
           slower.  You cannot use gprof on all systems if you specify this
           option, and you may have problems with debugging if you specify
           both this option and -g.

       -fbranch-target-load-optimize
           Perform branch target register load optimization before prologue
           / epilogue threading.  The use of target registers can typically
           be exposed only during reload, thus hoisting loads out of loops
           and doing inter-block scheduling needs a separate optimization
           pass.

       -fbranch-target-load-optimize2
           Perform branch target register load optimization after prologue /
           epilogue threading.

       -fbtr-bb-exclusive
           When performing branch target register load optimization, don't
           reuse branch target registers within any basic block.

       -fstdarg-opt
           Optimize the prologue of variadic argument functions with respect
           to usage of those arguments.

       -fsection-anchors
           Try to reduce the number of symbolic address calculations by
           using shared "anchor" symbols to address nearby objects.  This
           transformation can help to reduce the number of GOT entries and
           GOT accesses on some targets.

           For example, the implementation of the following function "foo":

                   static int a, b, c;
                   int foo (void) { return a + b + c; }

           usually calculates the addresses of all three variables, but if
           you compile it with -fsection-anchors, it accesses the variables
           from a common anchor point instead.  The effect is similar to the
           following pseudocode (which isn't valid C):

                   int foo (void)
                   {
                     register int *xr = &x;
                     return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
                   }

           Not all targets support this option.

       --param name=value
           In some places, GCC uses various constants to control the amount
           of optimization that is done.  For example, GCC does not inline
           functions that contain more than a certain number of
           instructions.  You can control some of these constants on the
           command line using the --param option.

           The names of specific parameters, and the meaning of the values,
           are tied to the internals of the compiler, and are subject to
           change without notice in future releases.

           In each case, the value is an integer.  The allowable choices for
           name are:

           predictable-branch-outcome
               When branch is predicted to be taken with probability lower
               than this threshold (in percent), then it is considered well
               predictable. The default is 10.

           max-rtl-if-conversion-insns
               RTL if-conversion tries to remove conditional branches around
               a block and replace them with conditionally executed
               instructions.  This parameter gives the maximum number of
               instructions in a block which should be considered for if-
               conversion.  The default is 10, though the compiler will also
               use other heuristics to decide whether if-conversion is
               likely to be profitable.

           max-crossjump-edges
               The maximum number of incoming edges to consider for cross-
               jumping.  The algorithm used by -fcrossjumping is O(N^2) in
               the number of edges incoming to each block.  Increasing
               values mean more aggressive optimization, making the
               compilation time increase with probably small improvement in
               executable size.

           min-crossjump-insns
               The minimum number of instructions that must be matched at
               the end of two blocks before cross-jumping is performed on
               them.  This value is ignored in the case where all
               instructions in the block being cross-jumped from are
               matched.  The default value is 5.

           max-grow-copy-bb-insns
               The maximum code size expansion factor when copying basic
               blocks instead of jumping.  The expansion is relative to a
               jump instruction.  The default value is 8.

           max-goto-duplication-insns
               The maximum number of instructions to duplicate to a block
               that jumps to a computed goto.  To avoid O(N^2) behavior in a
               number of passes, GCC factors computed gotos early in the
               compilation process, and unfactors them as late as possible.
               Only computed jumps at the end of a basic blocks with no more
               than max-goto-duplication-insns are unfactored.  The default
               value is 8.

           max-delay-slot-insn-search
               The maximum number of instructions to consider when looking
               for an instruction to fill a delay slot.  If more than this
               arbitrary number of instructions are searched, the time
               savings from filling the delay slot are minimal, so stop
               searching.  Increasing values mean more aggressive
               optimization, making the compilation time increase with
               probably small improvement in execution time.

           max-delay-slot-live-search
               When trying to fill delay slots, the maximum number of
               instructions to consider when searching for a block with
               valid live register information.  Increasing this arbitrarily
               chosen value means more aggressive optimization, increasing
               the compilation time.  This parameter should be removed when
               the delay slot code is rewritten to maintain the control-flow
               graph.

           max-gcse-memory
               The approximate maximum amount of memory that can be
               allocated in order to perform the global common subexpression
               elimination optimization.  If more memory than specified is
               required, the optimization is not done.

           max-gcse-insertion-ratio
               If the ratio of expression insertions to deletions is larger
               than this value for any expression, then RTL PRE inserts or
               removes the expression and thus leaves partially redundant
               computations in the instruction stream.  The default value is
               20.

           max-pending-list-length
               The maximum number of pending dependencies scheduling allows
               before flushing the current state and starting over.  Large
               functions with few branches or calls can create excessively
               large lists which needlessly consume memory and resources.

           max-modulo-backtrack-attempts
               The maximum number of backtrack attempts the scheduler should
               make when modulo scheduling a loop.  Larger values can
               exponentially increase compilation time.

           max-inline-insns-single
               Several parameters control the tree inliner used in GCC.
               This number sets the maximum number of instructions (counted
               in GCC's internal representation) in a single function that
               the tree inliner considers for inlining.  This only affects
               functions declared inline and methods implemented in a class
               declaration (C++).  The default value is 400.

           max-inline-insns-auto
               When you use -finline-functions (included in -O3), a lot of
               functions that would otherwise not be considered for inlining
               by the compiler are investigated.  To those functions, a
               different (more restrictive) limit compared to functions
               declared inline can be applied.  The default value is 40.

           inline-min-speedup
               When estimated performance improvement of caller + callee
               runtime exceeds this threshold (in precent), the function can
               be inlined regardless the limit on --param max-inline-insns-
               single and --param max-inline-insns-auto.

           large-function-insns
               The limit specifying really large functions.  For functions
               larger than this limit after inlining, inlining is
               constrained by --param large-function-growth.  This parameter
               is useful primarily to avoid extreme compilation time caused
               by non-linear algorithms used by the back end.  The default
               value is 2700.

           large-function-growth
               Specifies maximal growth of large function caused by inlining
               in percents.  The default value is 100 which limits large
               function growth to 2.0 times the original size.

           large-unit-insns
               The limit specifying large translation unit.  Growth caused
               by inlining of units larger than this limit is limited by
               --param inline-unit-growth.  For small units this might be
               too tight.  For example, consider a unit consisting of
               function A that is inline and B that just calls A three
               times.  If B is small relative to A, the growth of unit is
               300\% and yet such inlining is very sane.  For very large
               units consisting of small inlineable functions, however, the
               overall unit growth limit is needed to avoid exponential
               explosion of code size.  Thus for smaller units, the size is
               increased to --param large-unit-insns before applying --param
               inline-unit-growth.  The default is 10000.

           inline-unit-growth
               Specifies maximal overall growth of the compilation unit
               caused by inlining.  The default value is 20 which limits
               unit growth to 1.2 times the original size. Cold functions
               (either marked cold via an attribute or by profile feedback)
               are not accounted into the unit size.

           ipcp-unit-growth
               Specifies maximal overall growth of the compilation unit
               caused by interprocedural constant propagation.  The default
               value is 10 which limits unit growth to 1.1 times the
               original size.

           large-stack-frame
               The limit specifying large stack frames.  While inlining the
               algorithm is trying to not grow past this limit too much.
               The default value is 256 bytes.

           large-stack-frame-growth
               Specifies maximal growth of large stack frames caused by
               inlining in percents.  The default value is 1000 which limits
               large stack frame growth to 11 times the original size.

           max-inline-insns-recursive
           max-inline-insns-recursive-auto
               Specifies the maximum number of instructions an out-of-line
               copy of a self-recursive inline function can grow into by
               performing recursive inlining.

               --param max-inline-insns-recursive applies to functions
               declared inline.  For functions not declared inline,
               recursive inlining happens only when -finline-functions
               (included in -O3) is enabled; --param max-inline-insns-
               recursive-auto applies instead.  The default value is 450.

           max-inline-recursive-depth
           max-inline-recursive-depth-auto
               Specifies the maximum recursion depth used for recursive
               inlining.

               --param max-inline-recursive-depth applies to functions
               declared inline.  For functions not declared inline,
               recursive inlining happens only when -finline-functions
               (included in -O3) is enabled; --param max-inline-recursive-
               depth-auto applies instead.  The default value is 8.

           min-inline-recursive-probability
               Recursive inlining is profitable only for function having
               deep recursion in average and can hurt for function having
               little recursion depth by increasing the prologue size or
               complexity of function body to other optimizers.

               When profile feedback is available (see -fprofile-generate)
               the actual recursion depth can be guessed from probability
               that function recurses via a given call expression.  This
               parameter limits inlining only to call expressions whose
               probability exceeds the given threshold (in percents).  The
               default value is 10.

           early-inlining-insns
               Specify growth that the early inliner can make.  In effect it
               increases the amount of inlining for code having a large
               abstraction penalty.  The default value is 14.

           max-early-inliner-iterations
               Limit of iterations of the early inliner.  This basically
               bounds the number of nested indirect calls the early inliner
               can resolve.  Deeper chains are still handled by late
               inlining.

           comdat-sharing-probability
               Probability (in percent) that C++ inline function with comdat
               visibility are shared across multiple compilation units.  The
               default value is 20.

           profile-func-internal-id
               A parameter to control whether to use function internal id in
               profile database lookup. If the value is 0, the compiler uses
               an id that is based on function assembler name and filename,
               which makes old profile data more tolerant to source changes
               such as function reordering etc.  The default value is 0.

           min-vect-loop-bound
               The minimum number of iterations under which loops are not
               vectorized when -ftree-vectorize is used.  The number of
               iterations after vectorization needs to be greater than the
               value specified by this option to allow vectorization.  The
               default value is 0.

           gcse-cost-distance-ratio
               Scaling factor in calculation of maximum distance an
               expression can be moved by GCSE optimizations.  This is
               currently supported only in the code hoisting pass.  The
               bigger the ratio, the more aggressive code hoisting is with
               simple expressions, i.e., the expressions that have cost less
               than gcse-unrestricted-cost.  Specifying 0 disables hoisting
               of simple expressions.  The default value is 10.

           gcse-unrestricted-cost
               Cost, roughly measured as the cost of a single typical
               machine instruction, at which GCSE optimizations do not
               constrain the distance an expression can travel.  This is
               currently supported only in the code hoisting pass.  The
               lesser the cost, the more aggressive code hoisting is.
               Specifying 0 allows all expressions to travel unrestricted
               distances.  The default value is 3.

           max-hoist-depth
               The depth of search in the dominator tree for expressions to
               hoist.  This is used to avoid quadratic behavior in hoisting
               algorithm.  The value of 0 does not limit on the search, but
               may slow down compilation of huge functions.  The default
               value is 30.

           max-tail-merge-comparisons
               The maximum amount of similar bbs to compare a bb with.  This
               is used to avoid quadratic behavior in tree tail merging.
               The default value is 10.

           max-tail-merge-iterations
               The maximum amount of iterations of the pass over the
               function.  This is used to limit compilation time in tree
               tail merging.  The default value is 2.

           max-unrolled-insns
               The maximum number of instructions that a loop may have to be
               unrolled.  If a loop is unrolled, this parameter also
               determines how many times the loop code is unrolled.

           max-average-unrolled-insns
               The maximum number of instructions biased by probabilities of
               their execution that a loop may have to be unrolled.  If a
               loop is unrolled, this parameter also determines how many
               times the loop code is unrolled.

           max-unroll-times
               The maximum number of unrollings of a single loop.

           max-peeled-insns
               The maximum number of instructions that a loop may have to be
               peeled.  If a loop is peeled, this parameter also determines
               how many times the loop code is peeled.

           max-peel-times
               The maximum number of peelings of a single loop.

           max-peel-branches
               The maximum number of branches on the hot path through the
               peeled sequence.

           max-completely-peeled-insns
               The maximum number of insns of a completely peeled loop.

           max-completely-peel-times
               The maximum number of iterations of a loop to be suitable for
               complete peeling.

           max-completely-peel-loop-nest-depth
               The maximum depth of a loop nest suitable for complete
               peeling.

           max-unswitch-insns
               The maximum number of insns of an unswitched loop.

           max-unswitch-level
               The maximum number of branches unswitched in a single loop.

           lim-expensive
               The minimum cost of an expensive expression in the loop
               invariant motion.

           iv-consider-all-candidates-bound
               Bound on number of candidates for induction variables, below
               which all candidates are considered for each use in induction
               variable optimizations.  If there are more candidates than
               this, only the most relevant ones are considered to avoid
               quadratic time complexity.

           iv-max-considered-uses
               The induction variable optimizations give up on loops that
               contain more induction variable uses.

           iv-always-prune-cand-set-bound
               If the number of candidates in the set is smaller than this
               value, always try to remove unnecessary ivs from the set when
               adding a new one.

           scev-max-expr-size
               Bound on size of expressions used in the scalar evolutions
               analyzer.  Large expressions slow the analyzer.

           scev-max-expr-complexity
               Bound on the complexity of the expressions in the scalar
               evolutions analyzer.  Complex expressions slow the analyzer.

           vect-max-version-for-alignment-checks
               The maximum number of run-time checks that can be performed
               when doing loop versioning for alignment in the vectorizer.

           vect-max-version-for-alias-checks
               The maximum number of run-time checks that can be performed
               when doing loop versioning for alias in the vectorizer.

           vect-max-peeling-for-alignment
               The maximum number of loop peels to enhance access alignment
               for vectorizer. Value -1 means no limit.

           max-iterations-to-track
               The maximum number of iterations of a loop the brute-force
               algorithm for analysis of the number of iterations of the
               loop tries to evaluate.

           hot-bb-count-ws-permille
               A basic block profile count is considered hot if it
               contributes to the given permillage (i.e. 0...1000) of the
               entire profiled execution.

           hot-bb-frequency-fraction
               Select fraction of the entry block frequency of executions of
               basic block in function given basic block needs to have to be
               considered hot.

           max-predicted-iterations
               The maximum number of loop iterations we predict statically.
               This is useful in cases where a function contains a single
               loop with known bound and another loop with unknown bound.
               The known number of iterations is predicted correctly, while
               the unknown number of iterations average to roughly 10.  This
               means that the loop without bounds appears artificially cold
               relative to the other one.

           builtin-expect-probability
               Control the probability of the expression having the
               specified value. This parameter takes a percentage (i.e. 0
               ... 100) as input.  The default probability of 90 is obtained
               empirically.

           align-threshold
               Select fraction of the maximal frequency of executions of a
               basic block in a function to align the basic block.

           align-loop-iterations
               A loop expected to iterate at least the selected number of
               iterations is aligned.

           tracer-dynamic-coverage
           tracer-dynamic-coverage-feedback
               This value is used to limit superblock formation once the
               given percentage of executed instructions is covered.  This
               limits unnecessary code size expansion.

               The tracer-dynamic-coverage-feedback parameter is used only
               when profile feedback is available.  The real profiles (as
               opposed to statically estimated ones) are much less balanced
               allowing the threshold to be larger value.

           tracer-max-code-growth
               Stop tail duplication once code growth has reached given
               percentage.  This is a rather artificial limit, as most of
               the duplicates are eliminated later in cross jumping, so it
               may be set to much higher values than is the desired code
               growth.

           tracer-min-branch-ratio
               Stop reverse growth when the reverse probability of best edge
               is less than this threshold (in percent).

           tracer-min-branch-probability
           tracer-min-branch-probability-feedback
               Stop forward growth if the best edge has probability lower
               than this threshold.

               Similarly to tracer-dynamic-coverage two parameters are
               provided.  tracer-min-branch-probability-feedback is used for
               compilation with profile feedback and tracer-min-branch-
               probability compilation without.  The value for compilation
               with profile feedback needs to be more conservative (higher)
               in order to make tracer effective.

           max-cse-path-length
               The maximum number of basic blocks on path that CSE
               considers.  The default is 10.

           max-cse-insns
               The maximum number of instructions CSE processes before
               flushing.  The default is 1000.

           ggc-min-expand
               GCC uses a garbage collector to manage its own memory
               allocation.  This parameter specifies the minimum percentage
               by which the garbage collector's heap should be allowed to
               expand between collections.  Tuning this may improve
               compilation speed; it has no effect on code generation.

               The default is 30% + 70% * (RAM/1GB) with an upper bound of
               100% when RAM >= 1GB.  If "getrlimit" is available, the
               notion of "RAM" is the smallest of actual RAM and
               "RLIMIT_DATA" or "RLIMIT_AS".  If GCC is not able to
               calculate RAM on a particular platform, the lower bound of
               30% is used.  Setting this parameter and ggc-min-heapsize to
               zero causes a full collection to occur at every opportunity.
               This is extremely slow, but can be useful for debugging.

           ggc-min-heapsize
               Minimum size of the garbage collector's heap before it begins
               bothering to collect garbage.  The first collection occurs
               after the heap expands by ggc-min-expand% beyond ggc-min-
               heapsize.  Again, tuning this may improve compilation speed,
               and has no effect on code generation.

               The default is the smaller of RAM/8, RLIMIT_RSS, or a limit
               that tries to ensure that RLIMIT_DATA or RLIMIT_AS are not
               exceeded, but with a lower bound of 4096 (four megabytes) and
               an upper bound of 131072 (128 megabytes).  If GCC is not able
               to calculate RAM on a particular platform, the lower bound is
               used.  Setting this parameter very large effectively disables
               garbage collection.  Setting this parameter and ggc-min-
               expand to zero causes a full collection to occur at every
               opportunity.

           max-reload-search-insns
               The maximum number of instruction reload should look backward
               for equivalent register.  Increasing values mean more
               aggressive optimization, making the compilation time increase
               with probably slightly better performance.  The default value
               is 100.

           max-cselib-memory-locations
               The maximum number of memory locations cselib should take
               into account.  Increasing values mean more aggressive
               optimization, making the compilation time increase with
               probably slightly better performance.  The default value is
               500.

           max-sched-ready-insns
               The maximum number of instructions ready to be issued the
               scheduler should consider at any given time during the first
               scheduling pass.  Increasing values mean more thorough
               searches, making the compilation time increase with probably
               little benefit.  The default value is 100.

           max-sched-region-blocks
               The maximum number of blocks in a region to be considered for
               interblock scheduling.  The default value is 10.

           max-pipeline-region-blocks
               The maximum number of blocks in a region to be considered for
               pipelining in the selective scheduler.  The default value is
               15.

           max-sched-region-insns
               The maximum number of insns in a region to be considered for
               interblock scheduling.  The default value is 100.

           max-pipeline-region-insns
               The maximum number of insns in a region to be considered for
               pipelining in the selective scheduler.  The default value is
               200.

           min-spec-prob
               The minimum probability (in percents) of reaching a source
               block for interblock speculative scheduling.  The default
               value is 40.

           max-sched-extend-regions-iters
               The maximum number of iterations through CFG to extend
               regions.  A value of 0 (the default) disables region
               extensions.

           max-sched-insn-conflict-delay
               The maximum conflict delay for an insn to be considered for
               speculative motion.  The default value is 3.

           sched-spec-prob-cutoff
               The minimal probability of speculation success (in percents),
               so that speculative insns are scheduled.  The default value
               is 40.

           sched-state-edge-prob-cutoff
               The minimum probability an edge must have for the scheduler
               to save its state across it.  The default value is 10.

           sched-mem-true-dep-cost
               Minimal distance (in CPU cycles) between store and load
               targeting same memory locations.  The default value is 1.

           selsched-max-lookahead
               The maximum size of the lookahead window of selective
               scheduling.  It is a depth of search for available
               instructions.  The default value is 50.

           selsched-max-sched-times
               The maximum number of times that an instruction is scheduled
               during selective scheduling.  This is the limit on the number
               of iterations through which the instruction may be pipelined.
               The default value is 2.

           selsched-insns-to-rename
               The maximum number of best instructions in the ready list
               that are considered for renaming in the selective scheduler.
               The default value is 2.

           sms-min-sc
               The minimum value of stage count that swing modulo scheduler
               generates.  The default value is 2.

           max-last-value-rtl
               The maximum size measured as number of RTLs that can be
               recorded in an expression in combiner for a pseudo register
               as last known value of that register.  The default is 10000.

           max-combine-insns
               The maximum number of instructions the RTL combiner tries to
               combine.  The default value is 2 at -Og and 4 otherwise.

           integer-share-limit
               Small integer constants can use a shared data structure,
               reducing the compiler's memory usage and increasing its
               speed.  This sets the maximum value of a shared integer
               constant.  The default value is 256.

           ssp-buffer-size
               The minimum size of buffers (i.e. arrays) that receive stack
               smashing protection when -fstack-protection is used.

           min-size-for-stack-sharing
               The minimum size of variables taking part in stack slot
               sharing when not optimizing. The default value is 32.

           max-jump-thread-duplication-stmts
               Maximum number of statements allowed in a block that needs to
               be duplicated when threading jumps.

           max-fields-for-field-sensitive
               Maximum number of fields in a structure treated in a field
               sensitive manner during pointer analysis.  The default is
               zero for -O0 and -O1, and 100 for -Os, -O2, and -O3.

           prefetch-latency
               Estimate on average number of instructions that are executed
               before prefetch finishes.  The distance prefetched ahead is
               proportional to this constant.  Increasing this number may
               also lead to less streams being prefetched (see simultaneous-
               prefetches).

           simultaneous-prefetches
               Maximum number of prefetches that can run at the same time.

           l1-cache-line-size
               The size of cache line in L1 cache, in bytes.

           l1-cache-size
               The size of L1 cache, in kilobytes.

           l2-cache-size
               The size of L2 cache, in kilobytes.

           min-insn-to-prefetch-ratio
               The minimum ratio between the number of instructions and the
               number of prefetches to enable prefetching in a loop.

           prefetch-min-insn-to-mem-ratio
               The minimum ratio between the number of instructions and the
               number of memory references to enable prefetching in a loop.

           use-canonical-types
               Whether the compiler should use the "canonical" type system.
               By default, this should always be 1, which uses a more
               efficient internal mechanism for comparing types in C++ and
               Objective-C++.  However, if bugs in the canonical type system
               are causing compilation failures, set this value to 0 to
               disable canonical types.

           switch-conversion-max-branch-ratio
               Switch initialization conversion refuses to create arrays
               that are bigger than switch-conversion-max-branch-ratio times
               the number of branches in the switch.

           max-partial-antic-length
               Maximum length of the partial antic set computed during the
               tree partial redundancy elimination optimization (-ftree-pre)
               when optimizing at -O3 and above.  For some sorts of source
               code the enhanced partial redundancy elimination optimization
               can run away, consuming all of the memory available on the
               host machine.  This parameter sets a limit on the length of
               the sets that are computed, which prevents the runaway
               behavior.  Setting a value of 0 for this parameter allows an
               unlimited set length.

           sccvn-max-scc-size
               Maximum size of a strongly connected component (SCC) during
               SCCVN processing.  If this limit is hit, SCCVN processing for
               the whole function is not done and optimizations depending on
               it are disabled.  The default maximum SCC size is 10000.

           sccvn-max-alias-queries-per-access
               Maximum number of alias-oracle queries we perform when
               looking for redundancies for loads and stores.  If this limit
               is hit the search is aborted and the load or store is not
               considered redundant.  The number of queries is
               algorithmically limited to the number of stores on all paths
               from the load to the function entry.  The default maximum
               number of queries is 1000.

           ira-max-loops-num
               IRA uses regional register allocation by default.  If a
               function contains more loops than the number given by this
               parameter, only at most the given number of the most
               frequently-executed loops form regions for regional register
               allocation.  The default value of the parameter is 100.

           ira-max-conflict-table-size
               Although IRA uses a sophisticated algorithm to compress the
               conflict table, the table can still require excessive amounts
               of memory for huge functions.  If the conflict table for a
               function could be more than the size in MB given by this
               parameter, the register allocator instead uses a faster,
               simpler, and lower-quality algorithm that does not require
               building a pseudo-register conflict table.  The default value
               of the parameter is 2000.

           ira-loop-reserved-regs
               IRA can be used to evaluate more accurate register pressure
               in loops for decisions to move loop invariants (see -O3).
               The number of available registers reserved for some other
               purposes is given by this parameter.  The default value of
               the parameter is 2, which is the minimal number of registers
               needed by typical instructions.  This value is the best found
               from numerous experiments.

           lra-inheritance-ebb-probability-cutoff
               LRA tries to reuse values reloaded in registers in subsequent
               insns.  This optimization is called inheritance.  EBB is used
               as a region to do this optimization.  The parameter defines a
               minimal fall-through edge probability in percentage used to
               add BB to inheritance EBB in LRA.  The default value of the
               parameter is 40.  The value was chosen from numerous runs of
               SPEC2000 on x86-64.

           loop-invariant-max-bbs-in-loop
               Loop invariant motion can be very expensive, both in
               compilation time and in amount of needed compile-time memory,
               with very large loops.  Loops with more basic blocks than
               this parameter won't have loop invariant motion optimization
               performed on them.  The default value of the parameter is
               1000 for -O1 and 10000 for -O2 and above.

           loop-max-datarefs-for-datadeps
               Building data dependencies is expensive for very large loops.
               This parameter limits the number of data references in loops
               that are considered for data dependence analysis.  These
               large loops are no handled by the optimizations using loop
               data dependencies.  The default value is 1000.

           max-vartrack-size
               Sets a maximum number of hash table slots to use during
               variable tracking dataflow analysis of any function.  If this
               limit is exceeded with variable tracking at assignments
               enabled, analysis for that function is retried without it,
               after removing all debug insns from the function.  If the
               limit is exceeded even without debug insns, var tracking
               analysis is completely disabled for the function.  Setting
               the parameter to zero makes it unlimited.

           max-vartrack-expr-depth
               Sets a maximum number of recursion levels when attempting to
               map variable names or debug temporaries to value expressions.
               This trades compilation time for more complete debug
               information.  If this is set too low, value expressions that
               are available and could be represented in debug information
               may end up not being used; setting this higher may enable the
               compiler to find more complex debug expressions, but compile
               time and memory use may grow.  The default is 12.

           min-nondebug-insn-uid
               Use uids starting at this parameter for nondebug insns.  The
               range below the parameter is reserved exclusively for debug
               insns created by -fvar-tracking-assignments, but debug insns
               may get (non-overlapping) uids above it if the reserved range
               is exhausted.

           ipa-sra-ptr-growth-factor
               IPA-SRA replaces a pointer to an aggregate with one or more
               new parameters only when their cumulative size is less or
               equal to ipa-sra-ptr-growth-factor times the size of the
               original pointer parameter.

           sra-max-scalarization-size-Ospeed
           sra-max-scalarization-size-Osize
               The two Scalar Reduction of Aggregates passes (SRA and IPA-
               SRA) aim to replace scalar parts of aggregates with uses of
               independent scalar variables.  These parameters control the
               maximum size, in storage units, of aggregate which is
               considered for replacement when compiling for speed (sra-max-
               scalarization-size-Ospeed) or size (sra-max-scalarization-
               size-Osize) respectively.

           tm-max-aggregate-size
               When making copies of thread-local variables in a
               transaction, this parameter specifies the size in bytes after
               which variables are saved with the logging functions as
               opposed to save/restore code sequence pairs.  This option
               only applies when using -fgnu-tm.

           graphite-max-nb-scop-params
               To avoid exponential effects in the Graphite loop transforms,
               the number of parameters in a Static Control Part (SCoP) is
               bounded.  The default value is 10 parameters.  A variable
               whose value is unknown at compilation time and defined
               outside a SCoP is a parameter of the SCoP.

           graphite-max-bbs-per-function
               To avoid exponential effects in the detection of SCoPs, the
               size of the functions analyzed by Graphite is bounded.  The
               default value is 100 basic blocks.

           loop-block-tile-size
               Loop blocking or strip mining transforms, enabled with
               -floop-block or -floop-strip-mine, strip mine each loop in
               the loop nest by a given number of iterations.  The strip
               length can be changed using the loop-block-tile-size
               parameter.  The default value is 51 iterations.

           loop-unroll-jam-size
               Specify the unroll factor for the -floop-unroll-and-jam
               option.  The default value is 4.

           loop-unroll-jam-depth
               Specify the dimension to be unrolled (counting from the most
               inner loop) for the  -floop-unroll-and-jam.  The default
               value is 2.

           ipa-cp-value-list-size
               IPA-CP attempts to track all possible values and types passed
               to a function's parameter in order to propagate them and
               perform devirtualization.  ipa-cp-value-list-size is the
               maximum number of values and types it stores per one formal
               parameter of a function.

           ipa-cp-eval-threshold
               IPA-CP calculates its own score of cloning profitability
               heuristics and performs those cloning opportunities with
               scores that exceed ipa-cp-eval-threshold.

           ipa-cp-recursion-penalty
               Percentage penalty the recursive functions will receive when
               they are evaluated for cloning.

           ipa-cp-single-call-penalty
               Percentage penalty functions containg a single call to
               another function will receive when they are evaluated for
               cloning.

           ipa-max-agg-items
               IPA-CP is also capable to propagate a number of scalar values
               passed in an aggregate. ipa-max-agg-items controls the
               maximum number of such values per one parameter.

           ipa-cp-loop-hint-bonus
               When IPA-CP determines that a cloning candidate would make
               the number of iterations of a loop known, it adds a bonus of
               ipa-cp-loop-hint-bonus to the profitability score of the
               candidate.

           ipa-cp-array-index-hint-bonus
               When IPA-CP determines that a cloning candidate would make
               the index of an array access known, it adds a bonus of ipa-
               cp-array-index-hint-bonus to the profitability score of the
               candidate.

           ipa-max-aa-steps
               During its analysis of function bodies, IPA-CP employs alias
               analysis in order to track values pointed to by function
               parameters.  In order not spend too much time analyzing huge
               functions, it gives up and consider all memory clobbered
               after examining ipa-max-aa-steps statements modifying memory.

           lto-partitions
               Specify desired number of partitions produced during WHOPR
               compilation.  The number of partitions should exceed the
               number of CPUs used for compilation.  The default value is
               32.

           lto-min-partition
               Size of minimal partition for WHOPR (in estimated
               instructions).  This prevents expenses of splitting very
               small programs into too many partitions.

           cxx-max-namespaces-for-diagnostic-help
               The maximum number of namespaces to consult for suggestions
               when C++ name lookup fails for an identifier.  The default is
               1000.

           sink-frequency-threshold
               The maximum relative execution frequency (in percents) of the
               target block relative to a statement's original block to
               allow statement sinking of a statement.  Larger numbers
               result in more aggressive statement sinking.  The default
               value is 75.  A small positive adjustment is applied for
               statements with memory operands as those are even more
               profitable so sink.

           max-stores-to-sink
               The maximum number of conditional store pairs that can be
               sunk.  Set to 0 if either vectorization (-ftree-vectorize) or
               if-conversion (-ftree-loop-if-convert) is disabled.  The
               default is 2.

           allow-store-data-races
               Allow optimizers to introduce new data races on stores.  Set
               to 1 to allow, otherwise to 0.  This option is enabled by
               default at optimization level -Ofast.

           case-values-threshold
               The smallest number of different values for which it is best
               to use a jump-table instead of a tree of conditional
               branches.  If the value is 0, use the default for the
               machine.  The default is 0.

           tree-reassoc-width
               Set the maximum number of instructions executed in parallel
               in reassociated tree. This parameter overrides target
               dependent heuristics used by default if has non zero value.

           sched-pressure-algorithm
               Choose between the two available implementations of
               -fsched-pressure.  Algorithm 1 is the original implementation
               and is the more likely to prevent instructions from being
               reordered.  Algorithm 2 was designed to be a compromise
               between the relatively conservative approach taken by
               algorithm 1 and the rather aggressive approach taken by the
               default scheduler.  It relies more heavily on having a
               regular register file and accurate register pressure classes.
               See haifa-sched.c in the GCC sources for more details.

               The default choice depends on the target.

           max-slsr-cand-scan
               Set the maximum number of existing candidates that are
               considered when seeking a basis for a new straight-line
               strength reduction candidate.

           asan-globals
               Enable buffer overflow detection for global objects.  This
               kind of protection is enabled by default if you are using
               -fsanitize=address option.  To disable global objects
               protection use --param asan-globals=0.

           asan-stack
               Enable buffer overflow detection for stack objects.  This
               kind of protection is enabled by default when using
               -fsanitize=address.  To disable stack protection use --param
               asan-stack=0 option.

           asan-instrument-reads
               Enable buffer overflow detection for memory reads.  This kind
               of protection is enabled by default when using
               -fsanitize=address.  To disable memory reads protection use
               --param asan-instrument-reads=0.

           asan-instrument-writes
               Enable buffer overflow detection for memory writes.  This
               kind of protection is enabled by default when using
               -fsanitize=address.  To disable memory writes protection use
               --param asan-instrument-writes=0 option.

           asan-memintrin
               Enable detection for built-in functions.  This kind of
               protection is enabled by default when using
               -fsanitize=address.  To disable built-in functions protection
               use --param asan-memintrin=0.

           asan-use-after-return
               Enable detection of use-after-return.  This kind of
               protection is enabled by default when using
               -fsanitize=address option.  To disable use-after-return
               detection use --param asan-use-after-return=0.

           asan-instrumentation-with-call-threshold
               If number of memory accesses in function being instrumented
               is greater or equal to this number, use callbacks instead of
               inline checks.  E.g. to disable inline code use --param
               asan-instrumentation-with-call-threshold=0.

           chkp-max-ctor-size
               Static constructors generated by Pointer Bounds Checker may
               become very large and significantly increase compile time at
               optimization level -O1 and higher.  This parameter is a
               maximum nubmer of statements in a single generated
               constructor.  Default value is 5000.

           max-fsm-thread-path-insns
               Maximum number of instructions to copy when duplicating
               blocks on a finite state automaton jump thread path.  The
               default is 100.

           max-fsm-thread-length
               Maximum number of basic blocks on a finite state automaton
               jump thread path.  The default is 10.

           max-fsm-thread-paths
               Maximum number of new jump thread paths to create for a
               finite state automaton.  The default is 50.

           parloops-chunk-size
               Chunk size of omp schedule for loops parallelized by
               parloops.  The default is 0.

           parloops-schedule
               Schedule type of omp schedule for loops parallelized by
               parloops (static, dynamic, guided, auto, runtime).  The
               default is static.

           max-ssa-name-query-depth
               Maximum depth of recursion when querying properties of SSA
               names in things like fold routines.  One level of recursion
               corresponds to following a use-def chain.

           hsa-gen-debug-stores
               Enable emission of special debug stores within HSA kernels
               which are then read and reported by libgomp plugin.
               Generation of these stores is disabled by default, use
               --param hsa-gen-debug-stores=1 to enable it.

           max-speculative-devirt-maydefs
               The maximum number of may-defs we analyze when looking for a
               must-def specifying the dynamic type of an object that
               invokes a virtual call we may be able to devirtualize
               speculatively.

       Program Instrumentation Options

       GCC supports a number of command-line options that control adding
       run-time instrumentation to the code it normally generates.  For
       example, one purpose of instrumentation is collect profiling
       statistics for use in finding program hot spots, code coverage
       analysis, or profile-guided optimizations.  Another class of program
       instrumentation is adding run-time checking to detect programming
       errors like invalid pointer dereferences or out-of-bounds array
       accesses, as well as deliberately hostile attacks such as stack
       smashing or C++ vtable hijacking.  There is also a general hook which
       can be used to implement other forms of tracing or function-level
       instrumentation for debug or program analysis purposes.

       -p  Generate extra code to write profile information suitable for the
           analysis program prof.  You must use this option when compiling
           the source files you want data about, and you must also use it
           when linking.

       -pg Generate extra code to write profile information suitable for the
           analysis program gprof.  You must use this option when compiling
           the source files you want data about, and you must also use it
           when linking.

       -fprofile-arcs
           Add code so that program flow arcs are instrumented.  During
           execution the program records how many times each branch and call
           is executed and how many times it is taken or returns.  When the
           compiled program exits it saves this data to a file called
           auxname.gcda for each source file.  The data may be used for
           profile-directed optimizations (-fbranch-probabilities), or for
           test coverage analysis (-ftest-coverage).  Each object file's
           auxname is generated from the name of the output file, if
           explicitly specified and it is not the final executable,
           otherwise it is the basename of the source file.  In both cases
           any suffix is removed (e.g. foo.gcda for input file dir/foo.c, or
           dir/foo.gcda for output file specified as -o dir/foo.o).

       --coverage
           This option is used to compile and link code instrumented for
           coverage analysis.  The option is a synonym for -fprofile-arcs
           -ftest-coverage (when compiling) and -lgcov (when linking).  See
           the documentation for those options for more details.

           *   Compile the source files with -fprofile-arcs plus
               optimization and code generation options.  For test coverage
               analysis, use the additional -ftest-coverage option.  You do
               not need to profile every source file in a program.

           *   Link your object files with -lgcov or -fprofile-arcs (the
               latter implies the former).

           *   Run the program on a representative workload to generate the
               arc profile information.  This may be repeated any number of
               times.  You can run concurrent instances of your program, and
               provided that the file system supports locking, the data
               files will be correctly updated.  Also "fork" calls are
               detected and correctly handled (double counting will not
               happen).

           *   For profile-directed optimizations, compile the source files
               again with the same optimization and code generation options
               plus -fbranch-probabilities.

           *   For test coverage analysis, use gcov to produce human
               readable information from the .gcno and .gcda files.  Refer
               to the gcov documentation for further information.

           With -fprofile-arcs, for each function of your program GCC
           creates a program flow graph, then finds a spanning tree for the
           graph.  Only arcs that are not on the spanning tree have to be
           instrumented: the compiler adds code to count the number of times
           that these arcs are executed.  When an arc is the only exit or
           only entrance to a block, the instrumentation code can be added
           to the block; otherwise, a new basic block must be created to
           hold the instrumentation code.

       -ftest-coverage
           Produce a notes file that the gcov code-coverage utility can use
           to show program coverage.  Each source file's note file is called
           auxname.gcno.  Refer to the -fprofile-arcs option above for a
           description of auxname and instructions on how to generate test
           coverage data.  Coverage data matches the source files more
           closely if you do not optimize.

       -fprofile-dir=path
           Set the directory to search for the profile data files in to
           path.  This option affects only the profile data generated by
           -fprofile-generate, -ftest-coverage, -fprofile-arcs and used by
           -fprofile-use and -fbranch-probabilities and its related options.
           Both absolute and relative paths can be used.  By default, GCC
           uses the current directory as path, thus the profile data file
           appears in the same directory as the object file.

       -fprofile-generate
       -fprofile-generate=path
           Enable options usually used for instrumenting application to
           produce profile useful for later recompilation with profile
           feedback based optimization.  You must use -fprofile-generate
           both when compiling and when linking your program.

           The following options are enabled: -fprofile-arcs,
           -fprofile-values, -fvpt.

           If path is specified, GCC looks at the path to find the profile
           feedback data files. See -fprofile-dir.

           To optimize the program based on the collected profile
           information, use -fprofile-use.

       -fsanitize=address
           Enable AddressSanitizer, a fast memory error detector.  Memory
           access instructions are instrumented to detect out-of-bounds and
           use-after-free bugs.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizer > for
           more details.  The run-time behavior can be influenced using the
           ASAN_OPTIONS environment variable.  When set to "help=1", the
           available options are shown at startup of the instrumented
           program.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags >
           for a list of supported options.

       -fsanitize=kernel-address
           Enable AddressSanitizer for Linux kernel.  See
           <https://github.com/google/kasan/wiki > for more details.

       -fsanitize=thread
           Enable ThreadSanitizer, a fast data race detector.  Memory access
           instructions are instrumented to detect data race bugs.  See
           <https://github.com/google/sanitizers/wiki#threadsanitizer > for
           more details. The run-time behavior can be influenced using the
           TSAN_OPTIONS environment variable; see
           <https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags >
           for a list of supported options.

       -fsanitize=leak
           Enable LeakSanitizer, a memory leak detector.  This option only
           matters for linking of executables and if neither
           -fsanitize=address nor -fsanitize=thread is used.  In that case
           the executable is linked against a library that overrides
           "malloc" and other allocator functions.  See
           <https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer >
           for more details.  The run-time behavior can be influenced using
           the LSAN_OPTIONS environment variable.

       -fsanitize=undefined
           Enable UndefinedBehaviorSanitizer, a fast undefined behavior
           detector.  Various computations are instrumented to detect
           undefined behavior at runtime.  Current suboptions are:

           -fsanitize=shift
               This option enables checking that the result of a shift
               operation is not undefined.  Note that what exactly is
               considered undefined differs slightly between C and C++, as
               well as between ISO C90 and C99, etc.

           -fsanitize=integer-divide-by-zero
               Detect integer division by zero as well as "INT_MIN / -1"
               division.

           -fsanitize=unreachable
               With this option, the compiler turns the
               "__builtin_unreachable" call into a diagnostics message call
               instead.  When reaching the "__builtin_unreachable" call, the
               behavior is undefined.

           -fsanitize=vla-bound
               This option instructs the compiler to check that the size of
               a variable length array is positive.

           -fsanitize=null
               This option enables pointer checking.  Particularly, the
               application built with this option turned on will issue an
               error message when it tries to dereference a NULL pointer, or
               if a reference (possibly an rvalue reference) is bound to a
               NULL pointer, or if a method is invoked on an object pointed
               by a NULL pointer.

           -fsanitize=return
               This option enables return statement checking.  Programs
               built with this option turned on will issue an error message
               when the end of a non-void function is reached without
               actually returning a value.  This option works in C++ only.

           -fsanitize=signed-integer-overflow
               This option enables signed integer overflow checking.  We
               check that the result of "+", "*", and both unary and binary
               "-" does not overflow in the signed arithmetics.  Note,
               integer promotion rules must be taken into account.  That is,
               the following is not an overflow:

                       signed char a = SCHAR_MAX;
                       a++;

           -fsanitize=bounds
               This option enables instrumentation of array bounds.  Various
               out of bounds accesses are detected.  Flexible array members,
               flexible array member-like arrays, and initializers of
               variables with static storage are not instrumented.

           -fsanitize=bounds-strict
               This option enables strict instrumentation of array bounds.
               Most out of bounds accesses are detected, including flexible
               array members and flexible array member-like arrays.
               Initializers of variables with static storage are not
               instrumented.

           -fsanitize=alignment
               This option enables checking of alignment of pointers when
               they are dereferenced, or when a reference is bound to
               insufficiently aligned target, or when a method or
               constructor is invoked on insufficiently aligned object.

           -fsanitize=object-size
               This option enables instrumentation of memory references
               using the "__builtin_object_size" function.  Various out of
               bounds pointer accesses are detected.

           -fsanitize=float-divide-by-zero
               Detect floating-point division by zero.  Unlike other similar
               options, -fsanitize=float-divide-by-zero is not enabled by
               -fsanitize=undefined, since floating-point division by zero
               can be a legitimate way of obtaining infinities and NaNs.

           -fsanitize=float-cast-overflow
               This option enables floating-point type to integer conversion
               checking.  We check that the result of the conversion does
               not overflow.  Unlike other similar options,
               -fsanitize=float-cast-overflow is not enabled by
               -fsanitize=undefined.  This option does not work well with
               "FE_INVALID" exceptions enabled.

           -fsanitize=nonnull-attribute
               This option enables instrumentation of calls, checking
               whether null values are not passed to arguments marked as
               requiring a non-null value by the "nonnull" function
               attribute.

           -fsanitize=returns-nonnull-attribute
               This option enables instrumentation of return statements in
               functions marked with "returns_nonnull" function attribute,
               to detect returning of null values from such functions.

           -fsanitize=bool
               This option enables instrumentation of loads from bool.  If a
               value other than 0/1 is loaded, a run-time error is issued.

           -fsanitize=enum
               This option enables instrumentation of loads from an enum
               type.  If a value outside the range of values for the enum
               type is loaded, a run-time error is issued.

           -fsanitize=vptr
               This option enables instrumentation of C++ member function
               calls, member accesses and some conversions between pointers
               to base and derived classes, to verify the referenced object
               has the correct dynamic type.

           While -ftrapv causes traps for signed overflows to be emitted,
           -fsanitize=undefined gives a diagnostic message.  This currently
           works only for the C family of languages.

       -fno-sanitize=all
           This option disables all previously enabled sanitizers.
           -fsanitize=all is not allowed, as some sanitizers cannot be used
           together.

       -fasan-shadow-offset=number
           This option forces GCC to use custom shadow offset in
           AddressSanitizer checks.  It is useful for experimenting with
           different shadow memory layouts in Kernel AddressSanitizer.

       -fsanitize-sections=s1,s2,...
           Sanitize global variables in selected user-defined sections.  si
           may contain wildcards.

       -fsanitize-recover[=opts]
           -fsanitize-recover= controls error recovery mode for sanitizers
           mentioned in comma-separated list of opts.  Enabling this option
           for a sanitizer component causes it to attempt to continue
           running the program as if no error happened.  This means multiple
           runtime errors can be reported in a single program run, and the
           exit code of the program may indicate success even when errors
           have been reported.  The -fno-sanitize-recover= option can be
           used to alter this behavior: only the first detected error is
           reported and program then exits with a non-zero exit code.

           Currently this feature only works for -fsanitize=undefined (and
           its suboptions except for -fsanitize=unreachable and
           -fsanitize=return), -fsanitize=float-cast-overflow,
           -fsanitize=float-divide-by-zero, -fsanitize=kernel-address and
           -fsanitize=address.  For these sanitizers error recovery is
           turned on by default, except -fsanitize=address, for which this
           feature is experimental.  -fsanitize-recover=all and
           -fno-sanitize-recover=all is also accepted, the former enables
           recovery for all sanitizers that support it, the latter disables
           recovery for all sanitizers that support it.

           Syntax without explicit opts parameter is deprecated.  It is
           equivalent to

                   -fsanitize-recover=undefined,float-cast-overflow,float-divide-by-zero

           Similarly -fno-sanitize-recover is equivalent to

                   -fno-sanitize-recover=undefined,float-cast-overflow,float-divide-by-zero

       -fsanitize-undefined-trap-on-error
           The -fsanitize-undefined-trap-on-error option instructs the
           compiler to report undefined behavior using "__builtin_trap"
           rather than a "libubsan" library routine.  The advantage of this
           is that the "libubsan" library is not needed and is not linked
           in, so this is usable even in freestanding environments.

       -fsanitize-coverage=trace-pc
           Enable coverage-guided fuzzing code instrumentation.  Inserts a
           call to "__sanitizer_cov_trace_pc" into every basic block.

       -fbounds-check
           For front ends that support it, generate additional code to check
           that indices used to access arrays are within the declared range.
           This is currently only supported by the Java and Fortran front
           ends, where this option defaults to true and false respectively.

       -fcheck-pointer-bounds
           Enable Pointer Bounds Checker instrumentation.  Each memory
           reference is instrumented with checks of the pointer used for
           memory access against bounds associated with that pointer.

           Currently there is only an implementation for Intel MPX
           available, thus x86 GNU/Linux target and -mmpx are required to
           enable this feature.  MPX-based instrumentation requires a
           runtime library to enable MPX in hardware and handle bounds
           violation signals.  By default when -fcheck-pointer-bounds and
           -mmpx options are used to link a program, the GCC driver links
           against the libmpx and libmpxwrappers libraries.  Bounds checking
           on calls to dynamic libraries requires a linker with -z bndplt
           support; if GCC was configured with a linker without support for
           this option (including the Gold linker and older versions of ld),
           a warning is given if you link with -mmpx without also specifying
           -static, since the overall effectiveness of the bounds checking
           protection is reduced.  See also -static-libmpxwrappers.

           MPX-based instrumentation may be used for debugging and also may
           be included in production code to increase program security.
           Depending on usage, you may have different requirements for the
           runtime library.  The current version of the MPX runtime library
           is more oriented for use as a debugging tool.  MPX runtime
           library usage implies -lpthread.  See also -static-libmpx.  The
           runtime library  behavior can be influenced using various
           CHKP_RT_* environment variables.  See
           <https://gcc.gnu.org/wiki/Intel%20MPX%20support%20in%20the%20GCC%20compiler >
           for more details.

           Generated instrumentation may be controlled by various -fchkp-*
           options and by the "bnd_variable_size" structure field attribute
           and "bnd_legacy", and "bnd_instrument" function attributes.  GCC
           also provides a number of built-in functions for controlling the
           Pointer Bounds Checker.

       -fchkp-check-incomplete-type
           Generate pointer bounds checks for variables with incomplete
           type.  Enabled by default.

       -fchkp-narrow-bounds
           Controls bounds used by Pointer Bounds Checker for pointers to
           object fields.  If narrowing is enabled then field bounds are
           used.  Otherwise object bounds are used.  See also
           -fchkp-narrow-to-innermost-array and
           -fchkp-first-field-has-own-bounds.  Enabled by default.

       -fchkp-first-field-has-own-bounds
           Forces Pointer Bounds Checker to use narrowed bounds for the
           address of the first field in the structure.  By default a
           pointer to the first field has the same bounds as a pointer to
           the whole structure.

       -fchkp-narrow-to-innermost-array
           Forces Pointer Bounds Checker to use bounds of the innermost
           arrays in case of nested static array access.  By default this
           option is disabled and bounds of the outermost array are used.

       -fchkp-optimize
           Enables Pointer Bounds Checker optimizations.  Enabled by default
           at optimization levels -O, -O2, -O3.

       -fchkp-use-fast-string-functions
           Enables use of *_nobnd versions of string functions (not copying
           bounds) by Pointer Bounds Checker.  Disabled by default.

       -fchkp-use-nochk-string-functions
           Enables use of *_nochk versions of string functions (not checking
           bounds) by Pointer Bounds Checker.  Disabled by default.

       -fchkp-use-static-bounds
           Allow Pointer Bounds Checker to generate static bounds holding
           bounds of static variables.  Enabled by default.

       -fchkp-use-static-const-bounds
           Use statically-initialized bounds for constant bounds instead of
           generating them each time they are required.  By default enabled
           when -fchkp-use-static-bounds is enabled.

       -fchkp-treat-zero-dynamic-size-as-infinite
           With this option, objects with incomplete type whose dynamically-
           obtained size is zero are treated as having infinite size instead
           by Pointer Bounds Checker.  This option may be helpful if a
           program is linked with a library missing size information for
           some symbols.  Disabled by default.

       -fchkp-check-read
           Instructs Pointer Bounds Checker to generate checks for all read
           accesses to memory.  Enabled by default.

       -fchkp-check-write
           Instructs Pointer Bounds Checker to generate checks for all write
           accesses to memory.  Enabled by default.

       -fchkp-store-bounds
           Instructs Pointer Bounds Checker to generate bounds stores for
           pointer writes.  Enabled by default.

       -fchkp-instrument-calls
           Instructs Pointer Bounds Checker to pass pointer bounds to calls.
           Enabled by default.

       -fchkp-instrument-marked-only
           Instructs Pointer Bounds Checker to instrument only functions
           marked with the "bnd_instrument" attribute.  Disabled by default.

       -fchkp-use-wrappers
           Allows Pointer Bounds Checker to replace calls to built-in
           functions with calls to wrapper functions.  When
           -fchkp-use-wrappers is used to link a program, the GCC driver
           automatically links against libmpxwrappers.  See also
           -static-libmpxwrappers.  Enabled by default.

       -fstack-protector
           Emit extra code to check for buffer overflows, such as stack
           smashing attacks.  This is done by adding a guard variable to
           functions with vulnerable objects.  This includes functions that
           call "alloca", and functions with buffers larger than 8 bytes.
           The guards are initialized when a function is entered and then
           checked when the function exits.  If a guard check fails, an
           error message is printed and the program exits.

       -fstack-protector-all
           Like -fstack-protector except that all functions are protected.

       -fstack-protector-strong
           Like -fstack-protector but includes additional functions to be
           protected --- those that have local array definitions, or have
           references to local frame addresses.

       -fstack-protector-explicit
           Like -fstack-protector but only protects those functions which
           have the "stack_protect" attribute.

       -fstack-check
           Generate code to verify that you do not go beyond the boundary of
           the stack.  You should specify this flag if you are running in an
           environment with multiple threads, but you only rarely need to
           specify it in a single-threaded environment since stack overflow
           is automatically detected on nearly all systems if there is only
           one stack.

           Note that this switch does not actually cause checking to be
           done; the operating system or the language runtime must do that.
           The switch causes generation of code to ensure that they see the
           stack being extended.

           You can additionally specify a string parameter: no means no
           checking, generic means force the use of old-style checking,
           specific means use the best checking method and is equivalent to
           bare -fstack-check.

           Old-style checking is a generic mechanism that requires no
           specific target support in the compiler but comes with the
           following drawbacks:

           1.  Modified allocation strategy for large objects: they are
               always allocated dynamically if their size exceeds a fixed
               threshold.

           2.  Fixed limit on the size of the static frame of functions:
               when it is topped by a particular function, stack checking is
               not reliable and a warning is issued by the compiler.

           3.  Inefficiency: because of both the modified allocation
               strategy and the generic implementation, code performance is
               hampered.

           Note that old-style stack checking is also the fallback method
           for specific if no target support has been added in the compiler.

       -fstack-limit-register=reg
       -fstack-limit-symbol=sym
       -fno-stack-limit
           Generate code to ensure that the stack does not grow beyond a
           certain value, either the value of a register or the address of a
           symbol.  If a larger stack is required, a signal is raised at run
           time.  For most targets, the signal is raised before the stack
           overruns the boundary, so it is possible to catch the signal
           without taking special precautions.

           For instance, if the stack starts at absolute address 0x80000000
           and grows downwards, you can use the flags
           -fstack-limit-symbol=__stack_limit and
           -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of
           128KB.  Note that this may only work with the GNU linker.

           You can locally override stack limit checking by using the
           "no_stack_limit" function attribute.

       -fsplit-stack
           Generate code to automatically split the stack before it
           overflows.  The resulting program has a discontiguous stack which
           can only overflow if the program is unable to allocate any more
           memory.  This is most useful when running threaded programs, as
           it is no longer necessary to calculate a good stack size to use
           for each thread.  This is currently only implemented for the x86
           targets running GNU/Linux.

           When code compiled with -fsplit-stack calls code compiled without
           -fsplit-stack, there may not be much stack space available for
           the latter code to run.  If compiling all code, including library
           code, with -fsplit-stack is not an option, then the linker can
           fix up these calls so that the code compiled without
           -fsplit-stack always has a large stack.  Support for this is
           implemented in the gold linker in GNU binutils release 2.21 and
           later.

       -fvtable-verify=[std|preinit|none]
           This option is only available when compiling C++ code.  It turns
           on (or off, if using -fvtable-verify=none) the security feature
           that verifies at run time, for every virtual call, that the
           vtable pointer through which the call is made is valid for the
           type of the object, and has not been corrupted or overwritten.
           If an invalid vtable pointer is detected at run time, an error is
           reported and execution of the program is immediately halted.

           This option causes run-time data structures to be built at
           program startup, which are used for verifying the vtable
           pointers.  The options std and preinit control the timing of when
           these data structures are built.  In both cases the data
           structures are built before execution reaches "main".  Using
           -fvtable-verify=std causes the data structures to be built after
           shared libraries have been loaded and initialized.
           -fvtable-verify=preinit causes them to be built before shared
           libraries have been loaded and initialized.

           If this option appears multiple times in the command line with
           different values specified, none takes highest priority over both
           std and preinit; preinit takes priority over std.

       -fvtv-debug
           When used in conjunction with -fvtable-verify=std or
           -fvtable-verify=preinit, causes debug versions of the runtime
           functions for the vtable verification feature to be called.  This
           flag also causes the compiler to log information about which
           vtable pointers it finds for each class.  This information is
           written to a file named vtv_set_ptr_data.log in the directory
           named by the environment variable VTV_LOGS_DIR if that is defined
           or the current working directory otherwise.

           Note:  This feature appends data to the log file. If you want a
           fresh log file, be sure to delete any existing one.

       -fvtv-counts
           This is a debugging flag.  When used in conjunction with
           -fvtable-verify=std or -fvtable-verify=preinit, this causes the
           compiler to keep track of the total number of virtual calls it
           encounters and the number of verifications it inserts.  It also
           counts the number of calls to certain run-time library functions
           that it inserts and logs this information for each compilation
           unit.  The compiler writes this information to a file named
           vtv_count_data.log in the directory named by the environment
           variable VTV_LOGS_DIR if that is defined or the current working
           directory otherwise.  It also counts the size of the vtable
           pointer sets for each class, and writes this information to
           vtv_class_set_sizes.log in the same directory.

           Note:  This feature appends data to the log files.  To get fresh
           log files, be sure to delete any existing ones.

       -finstrument-functions
           Generate instrumentation calls for entry and exit to functions.
           Just after function entry and just before function exit, the
           following profiling functions are called with the address of the
           current function and its call site.  (On some platforms,
           "__builtin_return_address" does not work beyond the current
           function, so the call site information may not be available to
           the profiling functions otherwise.)

                   void __cyg_profile_func_enter (void *this_fn,
                                                  void *call_site);
                   void __cyg_profile_func_exit  (void *this_fn,
                                                  void *call_site);

           The first argument is the address of the start of the current
           function, which may be looked up exactly in the symbol table.

           This instrumentation is also done for functions expanded inline
           in other functions.  The profiling calls indicate where,
           conceptually, the inline function is entered and exited.  This
           means that addressable versions of such functions must be
           available.  If all your uses of a function are expanded inline,
           this may mean an additional expansion of code size.  If you use
           "extern inline" in your C code, an addressable version of such
           functions must be provided.  (This is normally the case anyway,
           but if you get lucky and the optimizer always expands the
           functions inline, you might have gotten away without providing
           static copies.)

           A function may be given the attribute "no_instrument_function",
           in which case this instrumentation is not done.  This can be
           used, for example, for the profiling functions listed above,
           high-priority interrupt routines, and any functions from which
           the profiling functions cannot safely be called (perhaps signal
           handlers, if the profiling routines generate output or allocate
           memory).

       -finstrument-functions-exclude-file-list=file,file,...
           Set the list of functions that are excluded from instrumentation
           (see the description of -finstrument-functions).  If the file
           that contains a function definition matches with one of file,
           then that function is not instrumented.  The match is done on
           substrings: if the file parameter is a substring of the file
           name, it is considered to be a match.

           For example:

                   -finstrument-functions-exclude-file-list=/bits/stl,include/sys

           excludes any inline function defined in files whose pathnames
           contain /bits/stl or include/sys.

           If, for some reason, you want to include letter , in one of sym,
           write ,. For example,
           -finstrument-functions-exclude-file-list=',,tmp' (note the single
           quote surrounding the option).

       -finstrument-functions-exclude-function-list=sym,sym,...
           This is similar to -finstrument-functions-exclude-file-list, but
           this option sets the list of function names to be excluded from
           instrumentation.  The function name to be matched is its user-
           visible name, such as "vector<int> blah(const vector<int> &)",
           not the internal mangled name (e.g.,
           "_Z4blahRSt6vectorIiSaIiEE").  The match is done on substrings:
           if the sym parameter is a substring of the function name, it is
           considered to be a match.  For C99 and C++ extended identifiers,
           the function name must be given in UTF-8, not using universal
           character names.

       Options Controlling the Preprocessor

       These options control the C preprocessor, which is run on each C
       source file before actual compilation.

       If you use the -E option, nothing is done except preprocessing.  Some
       of these options make sense only together with -E because they cause
       the preprocessor output to be unsuitable for actual compilation.

       -Wp,option
           You can use -Wp,option to bypass the compiler driver and pass
           option directly through to the preprocessor.  If option contains
           commas, it is split into multiple options at the commas.
           However, many options are modified, translated or interpreted by
           the compiler driver before being passed to the preprocessor, and
           -Wp forcibly bypasses this phase.  The preprocessor's direct
           interface is undocumented and subject to change, so whenever
           possible you should avoid using -Wp and let the driver handle the
           options instead.

       -Xpreprocessor option
           Pass option as an option to the preprocessor.  You can use this
           to supply system-specific preprocessor options that GCC does not
           recognize.

           If you want to pass an option that takes an argument, you must
           use -Xpreprocessor twice, once for the option and once for the
           argument.

       -no-integrated-cpp
           Perform preprocessing as a separate pass before compilation.  By
           default, GCC performs preprocessing as an integrated part of
           input tokenization and parsing.  If this option is provided, the
           appropriate language front end (cc1, cc1plus, or cc1obj for C,
           C++, and Objective-C, respectively) is instead invoked twice,
           once for preprocessing only and once for actual compilation of
           the preprocessed input.  This option may be useful in conjunction
           with the -B or -wrapper options to specify an alternate
           preprocessor or perform additional processing of the program
           source between normal preprocessing and compilation.

       -D name
           Predefine name as a macro, with definition 1.

       -D name=definition
           The contents of definition are tokenized and processed as if they
           appeared during translation phase three in a #define directive.
           In particular, the definition will be truncated by embedded
           newline characters.

           If you are invoking the preprocessor from a shell or shell-like
           program you may need to use the shell's quoting syntax to protect
           characters such as spaces that have a meaning in the shell
           syntax.

           If you wish to define a function-like macro on the command line,
           write its argument list with surrounding parentheses before the
           equals sign (if any).  Parentheses are meaningful to most shells,
           so you will need to quote the option.  With sh and csh,
           -D'name(args...)=definition' works.

           -D and -U options are processed in the order they are given on
           the command line.  All -imacros file and -include file options
           are processed after all -D and -U options.

       -U name
           Cancel any previous definition of name, either built in or
           provided with a -D option.

       -undef
           Do not predefine any system-specific or GCC-specific macros.  The
           standard predefined macros remain defined.

       -I dir
           Add the directory dir to the list of directories to be searched
           for header files.  Directories named by -I are searched before
           the standard system include directories.  If the directory dir is
           a standard system include directory, the option is ignored to
           ensure that the default search order for system directories and
           the special treatment of system headers are not defeated .  If
           dir begins with "=", then the "=" will be replaced by the sysroot
           prefix; see --sysroot and -isysroot.

       -o file
           Write output to file.  This is the same as specifying file as the
           second non-option argument to cpp.  gcc has a different
           interpretation of a second non-option argument, so you must use
           -o to specify the output file.

       -Wall
           Turns on all optional warnings which are desirable for normal
           code.  At present this is -Wcomment, -Wtrigraphs, -Wmultichar and
           a warning about integer promotion causing a change of sign in
           "#if" expressions.  Note that many of the preprocessor's warnings
           are on by default and have no options to control them.

       -Wcomment
       -Wcomments
           Warn whenever a comment-start sequence /* appears in a /*
           comment, or whenever a backslash-newline appears in a // comment.
           (Both forms have the same effect.)

       -Wtrigraphs
           Most trigraphs in comments cannot affect the meaning of the
           program.  However, a trigraph that would form an escaped newline
           (??/ at the end of a line) can, by changing where the comment
           begins or ends.  Therefore, only trigraphs that would form
           escaped newlines produce warnings inside a comment.

           This option is implied by -Wall.  If -Wall is not given, this
           option is still enabled unless trigraphs are enabled.  To get
           trigraph conversion without warnings, but get the other -Wall
           warnings, use -trigraphs -Wall -Wno-trigraphs.

       -Wtraditional
           Warn about certain constructs that behave differently in
           traditional and ISO C.  Also warn about ISO C constructs that
           have no traditional C equivalent, and problematic constructs
           which should be avoided.

       -Wundef
           Warn whenever an identifier which is not a macro is encountered
           in an #if directive, outside of defined.  Such identifiers are
           replaced with zero.

       -Wunused-macros
           Warn about macros defined in the main file that are unused.  A
           macro is used if it is expanded or tested for existence at least
           once.  The preprocessor will also warn if the macro has not been
           used at the time it is redefined or undefined.

           Built-in macros, macros defined on the command line, and macros
           defined in include files are not warned about.

           Note: If a macro is actually used, but only used in skipped
           conditional blocks, then CPP will report it as unused.  To avoid
           the warning in such a case, you might improve the scope of the
           macro's definition by, for example, moving it into the first
           skipped block.  Alternatively, you could provide a dummy use with
           something like:

                   #if defined the_macro_causing_the_warning
                   #endif

       -Wendif-labels
           Warn whenever an #else or an #endif are followed by text.  This
           usually happens in code of the form

                   #if FOO
                   ...
                   #else FOO
                   ...
                   #endif FOO

           The second and third "FOO" should be in comments, but often are
           not in older programs.  This warning is on by default.

       -Werror
           Make all warnings into hard errors.  Source code which triggers
           warnings will be rejected.

       -Wsystem-headers
           Issue warnings for code in system headers.  These are normally
           unhelpful in finding bugs in your own code, therefore suppressed.
           If you are responsible for the system library, you may want to
           see them.

       -w  Suppress all warnings, including those which GNU CPP issues by
           default.

       -pedantic
           Issue all the mandatory diagnostics listed in the C standard.
           Some of them are left out by default, since they trigger
           frequently on harmless code.

       -pedantic-errors
           Issue all the mandatory diagnostics, and make all mandatory
           diagnostics into errors.  This includes mandatory diagnostics
           that GCC issues without -pedantic but treats as warnings.

       -M  Instead of outputting the result of preprocessing, output a rule
           suitable for make describing the dependencies of the main source
           file.  The preprocessor outputs one make rule containing the
           object file name for that source file, a colon, and the names of
           all the included files, including those coming from -include or
           -imacros command-line options.

           Unless specified explicitly (with -MT or -MQ), the object file
           name consists of the name of the source file with any suffix
           replaced with object file suffix and with any leading directory
           parts removed.  If there are many included files then the rule is
           split into several lines using \-newline.  The rule has no
           commands.

           This option does not suppress the preprocessor's debug output,
           such as -dM.  To avoid mixing such debug output with the
           dependency rules you should explicitly specify the dependency
           output file with -MF, or use an environment variable like
           DEPENDENCIES_OUTPUT.  Debug output will still be sent to the
           regular output stream as normal.

           Passing -M to the driver implies -E, and suppresses warnings with
           an implicit -w.

       -MM Like -M but do not mention header files that are found in system
           header directories, nor header files that are included, directly
           or indirectly, from such a header.

           This implies that the choice of angle brackets or double quotes
           in an #include directive does not in itself determine whether
           that header will appear in -MM dependency output.  This is a
           slight change in semantics from GCC versions 3.0 and earlier.

       -MF file
           When used with -M or -MM, specifies a file to write the
           dependencies to.  If no -MF switch is given the preprocessor
           sends the rules to the same place it would have sent preprocessed
           output.

           When used with the driver options -MD or -MMD, -MF overrides the
           default dependency output file.

       -MG In conjunction with an option such as -M requesting dependency
           generation, -MG assumes missing header files are generated files
           and adds them to the dependency list without raising an error.
           The dependency filename is taken directly from the "#include"
           directive without prepending any path.  -MG also suppresses
           preprocessed output, as a missing header file renders this
           useless.

           This feature is used in automatic updating of makefiles.

       -MP This option instructs CPP to add a phony target for each
           dependency other than the main file, causing each to depend on
           nothing.  These dummy rules work around errors make gives if you
           remove header files without updating the Makefile to match.

           This is typical output:

                   test.o: test.c test.h

                   test.h:

       -MT target
           Change the target of the rule emitted by dependency generation.
           By default CPP takes the name of the main input file, deletes any
           directory components and any file suffix such as .c, and appends
           the platform's usual object suffix.  The result is the target.

           An -MT option will set the target to be exactly the string you
           specify.  If you want multiple targets, you can specify them as a
           single argument to -MT, or use multiple -MT options.

           For example, -MT '$(objpfx)foo.o' might give

                   $(objpfx)foo.o: foo.c

       -MQ target
           Same as -MT, but it quotes any characters which are special to
           Make.  -MQ '$(objpfx)foo.o' gives

                   $$(objpfx)foo.o: foo.c

           The default target is automatically quoted, as if it were given
           with -MQ.

       -MD -MD is equivalent to -M -MF file, except that -E is not implied.
           The driver determines file based on whether an -o option is
           given.  If it is, the driver uses its argument but with a suffix
           of .d, otherwise it takes the name of the input file, removes any
           directory components and suffix, and applies a .d suffix.

           If -MD is used in conjunction with -E, any -o switch is
           understood to specify the dependency output file, but if used
           without -E, each -o is understood to specify a target object
           file.

           Since -E is not implied, -MD can be used to generate a dependency
           output file as a side-effect of the compilation process.

       -MMD
           Like -MD except mention only user header files, not system header
           files.

       -fpch-deps
           When using precompiled headers, this flag will cause the
           dependency-output flags to also list the files from the
           precompiled header's dependencies.  If not specified only the
           precompiled header would be listed and not the files that were
           used to create it because those files are not consulted when a
           precompiled header is used.

       -fpch-preprocess
           This option allows use of a precompiled header together with -E.
           It inserts a special "#pragma", "#pragma GCC pch_preprocess
           "filename"" in the output to mark the place where the precompiled
           header was found, and its filename.  When -fpreprocessed is in
           use, GCC recognizes this "#pragma" and loads the PCH.

           This option is off by default, because the resulting preprocessed
           output is only really suitable as input to GCC.  It is switched
           on by -save-temps.

           You should not write this "#pragma" in your own code, but it is
           safe to edit the filename if the PCH file is available in a
           different location.  The filename may be absolute or it may be
           relative to GCC's current directory.

       -x c
       -x c++
       -x objective-c
       -x assembler-with-cpp
           Specify the source language: C, C++, Objective-C, or assembly.
           This has nothing to do with standards conformance or extensions;
           it merely selects which base syntax to expect.  If you give none
           of these options, cpp will deduce the language from the extension
           of the source file: .c, .cc, .m, or .S.  Some other common
           extensions for C++ and assembly are also recognized.  If cpp does
           not recognize the extension, it will treat the file as C; this is
           the most generic mode.

           Note: Previous versions of cpp accepted a -lang option which
           selected both the language and the standards conformance level.
           This option has been removed, because it conflicts with the -l
           option.

       -std=standard
       -ansi
           Specify the standard to which the code should conform.  Currently
           CPP knows about C and C++ standards; others may be added in the
           future.

           standard may be one of:

           "c90"
           "c89"
           "iso9899:1990"
               The ISO C standard from 1990.  c90 is the customary shorthand
               for this version of the standard.

               The -ansi option is equivalent to -std=c90.

           "iso9899:199409"
               The 1990 C standard, as amended in 1994.

           "iso9899:1999"
           "c99"
           "iso9899:199x"
           "c9x"
               The revised ISO C standard, published in December 1999.
               Before publication, this was known as C9X.

           "iso9899:2011"
           "c11"
           "c1x"
               The revised ISO C standard, published in December 2011.
               Before publication, this was known as C1X.

           "gnu90"
           "gnu89"
               The 1990 C standard plus GNU extensions.  This is the
               default.

           "gnu99"
           "gnu9x"
               The 1999 C standard plus GNU extensions.

           "gnu11"
           "gnu1x"
               The 2011 C standard plus GNU extensions.

           "c++98"
               The 1998 ISO C++ standard plus amendments.

           "gnu++98"
               The same as -std=c++98 plus GNU extensions.  This is the
               default for C++ code.

       -I- Split the include path.  Any directories specified with -I
           options before -I- are searched only for headers requested with
           "#include "file""; they are not searched for "#include <file>".
           If additional directories are specified with -I options after the
           -I-, those directories are searched for all #include directives.

           In addition, -I- inhibits the use of the directory of the current
           file directory as the first search directory for
           "#include "file"".  This option has been deprecated.

       -nostdinc
           Do not search the standard system directories for header files.
           Only the directories you have specified with -I options (and the
           directory of the current file, if appropriate) are searched.

       -nostdinc++
           Do not search for header files in the C++-specific standard
           directories, but do still search the other standard directories.
           (This option is used when building the C++ library.)

       -include file
           Process file as if "#include "file"" appeared as the first line
           of the primary source file.  However, the first directory
           searched for file is the preprocessor's working directory instead
           of the directory containing the main source file.  If not found
           there, it is searched for in the remainder of the "#include
           "..."" search chain as normal.

           If multiple -include options are given, the files are included in
           the order they appear on the command line.

       -imacros file
           Exactly like -include, except that any output produced by
           scanning file is thrown away.  Macros it defines remain defined.
           This allows you to acquire all the macros from a header without
           also processing its declarations.

           All files specified by -imacros are processed before all files
           specified by -include.

       -idirafter dir
           Search dir for header files, but do it after all directories
           specified with -I and the standard system directories have been
           exhausted.  dir is treated as a system include directory.  If dir
           begins with "=", then the "=" will be replaced by the sysroot
           prefix; see --sysroot and -isysroot.

       -iprefix prefix
           Specify prefix as the prefix for subsequent -iwithprefix options.
           If the prefix represents a directory, you should include the
           final /.

       -iwithprefix dir
       -iwithprefixbefore dir
           Append dir to the prefix specified previously with -iprefix, and
           add the resulting directory to the include search path.
           -iwithprefixbefore puts it in the same place -I would;
           -iwithprefix puts it where -idirafter would.

       -isysroot dir
           This option is like the --sysroot option, but applies only to
           header files (except for Darwin targets, where it applies to both
           header files and libraries).  See the --sysroot option for more
           information.

       -imultilib dir
           Use dir as a subdirectory of the directory containing target-
           specific C++ headers.

       -isystem dir
           Search dir for header files, after all directories specified by
           -I but before the standard system directories.  Mark it as a
           system directory, so that it gets the same special treatment as
           is applied to the standard system directories.  If dir begins
           with "=", then the "=" will be replaced by the sysroot prefix;
           see --sysroot and -isysroot.

       -iquote dir
           Search dir only for header files requested with
           "#include "file""; they are not searched for "#include <file>",
           before all directories specified by -I and before the standard
           system directories.  If dir begins with "=", then the "=" will be
           replaced by the sysroot prefix; see --sysroot and -isysroot.

       -fdirectives-only
           When preprocessing, handle directives, but do not expand macros.

           The option's behavior depends on the -E and -fpreprocessed
           options.

           With -E, preprocessing is limited to the handling of directives
           such as "#define", "#ifdef", and "#error".  Other preprocessor
           operations, such as macro expansion and trigraph conversion are
           not performed.  In addition, the -dD option is implicitly
           enabled.

           With -fpreprocessed, predefinition of command line and most
           builtin macros is disabled.  Macros such as "__LINE__", which are
           contextually dependent, are handled normally.  This enables
           compilation of files previously preprocessed with "-E
           -fdirectives-only".

           With both -E and -fpreprocessed, the rules for -fpreprocessed
           take precedence.  This enables full preprocessing of files
           previously preprocessed with "-E -fdirectives-only".

       -fdollars-in-identifiers
           Accept $ in identifiers.

       -fextended-identifiers
           Accept universal character names in identifiers.  This option is
           enabled by default for C99 (and later C standard versions) and
           C++.

       -fno-canonical-system-headers
           When preprocessing, do not shorten system header paths with
           canonicalization.

       -fpreprocessed
           Indicate to the preprocessor that the input file has already been
           preprocessed.  This suppresses things like macro expansion,
           trigraph conversion, escaped newline splicing, and processing of
           most directives.  The preprocessor still recognizes and removes
           comments, so that you can pass a file preprocessed with -C to the
           compiler without problems.  In this mode the integrated
           preprocessor is little more than a tokenizer for the front ends.

           -fpreprocessed is implicit if the input file has one of the
           extensions .i, .ii or .mi.  These are the extensions that GCC
           uses for preprocessed files created by -save-temps.

       -ftabstop=width
           Set the distance between tab stops.  This helps the preprocessor
           report correct column numbers in warnings or errors, even if tabs
           appear on the line.  If the value is less than 1 or greater than
           100, the option is ignored.  The default is 8.

       -fdebug-cpp
           This option is only useful for debugging GCC.  When used with -E,
           dumps debugging information about location maps.  Every token in
           the output is preceded by the dump of the map its location
           belongs to.  The dump of the map holding the location of a token
           would be:

                   {"P":F</file/path>;"F":F</includer/path>;"L":<line_num>;"C":<col_num>;"S":<system_header_p>;"M":<map_address>;"E":<macro_expansion_p>,"loc":<location>}

           When used without -E, this option has no effect.

       -ftrack-macro-expansion[=level]
           Track locations of tokens across macro expansions. This allows
           the compiler to emit diagnostic about the current macro expansion
           stack when a compilation error occurs in a macro expansion. Using
           this option makes the preprocessor and the compiler consume more
           memory. The level parameter can be used to choose the level of
           precision of token location tracking thus decreasing the memory
           consumption if necessary. Value 0 of level de-activates this
           option just as if no -ftrack-macro-expansion was present on the
           command line. Value 1 tracks tokens locations in a degraded mode
           for the sake of minimal memory overhead. In this mode all tokens
           resulting from the expansion of an argument of a function-like
           macro have the same location. Value 2 tracks tokens locations
           completely. This value is the most memory hungry.  When this
           option is given no argument, the default parameter value is 2.

           Note that "-ftrack-macro-expansion=2" is activated by default.

       -fexec-charset=charset
           Set the execution character set, used for string and character
           constants.  The default is UTF-8.  charset can be any encoding
           supported by the system's "iconv" library routine.

       -fwide-exec-charset=charset
           Set the wide execution character set, used for wide string and
           character constants.  The default is UTF-32 or UTF-16, whichever
           corresponds to the width of "wchar_t".  As with -fexec-charset,
           charset can be any encoding supported by the system's "iconv"
           library routine; however, you will have problems with encodings
           that do not fit exactly in "wchar_t".

       -finput-charset=charset
           Set the input character set, used for translation from the
           character set of the input file to the source character set used
           by GCC.  If the locale does not specify, or GCC cannot get this
           information from the locale, the default is UTF-8.  This can be
           overridden by either the locale or this command-line option.
           Currently the command-line option takes precedence if there's a
           conflict.  charset can be any encoding supported by the system's
           "iconv" library routine.

       -fworking-directory
           Enable generation of linemarkers in the preprocessor output that
           will let the compiler know the current working directory at the
           time of preprocessing.  When this option is enabled, the
           preprocessor will emit, after the initial linemarker, a second
           linemarker with the current working directory followed by two
           slashes.  GCC will use this directory, when it's present in the
           preprocessed input, as the directory emitted as the current
           working directory in some debugging information formats.  This
           option is implicitly enabled if debugging information is enabled,
           but this can be inhibited with the negated form
           -fno-working-directory.  If the -P flag is present in the command
           line, this option has no effect, since no "#line" directives are
           emitted whatsoever.

       -fno-show-column
           Do not print column numbers in diagnostics.  This may be
           necessary if diagnostics are being scanned by a program that does
           not understand the column numbers, such as dejagnu.

       -A predicate=answer
           Make an assertion with the predicate predicate and answer answer.
           This form is preferred to the older form -A predicate(answer),
           which is still supported, because it does not use shell special
           characters.

       -A -predicate=answer
           Cancel an assertion with the predicate predicate and answer
           answer.

       -dCHARS
           CHARS is a sequence of one or more of the following characters,
           and must not be preceded by a space.  Other characters are
           interpreted by the compiler proper, or reserved for future
           versions of GCC, and so are silently ignored.  If you specify
           characters whose behavior conflicts, the result is undefined.

           M   Instead of the normal output, generate a list of #define
               directives for all the macros defined during the execution of
               the preprocessor, including predefined macros.  This gives
               you a way of finding out what is predefined in your version
               of the preprocessor.  Assuming you have no file foo.h, the
               command

                       touch foo.h; cpp -dM foo.h

               will show all the predefined macros.

               If you use -dM without the -E option, -dM is interpreted as a
               synonym for -fdump-rtl-mach.

           D   Like M except in two respects: it does not include the
               predefined macros, and it outputs both the #define directives
               and the result of preprocessing.  Both kinds of output go to
               the standard output file.

           N   Like D, but emit only the macro names, not their expansions.

           I   Output #include directives in addition to the result of
               preprocessing.

           U   Like D except that only macros that are expanded, or whose
               definedness is tested in preprocessor directives, are output;
               the output is delayed until the use or test of the macro; and
               #undef directives are also output for macros tested but
               undefined at the time.

       -P  Inhibit generation of linemarkers in the output from the
           preprocessor.  This might be useful when running the preprocessor
           on something that is not C code, and will be sent to a program
           which might be confused by the linemarkers.

       -C  Do not discard comments.  All comments are passed through to the
           output file, except for comments in processed directives, which
           are deleted along with the directive.

           You should be prepared for side effects when using -C; it causes
           the preprocessor to treat comments as tokens in their own right.
           For example, comments appearing at the start of what would be a
           directive line have the effect of turning that line into an
           ordinary source line, since the first token on the line is no
           longer a #.

       -CC Do not discard comments, including during macro expansion.  This
           is like -C, except that comments contained within macros are also
           passed through to the output file where the macro is expanded.

           In addition to the side-effects of the -C option, the -CC option
           causes all C++-style comments inside a macro to be converted to
           C-style comments.  This is to prevent later use of that macro
           from inadvertently commenting out the remainder of the source
           line.

           The -CC option is generally used to support lint comments.

       -traditional-cpp
           Try to imitate the behavior of old-fashioned C preprocessors, as
           opposed to ISO C preprocessors.

       -trigraphs
           Process trigraph sequences.  These are three-character sequences,
           all starting with ??, that are defined by ISO C to stand for
           single characters.  For example, ??/ stands for \, so '??/n' is a
           character constant for a newline.  By default, GCC ignores
           trigraphs, but in standard-conforming modes it converts them.
           See the -std and -ansi options.

           The nine trigraphs and their replacements are

                   Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
                   Replacement:      [    ]    {    }    #    \    ^    |    ~

       -remap
           Enable special code to work around file systems which only permit
           very short file names, such as MS-DOS.

       --help
       --target-help
           Print text describing all the command-line options instead of
           preprocessing anything.

       -v  Verbose mode.  Print out GNU CPP's version number at the
           beginning of execution, and report the final form of the include
           path.

       -H  Print the name of each header file used, in addition to other
           normal activities.  Each name is indented to show how deep in the
           #include stack it is.  Precompiled header files are also printed,
           even if they are found to be invalid; an invalid precompiled
           header file is printed with ...x and a valid one with ...! .

       -version
       --version
           Print out GNU CPP's version number.  With one dash, proceed to
           preprocess as normal.  With two dashes, exit immediately.

       Passing Options to the Assembler

       You can pass options to the assembler.

       -Wa,option
           Pass option as an option to the assembler.  If option contains
           commas, it is split into multiple options at the commas.

       -Xassembler option
           Pass option as an option to the assembler.  You can use this to
           supply system-specific assembler options that GCC does not
           recognize.

           If you want to pass an option that takes an argument, you must
           use -Xassembler twice, once for the option and once for the
           argument.

       Options for Linking

       These options come into play when the compiler links object files
       into an executable output file.  They are meaningless if the compiler
       is not doing a link step.

       object-file-name
           A file name that does not end in a special recognized suffix is
           considered to name an object file or library.  (Object files are
           distinguished from libraries by the linker according to the file
           contents.)  If linking is done, these object files are used as
           input to the linker.

       -c
       -S
       -E  If any of these options is used, then the linker is not run, and
           object file names should not be used as arguments.

       -fuse-ld=bfd
           Use the bfd linker instead of the default linker.

       -fuse-ld=gold
           Use the gold linker instead of the default linker.

       -llibrary
       -l library
           Search the library named library when linking.  (The second
           alternative with the library as a separate argument is only for
           POSIX compliance and is not recommended.)

           It makes a difference where in the command you write this option;
           the linker searches and processes libraries and object files in
           the order they are specified.  Thus, foo.o -lz bar.o searches
           library z after file foo.o but before bar.o.  If bar.o refers to
           functions in z, those functions may not be loaded.

           The linker searches a standard list of directories for the
           library, which is actually a file named liblibrary.a.  The linker
           then uses this file as if it had been specified precisely by
           name.

           The directories searched include several standard system
           directories plus any that you specify with -L.

           Normally the files found this way are library files---archive
           files whose members are object files.  The linker handles an
           archive file by scanning through it for members which define
           symbols that have so far been referenced but not defined.  But if
           the file that is found is an ordinary object file, it is linked
           in the usual fashion.  The only difference between using an -l
           option and specifying a file name is that -l surrounds library
           with lib and .a and searches several directories.

       -lobjc
           You need this special case of the -l option in order to link an
           Objective-C or Objective-C++ program.

       -nostartfiles
           Do not use the standard system startup files when linking.  The
           standard system libraries are used normally, unless -nostdlib or
           -nodefaultlibs is used.

       -nodefaultlibs
           Do not use the standard system libraries when linking.  Only the
           libraries you specify are passed to the linker, and options
           specifying linkage of the system libraries, such as
           -static-libgcc or -shared-libgcc, are ignored.  The standard
           startup files are used normally, unless -nostartfiles is used.

           The compiler may generate calls to "memcmp", "memset", "memcpy"
           and "memmove".  These entries are usually resolved by entries in
           libc.  These entry points should be supplied through some other
           mechanism when this option is specified.

       -nostdlib
           Do not use the standard system startup files or libraries when
           linking.  No startup files and only the libraries you specify are
           passed to the linker, and options specifying linkage of the
           system libraries, such as -static-libgcc or -shared-libgcc, are
           ignored.

           The compiler may generate calls to "memcmp", "memset", "memcpy"
           and "memmove".  These entries are usually resolved by entries in
           libc.  These entry points should be supplied through some other
           mechanism when this option is specified.

           One of the standard libraries bypassed by -nostdlib and
           -nodefaultlibs is libgcc.a, a library of internal subroutines
           which GCC uses to overcome shortcomings of particular machines,
           or special needs for some languages.

           In most cases, you need libgcc.a even when you want to avoid
           other standard libraries.  In other words, when you specify
           -nostdlib or -nodefaultlibs you should usually specify -lgcc as
           well.  This ensures that you have no unresolved references to
           internal GCC library subroutines.  (An example of such an
           internal subroutine is "__main", used to ensure C++ constructors
           are called.)

       -pie
           Produce a position independent executable on targets that support
           it.  For predictable results, you must also specify the same set
           of options used for compilation (-fpie, -fPIE, or model
           suboptions) when you specify this linker option.

       -no-pie
           Don't produce a position independent executable.

       -rdynamic
           Pass the flag -export-dynamic to the ELF linker, on targets that
           support it. This instructs the linker to add all symbols, not
           only used ones, to the dynamic symbol table. This option is
           needed for some uses of "dlopen" or to allow obtaining backtraces
           from within a program.

       -s  Remove all symbol table and relocation information from the
           executable.

       -static
           On systems that support dynamic linking, this prevents linking
           with the shared libraries.  On other systems, this option has no
           effect.

       -shared
           Produce a shared object which can then be linked with other
           objects to form an executable.  Not all systems support this
           option.  For predictable results, you must also specify the same
           set of options used for compilation (-fpic, -fPIC, or model
           suboptions) when you specify this linker option.[1]

       -shared-libgcc
       -static-libgcc
           On systems that provide libgcc as a shared library, these options
           force the use of either the shared or static version,
           respectively.  If no shared version of libgcc was built when the
           compiler was configured, these options have no effect.

           There are several situations in which an application should use
           the shared libgcc instead of the static version.  The most common
           of these is when the application wishes to throw and catch
           exceptions across different shared libraries.  In that case, each
           of the libraries as well as the application itself should use the
           shared libgcc.

           Therefore, the G++ and GCJ drivers automatically add
           -shared-libgcc whenever you build a shared library or a main
           executable, because C++ and Java programs typically use
           exceptions, so this is the right thing to do.

           If, instead, you use the GCC driver to create shared libraries,
           you may find that they are not always linked with the shared
           libgcc.  If GCC finds, at its configuration time, that you have a
           non-GNU linker or a GNU linker that does not support option
           --eh-frame-hdr, it links the shared version of libgcc into shared
           libraries by default.  Otherwise, it takes advantage of the
           linker and optimizes away the linking with the shared version of
           libgcc, linking with the static version of libgcc by default.
           This allows exceptions to propagate through such shared
           libraries, without incurring relocation costs at library load
           time.

           However, if a library or main executable is supposed to throw or
           catch exceptions, you must link it using the G++ or GCJ driver,
           as appropriate for the languages used in the program, or using
           the option -shared-libgcc, such that it is linked with the shared
           libgcc.

       -static-libasan
           When the -fsanitize=address option is used to link a program, the
           GCC driver automatically links against libasan.  If libasan is
           available as a shared library, and the -static option is not
           used, then this links against the shared version of libasan.  The
           -static-libasan option directs the GCC driver to link libasan
           statically, without necessarily linking other libraries
           statically.

       -static-libtsan
           When the -fsanitize=thread option is used to link a program, the
           GCC driver automatically links against libtsan.  If libtsan is
           available as a shared library, and the -static option is not
           used, then this links against the shared version of libtsan.  The
           -static-libtsan option directs the GCC driver to link libtsan
           statically, without necessarily linking other libraries
           statically.

       -static-liblsan
           When the -fsanitize=leak option is used to link a program, the
           GCC driver automatically links against liblsan.  If liblsan is
           available as a shared library, and the -static option is not
           used, then this links against the shared version of liblsan.  The
           -static-liblsan option directs the GCC driver to link liblsan
           statically, without necessarily linking other libraries
           statically.

       -static-libubsan
           When the -fsanitize=undefined option is used to link a program,
           the GCC driver automatically links against libubsan.  If libubsan
           is available as a shared library, and the -static option is not
           used, then this links against the shared version of libubsan.
           The -static-libubsan option directs the GCC driver to link
           libubsan statically, without necessarily linking other libraries
           statically.

       -static-libmpx
           When the -fcheck-pointer bounds and -mmpx options are used to
           link a program, the GCC driver automatically links against
           libmpx.  If libmpx is available as a shared library, and the
           -static option is not used, then this links against the shared
           version of libmpx.  The -static-libmpx option directs the GCC
           driver to link libmpx statically, without necessarily linking
           other libraries statically.

       -static-libmpxwrappers
           When the -fcheck-pointer bounds and -mmpx options are used to
           link a program without also using -fno-chkp-use-wrappers, the GCC
           driver automatically links against libmpxwrappers.  If
           libmpxwrappers is available as a shared library, and the -static
           option is not used, then this links against the shared version of
           libmpxwrappers.  The -static-libmpxwrappers option directs the
           GCC driver to link libmpxwrappers statically, without necessarily
           linking other libraries statically.

       -static-libstdc++
           When the g++ program is used to link a C++ program, it normally
           automatically links against libstdc++.  If libstdc++ is available
           as a shared library, and the -static option is not used, then
           this links against the shared version of libstdc++.  That is
           normally fine.  However, it is sometimes useful to freeze the
           version of libstdc++ used by the program without going all the
           way to a fully static link.  The -static-libstdc++ option directs
           the g++ driver to link libstdc++ statically, without necessarily
           linking other libraries statically.

       -symbolic
           Bind references to global symbols when building a shared object.
           Warn about any unresolved references (unless overridden by the
           link editor option -Xlinker -z -Xlinker defs).  Only a few
           systems support this option.

       -T script
           Use script as the linker script.  This option is supported by
           most systems using the GNU linker.  On some targets, such as
           bare-board targets without an operating system, the -T option may
           be required when linking to avoid references to undefined
           symbols.

       -Xlinker option
           Pass option as an option to the linker.  You can use this to
           supply system-specific linker options that GCC does not
           recognize.

           If you want to pass an option that takes a separate argument, you
           must use -Xlinker twice, once for the option and once for the
           argument.  For example, to pass -assert definitions, you must
           write -Xlinker -assert -Xlinker definitions.  It does not work to
           write -Xlinker "-assert definitions", because this passes the
           entire string as a single argument, which is not what the linker
           expects.

           When using the GNU linker, it is usually more convenient to pass
           arguments to linker options using the option=value syntax than as
           separate arguments.  For example, you can specify -Xlinker
           -Map=output.map rather than -Xlinker -Map -Xlinker output.map.
           Other linkers may not support this syntax for command-line
           options.

       -Wl,option
           Pass option as an option to the linker.  If option contains
           commas, it is split into multiple options at the commas.  You can
           use this syntax to pass an argument to the option.  For example,
           -Wl,-Map,output.map passes -Map output.map to the linker.  When
           using the GNU linker, you can also get the same effect with
           -Wl,-Map=output.map.

       -u symbol
           Pretend the symbol symbol is undefined, to force linking of
           library modules to define it.  You can use -u multiple times with
           different symbols to force loading of additional library modules.

       -z keyword
           -z is passed directly on to the linker along with the keyword
           keyword. See the section in the documentation of your linker for
           permitted values and their meanings.

       Options for Directory Search

       These options specify directories to search for header files, for
       libraries and for parts of the compiler:

       -Idir
           Add the directory dir to the head of the list of directories to
           be searched for header files.  This can be used to override a
           system header file, substituting your own version, since these
           directories are searched before the system header file
           directories.  However, you should not use this option to add
           directories that contain vendor-supplied system header files (use
           -isystem for that).  If you use more than one -I option, the
           directories are scanned in left-to-right order; the standard
           system directories come after.

           If a standard system include directory, or a directory specified
           with -isystem, is also specified with -I, the -I option is
           ignored.  The directory is still searched but as a system
           directory at its normal position in the system include chain.
           This is to ensure that GCC's procedure to fix buggy system
           headers and the ordering for the "include_next" directive are not
           inadvertently changed.  If you really need to change the search
           order for system directories, use the -nostdinc and/or -isystem
           options.

       -iplugindir=dir
           Set the directory to search for plugins that are passed by
           -fplugin=name instead of -fplugin=path/name.so.  This option is
           not meant to be used by the user, but only passed by the driver.

       -iquotedir
           Add the directory dir to the head of the list of directories to
           be searched for header files only for the case of "#include
           "file""; they are not searched for "#include <file>", otherwise
           just like -I.

       -Ldir
           Add directory dir to the list of directories to be searched for
           -l.

       -Bprefix
           This option specifies where to find the executables, libraries,
           include files, and data files of the compiler itself.

           The compiler driver program runs one or more of the subprograms
           cpp, cc1, as and ld.  It tries prefix as a prefix for each
           program it tries to run, both with and without machine/version/
           for the corresponding target machine and compiler version.

           For each subprogram to be run, the compiler driver first tries
           the -B prefix, if any.  If that name is not found, or if -B is
           not specified, the driver tries two standard prefixes,
           /usr/lib/gcc/ and /usr/local/lib/gcc/.  If neither of those
           results in a file name that is found, the unmodified program name
           is searched for using the directories specified in your PATH
           environment variable.

           The compiler checks to see if the path provided by -B refers to a
           directory, and if necessary it adds a directory separator
           character at the end of the path.

           -B prefixes that effectively specify directory names also apply
           to libraries in the linker, because the compiler translates these
           options into -L options for the linker.  They also apply to
           include files in the preprocessor, because the compiler
           translates these options into -isystem options for the
           preprocessor.  In this case, the compiler appends include to the
           prefix.

           The runtime support file libgcc.a can also be searched for using
           the -B prefix, if needed.  If it is not found there, the two
           standard prefixes above are tried, and that is all.  The file is
           left out of the link if it is not found by those means.

           Another way to specify a prefix much like the -B prefix is to use
           the environment variable GCC_EXEC_PREFIX.

           As a special kludge, if the path provided by -B is [dir/]stageN/,
           where N is a number in the range 0 to 9, then it is replaced by
           [dir/]include.  This is to help with boot-strapping the compiler.

       -no-canonical-prefixes
           Do not expand any symbolic links, resolve references to /../ or
           /./, or make the path absolute when generating a relative prefix.

       --sysroot=dir
           Use dir as the logical root directory for headers and libraries.
           For example, if the compiler normally searches for headers in
           /usr/include and libraries in /usr/lib, it instead searches
           dir/usr/include and dir/usr/lib.

           If you use both this option and the -isysroot option, then the
           --sysroot option applies to libraries, but the -isysroot option
           applies to header files.

           The GNU linker (beginning with version 2.16) has the necessary
           support for this option.  If your linker does not support this
           option, the header file aspect of --sysroot still works, but the
           library aspect does not.

       --no-sysroot-suffix
           For some targets, a suffix is added to the root directory
           specified with --sysroot, depending on the other options used, so
           that headers may for example be found in dir/suffix/usr/include
           instead of dir/usr/include.  This option disables the addition of
           such a suffix.

       -I- This option has been deprecated.  Please use -iquote instead for
           -I directories before the -I- and remove the -I- option.  Any
           directories you specify with -I options before the -I- option are
           searched only for the case of "#include "file""; they are not
           searched for "#include <file>".

           If additional directories are specified with -I options after the
           -I- option, these directories are searched for all "#include"
           directives.  (Ordinarily all -I directories are used this way.)

           In addition, the -I- option inhibits the use of the current
           directory (where the current input file came from) as the first
           search directory for "#include "file"".  There is no way to
           override this effect of -I-.  With -I. you can specify searching
           the directory that is current when the compiler is invoked.  That
           is not exactly the same as what the preprocessor does by default,
           but it is often satisfactory.

           -I- does not inhibit the use of the standard system directories
           for header files.  Thus, -I- and -nostdinc are independent.

       Options for Code Generation Conventions

       These machine-independent options control the interface conventions
       used in code generation.

       Most of them have both positive and negative forms; the negative form
       of -ffoo is -fno-foo.  In the table below, only one of the forms is
       listed---the one that is not the default.  You can figure out the
       other form by either removing no- or adding it.

       -fstack-reuse=reuse-level
           This option controls stack space reuse for user declared
           local/auto variables and compiler generated temporaries.
           reuse_level can be all, named_vars, or none. all enables stack
           reuse for all local variables and temporaries, named_vars enables
           the reuse only for user defined local variables with names, and
           none disables stack reuse completely. The default value is all.
           The option is needed when the program extends the lifetime of a
           scoped local variable or a compiler generated temporary beyond
           the end point defined by the language.  When a lifetime of a
           variable ends, and if the variable lives in memory, the
           optimizing compiler has the freedom to reuse its stack space with
           other temporaries or scoped local variables whose live range does
           not overlap with it. Legacy code extending local lifetime is
           likely to break with the stack reuse optimization.

           For example,

                      int *p;
                      {
                        int local1;

                        p = &local1;
                        local1 = 10;
                        ....
                      }
                      {
                         int local2;
                         local2 = 20;
                         ...
                      }

                      if (*p == 10)  // out of scope use of local1
                        {

                        }

           Another example:

                      struct A
                      {
                          A(int k) : i(k), j(k) { }
                          int i;
                          int j;
                      };

                      A *ap;

                      void foo(const A& ar)
                      {
                         ap = &ar;
                      }

                      void bar()
                      {
                         foo(A(10)); // temp object's lifetime ends when foo returns

                         {
                           A a(20);
                           ....
                         }
                         ap->i+= 10;  // ap references out of scope temp whose space
                                      // is reused with a. What is the value of ap->i?
                      }

           The lifetime of a compiler generated temporary is well defined by
           the C++ standard. When a lifetime of a temporary ends, and if the
           temporary lives in memory, the optimizing compiler has the
           freedom to reuse its stack space with other temporaries or scoped
           local variables whose live range does not overlap with it.
           However some of the legacy code relies on the behavior of older
           compilers in which temporaries' stack space is not reused, the
           aggressive stack reuse can lead to runtime errors. This option is
           used to control the temporary stack reuse optimization.

       -ftrapv
           This option generates traps for signed overflow on addition,
           subtraction, multiplication operations.  The options -ftrapv and
           -fwrapv override each other, so using -ftrapv -fwrapv on the
           command-line results in -fwrapv being effective.  Note that only
           active options override, so using -ftrapv -fwrapv -fno-wrapv on
           the command-line results in -ftrapv being effective.

       -fwrapv
           This option instructs the compiler to assume that signed
           arithmetic overflow of addition, subtraction and multiplication
           wraps around using twos-complement representation.  This flag
           enables some optimizations and disables others.  This option is
           enabled by default for the Java front end, as required by the
           Java language specification.  The options -ftrapv and -fwrapv
           override each other, so using -ftrapv -fwrapv on the command-line
           results in -fwrapv being effective.  Note that only active
           options override, so using -ftrapv -fwrapv -fno-wrapv on the
           command-line results in -ftrapv being effective.

       -fexceptions
           Enable exception handling.  Generates extra code needed to
           propagate exceptions.  For some targets, this implies GCC
           generates frame unwind information for all functions, which can
           produce significant data size overhead, although it does not
           affect execution.  If you do not specify this option, GCC enables
           it by default for languages like C++ that normally require
           exception handling, and disables it for languages like C that do
           not normally require it.  However, you may need to enable this
           option when compiling C code that needs to interoperate properly
           with exception handlers written in C++.  You may also wish to
           disable this option if you are compiling older C++ programs that
           don't use exception handling.

       -fnon-call-exceptions
           Generate code that allows trapping instructions to throw
           exceptions.  Note that this requires platform-specific runtime
           support that does not exist everywhere.  Moreover, it only allows
           trapping instructions to throw exceptions, i.e. memory references
           or floating-point instructions.  It does not allow exceptions to
           be thrown from arbitrary signal handlers such as "SIGALRM".

       -fdelete-dead-exceptions
           Consider that instructions that may throw exceptions but don't
           otherwise contribute to the execution of the program can be
           optimized away.  This option is enabled by default for the Ada
           front end, as permitted by the Ada language specification.
           Optimization passes that cause dead exceptions to be removed are
           enabled independently at different optimization levels.

       -funwind-tables
           Similar to -fexceptions, except that it just generates any needed
           static data, but does not affect the generated code in any other
           way.  You normally do not need to enable this option; instead, a
           language processor that needs this handling enables it on your
           behalf.

       -fasynchronous-unwind-tables
           Generate unwind table in DWARF format, if supported by target
           machine.  The table is exact at each instruction boundary, so it
           can be used for stack unwinding from asynchronous events (such as
           debugger or garbage collector).

       -fno-gnu-unique
           On systems with recent GNU assembler and C library, the C++
           compiler uses the "STB_GNU_UNIQUE" binding to make sure that
           definitions of template static data members and static local
           variables in inline functions are unique even in the presence of
           "RTLD_LOCAL"; this is necessary to avoid problems with a library
           used by two different "RTLD_LOCAL" plugins depending on a
           definition in one of them and therefore disagreeing with the
           other one about the binding of the symbol.  But this causes
           "dlclose" to be ignored for affected DSOs; if your program relies
           on reinitialization of a DSO via "dlclose" and "dlopen", you can
           use -fno-gnu-unique.

       -fpcc-struct-return
           Return "short" "struct" and "union" values in memory like longer
           ones, rather than in registers.  This convention is less
           efficient, but it has the advantage of allowing intercallability
           between GCC-compiled files and files compiled with other
           compilers, particularly the Portable C Compiler (pcc).

           The precise convention for returning structures in memory depends
           on the target configuration macros.

           Short structures and unions are those whose size and alignment
           match that of some integer type.

           Warning: code compiled with the -fpcc-struct-return switch is not
           binary compatible with code compiled with the -freg-struct-return
           switch.  Use it to conform to a non-default application binary
           interface.

       -freg-struct-return
           Return "struct" and "union" values in registers when possible.
           This is more efficient for small structures than
           -fpcc-struct-return.

           If you specify neither -fpcc-struct-return nor
           -freg-struct-return, GCC defaults to whichever convention is
           standard for the target.  If there is no standard convention, GCC
           defaults to -fpcc-struct-return, except on targets where GCC is
           the principal compiler.  In those cases, we can choose the
           standard, and we chose the more efficient register return
           alternative.

           Warning: code compiled with the -freg-struct-return switch is not
           binary compatible with code compiled with the -fpcc-struct-return
           switch.  Use it to conform to a non-default application binary
           interface.

       -fshort-enums
           Allocate to an "enum" type only as many bytes as it needs for the
           declared range of possible values.  Specifically, the "enum" type
           is equivalent to the smallest integer type that has enough room.

           Warning: the -fshort-enums switch causes GCC to generate code
           that is not binary compatible with code generated without that
           switch.  Use it to conform to a non-default application binary
           interface.

       -fshort-wchar
           Override the underlying type for "wchar_t" to be "short unsigned
           int" instead of the default for the target.  This option is
           useful for building programs to run under WINE.

           Warning: the -fshort-wchar switch causes GCC to generate code
           that is not binary compatible with code generated without that
           switch.  Use it to conform to a non-default application binary
           interface.

       -fno-common
           In C code, controls the placement of uninitialized global
           variables.  Unix C compilers have traditionally permitted
           multiple definitions of such variables in different compilation
           units by placing the variables in a common block.  This is the
           behavior specified by -fcommon, and is the default for GCC on
           most targets.  On the other hand, this behavior is not required
           by ISO C, and on some targets may carry a speed or code size
           penalty on variable references.  The -fno-common option specifies
           that the compiler should place uninitialized global variables in
           the data section of the object file, rather than generating them
           as common blocks.  This has the effect that if the same variable
           is declared (without "extern") in two different compilations, you
           get a multiple-definition error when you link them.  In this
           case, you must compile with -fcommon instead.  Compiling with
           -fno-common is useful on targets for which it provides better
           performance, or if you wish to verify that the program will work
           on other systems that always treat uninitialized variable
           declarations this way.

       -fno-ident
           Ignore the "#ident" directive.

       -finhibit-size-directive
           Don't output a ".size" assembler directive, or anything else that
           would cause trouble if the function is split in the middle, and
           the two halves are placed at locations far apart in memory.  This
           option is used when compiling crtstuff.c; you should not need to
           use it for anything else.

       -fverbose-asm
           Put extra commentary information in the generated assembly code
           to make it more readable.  This option is generally only of use
           to those who actually need to read the generated assembly code
           (perhaps while debugging the compiler itself).

           -fno-verbose-asm, the default, causes the extra information to be
           omitted and is useful when comparing two assembler files.

       -frecord-gcc-switches
           This switch causes the command line used to invoke the compiler
           to be recorded into the object file that is being created.  This
           switch is only implemented on some targets and the exact format
           of the recording is target and binary file format dependent, but
           it usually takes the form of a section containing ASCII text.
           This switch is related to the -fverbose-asm switch, but that
           switch only records information in the assembler output file as
           comments, so it never reaches the object file.  See also
           -grecord-gcc-switches for another way of storing compiler options
           into the object file.

       -fpic
           Generate position-independent code (PIC) suitable for use in a
           shared library, if supported for the target machine.  Such code
           accesses all constant addresses through a global offset table
           (GOT).  The dynamic loader resolves the GOT entries when the
           program starts (the dynamic loader is not part of GCC; it is part
           of the operating system).  If the GOT size for the linked
           executable exceeds a machine-specific maximum size, you get an
           error message from the linker indicating that -fpic does not
           work; in that case, recompile with -fPIC instead.  (These
           maximums are 8k on the SPARC, 28k on AArch64 and 32k on the m68k
           and RS/6000.  The x86 has no such limit.)

           Position-independent code requires special support, and therefore
           works only on certain machines.  For the x86, GCC supports PIC
           for System V but not for the Sun 386i.  Code generated for the
           IBM RS/6000 is always position-independent.

           When this flag is set, the macros "__pic__" and "__PIC__" are
           defined to 1.

       -fPIC
           If supported for the target machine, emit position-independent
           code, suitable for dynamic linking and avoiding any limit on the
           size of the global offset table.  This option makes a difference
           on AArch64, m68k, PowerPC and SPARC.

           Position-independent code requires special support, and therefore
           works only on certain machines.

           When this flag is set, the macros "__pic__" and "__PIC__" are
           defined to 2.

       -fpie
       -fPIE
           These options are similar to -fpic and -fPIC, but generated
           position independent code can be only linked into executables.
           Usually these options are used when -pie GCC option is used
           during linking.

           -fpie and -fPIE both define the macros "__pie__" and "__PIE__".
           The macros have the value 1 for -fpie and 2 for -fPIE.

       -fno-plt
           Do not use the PLT for external function calls in position-
           independent code.  Instead, load the callee address at call sites
           from the GOT and branch to it.  This leads to more efficient code
           by eliminating PLT stubs and exposing GOT loads to optimizations.
           On architectures such as 32-bit x86 where PLT stubs expect the
           GOT pointer in a specific register, this gives more register
           allocation freedom to the compiler.  Lazy binding requires use of
           the PLT; with -fno-plt all external symbols are resolved at load
           time.

           Alternatively, the function attribute "noplt" can be used to
           avoid calls through the PLT for specific external functions.

           In position-dependent code, a few targets also convert calls to
           functions that are marked to not use the PLT to use the GOT
           instead.

       -fno-jump-tables
           Do not use jump tables for switch statements even where it would
           be more efficient than other code generation strategies.  This
           option is of use in conjunction with -fpic or -fPIC for building
           code that forms part of a dynamic linker and cannot reference the
           address of a jump table.  On some targets, jump tables do not
           require a GOT and this option is not needed.

       -ffixed-reg
           Treat the register named reg as a fixed register; generated code
           should never refer to it (except perhaps as a stack pointer,
           frame pointer or in some other fixed role).

           reg must be the name of a register.  The register names accepted
           are machine-specific and are defined in the "REGISTER_NAMES"
           macro in the machine description macro file.

           This flag does not have a negative form, because it specifies a
           three-way choice.

       -fcall-used-reg
           Treat the register named reg as an allocable register that is
           clobbered by function calls.  It may be allocated for temporaries
           or variables that do not live across a call.  Functions compiled
           this way do not save and restore the register reg.

           It is an error to use this flag with the frame pointer or stack
           pointer.  Use of this flag for other registers that have fixed
           pervasive roles in the machine's execution model produces
           disastrous results.

           This flag does not have a negative form, because it specifies a
           three-way choice.

       -fcall-saved-reg
           Treat the register named reg as an allocable register saved by
           functions.  It may be allocated even for temporaries or variables
           that live across a call.  Functions compiled this way save and
           restore the register reg if they use it.

           It is an error to use this flag with the frame pointer or stack
           pointer.  Use of this flag for other registers that have fixed
           pervasive roles in the machine's execution model produces
           disastrous results.

           A different sort of disaster results from the use of this flag
           for a register in which function values may be returned.

           This flag does not have a negative form, because it specifies a
           three-way choice.

       -fpack-struct[=n]
           Without a value specified, pack all structure members together
           without holes.  When a value is specified (which must be a small
           power of two), pack structure members according to this value,
           representing the maximum alignment (that is, objects with default
           alignment requirements larger than this are output potentially
           unaligned at the next fitting location.

           Warning: the -fpack-struct switch causes GCC to generate code
           that is not binary compatible with code generated without that
           switch.  Additionally, it makes the code suboptimal.  Use it to
           conform to a non-default application binary interface.

       -fleading-underscore
           This option and its counterpart, -fno-leading-underscore,
           forcibly change the way C symbols are represented in the object
           file.  One use is to help link with legacy assembly code.

           Warning: the -fleading-underscore switch causes GCC to generate
           code that is not binary compatible with code generated without
           that switch.  Use it to conform to a non-default application
           binary interface.  Not all targets provide complete support for
           this switch.

       -ftls-model=model
           Alter the thread-local storage model to be used.  The model
           argument should be one of global-dynamic, local-dynamic, initial-
           exec or local-exec.  Note that the choice is subject to
           optimization: the compiler may use a more efficient model for
           symbols not visible outside of the translation unit, or if -fpic
           is not given on the command line.

           The default without -fpic is initial-exec; with -fpic the default
           is global-dynamic.

       -fvisibility=[default|internal|hidden|protected]
           Set the default ELF image symbol visibility to the specified
           option---all symbols are marked with this unless overridden
           within the code.  Using this feature can very substantially
           improve linking and load times of shared object libraries,
           produce more optimized code, provide near-perfect API export and
           prevent symbol clashes.  It is strongly recommended that you use
           this in any shared objects you distribute.

           Despite the nomenclature, default always means public; i.e.,
           available to be linked against from outside the shared object.
           protected and internal are pretty useless in real-world usage so
           the only other commonly used option is hidden.  The default if
           -fvisibility isn't specified is default, i.e., make every symbol
           public.

           A good explanation of the benefits offered by ensuring ELF
           symbols have the correct visibility is given by "How To Write
           Shared Libraries" by Ulrich Drepper (which can be found at
           <http://www.akkadia.org/drepper/ >)---however a superior solution
           made possible by this option to marking things hidden when the
           default is public is to make the default hidden and mark things
           public.  This is the norm with DLLs on Windows and with
           -fvisibility=hidden and "__attribute__ ((visibility("default")))"
           instead of "__declspec(dllexport)" you get almost identical
           semantics with identical syntax.  This is a great boon to those
           working with cross-platform projects.

           For those adding visibility support to existing code, you may
           find "#pragma GCC visibility" of use.  This works by you
           enclosing the declarations you wish to set visibility for with
           (for example) "#pragma GCC visibility push(hidden)" and "#pragma
           GCC visibility pop".  Bear in mind that symbol visibility should
           be viewed as part of the API interface contract and thus all new
           code should always specify visibility when it is not the default;
           i.e., declarations only for use within the local DSO should
           always be marked explicitly as hidden as so to avoid PLT
           indirection overheads---making this abundantly clear also aids
           readability and self-documentation of the code.  Note that due to
           ISO C++ specification requirements, "operator new" and "operator
           delete" must always be of default visibility.

           Be aware that headers from outside your project, in particular
           system headers and headers from any other library you use, may
           not be expecting to be compiled with visibility other than the
           default.  You may need to explicitly say "#pragma GCC visibility
           push(default)" before including any such headers.

           "extern" declarations are not affected by -fvisibility, so a lot
           of code can be recompiled with -fvisibility=hidden with no
           modifications.  However, this means that calls to "extern"
           functions with no explicit visibility use the PLT, so it is more
           effective to use "__attribute ((visibility))" and/or "#pragma GCC
           visibility" to tell the compiler which "extern" declarations
           should be treated as hidden.

           Note that -fvisibility does affect C++ vague linkage entities.
           This means that, for instance, an exception class that is be
           thrown between DSOs must be explicitly marked with default
           visibility so that the type_info nodes are unified between the
           DSOs.

           An overview of these techniques, their benefits and how to use
           them is at <http://gcc.gnu.org/wiki/Visibility >.

       -fstrict-volatile-bitfields
           This option should be used if accesses to volatile bit-fields (or
           other structure fields, although the compiler usually honors
           those types anyway) should use a single access of the width of
           the field's type, aligned to a natural alignment if possible.
           For example, targets with memory-mapped peripheral registers
           might require all such accesses to be 16 bits wide; with this
           flag you can declare all peripheral bit-fields as "unsigned
           short" (assuming short is 16 bits on these targets) to force GCC
           to use 16-bit accesses instead of, perhaps, a more efficient
           32-bit access.

           If this option is disabled, the compiler uses the most efficient
           instruction.  In the previous example, that might be a 32-bit
           load instruction, even though that accesses bytes that do not
           contain any portion of the bit-field, or memory-mapped registers
           unrelated to the one being updated.

           In some cases, such as when the "packed" attribute is applied to
           a structure field, it may not be possible to access the field
           with a single read or write that is correctly aligned for the
           target machine.  In this case GCC falls back to generating
           multiple accesses rather than code that will fault or truncate
           the result at run time.

           Note:  Due to restrictions of the C/C++11 memory model, write
           accesses are not allowed to touch non bit-field members.  It is
           therefore recommended to define all bits of the field's type as
           bit-field members.

           The default value of this option is determined by the application
           binary interface for the target processor.

       -fsync-libcalls
           This option controls whether any out-of-line instance of the
           "__sync" family of functions may be used to implement the C++11
           "__atomic" family of functions.

           The default value of this option is enabled, thus the only useful
           form of the option is -fno-sync-libcalls.  This option is used in
           the implementation of the libatomic runtime library.

       GCC Developer Options

       This section describes command-line options that are primarily of
       interest to GCC developers, including options to support compiler
       testing and investigation of compiler bugs and compile-time
       performance problems.  This includes options that produce debug dumps
       at various points in the compilation; that print statistics such as
       memory use and execution time; and that print information about GCC's
       configuration, such as where it searches for libraries.  You should
       rarely need to use any of these options for ordinary compilation and
       linking tasks.

       -dletters
       -fdump-rtl-pass
       -fdump-rtl-pass=filename
           Says to make debugging dumps during compilation at times
           specified by letters.  This is used for debugging the RTL-based
           passes of the compiler.  The file names for most of the dumps are
           made by appending a pass number and a word to the dumpname, and
           the files are created in the directory of the output file.  In
           case of =filename option, the dump is output on the given file
           instead of the pass numbered dump files.  Note that the pass
           number is assigned as passes are registered into the pass
           manager.  Most passes are registered in the order that they will
           execute and for these passes the number corresponds to the pass
           execution order.  However, passes registered by plugins, passes
           specific to compilation targets, or passes that are otherwise
           registered after all the other passes are numbered higher than a
           pass named "final", even if they are executed earlier.  dumpname
           is generated from the name of the output file if explicitly
           specified and not an executable, otherwise it is the basename of
           the source file.  These switches may have different effects when
           -E is used for preprocessing.

           Debug dumps can be enabled with a -fdump-rtl switch or some -d
           option letters.  Here are the possible letters for use in pass
           and letters, and their meanings:

           -fdump-rtl-alignments
               Dump after branch alignments have been computed.

           -fdump-rtl-asmcons
               Dump after fixing rtl statements that have unsatisfied in/out
               constraints.

           -fdump-rtl-auto_inc_dec
               Dump after auto-inc-dec discovery.  This pass is only run on
               architectures that have auto inc or auto dec instructions.

           -fdump-rtl-barriers
               Dump after cleaning up the barrier instructions.

           -fdump-rtl-bbpart
               Dump after partitioning hot and cold basic blocks.

           -fdump-rtl-bbro
               Dump after block reordering.

           -fdump-rtl-btl1
           -fdump-rtl-btl2
               -fdump-rtl-btl1 and -fdump-rtl-btl2 enable dumping after the
               two branch target load optimization passes.

           -fdump-rtl-bypass
               Dump after jump bypassing and control flow optimizations.

           -fdump-rtl-combine
               Dump after the RTL instruction combination pass.

           -fdump-rtl-compgotos
               Dump after duplicating the computed gotos.

           -fdump-rtl-ce1
           -fdump-rtl-ce2
           -fdump-rtl-ce3
               -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3 enable
               dumping after the three if conversion passes.

           -fdump-rtl-cprop_hardreg
               Dump after hard register copy propagation.

           -fdump-rtl-csa
               Dump after combining stack adjustments.

           -fdump-rtl-cse1
           -fdump-rtl-cse2
               -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping after the
               two common subexpression elimination passes.

           -fdump-rtl-dce
               Dump after the standalone dead code elimination passes.

           -fdump-rtl-dbr
               Dump after delayed branch scheduling.

           -fdump-rtl-dce1
           -fdump-rtl-dce2
               -fdump-rtl-dce1 and -fdump-rtl-dce2 enable dumping after the
               two dead store elimination passes.

           -fdump-rtl-eh
               Dump after finalization of EH handling code.

           -fdump-rtl-eh_ranges
               Dump after conversion of EH handling range regions.

           -fdump-rtl-expand
               Dump after RTL generation.

           -fdump-rtl-fwprop1
           -fdump-rtl-fwprop2
               -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable dumping
               after the two forward propagation passes.

           -fdump-rtl-gcse1
           -fdump-rtl-gcse2
               -fdump-rtl-gcse1 and -fdump-rtl-gcse2 enable dumping after
               global common subexpression elimination.

           -fdump-rtl-init-regs
               Dump after the initialization of the registers.

           -fdump-rtl-initvals
               Dump after the computation of the initial value sets.

           -fdump-rtl-into_cfglayout
               Dump after converting to cfglayout mode.

           -fdump-rtl-ira
               Dump after iterated register allocation.

           -fdump-rtl-jump
               Dump after the second jump optimization.

           -fdump-rtl-loop2
               -fdump-rtl-loop2 enables dumping after the rtl loop
               optimization passes.

           -fdump-rtl-mach
               Dump after performing the machine dependent reorganization
               pass, if that pass exists.

           -fdump-rtl-mode_sw
               Dump after removing redundant mode switches.

           -fdump-rtl-rnreg
               Dump after register renumbering.

           -fdump-rtl-outof_cfglayout
               Dump after converting from cfglayout mode.

           -fdump-rtl-peephole2
               Dump after the peephole pass.

           -fdump-rtl-postreload
               Dump after post-reload optimizations.

           -fdump-rtl-pro_and_epilogue
               Dump after generating the function prologues and epilogues.

           -fdump-rtl-sched1
           -fdump-rtl-sched2
               -fdump-rtl-sched1 and -fdump-rtl-sched2 enable dumping after
               the basic block scheduling passes.

           -fdump-rtl-ree
               Dump after sign/zero extension elimination.

           -fdump-rtl-seqabstr
               Dump after common sequence discovery.

           -fdump-rtl-shorten
               Dump after shortening branches.

           -fdump-rtl-sibling
               Dump after sibling call optimizations.

           -fdump-rtl-split1
           -fdump-rtl-split2
           -fdump-rtl-split3
           -fdump-rtl-split4
           -fdump-rtl-split5
               These options enable dumping after five rounds of instruction
               splitting.

           -fdump-rtl-sms
               Dump after modulo scheduling.  This pass is only run on some
               architectures.

           -fdump-rtl-stack
               Dump after conversion from GCC's "flat register file"
               registers to the x87's stack-like registers.  This pass is
               only run on x86 variants.

           -fdump-rtl-subreg1
           -fdump-rtl-subreg2
               -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable dumping
               after the two subreg expansion passes.

           -fdump-rtl-unshare
               Dump after all rtl has been unshared.

           -fdump-rtl-vartrack
               Dump after variable tracking.

           -fdump-rtl-vregs
               Dump after converting virtual registers to hard registers.

           -fdump-rtl-web
               Dump after live range splitting.

           -fdump-rtl-regclass
           -fdump-rtl-subregs_of_mode_init
           -fdump-rtl-subregs_of_mode_finish
           -fdump-rtl-dfinit
           -fdump-rtl-dfinish
               These dumps are defined but always produce empty files.

           -da
           -fdump-rtl-all
               Produce all the dumps listed above.

           -dA Annotate the assembler output with miscellaneous debugging
               information.

           -dD Dump all macro definitions, at the end of preprocessing, in
               addition to normal output.

           -dH Produce a core dump whenever an error occurs.

           -dp Annotate the assembler output with a comment indicating which
               pattern and alternative is used.  The length of each
               instruction is also printed.

           -dP Dump the RTL in the assembler output as a comment before each
               instruction.  Also turns on -dp annotation.

           -dx Just generate RTL for a function instead of compiling it.
               Usually used with -fdump-rtl-expand.

       -fdump-noaddr
           When doing debugging dumps, suppress address output.  This makes
           it more feasible to use diff on debugging dumps for compiler
           invocations with different compiler binaries and/or different
           text / bss / data / heap / stack / dso start locations.

       -freport-bug
           Collect and dump debug information into a temporary file if an
           internal compiler error (ICE) occurs.

       -fdump-unnumbered
           When doing debugging dumps, suppress instruction numbers and
           address output.  This makes it more feasible to use diff on
           debugging dumps for compiler invocations with different options,
           in particular with and without -g.

       -fdump-unnumbered-links
           When doing debugging dumps (see -d option above), suppress
           instruction numbers for the links to the previous and next
           instructions in a sequence.

       -fdump-translation-unit (C++ only)
       -fdump-translation-unit-options (C++ only)
           Dump a representation of the tree structure for the entire
           translation unit to a file.  The file name is made by appending
           .tu to the source file name, and the file is created in the same
           directory as the output file.  If the -options form is used,
           options controls the details of the dump as described for the
           -fdump-tree options.

       -fdump-class-hierarchy (C++ only)
       -fdump-class-hierarchy-options (C++ only)
           Dump a representation of each class's hierarchy and virtual
           function table layout to a file.  The file name is made by
           appending .class to the source file name, and the file is created
           in the same directory as the output file.  If the -options form
           is used, options controls the details of the dump as described
           for the -fdump-tree options.

       -fdump-ipa-switch
           Control the dumping at various stages of inter-procedural
           analysis language tree to a file.  The file name is generated by
           appending a switch specific suffix to the source file name, and
           the file is created in the same directory as the output file.
           The following dumps are possible:

           all Enables all inter-procedural analysis dumps.

           cgraph
               Dumps information about call-graph optimization, unused
               function removal, and inlining decisions.

           inline
               Dump after function inlining.

       -fdump-passes
           Dump the list of optimization passes that are turned on and off
           by the current command-line options.

       -fdump-statistics-option
           Enable and control dumping of pass statistics in a separate file.
           The file name is generated by appending a suffix ending in
           .statistics to the source file name, and the file is created in
           the same directory as the output file.  If the -option form is
           used, -stats causes counters to be summed over the whole
           compilation unit while -details dumps every event as the passes
           generate them.  The default with no option is to sum counters for
           each function compiled.

       -fdump-tree-switch
       -fdump-tree-switch-options
       -fdump-tree-switch-options=filename
           Control the dumping at various stages of processing the
           intermediate language tree to a file.  The file name is generated
           by appending a switch-specific suffix to the source file name,
           and the file is created in the same directory as the output file.
           In case of =filename option, the dump is output on the given file
           instead of the auto named dump files.  If the -options form is
           used, options is a list of - separated options which control the
           details of the dump.  Not all options are applicable to all
           dumps; those that are not meaningful are ignored.  The following
           options are available

           address
               Print the address of each node.  Usually this is not
               meaningful as it changes according to the environment and
               source file.  Its primary use is for tying up a dump file
               with a debug environment.

           asmname
               If "DECL_ASSEMBLER_NAME" has been set for a given decl, use
               that in the dump instead of "DECL_NAME".  Its primary use is
               ease of use working backward from mangled names in the
               assembly file.

           slim
               When dumping front-end intermediate representations, inhibit
               dumping of members of a scope or body of a function merely
               because that scope has been reached.  Only dump such items
               when they are directly reachable by some other path.

               When dumping pretty-printed trees, this option inhibits
               dumping the bodies of control structures.

               When dumping RTL, print the RTL in slim (condensed) form
               instead of the default LISP-like representation.

           raw Print a raw representation of the tree.  By default, trees
               are pretty-printed into a C-like representation.

           details
               Enable more detailed dumps (not honored by every dump
               option). Also include information from the optimization
               passes.

           stats
               Enable dumping various statistics about the pass (not honored
               by every dump option).

           blocks
               Enable showing basic block boundaries (disabled in raw
               dumps).

           graph
               For each of the other indicated dump files (-fdump-rtl-pass),
               dump a representation of the control flow graph suitable for
               viewing with GraphViz to file.passid.pass.dot.  Each function
               in the file is pretty-printed as a subgraph, so that GraphViz
               can render them all in a single plot.

               This option currently only works for RTL dumps, and the RTL
               is always dumped in slim form.

           vops
               Enable showing virtual operands for every statement.

           lineno
               Enable showing line numbers for statements.

           uid Enable showing the unique ID ("DECL_UID") for each variable.

           verbose
               Enable showing the tree dump for each statement.

           eh  Enable showing the EH region number holding each statement.

           scev
               Enable showing scalar evolution analysis details.

           optimized
               Enable showing optimization information (only available in
               certain passes).

           missed
               Enable showing missed optimization information (only
               available in certain passes).

           note
               Enable other detailed optimization information (only
               available in certain passes).

           =filename
               Instead of an auto named dump file, output into the given
               file name. The file names stdout and stderr are treated
               specially and are considered already open standard streams.
               For example,

                       gcc -O2 -ftree-vectorize -fdump-tree-vect-blocks=foo.dump
                            -fdump-tree-pre=stderr file.c

               outputs vectorizer dump into foo.dump, while the PRE dump is
               output on to stderr. If two conflicting dump filenames are
               given for the same pass, then the latter option overrides the
               earlier one.

           split-paths
               Dump each function after splitting paths to loop backedges.
               The file name is made by appending .split-paths to the source
               file name.

           all Turn on all options, except raw, slim, verbose and lineno.

           optall
               Turn on all optimization options, i.e., optimized, missed,
               and note.

           The following tree dumps are possible:

           original
               Dump before any tree based optimization, to file.original.

           optimized
               Dump after all tree based optimization, to file.optimized.

           gimple
               Dump each function before and after the gimplification pass
               to a file.  The file name is made by appending .gimple to the
               source file name.

           cfg Dump the control flow graph of each function to a file.  The
               file name is made by appending .cfg to the source file name.

           ch  Dump each function after copying loop headers.  The file name
               is made by appending .ch to the source file name.

           ssa Dump SSA related information to a file.  The file name is
               made by appending .ssa to the source file name.

           alias
               Dump aliasing information for each function.  The file name
               is made by appending .alias to the source file name.

           ccp Dump each function after CCP.  The file name is made by
               appending .ccp to the source file name.

           storeccp
               Dump each function after STORE-CCP.  The file name is made by
               appending .storeccp to the source file name.

           pre Dump trees after partial redundancy elimination.  The file
               name is made by appending .pre to the source file name.

           fre Dump trees after full redundancy elimination.  The file name
               is made by appending .fre to the source file name.

           copyprop
               Dump trees after copy propagation.  The file name is made by
               appending .copyprop to the source file name.

           store_copyprop
               Dump trees after store copy-propagation.  The file name is
               made by appending .store_copyprop to the source file name.

           dce Dump each function after dead code elimination.  The file
               name is made by appending .dce to the source file name.

           sra Dump each function after performing scalar replacement of
               aggregates.  The file name is made by appending .sra to the
               source file name.

           sink
               Dump each function after performing code sinking.  The file
               name is made by appending .sink to the source file name.

           dom Dump each function after applying dominator tree
               optimizations.  The file name is made by appending .dom to
               the source file name.

           dse Dump each function after applying dead store elimination.
               The file name is made by appending .dse to the source file
               name.

           phiopt
               Dump each function after optimizing PHI nodes into
               straightline code.  The file name is made by appending
               .phiopt to the source file name.

           backprop
               Dump each function after back-propagating use information up
               the definition chain.  The file name is made by appending
               .backprop to the source file name.

           forwprop
               Dump each function after forward propagating single use
               variables.  The file name is made by appending .forwprop to
               the source file name.

           nrv Dump each function after applying the named return value
               optimization on generic trees.  The file name is made by
               appending .nrv to the source file name.

           vect
               Dump each function after applying vectorization of loops.
               The file name is made by appending .vect to the source file
               name.

           slp Dump each function after applying vectorization of basic
               blocks.  The file name is made by appending .slp to the
               source file name.

           vrp Dump each function after Value Range Propagation (VRP).  The
               file name is made by appending .vrp to the source file name.

           oaccdevlow
               Dump each function after applying device-specific OpenACC
               transformations.  The file name is made by appending
               .oaccdevlow to the source file name.

           all Enable all the available tree dumps with the flags provided
               in this option.

       -fopt-info
       -fopt-info-options
       -fopt-info-options=filename
           Controls optimization dumps from various optimization passes. If
           the -options form is used, options is a list of - separated
           option keywords to select the dump details and optimizations.

           The options can be divided into two groups: options describing
           the verbosity of the dump, and options describing which
           optimizations should be included. The options from both the
           groups can be freely mixed as they are non-overlapping. However,
           in case of any conflicts, the later options override the earlier
           options on the command line.

           The following options control the dump verbosity:

           optimized
               Print information when an optimization is successfully
               applied. It is up to a pass to decide which information is
               relevant. For example, the vectorizer passes print the source
               location of loops which are successfully vectorized.

           missed
               Print information about missed optimizations. Individual
               passes control which information to include in the output.

           note
               Print verbose information about optimizations, such as
               certain transformations, more detailed messages about
               decisions etc.

           all Print detailed optimization information. This includes
               optimized, missed, and note.

           One or more of the following option keywords can be used to
           describe a group of optimizations:

           ipa Enable dumps from all interprocedural optimizations.

           loop
               Enable dumps from all loop optimizations.

           inline
               Enable dumps from all inlining optimizations.

           vec Enable dumps from all vectorization optimizations.

           optall
               Enable dumps from all optimizations. This is a superset of
               the optimization groups listed above.

           If options is omitted, it defaults to optimized-optall, which
           means to dump all info about successful optimizations from all
           the passes.

           If the filename is provided, then the dumps from all the
           applicable optimizations are concatenated into the filename.
           Otherwise the dump is output onto stderr. Though multiple
           -fopt-info options are accepted, only one of them can include a
           filename. If other filenames are provided then all but the first
           such option are ignored.

           Note that the output filename is overwritten in case of multiple
           translation units. If a combined output from multiple translation
           units is desired, stderr should be used instead.

           In the following example, the optimization info is output to
           stderr:

                   gcc -O3 -fopt-info

           This example:

                   gcc -O3 -fopt-info-missed=missed.all

           outputs missed optimization report from all the passes into
           missed.all, and this one:

                   gcc -O2 -ftree-vectorize -fopt-info-vec-missed

           prints information about missed optimization opportunities from
           vectorization passes on stderr.  Note that -fopt-info-vec-missed
           is equivalent to -fopt-info-missed-vec.

           As another example,

                   gcc -O3 -fopt-info-inline-optimized-missed=inline.txt

           outputs information about missed optimizations as well as
           optimized locations from all the inlining passes into inline.txt.

           Finally, consider:

                   gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt

           Here the two output filenames vec.miss and loop.opt are in
           conflict since only one output file is allowed. In this case,
           only the first option takes effect and the subsequent options are
           ignored. Thus only vec.miss is produced which contains dumps from
           the vectorizer about missed opportunities.

       -fsched-verbose=n
           On targets that use instruction scheduling, this option controls
           the amount of debugging output the scheduler prints to the dump
           files.

           For n greater than zero, -fsched-verbose outputs the same
           information as -fdump-rtl-sched1 and -fdump-rtl-sched2.  For n
           greater than one, it also output basic block probabilities,
           detailed ready list information and unit/insn info.  For n
           greater than two, it includes RTL at abort point, control-flow
           and regions info.  And for n over four, -fsched-verbose also
           includes dependence info.

       -fenable-kind-pass
       -fdisable-kind-pass=range-list
           This is a set of options that are used to explicitly
           disable/enable optimization passes.  These options are intended
           for use for debugging GCC.  Compiler users should use regular
           options for enabling/disabling passes instead.

           -fdisable-ipa-pass
               Disable IPA pass pass. pass is the pass name.  If the same
               pass is statically invoked in the compiler multiple times,
               the pass name should be appended with a sequential number
               starting from 1.

           -fdisable-rtl-pass
           -fdisable-rtl-pass=range-list
               Disable RTL pass pass.  pass is the pass name.  If the same
               pass is statically invoked in the compiler multiple times,
               the pass name should be appended with a sequential number
               starting from 1.  range-list is a comma-separated list of
               function ranges or assembler names.  Each range is a number
               pair separated by a colon.  The range is inclusive in both
               ends.  If the range is trivial, the number pair can be
               simplified as a single number.  If the function's call graph
               node's uid falls within one of the specified ranges, the pass
               is disabled for that function.  The uid is shown in the
               function header of a dump file, and the pass names can be
               dumped by using option -fdump-passes.

           -fdisable-tree-pass
           -fdisable-tree-pass=range-list
               Disable tree pass pass.  See -fdisable-rtl for the
               description of option arguments.

           -fenable-ipa-pass
               Enable IPA pass pass.  pass is the pass name.  If the same
               pass is statically invoked in the compiler multiple times,
               the pass name should be appended with a sequential number
               starting from 1.

           -fenable-rtl-pass
           -fenable-rtl-pass=range-list
               Enable RTL pass pass.  See -fdisable-rtl for option argument
               description and examples.

           -fenable-tree-pass
           -fenable-tree-pass=range-list
               Enable tree pass pass.  See -fdisable-rtl for the description
               of option arguments.

           Here are some examples showing uses of these options.

                   # disable ccp1 for all functions
                      -fdisable-tree-ccp1
                   # disable complete unroll for function whose cgraph node uid is 1
                      -fenable-tree-cunroll=1
                   # disable gcse2 for functions at the following ranges [1,1],
                   # [300,400], and [400,1000]
                   # disable gcse2 for functions foo and foo2
                      -fdisable-rtl-gcse2=foo,foo2
                   # disable early inlining
                      -fdisable-tree-einline
                   # disable ipa inlining
                      -fdisable-ipa-inline
                   # enable tree full unroll
                      -fenable-tree-unroll

       -fchecking
           Enable internal consistency checking.  The default depends on the
           compiler configuration.

       -frandom-seed=string
           This option provides a seed that GCC uses in place of random
           numbers in generating certain symbol names that have to be
           different in every compiled file.  It is also used to place
           unique stamps in coverage data files and the object files that
           produce them.  You can use the -frandom-seed option to produce
           reproducibly identical object files.

           The string can either be a number (decimal, octal or hex) or an
           arbitrary string (in which case it's converted to a number by
           computing CRC32).

           The string should be different for every file you compile.

       -save-temps
       -save-temps=cwd
           Store the usual "temporary" intermediate files permanently; place
           them in the current directory and name them based on the source
           file.  Thus, compiling foo.c with -c -save-temps produces files
           foo.i and foo.s, as well as foo.o.  This creates a preprocessed
           foo.i output file even though the compiler now normally uses an
           integrated preprocessor.

           When used in combination with the -x command-line option,
           -save-temps is sensible enough to avoid over writing an input
           source file with the same extension as an intermediate file.  The
           corresponding intermediate file may be obtained by renaming the
           source file before using -save-temps.

           If you invoke GCC in parallel, compiling several different source
           files that share a common base name in different subdirectories
           or the same source file compiled for multiple output
           destinations, it is likely that the different parallel compilers
           will interfere with each other, and overwrite the temporary
           files.  For instance:

                   gcc -save-temps -o outdir1/foo.o indir1/foo.c&
                   gcc -save-temps -o outdir2/foo.o indir2/foo.c&

           may result in foo.i and foo.o being written to simultaneously by
           both compilers.

       -save-temps=obj
           Store the usual "temporary" intermediate files permanently.  If
           the -o option is used, the temporary files are based on the
           object file.  If the -o option is not used, the -save-temps=obj
           switch behaves like -save-temps.

           For example:

                   gcc -save-temps=obj -c foo.c
                   gcc -save-temps=obj -c bar.c -o dir/xbar.o
                   gcc -save-temps=obj foobar.c -o dir2/yfoobar

           creates foo.i, foo.s, dir/xbar.i, dir/xbar.s, dir2/yfoobar.i,
           dir2/yfoobar.s, and dir2/yfoobar.o.

       -time[=file]
           Report the CPU time taken by each subprocess in the compilation
           sequence.  For C source files, this is the compiler proper and
           assembler (plus the linker if linking is done).

           Without the specification of an output file, the output looks
           like this:

                   # cc1 0.12 0.01
                   # as 0.00 0.01

           The first number on each line is the "user time", that is time
           spent executing the program itself.  The second number is "system
           time", time spent executing operating system routines on behalf
           of the program.  Both numbers are in seconds.

           With the specification of an output file, the output is appended
           to the named file, and it looks like this:

                   0.12 0.01 cc1 <options>
                   0.00 0.01 as <options>

           The "user time" and the "system time" are moved before the
           program name, and the options passed to the program are
           displayed, so that one can later tell what file was being
           compiled, and with which options.

       -fdump-final-insns[=file]
           Dump the final internal representation (RTL) to file.  If the
           optional argument is omitted (or if file is "."), the name of the
           dump file is determined by appending ".gkd" to the compilation
           output file name.

       -fcompare-debug[=opts]
           If no error occurs during compilation, run the compiler a second
           time, adding opts and -fcompare-debug-second to the arguments
           passed to the second compilation.  Dump the final internal
           representation in both compilations, and print an error if they
           differ.

           If the equal sign is omitted, the default -gtoggle is used.

           The environment variable GCC_COMPARE_DEBUG, if defined, non-empty
           and nonzero, implicitly enables -fcompare-debug.  If
           GCC_COMPARE_DEBUG is defined to a string starting with a dash,
           then it is used for opts, otherwise the default -gtoggle is used.

           -fcompare-debug=, with the equal sign but without opts, is
           equivalent to -fno-compare-debug, which disables the dumping of
           the final representation and the second compilation, preventing
           even GCC_COMPARE_DEBUG from taking effect.

           To verify full coverage during -fcompare-debug testing, set
           GCC_COMPARE_DEBUG to say -fcompare-debug-not-overridden, which
           GCC rejects as an invalid option in any actual compilation
           (rather than preprocessing, assembly or linking).  To get just a
           warning, setting GCC_COMPARE_DEBUG to -w%n-fcompare-debug not
           overridden will do.

       -fcompare-debug-second
           This option is implicitly passed to the compiler for the second
           compilation requested by -fcompare-debug, along with options to
           silence warnings, and omitting other options that would cause
           side-effect compiler outputs to files or to the standard output.
           Dump files and preserved temporary files are renamed so as to
           contain the ".gk" additional extension during the second
           compilation, to avoid overwriting those generated by the first.

           When this option is passed to the compiler driver, it causes the
           first compilation to be skipped, which makes it useful for little
           other than debugging the compiler proper.

       -gtoggle
           Turn off generation of debug info, if leaving out this option
           generates it, or turn it on at level 2 otherwise.  The position
           of this argument in the command line does not matter; it takes
           effect after all other options are processed, and it does so only
           once, no matter how many times it is given.  This is mainly
           intended to be used with -fcompare-debug.

       -fvar-tracking-assignments-toggle
           Toggle -fvar-tracking-assignments, in the same way that -gtoggle
           toggles -g.

       -Q  Makes the compiler print out each function name as it is
           compiled, and print some statistics about each pass when it
           finishes.

       -ftime-report
           Makes the compiler print some statistics about the time consumed
           by each pass when it finishes.

       -fira-verbose=n
           Control the verbosity of the dump file for the integrated
           register allocator.  The default value is 5.  If the value n is
           greater or equal to 10, the dump output is sent to stderr using
           the same format as n minus 10.

       -flto-report
           Prints a report with internal details on the workings of the
           link-time optimizer.  The contents of this report vary from
           version to version.  It is meant to be useful to GCC developers
           when processing object files in LTO mode (via -flto).

           Disabled by default.

       -flto-report-wpa
           Like -flto-report, but only print for the WPA phase of Link Time
           Optimization.

       -fmem-report
           Makes the compiler print some statistics about permanent memory
           allocation when it finishes.

       -fmem-report-wpa
           Makes the compiler print some statistics about permanent memory
           allocation for the WPA phase only.

       -fpre-ipa-mem-report
       -fpost-ipa-mem-report
           Makes the compiler print some statistics about permanent memory
           allocation before or after interprocedural optimization.

       -fprofile-report
           Makes the compiler print some statistics about consistency of the
           (estimated) profile and effect of individual passes.

       -fstack-usage
           Makes the compiler output stack usage information for the
           program, on a per-function basis.  The filename for the dump is
           made by appending .su to the auxname.  auxname is generated from
           the name of the output file, if explicitly specified and it is
           not an executable, otherwise it is the basename of the source
           file.  An entry is made up of three fields:

           *   The name of the function.

           *   A number of bytes.

           *   One or more qualifiers: "static", "dynamic", "bounded".

           The qualifier "static" means that the function manipulates the
           stack statically: a fixed number of bytes are allocated for the
           frame on function entry and released on function exit; no stack
           adjustments are otherwise made in the function.  The second field
           is this fixed number of bytes.

           The qualifier "dynamic" means that the function manipulates the
           stack dynamically: in addition to the static allocation described
           above, stack adjustments are made in the body of the function,
           for example to push/pop arguments around function calls.  If the
           qualifier "bounded" is also present, the amount of these
           adjustments is bounded at compile time and the second field is an
           upper bound of the total amount of stack used by the function.
           If it is not present, the amount of these adjustments is not
           bounded at compile time and the second field only represents the
           bounded part.

       -fstats
           Emit statistics about front-end processing at the end of the
           compilation.  This option is supported only by the C++ front end,
           and the information is generally only useful to the G++
           development team.

       -fdbg-cnt-list
           Print the name and the counter upper bound for all debug
           counters.

       -fdbg-cnt=counter-value-list
           Set the internal debug counter upper bound.  counter-value-list
           is a comma-separated list of name:value pairs which sets the
           upper bound of each debug counter name to value.  All debug
           counters have the initial upper bound of "UINT_MAX"; thus
           "dbg_cnt" returns true always unless the upper bound is set by
           this option.  For example, with -fdbg-cnt=dce:10,tail_call:0,
           "dbg_cnt(dce)" returns true only for first 10 invocations.

       -print-file-name=library
           Print the full absolute name of the library file library that
           would be used when linking---and don't do anything else.  With
           this option, GCC does not compile or link anything; it just
           prints the file name.

       -print-multi-directory
           Print the directory name corresponding to the multilib selected
           by any other switches present in the command line.  This
           directory is supposed to exist in GCC_EXEC_PREFIX.

       -print-multi-lib
           Print the mapping from multilib directory names to compiler
           switches that enable them.  The directory name is separated from
           the switches by ;, and each switch starts with an @ instead of
           the -, without spaces between multiple switches.  This is
           supposed to ease shell processing.

       -print-multi-os-directory
           Print the path to OS libraries for the selected multilib,
           relative to some lib subdirectory.  If OS libraries are present
           in the lib subdirectory and no multilibs are used, this is
           usually just ., if OS libraries are present in libsuffix sibling
           directories this prints e.g. ../lib64, ../lib or ../lib32, or if
           OS libraries are present in lib/subdir subdirectories it prints
           e.g. amd64, sparcv9 or ev6.

       -print-multiarch
           Print the path to OS libraries for the selected multiarch,
           relative to some lib subdirectory.

       -print-prog-name=program
           Like -print-file-name, but searches for a program such as cpp.

       -print-libgcc-file-name
           Same as -print-file-name=libgcc.a.

           This is useful when you use -nostdlib or -nodefaultlibs but you
           do want to link with libgcc.a.  You can do:

                   gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

       -print-search-dirs
           Print the name of the configured installation directory and a
           list of program and library directories gcc searches---and don't
           do anything else.

           This is useful when gcc prints the error message installation
           problem, cannot exec cpp0: No such file or directory.  To resolve
           this you either need to put cpp0 and the other compiler
           components where gcc expects to find them, or you can set the
           environment variable GCC_EXEC_PREFIX to the directory where you
           installed them.  Don't forget the trailing /.

       -print-sysroot
           Print the target sysroot directory that is used during
           compilation.  This is the target sysroot specified either at
           configure time or using the --sysroot option, possibly with an
           extra suffix that depends on compilation options.  If no target
           sysroot is specified, the option prints nothing.

       -print-sysroot-headers-suffix
           Print the suffix added to the target sysroot when searching for
           headers, or give an error if the compiler is not configured with
           such a suffix---and don't do anything else.

       -dumpmachine
           Print the compiler's target machine (for example,
           i686-pc-linux-gnu)---and don't do anything else.

       -dumpversion
           Print the compiler version (for example, 3.0)---and don't do
           anything else.

       -dumpspecs
           Print the compiler's built-in specs---and don't do anything else.
           (This is used when GCC itself is being built.)

       Machine-Dependent Options

       Each target machine supported by GCC can have its own options---for
       example, to allow you to compile for a particular processor variant
       or ABI, or to control optimizations specific to that machine.  By
       convention, the names of machine-specific options start with -m.

       Some configurations of the compiler also support additional target-
       specific options, usually for compatibility with other compilers on
       the same platform.

       AArch64 Options

       These options are defined for AArch64 implementations:

       -mabi=name
           Generate code for the specified data model.  Permissible values
           are ilp32 for SysV-like data model where int, long int and
           pointer are 32-bit, and lp64 for SysV-like data model where int
           is 32-bit, but long int and pointer are 64-bit.

           The default depends on the specific target configuration.  Note
           that the LP64 and ILP32 ABIs are not link-compatible; you must
           compile your entire program with the same ABI, and link with a
           compatible set of libraries.

       -mbig-endian
           Generate big-endian code.  This is the default when GCC is
           configured for an aarch64_be-*-* target.

       -mgeneral-regs-only
           Generate code which uses only the general-purpose registers.
           This will prevent the compiler from using floating-point and
           Advanced SIMD registers but will not impose any restrictions on
           the assembler.

       -mlittle-endian
           Generate little-endian code.  This is the default when GCC is
           configured for an aarch64-*-* but not an aarch64_be-*-* target.

       -mcmodel=tiny
           Generate code for the tiny code model.  The program and its
           statically defined symbols must be within 1GB of each other.
           Pointers are 64 bits.  Programs can be statically or dynamically
           linked.  This model is not fully implemented and mostly treated
           as small.

       -mcmodel=small
           Generate code for the small code model.  The program and its
           statically defined symbols must be within 4GB of each other.
           Pointers are 64 bits.  Programs can be statically or dynamically
           linked.  This is the default code model.

       -mcmodel=large
           Generate code for the large code model.  This makes no
           assumptions about addresses and sizes of sections.  Pointers are
           64 bits.  Programs can be statically linked only.

       -mstrict-align
           Do not assume that unaligned memory references are handled by the
           system.

       -momit-leaf-frame-pointer
       -mno-omit-leaf-frame-pointer
           Omit or keep the frame pointer in leaf functions.  The former
           behavior is the default.

       -mtls-dialect=desc
           Use TLS descriptors as the thread-local storage mechanism for
           dynamic accesses of TLS variables.  This is the default.

       -mtls-dialect=traditional
           Use traditional TLS as the thread-local storage mechanism for
           dynamic accesses of TLS variables.

       -mtls-size=size
           Specify bit size of immediate TLS offsets.  Valid values are 12,
           24, 32, 48.  This option depends on binutils higher than 2.25.

       -mfix-cortex-a53-835769
       -mno-fix-cortex-a53-835769
           Enable or disable the workaround for the ARM Cortex-A53 erratum
           number 835769.  This involves inserting a NOP instruction between
           memory instructions and 64-bit integer multiply-accumulate
           instructions.

       -mfix-cortex-a53-843419
       -mno-fix-cortex-a53-843419
           Enable or disable the workaround for the ARM Cortex-A53 erratum
           number 843419.  This erratum workaround is made at link time and
           this will only pass the corresponding flag to the linker.

       -mlow-precision-recip-sqrt
       -mno-low-precision-recip-sqrt
           When calculating the reciprocal square root approximation, uses
           one less step than otherwise, thus reducing latency and
           precision.  This is only relevant if -ffast-math enables the
           reciprocal square root approximation, which in turn depends on
           the target processor.

       -march=name
           Specify the name of the target architecture and, optionally, one
           or more feature modifiers.  This option has the form
           -march=arch{+[no]feature}*.

           The permissible values for arch are armv8-a, armv8.1-a or native.

           The value armv8.1-a implies armv8-a and enables compiler support
           for the ARMv8.1 architecture extension.  In particular, it
           enables the +crc and +lse features.

           The value native is available on native AArch64 GNU/Linux and
           causes the compiler to pick the architecture of the host system.
           This option has no effect if the compiler is unable to recognize
           the architecture of the host system,

           The permissible values for feature are listed in the sub-section
           on aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers.
           Where conflicting feature modifiers are specified, the right-most
           feature is used.

           GCC uses name to determine what kind of instructions it can emit
           when generating assembly code.  If -march is specified without
           either of -mtune or -mcpu also being specified, the code is tuned
           to perform well across a range of target processors implementing
           the target architecture.

       -mtune=name
           Specify the name of the target processor for which GCC should
           tune the performance of the code.  Permissible values for this
           option are: generic, cortex-a35, cortex-a53, cortex-a57,
           cortex-a72, exynos-m1, qdf24xx, thunderx, xgene1.

           Additionally, this option can specify that GCC should tune the
           performance of the code for a big.LITTLE system.  Permissible
           values for this option are: cortex-a57.cortex-a53,
           cortex-a72.cortex-a53.

           Additionally on native AArch64 GNU/Linux systems the value native
           is available.  This option causes the compiler to pick the
           architecture of and tune the performance of the code for the
           processor of the host system.  This option has no effect if the
           compiler is unable to recognize the architecture of the host
           system.

           Where none of -mtune=, -mcpu= or -march= are specified, the code
           is tuned to perform well across a range of target processors.

           This option cannot be suffixed by feature modifiers.

       -mcpu=name
           Specify the name of the target processor, optionally suffixed by
           one or more feature modifiers.  This option has the form
           -mcpu=cpu{+[no]feature}*, where the permissible values for cpu
           are the same as those available for -mtune.  The permissible
           values for feature are documented in the sub-section on
           aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers.
           Where conflicting feature modifiers are specified, the right-most
           feature is used.

           Additionally on native AArch64 GNU/Linux systems the value native
           is available.  This option causes the compiler to tune the
           performance of the code for the processor of the host system.
           This option has no effect if the compiler is unable to recognize
           the architecture of the host system.

           GCC uses name to determine what kind of instructions it can emit
           when generating assembly code (as if by -march) and to determine
           the target processor for which to tune for performance (as if by
           -mtune).  Where this option is used in conjunction with -march or
           -mtune, those options take precedence over the appropriate part
           of this option.

       -moverride=string
           Override tuning decisions made by the back-end in response to a
           -mtune= switch.  The syntax, semantics, and accepted values for
           string in this option are not guaranteed to be consistent across
           releases.

           This option is only intended to be useful when developing GCC.

       -mpc-relative-literal-loads
           Enable PC relative literal loads. If this option is used, literal
           pools are assumed to have a range of up to 1MiB and an
           appropriate instruction sequence is used. This option has no
           impact when used with -mcmodel=tiny.

       -march and -mcpu Feature Modifiers

       Feature modifiers used with -march and -mcpu can be any of the
       following and their inverses nofeature:

       crc Enable CRC extension.  This is on by default for
           -march=armv8.1-a.

       crypto
           Enable Crypto extension.  This also enables Advanced SIMD and
           floating-point instructions.

       fp  Enable floating-point instructions.  This is on by default for
           all possible values for options -march and -mcpu.

       simd
           Enable Advanced SIMD instructions.  This also enables floating-
           point instructions.  This is on by default for all possible
           values for options -march and -mcpu.

       lse Enable Large System Extension instructions.  This is on by
           default for -march=armv8.1-a.

       That is, crypto implies simd implies fp.  Conversely, nofp (or
       equivalently, -mgeneral-regs-only) implies nosimd implies nocrypto.

       Adapteva Epiphany Options

       These -m options are defined for Adapteva Epiphany:

       -mhalf-reg-file
           Don't allocate any register in the range "r32"..."r63".  That
           allows code to run on hardware variants that lack these
           registers.

       -mprefer-short-insn-regs
           Preferentially allocate registers that allow short instruction
           generation.  This can result in increased instruction count, so
           this may either reduce or increase overall code size.

       -mbranch-cost=num
           Set the cost of branches to roughly num "simple" instructions.
           This cost is only a heuristic and is not guaranteed to produce
           consistent results across releases.

       -mcmove
           Enable the generation of conditional moves.

       -mnops=num
           Emit num NOPs before every other generated instruction.

       -mno-soft-cmpsf
           For single-precision floating-point comparisons, emit an "fsub"
           instruction and test the flags.  This is faster than a software
           comparison, but can get incorrect results in the presence of
           NaNs, or when two different small numbers are compared such that
           their difference is calculated as zero.  The default is
           -msoft-cmpsf, which uses slower, but IEEE-compliant, software
           comparisons.

       -mstack-offset=num
           Set the offset between the top of the stack and the stack
           pointer.  E.g., a value of 8 means that the eight bytes in the
           range "sp+0...sp+7" can be used by leaf functions without stack
           allocation.  Values other than 8 or 16 are untested and unlikely
           to work.  Note also that this option changes the ABI; compiling a
           program with a different stack offset than the libraries have
           been compiled with generally does not work.  This option can be
           useful if you want to evaluate if a different stack offset would
           give you better code, but to actually use a different stack
           offset to build working programs, it is recommended to configure
           the toolchain with the appropriate --with-stack-offset=num
           option.

       -mno-round-nearest
           Make the scheduler assume that the rounding mode has been set to
           truncating.  The default is -mround-nearest.

       -mlong-calls
           If not otherwise specified by an attribute, assume all calls
           might be beyond the offset range of the "b" / "bl" instructions,
           and therefore load the function address into a register before
           performing a (otherwise direct) call.  This is the default.

       -mshort-calls
           If not otherwise specified by an attribute, assume all direct
           calls are in the range of the "b" / "bl" instructions, so use
           these instructions for direct calls.  The default is
           -mlong-calls.

       -msmall16
           Assume addresses can be loaded as 16-bit unsigned values.  This
           does not apply to function addresses for which -mlong-calls
           semantics are in effect.

       -mfp-mode=mode
           Set the prevailing mode of the floating-point unit.  This
           determines the floating-point mode that is provided and expected
           at function call and return time.  Making this mode match the
           mode you predominantly need at function start can make your
           programs smaller and faster by avoiding unnecessary mode
           switches.

           mode can be set to one the following values:

           caller
               Any mode at function entry is valid, and retained or restored
               when the function returns, and when it calls other functions.
               This mode is useful for compiling libraries or other
               compilation units you might want to incorporate into
               different programs with different prevailing FPU modes, and
               the convenience of being able to use a single object file
               outweighs the size and speed overhead for any extra mode
               switching that might be needed, compared with what would be
               needed with a more specific choice of prevailing FPU mode.

           truncate
               This is the mode used for floating-point calculations with
               truncating (i.e. round towards zero) rounding mode.  That
               includes conversion from floating point to integer.

           round-nearest
               This is the mode used for floating-point calculations with
               round-to-nearest-or-even rounding mode.

           int This is the mode used to perform integer calculations in the
               FPU, e.g.  integer multiply, or integer multiply-and-
               accumulate.

           The default is -mfp-mode=caller

       -mnosplit-lohi
       -mno-postinc
       -mno-postmodify
           Code generation tweaks that disable, respectively, splitting of
           32-bit loads, generation of post-increment addresses, and
           generation of post-modify addresses.  The defaults are msplit-
           lohi, -mpost-inc, and -mpost-modify.

       -mnovect-double
           Change the preferred SIMD mode to SImode.  The default is
           -mvect-double, which uses DImode as preferred SIMD mode.

       -max-vect-align=num
           The maximum alignment for SIMD vector mode types.  num may be 4
           or 8.  The default is 8.  Note that this is an ABI change, even
           though many library function interfaces are unaffected if they
           don't use SIMD vector modes in places that affect size and/or
           alignment of relevant types.

       -msplit-vecmove-early
           Split vector moves into single word moves before reload.  In
           theory this can give better register allocation, but so far the
           reverse seems to be generally the case.

       -m1reg-reg
           Specify a register to hold the constant -1, which makes loading
           small negative constants and certain bitmasks faster.  Allowable
           values for reg are r43 and r63, which specify use of that
           register as a fixed register, and none, which means that no
           register is used for this purpose.  The default is -m1reg-none.

       ARC Options

       The following options control the architecture variant for which code
       is being compiled:

       -mbarrel-shifter
           Generate instructions supported by barrel shifter.  This is the
           default unless -mcpu=ARC601 or -mcpu=ARCEM is in effect.

       -mcpu=cpu
           Set architecture type, register usage, and instruction scheduling
           parameters for cpu.  There are also shortcut alias options
           available for backward compatibility and convenience.  Supported
           values for cpu are

           ARC600
           arc600
               Compile for ARC600.  Aliases: -mA6, -mARC600.

           ARC601
           arc601
               Compile for ARC601.  Alias: -mARC601.

           ARC700
           arc700
               Compile for ARC700.  Aliases: -mA7, -mARC700.  This is the
               default when configured with --with-cpu=arc700.

           ARCEM
           arcem
               Compile for ARC EM.

           ARCHS
           archs
               Compile for ARC HS.

       -mdpfp
       -mdpfp-compact
           FPX: Generate Double Precision FPX instructions, tuned for the
           compact implementation.

       -mdpfp-fast
           FPX: Generate Double Precision FPX instructions, tuned for the
           fast implementation.

       -mno-dpfp-lrsr
           Disable LR and SR instructions from using FPX extension aux
           registers.

       -mea
           Generate Extended arithmetic instructions.  Currently only
           "divaw", "adds", "subs", and "sat16" are supported.  This is
           always enabled for -mcpu=ARC700.

       -mno-mpy
           Do not generate mpy instructions for ARC700.

       -mmul32x16
           Generate 32x16 bit multiply and mac instructions.

       -mmul64
           Generate mul64 and mulu64 instructions.  Only valid for
           -mcpu=ARC600.

       -mnorm
           Generate norm instruction.  This is the default if -mcpu=ARC700
           is in effect.

       -mspfp
       -mspfp-compact
           FPX: Generate Single Precision FPX instructions, tuned for the
           compact implementation.

       -mspfp-fast
           FPX: Generate Single Precision FPX instructions, tuned for the
           fast implementation.

       -msimd
           Enable generation of ARC SIMD instructions via target-specific
           builtins.  Only valid for -mcpu=ARC700.

       -msoft-float
           This option ignored; it is provided for compatibility purposes
           only.  Software floating point code is emitted by default, and
           this default can overridden by FPX options; mspfp, mspfp-compact,
           or mspfp-fast for single precision, and mdpfp, mdpfp-compact, or
           mdpfp-fast for double precision.

       -mswap
           Generate swap instructions.

       -matomic
           This enables Locked Load/Store Conditional extension to implement
           atomic memopry built-in functions.  Not available for ARC 6xx or
           ARC EM cores.

       -mdiv-rem
           Enable DIV/REM instructions for ARCv2 cores.

       -mcode-density
           Enable code density instructions for ARC EM, default on for ARC
           HS.

       -mll64
           Enable double load/store operations for ARC HS cores.

       -mmpy-option=multo
           Compile ARCv2 code with a multiplier design option.  wlh1 is the
           default value.  The recognized values for multo are:

           0   No multiplier available.

           1   The multiply option is set to w: 16x16 multiplier, fully
               pipelined.  The following instructions are enabled: MPYW, and
               MPYUW.

           2   The multiply option is set to wlh1: 32x32 multiplier, fully
               pipelined (1 stage).  The following instructions are
               additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

           3   The multiply option is set to wlh2: 32x32 multiplier, fully
               pipelined (2 stages).  The following instructions are
               additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

           4   The multiply option is set to wlh3: Two 16x16 multiplier,
               blocking, sequential.  The following instructions are
               additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

           5   The multiply option is set to wlh4: One 16x16 multiplier,
               blocking, sequential.  The following instructions are
               additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

           6   The multiply option is set to wlh5: One 32x4 multiplier,
               blocking, sequential.  The following instructions are
               additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

           This option is only available for ARCv2 cores.

       -mfpu=fpu
           Enables specific floating-point hardware extension for ARCv2
           core.  Supported values for fpu are:

           fpus
               Enables support for single precision floating point hardware
               extensions.

           fpud
               Enables support for double precision floating point hardware
               extensions.  The single precision floating point extension is
               also enabled.  Not available for ARC EM.

           fpuda
               Enables support for double precision floating point hardware
               extensions using double precision assist instructions.  The
               single precision floating point extension is also enabled.
               This option is only available for ARC EM.

           fpuda_div
               Enables support for double precision floating point hardware
               extensions using double precision assist instructions, and
               simple precision square-root and divide hardware extensions.
               The single precision floating point extension is also
               enabled.  This option is only available for ARC EM.

           fpuda_fma
               Enables support for double precision floating point hardware
               extensions using double precision assist instructions, and
               simple precision fused multiple and add hardware extension.
               The single precision floating point extension is also
               enabled.  This option is only available for ARC EM.

           fpuda_all
               Enables support for double precision floating point hardware
               extensions using double precision assist instructions, and
               all simple precision hardware extensions.  The single
               precision floating point extension is also enabled.  This
               option is only available for ARC EM.

           fpus_div
               Enables support for single precision floating point, and
               single precision square-root and divide hardware extensions.

           fpud_div
               Enables support for double precision floating point, and
               double precision square-root and divide hardware extensions.
               This option includes option fpus_div. Not available for ARC
               EM.

           fpus_fma
               Enables support for single precision floating point, and
               single precision fused multiple and add hardware extensions.

           fpud_fma
               Enables support for double precision floating point, and
               double precision fused multiple and add hardware extensions.
               This option includes option fpus_fma.  Not available for ARC
               EM.

           fpus_all
               Enables support for all single precision floating point
               hardware extensions.

           fpud_all
               Enables support for all single and double precision floating
               point hardware extensions.  Not available for ARC EM.

       The following options are passed through to the assembler, and also
       define preprocessor macro symbols.

       -mdsp-packa
           Passed down to the assembler to enable the DSP Pack A extensions.
           Also sets the preprocessor symbol "__Xdsp_packa".

       -mdvbf
           Passed down to the assembler to enable the dual viterbi butterfly
           extension.  Also sets the preprocessor symbol "__Xdvbf".

       -mlock
           Passed down to the assembler to enable the Locked Load/Store
           Conditional extension.  Also sets the preprocessor symbol
           "__Xlock".

       -mmac-d16
           Passed down to the assembler.  Also sets the preprocessor symbol
           "__Xxmac_d16".

       -mmac-24
           Passed down to the assembler.  Also sets the preprocessor symbol
           "__Xxmac_24".

       -mrtsc
           Passed down to the assembler to enable the 64-bit Time-Stamp
           Counter extension instruction.  Also sets the preprocessor symbol
           "__Xrtsc".

       -mswape
           Passed down to the assembler to enable the swap byte ordering
           extension instruction.  Also sets the preprocessor symbol
           "__Xswape".

       -mtelephony
           Passed down to the assembler to enable dual and single operand
           instructions for telephony.  Also sets the preprocessor symbol
           "__Xtelephony".

       -mxy
           Passed down to the assembler to enable the XY Memory extension.
           Also sets the preprocessor symbol "__Xxy".

       The following options control how the assembly code is annotated:

       -misize
           Annotate assembler instructions with estimated addresses.

       -mannotate-align
           Explain what alignment considerations lead to the decision to
           make an instruction short or long.

       The following options are passed through to the linker:

       -marclinux
           Passed through to the linker, to specify use of the "arclinux"
           emulation.  This option is enabled by default in tool chains
           built for "arc-linux-uclibc" and "arceb-linux-uclibc" targets
           when profiling is not requested.

       -marclinux_prof
           Passed through to the linker, to specify use of the
           "arclinux_prof" emulation.  This option is enabled by default in
           tool chains built for "arc-linux-uclibc" and "arceb-linux-uclibc"
           targets when profiling is requested.

       The following options control the semantics of generated code:

       -mlong-calls
           Generate call insns as register indirect calls, thus providing
           access to the full 32-bit address range.

       -mmedium-calls
           Don't use less than 25 bit addressing range for calls, which is
           the offset available for an unconditional branch-and-link
           instruction.  Conditional execution of function calls is
           suppressed, to allow use of the 25-bit range, rather than the
           21-bit range with conditional branch-and-link.  This is the
           default for tool chains built for "arc-linux-uclibc" and
           "arceb-linux-uclibc" targets.

       -mno-sdata
           Do not generate sdata references.  This is the default for tool
           chains built for "arc-linux-uclibc" and "arceb-linux-uclibc"
           targets.

       -mucb-mcount
           Instrument with mcount calls as used in UCB code.  I.e. do the
           counting in the callee, not the caller.  By default ARC
           instrumentation counts in the caller.

       -mvolatile-cache
           Use ordinarily cached memory accesses for volatile references.
           This is the default.

       -mno-volatile-cache
           Enable cache bypass for volatile references.

       The following options fine tune code generation:

       -malign-call
           Do alignment optimizations for call instructions.

       -mauto-modify-reg
           Enable the use of pre/post modify with register displacement.

       -mbbit-peephole
           Enable bbit peephole2.

       -mno-brcc
           This option disables a target-specific pass in arc_reorg to
           generate "BRcc" instructions.  It has no effect on "BRcc"
           generation driven by the combiner pass.

       -mcase-vector-pcrel
           Use pc-relative switch case tables - this enables case table
           shortening.  This is the default for -Os.

       -mcompact-casesi
           Enable compact casesi pattern.  This is the default for -Os.

       -mno-cond-exec
           Disable ARCompact specific pass to generate conditional execution
           instructions.  Due to delay slot scheduling and interactions
           between operand numbers, literal sizes, instruction lengths, and
           the support for conditional execution, the target-independent
           pass to generate conditional execution is often lacking, so the
           ARC port has kept a special pass around that tries to find more
           conditional execution generating opportunities after register
           allocation, branch shortening, and delay slot scheduling have
           been done.  This pass generally, but not always, improves
           performance and code size, at the cost of extra compilation time,
           which is why there is an option to switch it off.  If you have a
           problem with call instructions exceeding their allowable offset
           range because they are conditionalized, you should consider using
           -mmedium-calls instead.

       -mearly-cbranchsi
           Enable pre-reload use of the cbranchsi pattern.

       -mexpand-adddi
           Expand "adddi3" and "subdi3" at rtl generation time into "add.f",
           "adc" etc.

       -mindexed-loads
           Enable the use of indexed loads.  This can be problematic because
           some optimizers then assume that indexed stores exist, which is
           not the case.

           Enable Local Register Allocation.  This is still experimental for
           ARC, so by default the compiler uses standard reload (i.e.
           -mno-lra).

       -mlra-priority-none
           Don't indicate any priority for target registers.

       -mlra-priority-compact
           Indicate target register priority for r0..r3 / r12..r15.

       -mlra-priority-noncompact
           Reduce target register priority for r0..r3 / r12..r15.

       -mno-millicode
           When optimizing for size (using -Os), prologues and epilogues
           that have to save or restore a large number of registers are
           often shortened by using call to a special function in libgcc;
           this is referred to as a millicode call.  As these calls can pose
           performance issues, and/or cause linking issues when linking in a
           nonstandard way, this option is provided to turn off millicode
           call generation.

       -mmixed-code
           Tweak register allocation to help 16-bit instruction generation.
           This generally has the effect of decreasing the average
           instruction size while increasing the instruction count.

       -mq-class
           Enable 'q' instruction alternatives.  This is the default for
           -Os.

       -mRcq
           Enable Rcq constraint handling - most short code generation
           depends on this.  This is the default.

       -mRcw
           Enable Rcw constraint handling - ccfsm condexec mostly depends on
           this.  This is the default.

       -msize-level=level
           Fine-tune size optimization with regards to instruction lengths
           and alignment.  The recognized values for level are:

           0   No size optimization.  This level is deprecated and treated
               like 1.

           1   Short instructions are used opportunistically.

           2   In addition, alignment of loops and of code after barriers
               are dropped.

           3   In addition, optional data alignment is dropped, and the
               option Os is enabled.

           This defaults to 3 when -Os is in effect.  Otherwise, the
           behavior when this is not set is equivalent to level 1.

       -mtune=cpu
           Set instruction scheduling parameters for cpu, overriding any
           implied by -mcpu=.

           Supported values for cpu are

           ARC600
               Tune for ARC600 cpu.

           ARC601
               Tune for ARC601 cpu.

           ARC700
               Tune for ARC700 cpu with standard multiplier block.

           ARC700-xmac
               Tune for ARC700 cpu with XMAC block.

           ARC725D
               Tune for ARC725D cpu.

           ARC750D
               Tune for ARC750D cpu.

       -mmultcost=num
           Cost to assume for a multiply instruction, with 4 being equal to
           a normal instruction.

       -munalign-prob-threshold=probability
           Set probability threshold for unaligning branches.  When tuning
           for ARC700 and optimizing for speed, branches without filled
           delay slot are preferably emitted unaligned and long, unless
           profiling indicates that the probability for the branch to be
           taken is below probability.  The default is (REG_BR_PROB_BASE/2),
           i.e. 5000.

       The following options are maintained for backward compatibility, but
       are now deprecated and will be removed in a future release:

       -margonaut
           Obsolete FPX.

       -mbig-endian
       -EB Compile code for big endian targets.  Use of these options is now
           deprecated.  Users wanting big-endian code, should use the
           "arceb-elf32" and "arceb-linux-uclibc" targets when building the
           tool chain, for which big-endian is the default.

       -mlittle-endian
       -EL Compile code for little endian targets.  Use of these options is
           now deprecated.  Users wanting little-endian code should use the
           "arc-elf32" and "arc-linux-uclibc" targets when building the tool
           chain, for which little-endian is the default.

       -mbarrel_shifter
           Replaced by -mbarrel-shifter.

       -mdpfp_compact
           Replaced by -mdpfp-compact.

       -mdpfp_fast
           Replaced by -mdpfp-fast.

       -mdsp_packa
           Replaced by -mdsp-packa.

       -mEA
           Replaced by -mea.

       -mmac_24
           Replaced by -mmac-24.

       -mmac_d16
           Replaced by -mmac-d16.

       -mspfp_compact
           Replaced by -mspfp-compact.

       -mspfp_fast
           Replaced by -mspfp-fast.

       -mtune=cpu
           Values arc600, arc601, arc700 and arc700-xmac for cpu are
           replaced by ARC600, ARC601, ARC700 and ARC700-xmac respectively

       -multcost=num
           Replaced by -mmultcost.

       ARM Options

       These -m options are defined for the ARM port:

       -mabi=name
           Generate code for the specified ABI.  Permissible values are:
           apcs-gnu, atpcs, aapcs, aapcs-linux and iwmmxt.

       -mapcs-frame
           Generate a stack frame that is compliant with the ARM Procedure
           Call Standard for all functions, even if this is not strictly
           necessary for correct execution of the code.  Specifying
           -fomit-frame-pointer with this option causes the stack frames not
           to be generated for leaf functions.  The default is
           -mno-apcs-frame.  This option is deprecated.

       -mapcs
           This is a synonym for -mapcs-frame and is deprecated.

       -mthumb-interwork
           Generate code that supports calling between the ARM and Thumb
           instruction sets.  Without this option, on pre-v5 architectures,
           the two instruction sets cannot be reliably used inside one
           program.  The default is -mno-thumb-interwork, since slightly
           larger code is generated when -mthumb-interwork is specified.  In
           AAPCS configurations this option is meaningless.

       -mno-sched-prolog
           Prevent the reordering of instructions in the function prologue,
           or the merging of those instruction with the instructions in the
           function's body.  This means that all functions start with a
           recognizable set of instructions (or in fact one of a choice from
           a small set of different function prologues), and this
           information can be used to locate the start of functions inside
           an executable piece of code.  The default is -msched-prolog.

       -mfloat-abi=name
           Specifies which floating-point ABI to use.  Permissible values
           are: soft, softfp and hard.

           Specifying soft causes GCC to generate output containing library
           calls for floating-point operations.  softfp allows the
           generation of code using hardware floating-point instructions,
           but still uses the soft-float calling conventions.  hard allows
           generation of floating-point instructions and uses FPU-specific
           calling conventions.

           The default depends on the specific target configuration.  Note
           that the hard-float and soft-float ABIs are not link-compatible;
           you must compile your entire program with the same ABI, and link
           with a compatible set of libraries.

       -mlittle-endian
           Generate code for a processor running in little-endian mode.
           This is the default for all standard configurations.

       -mbig-endian
           Generate code for a processor running in big-endian mode; the
           default is to compile code for a little-endian processor.

       -march=name
           This specifies the name of the target ARM architecture.  GCC uses
           this name to determine what kind of instructions it can emit when
           generating assembly code.  This option can be used in conjunction
           with or instead of the -mcpu= option.  Permissible names are:
           armv2, armv2a, armv3, armv3m, armv4, armv4t, armv5, armv5t,
           armv5e, armv5te, armv6, armv6j, armv6t2, armv6z, armv6kz,
           armv6-m, armv7, armv7-a, armv7-r, armv7-m, armv7e-m, armv7ve,
           armv8-a, armv8-a+crc, armv8.1-a, armv8.1-a+crc, iwmmxt, iwmmxt2,
           ep9312.

           Architecture revisions older than armv4t are deprecated.

           -march=armv7ve is the armv7-a architecture with virtualization
           extensions.

           -march=armv8-a+crc enables code generation for the ARMv8-A
           architecture together with the optional CRC32 extensions.

           -march=native causes the compiler to auto-detect the architecture
           of the build computer.  At present, this feature is only
           supported on GNU/Linux, and not all architectures are recognized.
           If the auto-detect is unsuccessful the option has no effect.

       -mtune=name
           This option specifies the name of the target ARM processor for
           which GCC should tune the performance of the code.  For some ARM
           implementations better performance can be obtained by using this
           option.  Permissible names are: arm2, arm250, arm3, arm6, arm60,
           arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di,
           arm7dmi, arm70, arm700, arm700i, arm710, arm710c, arm7100,
           arm720, arm7500, arm7500fe, arm7tdmi, arm7tdmi-s, arm710t,
           arm720t, arm740t, strongarm, strongarm110, strongarm1100,
           strongarm1110, arm8, arm810, arm9, arm9e, arm920, arm920t,
           arm922t, arm946e-s, arm966e-s, arm968e-s, arm926ej-s, arm940t,
           arm9tdmi, arm10tdmi, arm1020t, arm1026ej-s, arm10e, arm1020e,
           arm1022e, arm1136j-s, arm1136jf-s, mpcore, mpcorenovfp,
           arm1156t2-s, arm1156t2f-s, arm1176jz-s, arm1176jzf-s,
           generic-armv7-a, cortex-a5, cortex-a7, cortex-a8, cortex-a9,
           cortex-a12, cortex-a15, cortex-a17, cortex-a32, cortex-a35,
           cortex-a53, cortex-a57, cortex-a72, cortex-r4, cortex-r4f,
           cortex-r5, cortex-r7, cortex-r8, cortex-m7, cortex-m4, cortex-m3,
           cortex-m1, cortex-m0, cortex-m0plus, cortex-m1.small-multiply,
           cortex-m0.small-multiply, cortex-m0plus.small-multiply,
           exynos-m1, qdf24xx, marvell-pj4, xscale, iwmmxt, iwmmxt2, ep9312,
           fa526, fa626, fa606te, fa626te, fmp626, fa726te, xgene1.

           Additionally, this option can specify that GCC should tune the
           performance of the code for a big.LITTLE system.  Permissible
           names are: cortex-a15.cortex-a7, cortex-a17.cortex-a7,
           cortex-a57.cortex-a53, cortex-a72.cortex-a53.

           -mtune=generic-arch specifies that GCC should tune the
           performance for a blend of processors within architecture arch.
           The aim is to generate code that run well on the current most
           popular processors, balancing between optimizations that benefit
           some CPUs in the range, and avoiding performance pitfalls of
           other CPUs.  The effects of this option may change in future GCC
           versions as CPU models come and go.

           -mtune=native causes the compiler to auto-detect the CPU of the
           build computer.  At present, this feature is only supported on
           GNU/Linux, and not all architectures are recognized.  If the
           auto-detect is unsuccessful the option has no effect.

       -mcpu=name
           This specifies the name of the target ARM processor.  GCC uses
           this name to derive the name of the target ARM architecture (as
           if specified by -march) and the ARM processor type for which to
           tune for performance (as if specified by -mtune).  Where this
           option is used in conjunction with -march or -mtune, those
           options take precedence over the appropriate part of this option.

           Permissible names for this option are the same as those for
           -mtune.

           -mcpu=generic-arch is also permissible, and is equivalent to
           -march=arch -mtune=generic-arch.  See -mtune for more
           information.

           -mcpu=native causes the compiler to auto-detect the CPU of the
           build computer.  At present, this feature is only supported on
           GNU/Linux, and not all architectures are recognized.  If the
           auto-detect is unsuccessful the option has no effect.

       -mfpu=name
           This specifies what floating-point hardware (or hardware
           emulation) is available on the target.  Permissible names are:
           vfp, vfpv3, vfpv3-fp16, vfpv3-d16, vfpv3-d16-fp16, vfpv3xd,
           vfpv3xd-fp16, neon, neon-fp16, vfpv4, vfpv4-d16, fpv4-sp-d16,
           neon-vfpv4, fpv5-d16, fpv5-sp-d16, fp-armv8, neon-fp-armv8 and
           crypto-neon-fp-armv8.

           If -msoft-float is specified this specifies the format of
           floating-point values.

           If the selected floating-point hardware includes the NEON
           extension (e.g. -mfpu=neon), note that floating-point operations
           are not generated by GCC's auto-vectorization pass unless
           -funsafe-math-optimizations is also specified.  This is because
           NEON hardware does not fully implement the IEEE 754 standard for
           floating-point arithmetic (in particular denormal values are
           treated as zero), so the use of NEON instructions may lead to a
           loss of precision.

           You can also set the fpu name at function level by using the
           "target("fpu=")" function attributes or pragmas.

       -mfp16-format=name
           Specify the format of the "__fp16" half-precision floating-point
           type.  Permissible names are none, ieee, and alternative; the
           default is none, in which case the "__fp16" type is not defined.

       -mstructure-size-boundary=n
           The sizes of all structures and unions are rounded up to a
           multiple of the number of bits set by this option.  Permissible
           values are 8, 32 and 64.  The default value varies for different
           toolchains.  For the COFF targeted toolchain the default value is
           8.  A value of 64 is only allowed if the underlying ABI supports
           it.

           Specifying a larger number can produce faster, more efficient
           code, but can also increase the size of the program.  Different
           values are potentially incompatible.  Code compiled with one
           value cannot necessarily expect to work with code or libraries
           compiled with another value, if they exchange information using
           structures or unions.

       -mabort-on-noreturn
           Generate a call to the function "abort" at the end of a
           "noreturn" function.  It is executed if the function tries to
           return.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the
           address of the function into a register and then performing a
           subroutine call on this register.  This switch is needed if the
           target function lies outside of the 64-megabyte addressing range
           of the offset-based version of subroutine call instruction.

           Even if this switch is enabled, not all function calls are turned
           into long calls.  The heuristic is that static functions,
           functions that have the "short_call" attribute, functions that
           are inside the scope of a "#pragma no_long_calls" directive, and
           functions whose definitions have already been compiled within the
           current compilation unit are not turned into long calls.  The
           exceptions to this rule are that weak function definitions,
           functions with the "long_call" attribute or the "section"
           attribute, and functions that are within the scope of a "#pragma
           long_calls" directive are always turned into long calls.

           This feature is not enabled by default.  Specifying
           -mno-long-calls restores the default behavior, as does placing
           the function calls within the scope of a "#pragma long_calls_off"
           directive.  Note these switches have no effect on how the
           compiler generates code to handle function calls via function
           pointers.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather
           than loading it in the prologue for each function.  The runtime
           system is responsible for initializing this register with an
           appropriate value before execution begins.

       -mpic-register=reg
           Specify the register to be used for PIC addressing.  For standard
           PIC base case, the default is any suitable register determined by
           compiler.  For single PIC base case, the default is R9 if target
           is EABI based or stack-checking is enabled, otherwise the default
           is R10.

       -mpic-data-is-text-relative
           Assume that each data segments are relative to text segment at
           load time.  Therefore, it permits addressing data using PC-
           relative operations.  This option is on by default for targets
           other than VxWorks RTP.

       -mpoke-function-name
           Write the name of each function into the text section, directly
           preceding the function prologue.  The generated code is similar
           to this:

                        t0
                            .ascii "arm_poke_function_name", 0
                            .align
                        t1
                            .word 0xff000000 + (t1 - t0)
                        arm_poke_function_name
                            mov     ip, sp
                            stmfd   sp!, {fp, ip, lr, pc}
                            sub     fp, ip, #4

           When performing a stack backtrace, code can inspect the value of
           "pc" stored at "fp + 0".  If the trace function then looks at
           location "pc - 12" and the top 8 bits are set, then we know that
           there is a function name embedded immediately preceding this
           location and has length "((pc[-3]) & 0xff000000)".

       -mthumb
       -marm
           Select between generating code that executes in ARM and Thumb
           states.  The default for most configurations is to generate code
           that executes in ARM state, but the default can be changed by
           configuring GCC with the --with-mode=state configure option.

           You can also override the ARM and Thumb mode for each function by
           using the "target("thumb")" and "target("arm")" function
           attributes or pragmas.

       -mtpcs-frame
           Generate a stack frame that is compliant with the Thumb Procedure
           Call Standard for all non-leaf functions.  (A leaf function is
           one that does not call any other functions.)  The default is
           -mno-tpcs-frame.

       -mtpcs-leaf-frame
           Generate a stack frame that is compliant with the Thumb Procedure
           Call Standard for all leaf functions.  (A leaf function is one
           that does not call any other functions.)  The default is
           -mno-apcs-leaf-frame.

       -mcallee-super-interworking
           Gives all externally visible functions in the file being compiled
           an ARM instruction set header which switches to Thumb mode before
           executing the rest of the function.  This allows these functions
           to be called from non-interworking code.  This option is not
           valid in AAPCS configurations because interworking is enabled by
           default.

       -mcaller-super-interworking
           Allows calls via function pointers (including virtual functions)
           to execute correctly regardless of whether the target code has
           been compiled for interworking or not.  There is a small overhead
           in the cost of executing a function pointer if this option is
           enabled.  This option is not valid in AAPCS configurations
           because interworking is enabled by default.

       -mtp=name
           Specify the access model for the thread local storage pointer.
           The valid models are soft, which generates calls to
           "__aeabi_read_tp", cp15, which fetches the thread pointer from
           "cp15" directly (supported in the arm6k architecture), and auto,
           which uses the best available method for the selected processor.
           The default setting is auto.

       -mtls-dialect=dialect
           Specify the dialect to use for accessing thread local storage.
           Two dialects are supported---gnu and gnu2.  The gnu dialect
           selects the original GNU scheme for supporting local and global
           dynamic TLS models.  The gnu2 dialect selects the GNU descriptor
           scheme, which provides better performance for shared libraries.
           The GNU descriptor scheme is compatible with the original scheme,
           but does require new assembler, linker and library support.
           Initial and local exec TLS models are unaffected by this option
           and always use the original scheme.

       -mword-relocations
           Only generate absolute relocations on word-sized values (i.e.
           R_ARM_ABS32).  This is enabled by default on targets (uClinux,
           SymbianOS) where the runtime loader imposes this restriction, and
           when -fpic or -fPIC is specified.

       -mfix-cortex-m3-ldrd
           Some Cortex-M3 cores can cause data corruption when "ldrd"
           instructions with overlapping destination and base registers are
           used.  This option avoids generating these instructions.  This
           option is enabled by default when -mcpu=cortex-m3 is specified.

       -munaligned-access
       -mno-unaligned-access
           Enables (or disables) reading and writing of 16- and 32- bit
           values from addresses that are not 16- or 32- bit aligned.  By
           default unaligned access is disabled for all pre-ARMv6 and all
           ARMv6-M architectures, and enabled for all other architectures.
           If unaligned access is not enabled then words in packed data
           structures are accessed a byte at a time.

           The ARM attribute "Tag_CPU_unaligned_access" is set in the
           generated object file to either true or false, depending upon the
           setting of this option.  If unaligned access is enabled then the
           preprocessor symbol "__ARM_FEATURE_UNALIGNED" is also defined.

       -mneon-for-64bits
           Enables using Neon to handle scalar 64-bits operations. This is
           disabled by default since the cost of moving data from core
           registers to Neon is high.

       -mslow-flash-data
           Assume loading data from flash is slower than fetching
           instruction.  Therefore literal load is minimized for better
           performance.  This option is only supported when compiling for
           ARMv7 M-profile and off by default.

       -masm-syntax-unified
           Assume inline assembler is using unified asm syntax.  The default
           is currently off which implies divided syntax.  This option has
           no impact on Thumb2. However, this may change in future releases
           of GCC.  Divided syntax should be considered deprecated.

       -mrestrict-it
           Restricts generation of IT blocks to conform to the rules of
           ARMv8.  IT blocks can only contain a single 16-bit instruction
           from a select set of instructions. This option is on by default
           for ARMv8 Thumb mode.

       -mprint-tune-info
           Print CPU tuning information as comment in assembler file.  This
           is an option used only for regression testing of the compiler and
           not intended for ordinary use in compiling code.  This option is
           disabled by default.

       AVR Options

       These options are defined for AVR implementations:

       -mmcu=mcu
           Specify Atmel AVR instruction set architectures (ISA) or MCU
           type.

           The default for this option is@tie{}avr2.

           GCC supports the following AVR devices and ISAs:

           "avr2"
               "Classic" devices with up to 8@tie{}KiB of program memory.
               mcu@tie{}= "attiny22", "attiny26", "at90c8534", "at90s2313",
               "at90s2323", "at90s2333", "at90s2343", "at90s4414",
               "at90s4433", "at90s4434", "at90s8515", "at90s8535".

           "avr25"
               "Classic" devices with up to 8@tie{}KiB of program memory and
               with the "MOVW" instruction.  mcu@tie{}= "ata5272",
               "ata6616c", "attiny13", "attiny13a", "attiny2313",
               "attiny2313a", "attiny24", "attiny24a", "attiny25",
               "attiny261", "attiny261a", "attiny43u", "attiny4313",
               "attiny44", "attiny44a", "attiny441", "attiny45",
               "attiny461", "attiny461a", "attiny48", "attiny828",
               "attiny84", "attiny84a", "attiny841", "attiny85",
               "attiny861", "attiny861a", "attiny87", "attiny88",
               "at86rf401".

           "avr3"
               "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB of
               program memory.  mcu@tie{}= "at43usb355", "at76c711".

           "avr31"
               "Classic" devices with 128@tie{}KiB of program memory.
               mcu@tie{}= "atmega103", "at43usb320".

           "avr35"
               "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB of
               program memory and with the "MOVW" instruction.  mcu@tie{}=
               "ata5505", "ata6617c", "ata664251", "atmega16u2",
               "atmega32u2", "atmega8u2", "attiny1634", "attiny167",
               "at90usb162", "at90usb82".

           "avr4"
               "Enhanced" devices with up to 8@tie{}KiB of program memory.
               mcu@tie{}= "ata6285", "ata6286", "ata6289", "ata6612c",
               "atmega48", "atmega48a", "atmega48p", "atmega48pa",
               "atmega48pb", "atmega8", "atmega8a", "atmega8hva",
               "atmega8515", "atmega8535", "atmega88", "atmega88a",
               "atmega88p", "atmega88pa", "atmega88pb", "at90pwm1",
               "at90pwm2", "at90pwm2b", "at90pwm3", "at90pwm3b",
               "at90pwm81".

           "avr5"
               "Enhanced" devices with 16@tie{}KiB up to 64@tie{}KiB of
               program memory.  mcu@tie{}= "ata5702m322", "ata5782",
               "ata5790", "ata5790n", "ata5791", "ata5795", "ata5831",
               "ata6613c", "ata6614q", "ata8210", "ata8510", "atmega16",
               "atmega16a", "atmega16hva", "atmega16hva2", "atmega16hvb",
               "atmega16hvbrevb", "atmega16m1", "atmega16u4", "atmega161",
               "atmega162", "atmega163", "atmega164a", "atmega164p",
               "atmega164pa", "atmega165", "atmega165a", "atmega165p",
               "atmega165pa", "atmega168", "atmega168a", "atmega168p",
               "atmega168pa", "atmega168pb", "atmega169", "atmega169a",
               "atmega169p", "atmega169pa", "atmega32", "atmega32a",
               "atmega32c1", "atmega32hvb", "atmega32hvbrevb", "atmega32m1",
               "atmega32u4", "atmega32u6", "atmega323", "atmega324a",
               "atmega324p", "atmega324pa", "atmega325", "atmega325a",
               "atmega325p", "atmega325pa", "atmega3250", "atmega3250a",
               "atmega3250p", "atmega3250pa", "atmega328", "atmega328p",
               "atmega328pb", "atmega329", "atmega329a", "atmega329p",
               "atmega329pa", "atmega3290", "atmega3290a", "atmega3290p",
               "atmega3290pa", "atmega406", "atmega64", "atmega64a",
               "atmega64c1", "atmega64hve", "atmega64hve2", "atmega64m1",
               "atmega64rfr2", "atmega640", "atmega644", "atmega644a",
               "atmega644p", "atmega644pa", "atmega644rfr2", "atmega645",
               "atmega645a", "atmega645p", "atmega6450", "atmega6450a",
               "atmega6450p", "atmega649", "atmega649a", "atmega649p",
               "atmega6490", "atmega6490a", "atmega6490p", "at90can32",
               "at90can64", "at90pwm161", "at90pwm216", "at90pwm316",
               "at90scr100", "at90usb646", "at90usb647", "at94k", "m3000".

           "avr51"
               "Enhanced" devices with 128@tie{}KiB of program memory.
               mcu@tie{}= "atmega128", "atmega128a", "atmega128rfa1",
               "atmega128rfr2", "atmega1280", "atmega1281", "atmega1284",
               "atmega1284p", "atmega1284rfr2", "at90can128", "at90usb1286",
               "at90usb1287".

           "avr6"
               "Enhanced" devices with 3-byte PC, i.e. with more than
               128@tie{}KiB of program memory.  mcu@tie{}= "atmega256rfr2",
               "atmega2560", "atmega2561", "atmega2564rfr2".

           "avrxmega2"
               "XMEGA" devices with more than 8@tie{}KiB and up to
               64@tie{}KiB of program memory.  mcu@tie{}= "atxmega16a4",
               "atxmega16a4u", "atxmega16c4", "atxmega16d4", "atxmega16e5",
               "atxmega32a4", "atxmega32a4u", "atxmega32c3", "atxmega32c4",
               "atxmega32d3", "atxmega32d4", "atxmega32e5", "atxmega8e5".

           "avrxmega4"
               "XMEGA" devices with more than 64@tie{}KiB and up to
               128@tie{}KiB of program memory.  mcu@tie{}= "atxmega64a3",
               "atxmega64a3u", "atxmega64a4u", "atxmega64b1", "atxmega64b3",
               "atxmega64c3", "atxmega64d3", "atxmega64d4".

           "avrxmega5"
               "XMEGA" devices with more than 64@tie{}KiB and up to
               128@tie{}KiB of program memory and more than 64@tie{}KiB of
               RAM.  mcu@tie{}= "atxmega64a1", "atxmega64a1u".

           "avrxmega6"
               "XMEGA" devices with more than 128@tie{}KiB of program
               memory.  mcu@tie{}= "atxmega128a3", "atxmega128a3u",
               "atxmega128b1", "atxmega128b3", "atxmega128c3",
               "atxmega128d3", "atxmega128d4", "atxmega192a3",
               "atxmega192a3u", "atxmega192c3", "atxmega192d3",
               "atxmega256a3", "atxmega256a3b", "atxmega256a3bu",
               "atxmega256a3u", "atxmega256c3", "atxmega256d3",
               "atxmega384c3", "atxmega384d3".

           "avrxmega7"
               "XMEGA" devices with more than 128@tie{}KiB of program memory
               and more than 64@tie{}KiB of RAM.  mcu@tie{}= "atxmega128a1",
               "atxmega128a1u", "atxmega128a4u".

           "avrtiny"
               "TINY" Tiny core devices with 512@tie{}B up to 4@tie{}KiB of
               program memory.  mcu@tie{}= "attiny10", "attiny20",
               "attiny4", "attiny40", "attiny5", "attiny9".

           "avr1"
               This ISA is implemented by the minimal AVR core and supported
               for assembler only.  mcu@tie{}= "attiny11", "attiny12",
               "attiny15", "attiny28", "at90s1200".

       -maccumulate-args
           Accumulate outgoing function arguments and acquire/release the
           needed stack space for outgoing function arguments once in
           function prologue/epilogue.  Without this option, outgoing
           arguments are pushed before calling a function and popped
           afterwards.

           Popping the arguments after the function call can be expensive on
           AVR so that accumulating the stack space might lead to smaller
           executables because arguments need not to be removed from the
           stack after such a function call.

           This option can lead to reduced code size for functions that
           perform several calls to functions that get their arguments on
           the stack like calls to printf-like functions.

       -mbranch-cost=cost
           Set the branch costs for conditional branch instructions to cost.
           Reasonable values for cost are small, non-negative integers. The
           default branch cost is 0.

       -mcall-prologues
           Functions prologues/epilogues are expanded as calls to
           appropriate subroutines.  Code size is smaller.

       -mint8
           Assume "int" to be 8-bit integer.  This affects the sizes of all
           types: a "char" is 1 byte, an "int" is 1 byte, a "long" is 2
           bytes, and "long long" is 4 bytes.  Please note that this option
           does not conform to the C standards, but it results in smaller
           code size.

       -mn-flash=num
           Assume that the flash memory has a size of num times 64@tie{}KiB.

       -mno-interrupts
           Generated code is not compatible with hardware interrupts.  Code
           size is smaller.

       -mrelax
           Try to replace "CALL" resp. "JMP" instruction by the shorter
           "RCALL" resp. "RJMP" instruction if applicable.  Setting -mrelax
           just adds the --mlink-relax option to the assembler's command
           line and the --relax option to the linker's command line.

           Jump relaxing is performed by the linker because jump offsets are
           not known before code is located. Therefore, the assembler code
           generated by the compiler is the same, but the instructions in
           the executable may differ from instructions in the assembler
           code.

           Relaxing must be turned on if linker stubs are needed, see the
           section on "EIND" and linker stubs below.

       -mrmw
           Assume that the device supports the Read-Modify-Write
           instructions "XCH", "LAC", "LAS" and "LAT".

       -msp8
           Treat the stack pointer register as an 8-bit register, i.e.
           assume the high byte of the stack pointer is zero.  In general,
           you don't need to set this option by hand.

           This option is used internally by the compiler to select and
           build multilibs for architectures "avr2" and "avr25".  These
           architectures mix devices with and without "SPH".  For any
           setting other than -mmcu=avr2 or -mmcu=avr25 the compiler driver
           adds or removes this option from the compiler proper's command
           line, because the compiler then knows if the device or
           architecture has an 8-bit stack pointer and thus no "SPH"
           register or not.

       -mstrict-X
           Use address register "X" in a way proposed by the hardware.  This
           means that "X" is only used in indirect, post-increment or pre-
           decrement addressing.

           Without this option, the "X" register may be used in the same way
           as "Y" or "Z" which then is emulated by additional instructions.
           For example, loading a value with "X+const" addressing with a
           small non-negative "const < 64" to a register Rn is performed as

                   adiw r26, const   ; X += const
                   ld   <Rn>, X        ; <Rn> = *X
                   sbiw r26, const   ; X -= const

       -mtiny-stack
           Only change the lower 8@tie{}bits of the stack pointer.

       -nodevicelib
           Don't link against AVR-LibC's device specific library "libdev.a".

       -Waddr-space-convert
           Warn about conversions between address spaces in the case where
           the resulting address space is not contained in the incoming
           address space.

       "EIND" and Devices with More Than 128 Ki Bytes of Flash

       Pointers in the implementation are 16@tie{}bits wide.  The address of
       a function or label is represented as word address so that indirect
       jumps and calls can target any code address in the range of
       64@tie{}Ki words.

       In order to facilitate indirect jump on devices with more than
       128@tie{}Ki bytes of program memory space, there is a special
       function register called "EIND" that serves as most significant part
       of the target address when "EICALL" or "EIJMP" instructions are used.

       Indirect jumps and calls on these devices are handled as follows by
       the compiler and are subject to some limitations:

       *   The compiler never sets "EIND".

       *   The compiler uses "EIND" implicitly in "EICALL"/"EIJMP"
           instructions or might read "EIND" directly in order to emulate an
           indirect call/jump by means of a "RET" instruction.

       *   The compiler assumes that "EIND" never changes during the startup
           code or during the application. In particular, "EIND" is not
           saved/restored in function or interrupt service routine
           prologue/epilogue.

       *   For indirect calls to functions and computed goto, the linker
           generates stubs. Stubs are jump pads sometimes also called
           trampolines. Thus, the indirect call/jump jumps to such a stub.
           The stub contains a direct jump to the desired address.

       *   Linker relaxation must be turned on so that the linker generates
           the stubs correctly in all situations. See the compiler option
           -mrelax and the linker option --relax.  There are corner cases
           where the linker is supposed to generate stubs but aborts without
           relaxation and without a helpful error message.

       *   The default linker script is arranged for code with "EIND = 0".
           If code is supposed to work for a setup with "EIND != 0", a
           custom linker script has to be used in order to place the
           sections whose name start with ".trampolines" into the segment
           where "EIND" points to.

       *   The startup code from libgcc never sets "EIND".  Notice that
           startup code is a blend of code from libgcc and AVR-LibC.  For
           the impact of AVR-LibC on "EIND", see the AVR-LibC user manual
           ("http://nongnu.org/avr-libc/user-manual/").

       *   It is legitimate for user-specific startup code to set up "EIND"
           early, for example by means of initialization code located in
           section ".init3". Such code runs prior to general startup code
           that initializes RAM and calls constructors, but after the bit of
           startup code from AVR-LibC that sets "EIND" to the segment where
           the vector table is located.

                   #include <avr/io.h>

                   static void
                   __attribute__((section(".init3"),naked,used,no_instrument_function))
                   init3_set_eind (void)
                   {
                     __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
                                     "out %i0,r24" :: "n" (&EIND) : "r24","memory");
                   }

           The "__trampolines_start" symbol is defined in the linker script.

       *   Stubs are generated automatically by the linker if the following
           two conditions are met:

           -<The address of a label is taken by means of the "gs" modifier>
               (short for generate stubs) like so:

                       LDI r24, lo8(gs(<func>))
                       LDI r25, hi8(gs(<func>))

           -<The final location of that label is in a code segment>
               outside the segment where the stubs are located.

       *   The compiler emits such "gs" modifiers for code labels in the
           following situations:

           -<Taking address of a function or code label.>
           -<Computed goto.>
           -<If prologue-save function is used, see -mcall-prologues>
               command-line option.

           -<Switch/case dispatch tables. If you do not want such dispatch>
               tables you can specify the -fno-jump-tables command-line
               option.

           -<C and C++ constructors/destructors called during
           startup/shutdown.>
           -<If the tools hit a "gs()" modifier explained above.>
       *   Jumping to non-symbolic addresses like so is not supported:

                   int main (void)
                   {
                       /* Call function at word address 0x2 */
                       return ((int(*)(void)) 0x2)();
                   }

           Instead, a stub has to be set up, i.e. the function has to be
           called through a symbol ("func_4" in the example):

                   int main (void)
                   {
                       extern int func_4 (void);

                       /* Call function at byte address 0x4 */
                       return func_4();
                   }

           and the application be linked with -Wl,--defsym,func_4=0x4.
           Alternatively, "func_4" can be defined in the linker script.

       Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special
       Function Registers

       Some AVR devices support memories larger than the 64@tie{}KiB range
       that can be accessed with 16-bit pointers.  To access memory
       locations outside this 64@tie{}KiB range, the contentent of a "RAMP"
       register is used as high part of the address: The "X", "Y", "Z"
       address register is concatenated with the "RAMPX", "RAMPY", "RAMPZ"
       special function register, respectively, to get a wide address.
       Similarly, "RAMPD" is used together with direct addressing.

       *   The startup code initializes the "RAMP" special function
           registers with zero.

       *   If a AVR Named Address Spaces,named address space other than
           generic or "__flash" is used, then "RAMPZ" is set as needed
           before the operation.

       *   If the device supports RAM larger than 64@tie{}KiB and the
           compiler needs to change "RAMPZ" to accomplish an operation,
           "RAMPZ" is reset to zero after the operation.

       *   If the device comes with a specific "RAMP" register, the ISR
           prologue/epilogue saves/restores that SFR and initializes it with
           zero in case the ISR code might (implicitly) use it.

       *   RAM larger than 64@tie{}KiB is not supported by GCC for AVR
           targets.  If you use inline assembler to read from locations
           outside the 16-bit address range and change one of the "RAMP"
           registers, you must reset it to zero after the access.

       AVR Built-in Macros

       GCC defines several built-in macros so that the user code can test
       for the presence or absence of features.  Almost any of the following
       built-in macros are deduced from device capabilities and thus
       triggered by the -mmcu= command-line option.

       For even more AVR-specific built-in macros see AVR Named Address
       Spaces and AVR Built-in Functions.

       "__AVR_ARCH__"
           Build-in macro that resolves to a decimal number that identifies
           the architecture and depends on the -mmcu=mcu option.  Possible
           values are:

           2, 25, 3, 31, 35, 4, 5, 51, 6

           for mcu="avr2", "avr25", "avr3", "avr31", "avr35", "avr4",
           "avr5", "avr51", "avr6",

           respectively and

           100, 102, 104, 105, 106, 107

           for mcu="avrtiny", "avrxmega2", "avrxmega4", "avrxmega5",
           "avrxmega6", "avrxmega7", respectively.  If mcu specifies a
           device, this built-in macro is set accordingly. For example, with
           -mmcu=atmega8 the macro is defined to 4.

       "__AVR_Device__"
           Setting -mmcu=device defines this built-in macro which reflects
           the device's name. For example, -mmcu=atmega8 defines the built-
           in macro "__AVR_ATmega8__", -mmcu=attiny261a defines
           "__AVR_ATtiny261A__", etc.

           The built-in macros' names follow the scheme "__AVR_Device__"
           where Device is the device name as from the AVR user manual. The
           difference between Device in the built-in macro and device in
           -mmcu=device is that the latter is always lowercase.

           If device is not a device but only a core architecture like
           avr51, this macro is not defined.

       "__AVR_DEVICE_NAME__"
           Setting -mmcu=device defines this built-in macro to the device's
           name. For example, with -mmcu=atmega8 the macro is defined to
           "atmega8".

           If device is not a device but only a core architecture like
           avr51, this macro is not defined.

       "__AVR_XMEGA__"
           The device / architecture belongs to the XMEGA family of devices.

       "__AVR_HAVE_ELPM__"
           The device has the "ELPM" instruction.

       "__AVR_HAVE_ELPMX__"
           The device has the "ELPM Rn,Z" and "ELPM Rn,Z+" instructions.

       "__AVR_HAVE_MOVW__"
           The device has the "MOVW" instruction to perform 16-bit register-
           register moves.

       "__AVR_HAVE_LPMX__"
           The device has the "LPM Rn,Z" and "LPM Rn,Z+" instructions.

       "__AVR_HAVE_MUL__"
           The device has a hardware multiplier.

       "__AVR_HAVE_JMP_CALL__"
           The device has the "JMP" and "CALL" instructions.  This is the
           case for devices with at least 16@tie{}KiB of program memory.

       "__AVR_HAVE_EIJMP_EICALL__"
       "__AVR_3_BYTE_PC__"
           The device has the "EIJMP" and "EICALL" instructions.  This is
           the case for devices with more than 128@tie{}KiB of program
           memory.  This also means that the program counter (PC) is
           3@tie{}bytes wide.

       "__AVR_2_BYTE_PC__"
           The program counter (PC) is 2@tie{}bytes wide. This is the case
           for devices with up to 128@tie{}KiB of program memory.

       "__AVR_HAVE_8BIT_SP__"
       "__AVR_HAVE_16BIT_SP__"
           The stack pointer (SP) register is treated as 8-bit respectively
           16-bit register by the compiler.  The definition of these macros
           is affected by -mtiny-stack.

       "__AVR_HAVE_SPH__"
       "__AVR_SP8__"
           The device has the SPH (high part of stack pointer) special
           function register or has an 8-bit stack pointer, respectively.
           The definition of these macros is affected by -mmcu= and in the
           cases of -mmcu=avr2 and -mmcu=avr25 also by -msp8.

       "__AVR_HAVE_RAMPD__"
       "__AVR_HAVE_RAMPX__"
       "__AVR_HAVE_RAMPY__"
       "__AVR_HAVE_RAMPZ__"
           The device has the "RAMPD", "RAMPX", "RAMPY", "RAMPZ" special
           function register, respectively.

       "__NO_INTERRUPTS__"
           This macro reflects the -mno-interrupts command-line option.

       "__AVR_ERRATA_SKIP__"
       "__AVR_ERRATA_SKIP_JMP_CALL__"
           Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit
           instructions because of a hardware erratum.  Skip instructions
           are "SBRS", "SBRC", "SBIS", "SBIC" and "CPSE".  The second macro
           is only defined if "__AVR_HAVE_JMP_CALL__" is also set.

       "__AVR_ISA_RMW__"
           The device has Read-Modify-Write instructions (XCH, LAC, LAS and
           LAT).

       "__AVR_SFR_OFFSET__=offset"
           Instructions that can address I/O special function registers
           directly like "IN", "OUT", "SBI", etc. may use a different
           address as if addressed by an instruction to access RAM like "LD"
           or "STS". This offset depends on the device architecture and has
           to be subtracted from the RAM address in order to get the
           respective I/O@tie{}address.

       "__WITH_AVRLIBC__"
           The compiler is configured to be used together with AVR-Libc.
           See the --with-avrlibc configure option.

       Blackfin Options

       -mcpu=cpu[-sirevision]
           Specifies the name of the target Blackfin processor.  Currently,
           cpu can be one of bf512, bf514, bf516, bf518, bf522, bf523,
           bf524, bf525, bf526, bf527, bf531, bf532, bf533, bf534, bf536,
           bf537, bf538, bf539, bf542, bf544, bf547, bf548, bf549, bf542m,
           bf544m, bf547m, bf548m, bf549m, bf561, bf592.

           The optional sirevision specifies the silicon revision of the
           target Blackfin processor.  Any workarounds available for the
           targeted silicon revision are enabled.  If sirevision is none, no
           workarounds are enabled.  If sirevision is any, all workarounds
           for the targeted processor are enabled.  The
           "__SILICON_REVISION__" macro is defined to two hexadecimal digits
           representing the major and minor numbers in the silicon revision.
           If sirevision is none, the "__SILICON_REVISION__" is not defined.
           If sirevision is any, the "__SILICON_REVISION__" is defined to be
           0xffff.  If this optional sirevision is not used, GCC assumes the
           latest known silicon revision of the targeted Blackfin processor.

           GCC defines a preprocessor macro for the specified cpu.  For the
           bfin-elf toolchain, this option causes the hardware BSP provided
           by libgloss to be linked in if -msim is not given.

           Without this option, bf532 is used as the processor by default.

           Note that support for bf561 is incomplete.  For bf561, only the
           preprocessor macro is defined.

       -msim
           Specifies that the program will be run on the simulator.  This
           causes the simulator BSP provided by libgloss to be linked in.
           This option has effect only for bfin-elf toolchain.  Certain
           other options, such as -mid-shared-library and -mfdpic, imply
           -msim.

       -momit-leaf-frame-pointer
           Don't keep the frame pointer in a register for leaf functions.
           This avoids the instructions to save, set up and restore frame
           pointers and makes an extra register available in leaf functions.
           The option -fomit-frame-pointer removes the frame pointer for all
           functions, which might make debugging harder.

       -mspecld-anomaly
           When enabled, the compiler ensures that the generated code does
           not contain speculative loads after jump instructions. If this
           option is used, "__WORKAROUND_SPECULATIVE_LOADS" is defined.

       -mno-specld-anomaly
           Don't generate extra code to prevent speculative loads from
           occurring.

       -mcsync-anomaly
           When enabled, the compiler ensures that the generated code does
           not contain CSYNC or SSYNC instructions too soon after
           conditional branches.  If this option is used,
           "__WORKAROUND_SPECULATIVE_SYNCS" is defined.

       -mno-csync-anomaly
           Don't generate extra code to prevent CSYNC or SSYNC instructions
           from occurring too soon after a conditional branch.

       -mlow-64k
           When enabled, the compiler is free to take advantage of the
           knowledge that the entire program fits into the low 64k of
           memory.

       -mno-low-64k
           Assume that the program is arbitrarily large.  This is the
           default.

       -mstack-check-l1
           Do stack checking using information placed into L1 scratchpad
           memory by the uClinux kernel.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID
           method.  This allows for execute in place and shared libraries in
           an environment without virtual memory management.  This option
           implies -fPIC.  With a bfin-elf target, this option implies
           -msim.

       -mno-id-shared-library
           Generate code that doesn't assume ID-based shared libraries are
           being used.  This is the default.

       -mleaf-id-shared-library
           Generate code that supports shared libraries via the library ID
           method, but assumes that this library or executable won't link
           against any other ID shared libraries.  That allows the compiler
           to use faster code for jumps and calls.

       -mno-leaf-id-shared-library
           Do not assume that the code being compiled won't link against any
           ID shared libraries.  Slower code is generated for jump and call
           insns.

       -mshared-library-id=n
           Specifies the identification number of the ID-based shared
           library being compiled.  Specifying a value of 0 generates more
           compact code; specifying other values forces the allocation of
           that number to the current library but is no more space- or time-
           efficient than omitting this option.

       -msep-data
           Generate code that allows the data segment to be located in a
           different area of memory from the text segment.  This allows for
           execute in place in an environment without virtual memory
           management by eliminating relocations against the text section.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text
           segment.  This is the default.

       -mlong-calls
       -mno-long-calls
           Tells the compiler to perform function calls by first loading the
           address of the function into a register and then performing a
           subroutine call on this register.  This switch is needed if the
           target function lies outside of the 24-bit addressing range of
           the offset-based version of subroutine call instruction.

           This feature is not enabled by default.  Specifying
           -mno-long-calls restores the default behavior.  Note these
           switches have no effect on how the compiler generates code to
           handle function calls via function pointers.

       -mfast-fp
           Link with the fast floating-point library. This library relaxes
           some of the IEEE floating-point standard's rules for checking
           inputs against Not-a-Number (NAN), in the interest of
           performance.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions
           that are not known to bind locally.  It has no effect without
           -mfdpic.

       -mmulticore
           Build a standalone application for multicore Blackfin processors.
           This option causes proper start files and link scripts supporting
           multicore to be used, and defines the macro "__BFIN_MULTICORE".
           It can only be used with -mcpu=bf561[-sirevision].

           This option can be used with -mcorea or -mcoreb, which selects
           the one-application-per-core programming model.  Without -mcorea
           or -mcoreb, the single-application/dual-core programming model is
           used. In this model, the main function of Core B should be named
           as "coreb_main".

           If this option is not used, the single-core application
           programming model is used.

       -mcorea
           Build a standalone application for Core A of BF561 when using the
           one-application-per-core programming model. Proper start files
           and link scripts are used to support Core A, and the macro
           "__BFIN_COREA" is defined.  This option can only be used in
           conjunction with -mmulticore.

       -mcoreb
           Build a standalone application for Core B of BF561 when using the
           one-application-per-core programming model. Proper start files
           and link scripts are used to support Core B, and the macro
           "__BFIN_COREB" is defined. When this option is used, "coreb_main"
           should be used instead of "main".  This option can only be used
           in conjunction with -mmulticore.

       -msdram
           Build a standalone application for SDRAM. Proper start files and
           link scripts are used to put the application into SDRAM, and the
           macro "__BFIN_SDRAM" is defined.  The loader should initialize
           SDRAM before loading the application.

       -micplb
           Assume that ICPLBs are enabled at run time.  This has an effect
           on certain anomaly workarounds.  For Linux targets, the default
           is to assume ICPLBs are enabled; for standalone applications the
           default is off.

       C6X Options

       -march=name
           This specifies the name of the target architecture.  GCC uses
           this name to determine what kind of instructions it can emit when
           generating assembly code.  Permissible names are: c62x, c64x,
           c64x+, c67x, c67x+, c674x.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default.

       -msim
           Choose startup files and linker script suitable for the
           simulator.

       -msdata=default
           Put small global and static data in the ".neardata" section,
           which is pointed to by register "B14".  Put small uninitialized
           global and static data in the ".bss" section, which is adjacent
           to the ".neardata" section.  Put small read-only data into the
           ".rodata" section.  The corresponding sections used for large
           pieces of data are ".fardata", ".far" and ".const".

       -msdata=all
           Put all data, not just small objects, into the sections reserved
           for small data, and use addressing relative to the "B14" register
           to access them.

       -msdata=none
           Make no use of the sections reserved for small data, and use
           absolute addresses to access all data.  Put all initialized
           global and static data in the ".fardata" section, and all
           uninitialized data in the ".far" section.  Put all constant data
           into the ".const" section.

       CRIS Options

       These options are defined specifically for the CRIS ports.

       -march=architecture-type
       -mcpu=architecture-type
           Generate code for the specified architecture.  The choices for
           architecture-type are v3, v8 and v10 for respectively ETRAX 4,
           ETRAX 100, and ETRAX 100 LX.  Default is v0 except for cris-axis-
           linux-gnu, where the default is v10.

       -mtune=architecture-type
           Tune to architecture-type everything applicable about the
           generated code, except for the ABI and the set of available
           instructions.  The choices for architecture-type are the same as
           for -march=architecture-type.

       -mmax-stack-frame=n
           Warn when the stack frame of a function exceeds n bytes.

       -metrax4
       -metrax100
           The options -metrax4 and -metrax100 are synonyms for -march=v3
           and -march=v8 respectively.

       -mmul-bug-workaround
       -mno-mul-bug-workaround
           Work around a bug in the "muls" and "mulu" instructions for CPU
           models where it applies.  This option is active by default.

       -mpdebug
           Enable CRIS-specific verbose debug-related information in the
           assembly code.  This option also has the effect of turning off
           the #NO_APP formatted-code indicator to the assembler at the
           beginning of the assembly file.

       -mcc-init
           Do not use condition-code results from previous instruction;
           always emit compare and test instructions before use of condition
           codes.

       -mno-side-effects
           Do not emit instructions with side effects in addressing modes
           other than post-increment.

       -mstack-align
       -mno-stack-align
       -mdata-align
       -mno-data-align
       -mconst-align
       -mno-const-align
           These options (no- options) arrange (eliminate arrangements) for
           the stack frame, individual data and constants to be aligned for
           the maximum single data access size for the chosen CPU model.
           The default is to arrange for 32-bit alignment.  ABI details such
           as structure layout are not affected by these options.

       -m32-bit
       -m16-bit
       -m8-bit
           Similar to the stack- data- and const-align options above, these
           options arrange for stack frame, writable data and constants to
           all be 32-bit, 16-bit or 8-bit aligned.  The default is 32-bit
           alignment.

       -mno-prologue-epilogue
       -mprologue-epilogue
           With -mno-prologue-epilogue, the normal function prologue and
           epilogue which set up the stack frame are omitted and no return
           instructions or return sequences are generated in the code.  Use
           this option only together with visual inspection of the compiled
           code: no warnings or errors are generated when call-saved
           registers must be saved, or storage for local variables needs to
           be allocated.

       -mno-gotplt
       -mgotplt
           With -fpic and -fPIC, don't generate (do generate) instruction
           sequences that load addresses for functions from the PLT part of
           the GOT rather than (traditional on other architectures) calls to
           the PLT.  The default is -mgotplt.

       -melf
           Legacy no-op option only recognized with the cris-axis-elf and
           cris-axis-linux-gnu targets.

       -mlinux
           Legacy no-op option only recognized with the cris-axis-linux-gnu
           target.

       -sim
           This option, recognized for the cris-axis-elf, arranges to link
           with input-output functions from a simulator library.  Code,
           initialized data and zero-initialized data are allocated
           consecutively.

       -sim2
           Like -sim, but pass linker options to locate initialized data at
           0x40000000 and zero-initialized data at 0x80000000.

       CR16 Options

       These options are defined specifically for the CR16 ports.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by
           default.

       -mcr16cplus
       -mcr16c
           Generate code for CR16C or CR16C+ architecture. CR16C+
           architecture is default.

       -msim
           Links the library libsim.a which is in compatible with simulator.
           Applicable to ELF compiler only.

       -mint32
           Choose integer type as 32-bit wide.

       -mbit-ops
           Generates "sbit"/"cbit" instructions for bit manipulations.

       -mdata-model=model
           Choose a data model. The choices for model are near, far or
           medium. medium is default.  However, far is not valid with
           -mcr16c, as the CR16C architecture does not support the far data
           model.

       Darwin Options

       These options are defined for all architectures running the Darwin
       operating system.

       FSF GCC on Darwin does not create "fat" object files; it creates an
       object file for the single architecture that GCC was built to target.
       Apple's GCC on Darwin does create "fat" files if multiple -arch
       options are used; it does so by running the compiler or linker
       multiple times and joining the results together with lipo.

       The subtype of the file created (like ppc7400 or ppc970 or i686) is
       determined by the flags that specify the ISA that GCC is targeting,
       like -mcpu or -march.  The -force_cpusubtype_ALL option can be used
       to override this.

       The Darwin tools vary in their behavior when presented with an ISA
       mismatch.  The assembler, as, only permits instructions to be used
       that are valid for the subtype of the file it is generating, so you
       cannot put 64-bit instructions in a ppc750 object file.  The linker
       for shared libraries, /usr/bin/libtool, fails and prints an error if
       asked to create a shared library with a less restrictive subtype than
       its input files (for instance, trying to put a ppc970 object file in
       a ppc7400 library).  The linker for executables, ld, quietly gives
       the executable the most restrictive subtype of any of its input
       files.

       -Fdir
           Add the framework directory dir to the head of the list of
           directories to be searched for header files.  These directories
           are interleaved with those specified by -I options and are
           scanned in a left-to-right order.

           A framework directory is a directory with frameworks in it.  A
           framework is a directory with a Headers and/or PrivateHeaders
           directory contained directly in it that ends in .framework.  The
           name of a framework is the name of this directory excluding the
           .framework.  Headers associated with the framework are found in
           one of those two directories, with Headers being searched first.
           A subframework is a framework directory that is in a framework's
           Frameworks directory.  Includes of subframework headers can only
           appear in a header of a framework that contains the subframework,
           or in a sibling subframework header.  Two subframeworks are
           siblings if they occur in the same framework.  A subframework
           should not have the same name as a framework; a warning is issued
           if this is violated.  Currently a subframework cannot have
           subframeworks; in the future, the mechanism may be extended to
           support this.  The standard frameworks can be found in
           /System/Library/Frameworks and /Library/Frameworks.  An example
           include looks like "#include <Framework/header.h>", where
           Framework denotes the name of the framework and header.h is found
           in the PrivateHeaders or Headers directory.

       -iframeworkdir
           Like -F except the directory is a treated as a system directory.
           The main difference between this -iframework and -F is that with
           -iframework the compiler does not warn about constructs contained
           within header files found via dir.  This option is valid only for
           the C family of languages.

       -gused
           Emit debugging information for symbols that are used.  For stabs
           debugging format, this enables -feliminate-unused-debug-symbols.
           This is by default ON.

       -gfull
           Emit debugging information for all symbols and types.

       -mmacosx-version-min=version
           The earliest version of MacOS X that this executable will run on
           is version.  Typical values of version include 10.1, 10.2, and
           10.3.9.

           If the compiler was built to use the system's headers by default,
           then the default for this option is the system version on which
           the compiler is running, otherwise the default is to make choices
           that are compatible with as many systems and code bases as
           possible.

       -mkernel
           Enable kernel development mode.  The -mkernel option sets
           -static, -fno-common, -fno-use-cxa-atexit, -fno-exceptions,
           -fno-non-call-exceptions, -fapple-kext, -fno-weak and -fno-rtti
           where applicable.  This mode also sets -mno-altivec,
           -msoft-float, -fno-builtin and -mlong-branch for PowerPC targets.

       -mone-byte-bool
           Override the defaults for "bool" so that "sizeof(bool)==1".  By
           default "sizeof(bool)" is 4 when compiling for Darwin/PowerPC and
           1 when compiling for Darwin/x86, so this option has no effect on
           x86.

           Warning: The -mone-byte-bool switch causes GCC to generate code
           that is not binary compatible with code generated without that
           switch.  Using this switch may require recompiling all other
           modules in a program, including system libraries.  Use this
           switch to conform to a non-default data model.

       -mfix-and-continue
       -ffix-and-continue
       -findirect-data
           Generate code suitable for fast turnaround development, such as
           to allow GDB to dynamically load .o files into already-running
           programs.  -findirect-data and -ffix-and-continue are provided
           for backwards compatibility.

       -all_load
           Loads all members of static archive libraries.  See man ld(1) for
           more information.

       -arch_errors_fatal
           Cause the errors having to do with files that have the wrong
           architecture to be fatal.

       -bind_at_load
           Causes the output file to be marked such that the dynamic linker
           will bind all undefined references when the file is loaded or
           launched.

       -bundle
           Produce a Mach-o bundle format file.  See man ld(1) for more
           information.

       -bundle_loader executable
           This option specifies the executable that will load the build
           output file being linked.  See man ld(1) for more information.

       -dynamiclib
           When passed this option, GCC produces a dynamic library instead
           of an executable when linking, using the Darwin libtool command.

       -force_cpusubtype_ALL
           This causes GCC's output file to have the ALL subtype, instead of
           one controlled by the -mcpu or -march option.

       -allowable_client  client_name
       -client_name
       -compatibility_version
       -current_version
       -dead_strip
       -dependency-file
       -dylib_file
       -dylinker_install_name
       -dynamic
       -exported_symbols_list
       -filelist
       -flat_namespace
       -force_flat_namespace
       -headerpad_max_install_names
       -image_base
       -init
       -install_name
       -keep_private_externs
       -multi_module
       -multiply_defined
       -multiply_defined_unused
       -noall_load
       -no_dead_strip_inits_and_terms
       -nofixprebinding
       -nomultidefs
       -noprebind
       -noseglinkedit
       -pagezero_size
       -prebind
       -prebind_all_twolevel_modules
       -private_bundle
       -read_only_relocs
       -sectalign
       -sectobjectsymbols
       -whyload
       -seg1addr
       -sectcreate
       -sectobjectsymbols
       -sectorder
       -segaddr
       -segs_read_only_addr
       -segs_read_write_addr
       -seg_addr_table
       -seg_addr_table_filename
       -seglinkedit
       -segprot
       -segs_read_only_addr
       -segs_read_write_addr
       -single_module
       -static
       -sub_library
       -sub_umbrella
       -twolevel_namespace
       -umbrella
       -undefined
       -unexported_symbols_list
       -weak_reference_mismatches
       -whatsloaded
           These options are passed to the Darwin linker.  The Darwin linker
           man page describes them in detail.

       DEC Alpha Options

       These -m options are defined for the DEC Alpha implementations:

       -mno-soft-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions for
           floating-point operations.  When -msoft-float is specified,
           functions in libgcc.a are used to perform floating-point
           operations.  Unless they are replaced by routines that emulate
           the floating-point operations, or compiled in such a way as to
           call such emulations routines, these routines issue floating-
           point operations.   If you are compiling for an Alpha without
           floating-point operations, you must ensure that the library is
           built so as not to call them.

           Note that Alpha implementations without floating-point operations
           are required to have floating-point registers.

       -mfp-reg
       -mno-fp-regs
           Generate code that uses (does not use) the floating-point
           register set.  -mno-fp-regs implies -msoft-float.  If the
           floating-point register set is not used, floating-point operands
           are passed in integer registers as if they were integers and
           floating-point results are passed in $0 instead of $f0.  This is
           a non-standard calling sequence, so any function with a floating-
           point argument or return value called by code compiled with
           -mno-fp-regs must also be compiled with that option.

           A typical use of this option is building a kernel that does not
           use, and hence need not save and restore, any floating-point
           registers.

       -mieee
           The Alpha architecture implements floating-point hardware
           optimized for maximum performance.  It is mostly compliant with
           the IEEE floating-point standard.  However, for full compliance,
           software assistance is required.  This option generates code
           fully IEEE-compliant code except that the inexact-flag is not
           maintained (see below).  If this option is turned on, the
           preprocessor macro "_IEEE_FP" is defined during compilation.  The
           resulting code is less efficient but is able to correctly support
           denormalized numbers and exceptional IEEE values such as not-a-
           number and plus/minus infinity.  Other Alpha compilers call this
           option -ieee_with_no_inexact.

       -mieee-with-inexact
           This is like -mieee except the generated code also maintains the
           IEEE inexact-flag.  Turning on this option causes the generated
           code to implement fully-compliant IEEE math.  In addition to
           "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor macro.
           On some Alpha implementations the resulting code may execute
           significantly slower than the code generated by default.  Since
           there is very little code that depends on the inexact-flag, you
           should normally not specify this option.  Other Alpha compilers
           call this option -ieee_with_inexact.

       -mfp-trap-mode=trap-mode
           This option controls what floating-point related traps are
           enabled.  Other Alpha compilers call this option -fptm trap-mode.
           The trap mode can be set to one of four values:

           n   This is the default (normal) setting.  The only traps that
               are enabled are the ones that cannot be disabled in software
               (e.g., division by zero trap).

           u   In addition to the traps enabled by n, underflow traps are
               enabled as well.

           su  Like u, but the instructions are marked to be safe for
               software completion (see Alpha architecture manual for
               details).

           sui Like su, but inexact traps are enabled as well.

       -mfp-rounding-mode=rounding-mode
           Selects the IEEE rounding mode.  Other Alpha compilers call this
           option -fprm rounding-mode.  The rounding-mode can be one of:

           n   Normal IEEE rounding mode.  Floating-point numbers are
               rounded towards the nearest machine number or towards the
               even machine number in case of a tie.

           m   Round towards minus infinity.

           c   Chopped rounding mode.  Floating-point numbers are rounded
               towards zero.

           d   Dynamic rounding mode.  A field in the floating-point control
               register (fpcr, see Alpha architecture reference manual)
               controls the rounding mode in effect.  The C library
               initializes this register for rounding towards plus infinity.
               Thus, unless your program modifies the fpcr, d corresponds to
               round towards plus infinity.

       -mtrap-precision=trap-precision
           In the Alpha architecture, floating-point traps are imprecise.
           This means without software assistance it is impossible to
           recover from a floating trap and program execution normally needs
           to be terminated.  GCC can generate code that can assist
           operating system trap handlers in determining the exact location
           that caused a floating-point trap.  Depending on the requirements
           of an application, different levels of precisions can be
           selected:

           p   Program precision.  This option is the default and means a
               trap handler can only identify which program caused a
               floating-point exception.

           f   Function precision.  The trap handler can determine the
               function that caused a floating-point exception.

           i   Instruction precision.  The trap handler can determine the
               exact instruction that caused a floating-point exception.

           Other Alpha compilers provide the equivalent options called
           -scope_safe and -resumption_safe.

       -mieee-conformant
           This option marks the generated code as IEEE conformant.  You
           must not use this option unless you also specify
           -mtrap-precision=i and either -mfp-trap-mode=su or
           -mfp-trap-mode=sui.  Its only effect is to emit the line .eflag
           48 in the function prologue of the generated assembly file.

       -mbuild-constants
           Normally GCC examines a 32- or 64-bit integer constant to see if
           it can construct it from smaller constants in two or three
           instructions.  If it cannot, it outputs the constant as a literal
           and generates code to load it from the data segment at run time.

           Use this option to require GCC to construct all integer constants
           using code, even if it takes more instructions (the maximum is
           six).

           You typically use this option to build a shared library dynamic
           loader.  Itself a shared library, it must relocate itself in
           memory before it can find the variables and constants in its own
           data segment.

       -mbwx
       -mno-bwx
       -mcix
       -mno-cix
       -mfix
       -mno-fix
       -mmax
       -mno-max
           Indicate whether GCC should generate code to use the optional
           BWX, CIX, FIX and MAX instruction sets.  The default is to use
           the instruction sets supported by the CPU type specified via
           -mcpu= option or that of the CPU on which GCC was built if none
           is specified.

       -mfloat-vax
       -mfloat-ieee
           Generate code that uses (does not use) VAX F and G floating-point
           arithmetic instead of IEEE single and double precision.

       -mexplicit-relocs
       -mno-explicit-relocs
           Older Alpha assemblers provided no way to generate symbol
           relocations except via assembler macros.  Use of these macros
           does not allow optimal instruction scheduling.  GNU binutils as
           of version 2.12 supports a new syntax that allows the compiler to
           explicitly mark which relocations should apply to which
           instructions.  This option is mostly useful for debugging, as GCC
           detects the capabilities of the assembler when it is built and
           sets the default accordingly.

       -msmall-data
       -mlarge-data
           When -mexplicit-relocs is in effect, static data is accessed via
           gp-relative relocations.  When -msmall-data is used, objects 8
           bytes long or smaller are placed in a small data area (the
           ".sdata" and ".sbss" sections) and are accessed via 16-bit
           relocations off of the $gp register.  This limits the size of the
           small data area to 64KB, but allows the variables to be directly
           accessed via a single instruction.

           The default is -mlarge-data.  With this option the data area is
           limited to just below 2GB.  Programs that require more than 2GB
           of data must use "malloc" or "mmap" to allocate the data in the
           heap instead of in the program's data segment.

           When generating code for shared libraries, -fpic implies
           -msmall-data and -fPIC implies -mlarge-data.

       -msmall-text
       -mlarge-text
           When -msmall-text is used, the compiler assumes that the code of
           the entire program (or shared library) fits in 4MB, and is thus
           reachable with a branch instruction.  When -msmall-data is used,
           the compiler can assume that all local symbols share the same $gp
           value, and thus reduce the number of instructions required for a
           function call from 4 to 1.

           The default is -mlarge-text.

       -mcpu=cpu_type
           Set the instruction set and instruction scheduling parameters for
           machine type cpu_type.  You can specify either the EV style name
           or the corresponding chip number.  GCC supports scheduling
           parameters for the EV4, EV5 and EV6 family of processors and
           chooses the default values for the instruction set from the
           processor you specify.  If you do not specify a processor type,
           GCC defaults to the processor on which the compiler was built.

           Supported values for cpu_type are

           ev4
           ev45
           21064
               Schedules as an EV4 and has no instruction set extensions.

           ev5
           21164
               Schedules as an EV5 and has no instruction set extensions.

           ev56
           21164a
               Schedules as an EV5 and supports the BWX extension.

           pca56
           21164pc
           21164PC
               Schedules as an EV5 and supports the BWX and MAX extensions.

           ev6
           21264
               Schedules as an EV6 and supports the BWX, FIX, and MAX
               extensions.

           ev67
           21264a
               Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX
               extensions.

           Native toolchains also support the value native, which selects
           the best architecture option for the host processor.
           -mcpu=native has no effect if GCC does not recognize the
           processor.

       -mtune=cpu_type
           Set only the instruction scheduling parameters for machine type
           cpu_type.  The instruction set is not changed.

           Native toolchains also support the value native, which selects
           the best architecture option for the host processor.
           -mtune=native has no effect if GCC does not recognize the
           processor.

       -mmemory-latency=time
           Sets the latency the scheduler should assume for typical memory
           references as seen by the application.  This number is highly
           dependent on the memory access patterns used by the application
           and the size of the external cache on the machine.

           Valid options for time are

           number
               A decimal number representing clock cycles.

           L1
           L2
           L3
           main
               The compiler contains estimates of the number of clock cycles
               for "typical" EV4 & EV5 hardware for the Level 1, 2 & 3
               caches (also called Dcache, Scache, and Bcache), as well as
               to main memory.  Note that L3 is only valid for EV5.

       FR30 Options

       These options are defined specifically for the FR30 port.

       -msmall-model
           Use the small address space model.  This can produce smaller
           code, but it does assume that all symbolic values and addresses
           fit into a 20-bit range.

       -mno-lsim
           Assume that runtime support has been provided and so there is no
           need to include the simulator library (libsim.a) on the linker
           command line.

       FT32 Options

       These options are defined specifically for the FT32 port.

       -msim
           Specifies that the program will be run on the simulator.  This
           causes an alternate runtime startup and library to be linked.
           You must not use this option when generating programs that will
           run on real hardware; you must provide your own runtime library
           for whatever I/O functions are needed.

       -mlra
           Enable Local Register Allocation.  This is still experimental for
           FT32, so by default the compiler uses standard reload.

       -mnodiv
           Do not use div and mod instructions.

       FRV Options

       -mgpr-32
           Only use the first 32 general-purpose registers.

       -mgpr-64
           Use all 64 general-purpose registers.

       -mfpr-32
           Use only the first 32 floating-point registers.

       -mfpr-64
           Use all 64 floating-point registers.

       -mhard-float
           Use hardware instructions for floating-point operations.

       -msoft-float
           Use library routines for floating-point operations.

       -malloc-cc
           Dynamically allocate condition code registers.

       -mfixed-cc
           Do not try to dynamically allocate condition code registers, only
           use "icc0" and "fcc0".

       -mdword
           Change ABI to use double word insns.

       -mno-dword
           Do not use double word instructions.

       -mdouble
           Use floating-point double instructions.

       -mno-double
           Do not use floating-point double instructions.

       -mmedia
           Use media instructions.

       -mno-media
           Do not use media instructions.

       -mmuladd
           Use multiply and add/subtract instructions.

       -mno-muladd
           Do not use multiply and add/subtract instructions.

       -mfdpic
           Select the FDPIC ABI, which uses function descriptors to
           represent pointers to functions.  Without any PIC/PIE-related
           options, it implies -fPIE.  With -fpic or -fpie, it assumes GOT
           entries and small data are within a 12-bit range from the GOT
           base address; with -fPIC or -fPIE, GOT offsets are computed with
           32 bits.  With a bfin-elf target, this option implies -msim.

       -minline-plt
           Enable inlining of PLT entries in function calls to functions
           that are not known to bind locally.  It has no effect without
           -mfdpic.  It's enabled by default if optimizing for speed and
           compiling for shared libraries (i.e., -fPIC or -fpic), or when an
           optimization option such as -O3 or above is present in the
           command line.

       -mTLS
           Assume a large TLS segment when generating thread-local code.

       -mtls
           Do not assume a large TLS segment when generating thread-local
           code.

       -mgprel-ro
           Enable the use of "GPREL" relocations in the FDPIC ABI for data
           that is known to be in read-only sections.  It's enabled by
           default, except for -fpic or -fpie: even though it may help make
           the global offset table smaller, it trades 1 instruction for 4.
           With -fPIC or -fPIE, it trades 3 instructions for 4, one of which
           may be shared by multiple symbols, and it avoids the need for a
           GOT entry for the referenced symbol, so it's more likely to be a
           win.  If it is not, -mno-gprel-ro can be used to disable it.

       -multilib-library-pic
           Link with the (library, not FD) pic libraries.  It's implied by
           -mlibrary-pic, as well as by -fPIC and -fpic without -mfdpic.
           You should never have to use it explicitly.

       -mlinked-fp
           Follow the EABI requirement of always creating a frame pointer
           whenever a stack frame is allocated.  This option is enabled by
           default and can be disabled with -mno-linked-fp.

       -mlong-calls
           Use indirect addressing to call functions outside the current
           compilation unit.  This allows the functions to be placed
           anywhere within the 32-bit address space.

       -malign-labels
           Try to align labels to an 8-byte boundary by inserting NOPs into
           the previous packet.  This option only has an effect when VLIW
           packing is enabled.  It doesn't create new packets; it merely
           adds NOPs to existing ones.

       -mlibrary-pic
           Generate position-independent EABI code.

       -macc-4
           Use only the first four media accumulator registers.

       -macc-8
           Use all eight media accumulator registers.

       -mpack
           Pack VLIW instructions.

       -mno-pack
           Do not pack VLIW instructions.

       -mno-eflags
           Do not mark ABI switches in e_flags.

       -mcond-move
           Enable the use of conditional-move instructions (default).

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mno-cond-move
           Disable the use of conditional-move instructions.

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mscc
           Enable the use of conditional set instructions (default).

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mno-scc
           Disable the use of conditional set instructions.

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mcond-exec
           Enable the use of conditional execution (default).

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mno-cond-exec
           Disable the use of conditional execution.

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mvliw-branch
           Run a pass to pack branches into VLIW instructions (default).

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mno-vliw-branch
           Do not run a pass to pack branches into VLIW instructions.

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mmulti-cond-exec
           Enable optimization of "&&" and "||" in conditional execution
           (default).

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mno-multi-cond-exec
           Disable optimization of "&&" and "||" in conditional execution.

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mnested-cond-exec
           Enable nested conditional execution optimizations (default).

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -mno-nested-cond-exec
           Disable nested conditional execution optimizations.

           This switch is mainly for debugging the compiler and will likely
           be removed in a future version.

       -moptimize-membar
           This switch removes redundant "membar" instructions from the
           compiler-generated code.  It is enabled by default.

       -mno-optimize-membar
           This switch disables the automatic removal of redundant "membar"
           instructions from the generated code.

       -mtomcat-stats
           Cause gas to print out tomcat statistics.

       -mcpu=cpu
           Select the processor type for which to generate code.  Possible
           values are frv, fr550, tomcat, fr500, fr450, fr405, fr400, fr300
           and simple.

       GNU/Linux Options

       These -m options are defined for GNU/Linux targets:

       -mglibc
           Use the GNU C library.  This is the default except on
           *-*-linux-*uclibc*, *-*-linux-*musl* and *-*-linux-*android*
           targets.

       -muclibc
           Use uClibc C library.  This is the default on *-*-linux-*uclibc*
           targets.

       -mmusl
           Use the musl C library.  This is the default on *-*-linux-*musl*
           targets.

       -mbionic
           Use Bionic C library.  This is the default on *-*-linux-*android*
           targets.

       -mandroid
           Compile code compatible with Android platform.  This is the
           default on *-*-linux-*android* targets.

           When compiling, this option enables -mbionic, -fPIC,
           -fno-exceptions and -fno-rtti by default.  When linking, this
           option makes the GCC driver pass Android-specific options to the
           linker.  Finally, this option causes the preprocessor macro
           "__ANDROID__" to be defined.

       -tno-android-cc
           Disable compilation effects of -mandroid, i.e., do not enable
           -mbionic, -fPIC, -fno-exceptions and -fno-rtti by default.

       -tno-android-ld
           Disable linking effects of -mandroid, i.e., pass standard Linux
           linking options to the linker.

       H8/300 Options

       These -m options are defined for the H8/300 implementations:

       -mrelax
           Shorten some address references at link time, when possible; uses
           the linker option -relax.

       -mh Generate code for the H8/300H.

       -ms Generate code for the H8S.

       -mn Generate code for the H8S and H8/300H in the normal mode.  This
           switch must be used either with -mh or -ms.

       -ms2600
           Generate code for the H8S/2600.  This switch must be used with
           -ms.

       -mexr
           Extended registers are stored on stack before execution of
           function with monitor attribute. Default option is -mexr.  This
           option is valid only for H8S targets.

       -mno-exr
           Extended registers are not stored on stack before execution of
           function with monitor attribute. Default option is -mno-exr.
           This option is valid only for H8S targets.

       -mint32
           Make "int" data 32 bits by default.

       -malign-300
           On the H8/300H and H8S, use the same alignment rules as for the
           H8/300.  The default for the H8/300H and H8S is to align longs
           and floats on 4-byte boundaries.  -malign-300 causes them to be
           aligned on 2-byte boundaries.  This option has no effect on the
           H8/300.

       HPPA Options

       These -m options are defined for the HPPA family of computers:

       -march=architecture-type
           Generate code for the specified architecture.  The choices for
           architecture-type are 1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for
           PA 2.0 processors.  Refer to /usr/lib/sched.models on an HP-UX
           system to determine the proper architecture option for your
           machine.  Code compiled for lower numbered architectures runs on
           higher numbered architectures, but not the other way around.

       -mpa-risc-1-0
       -mpa-risc-1-1
       -mpa-risc-2-0
           Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively.

       -mjump-in-delay
           This option is ignored and provided for compatibility purposes
           only.

       -mdisable-fpregs
           Prevent floating-point registers from being used in any manner.
           This is necessary for compiling kernels that perform lazy context
           switching of floating-point registers.  If you use this option
           and attempt to perform floating-point operations, the compiler
           aborts.

       -mdisable-indexing
           Prevent the compiler from using indexing address modes.  This
           avoids some rather obscure problems when compiling MIG generated
           code under MACH.

       -mno-space-regs
           Generate code that assumes the target has no space registers.
           This allows GCC to generate faster indirect calls and use
           unscaled index address modes.

           Such code is suitable for level 0 PA systems and kernels.

       -mfast-indirect-calls
           Generate code that assumes calls never cross space boundaries.
           This allows GCC to emit code that performs faster indirect calls.

           This option does not work in the presence of shared libraries or
           nested functions.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed
           registers.  A fixed register is one that the register allocator
           cannot use.  This is useful when compiling kernel code.  A
           register range is specified as two registers separated by a dash.
           Multiple register ranges can be specified separated by a comma.

       -mlong-load-store
           Generate 3-instruction load and store sequences as sometimes
           required by the HP-UX 10 linker.  This is equivalent to the +k
           option to the HP compilers.

       -mportable-runtime
           Use the portable calling conventions proposed by HP for ELF
           systems.

       -mgas
           Enable the use of assembler directives only GAS understands.

       -mschedule=cpu-type
           Schedule code according to the constraints for the machine type
           cpu-type.  The choices for cpu-type are 700 7100, 7100LC, 7200,
           7300 and 8000.  Refer to /usr/lib/sched.models on an HP-UX system
           to determine the proper scheduling option for your machine.  The
           default scheduling is 8000.

       -mlinker-opt
           Enable the optimization pass in the HP-UX linker.  Note this
           makes symbolic debugging impossible.  It also triggers a bug in
           the HP-UX 8 and HP-UX 9 linkers in which they give bogus error
           messages when linking some programs.

       -msoft-float
           Generate output containing library calls for floating point.
           Warning: the requisite libraries are not available for all HPPA
           targets.  Normally the facilities of the machine's usual C
           compiler are used, but this cannot be done directly in cross-
           compilation.  You must make your own arrangements to provide
           suitable library functions for cross-compilation.

           -msoft-float changes the calling convention in the output file;
           therefore, it is only useful if you compile all of a program with
           this option.  In particular, you need to compile libgcc.a, the
           library that comes with GCC, with -msoft-float in order for this
           to work.

       -msio
           Generate the predefine, "_SIO", for server IO.  The default is
           -mwsio.  This generates the predefines, "__hp9000s700",
           "__hp9000s700__" and "_WSIO", for workstation IO.  These options
           are available under HP-UX and HI-UX.

       -mgnu-ld
           Use options specific to GNU ld.  This passes -shared to ld when
           building a shared library.  It is the default when GCC is
           configured, explicitly or implicitly, with the GNU linker.  This
           option does not affect which ld is called; it only changes what
           parameters are passed to that ld.  The ld that is called is
           determined by the --with-ld configure option, GCC's program
           search path, and finally by the user's PATH.  The linker used by
           GCC can be printed using which `gcc -print-prog-name=ld`.  This
           option is only available on the 64-bit HP-UX GCC, i.e. configured
           with hppa*64*-*-hpux*.

       -mhp-ld
           Use options specific to HP ld.  This passes -b to ld when
           building a shared library and passes +Accept TypeMismatch to ld
           on all links.  It is the default when GCC is configured,
           explicitly or implicitly, with the HP linker.  This option does
           not affect which ld is called; it only changes what parameters
           are passed to that ld.  The ld that is called is determined by
           the --with-ld configure option, GCC's program search path, and
           finally by the user's PATH.  The linker used by GCC can be
           printed using which `gcc -print-prog-name=ld`.  This option is
           only available on the 64-bit HP-UX GCC, i.e. configured with
           hppa*64*-*-hpux*.

       -mlong-calls
           Generate code that uses long call sequences.  This ensures that a
           call is always able to reach linker generated stubs.  The default
           is to generate long calls only when the distance from the call
           site to the beginning of the function or translation unit, as the
           case may be, exceeds a predefined limit set by the branch type
           being used.  The limits for normal calls are 7,600,000 and
           240,000 bytes, respectively for the PA 2.0 and PA 1.X
           architectures.  Sibcalls are always limited at 240,000 bytes.

           Distances are measured from the beginning of functions when using
           the -ffunction-sections option, or when using the -mgas and
           -mno-portable-runtime options together under HP-UX with the SOM
           linker.

           It is normally not desirable to use this option as it degrades
           performance.  However, it may be useful in large applications,
           particularly when partial linking is used to build the
           application.

           The types of long calls used depends on the capabilities of the
           assembler and linker, and the type of code being generated.  The
           impact on systems that support long absolute calls, and long pic
           symbol-difference or pc-relative calls should be relatively
           small.  However, an indirect call is used on 32-bit ELF systems
           in pic code and it is quite long.

       -munix=unix-std
           Generate compiler predefines and select a startfile for the
           specified UNIX standard.  The choices for unix-std are 93, 95 and
           98.  93 is supported on all HP-UX versions.  95 is available on
           HP-UX 10.10 and later.  98 is available on HP-UX 11.11 and later.
           The default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10
           though to 11.00, and 98 for HP-UX 11.11 and later.

           -munix=93 provides the same predefines as GCC 3.3 and 3.4.
           -munix=95 provides additional predefines for "XOPEN_UNIX" and
           "_XOPEN_SOURCE_EXTENDED", and the startfile unix95.o.  -munix=98
           provides additional predefines for "_XOPEN_UNIX",
           "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and
           "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o.

           It is important to note that this option changes the interfaces
           for various library routines.  It also affects the operational
           behavior of the C library.  Thus, extreme care is needed in using
           this option.

           Library code that is intended to operate with more than one UNIX
           standard must test, set and restore the variable
           "__xpg4_extended_mask" as appropriate.  Most GNU software doesn't
           provide this capability.

       -nolibdld
           Suppress the generation of link options to search libdld.sl when
           the -static option is specified on HP-UX 10 and later.

       -static
           The HP-UX implementation of setlocale in libc has a dependency on
           libdld.sl.  There isn't an archive version of libdld.sl.  Thus,
           when the -static option is specified, special link options are
           needed to resolve this dependency.

           On HP-UX 10 and later, the GCC driver adds the necessary options
           to link with libdld.sl when the -static option is specified.
           This causes the resulting binary to be dynamic.  On the 64-bit
           port, the linkers generate dynamic binaries by default in any
           case.  The -nolibdld option can be used to prevent the GCC driver
           from adding these link options.

       -threads
           Add support for multithreading with the dce thread library under
           HP-UX.  This option sets flags for both the preprocessor and
           linker.

       IA-64 Options

       These are the -m options defined for the Intel IA-64 architecture.

       -mbig-endian
           Generate code for a big-endian target.  This is the default for
           HP-UX.

       -mlittle-endian
           Generate code for a little-endian target.  This is the default
           for AIX5 and GNU/Linux.

       -mgnu-as
       -mno-gnu-as
           Generate (or don't) code for the GNU assembler.  This is the
           default.

       -mgnu-ld
       -mno-gnu-ld
           Generate (or don't) code for the GNU linker.  This is the
           default.

       -mno-pic
           Generate code that does not use a global pointer register.  The
           result is not position independent code, and violates the IA-64
           ABI.

       -mvolatile-asm-stop
       -mno-volatile-asm-stop
           Generate (or don't) a stop bit immediately before and after
           volatile asm statements.

       -mregister-names
       -mno-register-names
           Generate (or don't) in, loc, and out register names for the
           stacked registers.  This may make assembler output more readable.

       -mno-sdata
       -msdata
           Disable (or enable) optimizations that use the small data
           section.  This may be useful for working around optimizer bugs.

       -mconstant-gp
           Generate code that uses a single constant global pointer value.
           This is useful when compiling kernel code.

       -mauto-pic
           Generate code that is self-relocatable.  This implies
           -mconstant-gp.  This is useful when compiling firmware code.

       -minline-float-divide-min-latency
           Generate code for inline divides of floating-point values using
           the minimum latency algorithm.

       -minline-float-divide-max-throughput
           Generate code for inline divides of floating-point values using
           the maximum throughput algorithm.

       -mno-inline-float-divide
           Do not generate inline code for divides of floating-point values.

       -minline-int-divide-min-latency
           Generate code for inline divides of integer values using the
           minimum latency algorithm.

       -minline-int-divide-max-throughput
           Generate code for inline divides of integer values using the
           maximum throughput algorithm.

       -mno-inline-int-divide
           Do not generate inline code for divides of integer values.

       -minline-sqrt-min-latency
           Generate code for inline square roots using the minimum latency
           algorithm.

       -minline-sqrt-max-throughput
           Generate code for inline square roots using the maximum
           throughput algorithm.

       -mno-inline-sqrt
           Do not generate inline code for "sqrt".

       -mfused-madd
       -mno-fused-madd
           Do (don't) generate code that uses the fused multiply/add or
           multiply/subtract instructions.  The default is to use these
           instructions.

       -mno-dwarf2-asm
       -mdwarf2-asm
           Don't (or do) generate assembler code for the DWARF line number
           debugging info.  This may be useful when not using the GNU
           assembler.

       -mearly-stop-bits
       -mno-early-stop-bits
           Allow stop bits to be placed earlier than immediately preceding
           the instruction that triggered the stop bit.  This can improve
           instruction scheduling, but does not always do so.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed
           registers.  A fixed register is one that the register allocator
           cannot use.  This is useful when compiling kernel code.  A
           register range is specified as two registers separated by a dash.
           Multiple register ranges can be specified separated by a comma.

       -mtls-size=tls-size
           Specify bit size of immediate TLS offsets.  Valid values are 14,
           22, and 64.

       -mtune=cpu-type
           Tune the instruction scheduling for a particular CPU, Valid
           values are itanium, itanium1, merced, itanium2, and mckinley.

       -milp32
       -mlp64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit
           environment sets int, long and pointer to 32 bits.  The 64-bit
           environment sets int to 32 bits and long and pointer to 64 bits.
           These are HP-UX specific flags.

       -mno-sched-br-data-spec
       -msched-br-data-spec
           (Dis/En)able data speculative scheduling before reload.  This
           results in generation of "ld.a" instructions and the
           corresponding check instructions ("ld.c" / "chk.a").  The default
           setting is disabled.

       -msched-ar-data-spec
       -mno-sched-ar-data-spec
           (En/Dis)able data speculative scheduling after reload.  This
           results in generation of "ld.a" instructions and the
           corresponding check instructions ("ld.c" / "chk.a").  The default
           setting is enabled.

       -mno-sched-control-spec
       -msched-control-spec
           (Dis/En)able control speculative scheduling.  This feature is
           available only during region scheduling (i.e. before reload).
           This results in generation of the "ld.s" instructions and the
           corresponding check instructions "chk.s".  The default setting is
           disabled.

       -msched-br-in-data-spec
       -mno-sched-br-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are
           dependent on the data speculative loads before reload.  This is
           effective only with -msched-br-data-spec enabled.  The default
           setting is enabled.

       -msched-ar-in-data-spec
       -mno-sched-ar-in-data-spec
           (En/Dis)able speculative scheduling of the instructions that are
           dependent on the data speculative loads after reload.  This is
           effective only with -msched-ar-data-spec enabled.  The default
           setting is enabled.

       -msched-in-control-spec
       -mno-sched-in-control-spec
           (En/Dis)able speculative scheduling of the instructions that are
           dependent on the control speculative loads.  This is effective
           only with -msched-control-spec enabled.  The default setting is
           enabled.

       -mno-sched-prefer-non-data-spec-insns
       -msched-prefer-non-data-spec-insns
           If enabled, data-speculative instructions are chosen for schedule
           only if there are no other choices at the moment.  This makes the
           use of the data speculation much more conservative.  The default
           setting is disabled.

       -mno-sched-prefer-non-control-spec-insns
       -msched-prefer-non-control-spec-insns
           If enabled, control-speculative instructions are chosen for
           schedule only if there are no other choices at the moment.  This
           makes the use of the control speculation much more conservative.
           The default setting is disabled.

       -mno-sched-count-spec-in-critical-path
       -msched-count-spec-in-critical-path
           If enabled, speculative dependencies are considered during
           computation of the instructions priorities.  This makes the use
           of the speculation a bit more conservative.  The default setting
           is disabled.

       -msched-spec-ldc
           Use a simple data speculation check.  This option is on by
           default.

       -msched-control-spec-ldc
           Use a simple check for control speculation.  This option is on by
           default.

       -msched-stop-bits-after-every-cycle
           Place a stop bit after every cycle when scheduling.  This option
           is on by default.

       -msched-fp-mem-deps-zero-cost
           Assume that floating-point stores and loads are not likely to
           cause a conflict when placed into the same instruction group.
           This option is disabled by default.

       -msel-sched-dont-check-control-spec
           Generate checks for control speculation in selective scheduling.
           This flag is disabled by default.

       -msched-max-memory-insns=max-insns
           Limit on the number of memory insns per instruction group, giving
           lower priority to subsequent memory insns attempting to schedule
           in the same instruction group. Frequently useful to prevent cache
           bank conflicts.  The default value is 1.

       -msched-max-memory-insns-hard-limit
           Makes the limit specified by msched-max-memory-insns a hard
           limit, disallowing more than that number in an instruction group.
           Otherwise, the limit is "soft", meaning that non-memory
           operations are preferred when the limit is reached, but memory
           operations may still be scheduled.

       LM32 Options

       These -m options are defined for the LatticeMico32 architecture:

       -mbarrel-shift-enabled
           Enable barrel-shift instructions.

       -mdivide-enabled
           Enable divide and modulus instructions.

       -mmultiply-enabled
           Enable multiply instructions.

       -msign-extend-enabled
           Enable sign extend instructions.

       -muser-enabled
           Enable user-defined instructions.

       M32C Options

       -mcpu=name
           Select the CPU for which code is generated.  name may be one of
           r8c for the R8C/Tiny series, m16c for the M16C (up to /60)
           series, m32cm for the M16C/80 series, or m32c for the M32C/80
           series.

       -msim
           Specifies that the program will be run on the simulator.  This
           causes an alternate runtime library to be linked in which
           supports, for example, file I/O.  You must not use this option
           when generating programs that will run on real hardware; you must
           provide your own runtime library for whatever I/O functions are
           needed.

       -memregs=number
           Specifies the number of memory-based pseudo-registers GCC uses
           during code generation.  These pseudo-registers are used like
           real registers, so there is a tradeoff between GCC's ability to
           fit the code into available registers, and the performance
           penalty of using memory instead of registers.  Note that all
           modules in a program must be compiled with the same value for
           this option.  Because of that, you must not use this option with
           GCC's default runtime libraries.

       M32R/D Options

       These -m options are defined for Renesas M32R/D architectures:

       -m32r2
           Generate code for the M32R/2.

       -m32rx
           Generate code for the M32R/X.

       -m32r
           Generate code for the M32R.  This is the default.

       -mmodel=small
           Assume all objects live in the lower 16MB of memory (so that
           their addresses can be loaded with the "ld24" instruction), and
           assume all subroutines are reachable with the "bl" instruction.
           This is the default.

           The addressability of a particular object can be set with the
           "model" attribute.

       -mmodel=medium
           Assume objects may be anywhere in the 32-bit address space (the
           compiler generates "seth/add3" instructions to load their
           addresses), and assume all subroutines are reachable with the
           "bl" instruction.

       -mmodel=large
           Assume objects may be anywhere in the 32-bit address space (the
           compiler generates "seth/add3" instructions to load their
           addresses), and assume subroutines may not be reachable with the
           "bl" instruction (the compiler generates the much slower
           "seth/add3/jl" instruction sequence).

       -msdata=none
           Disable use of the small data area.  Variables are put into one
           of ".data", ".bss", or ".rodata" (unless the "section" attribute
           has been specified).  This is the default.

           The small data area consists of sections ".sdata" and ".sbss".
           Objects may be explicitly put in the small data area with the
           "section" attribute using one of these sections.

       -msdata=sdata
           Put small global and static data in the small data area, but do
           not generate special code to reference them.

       -msdata=use
           Put small global and static data in the small data area, and
           generate special instructions to reference them.

       -G num
           Put global and static objects less than or equal to num bytes
           into the small data or BSS sections instead of the normal data or
           BSS sections.  The default value of num is 8.  The -msdata option
           must be set to one of sdata or use for this option to have any
           effect.

           All modules should be compiled with the same -G num value.
           Compiling with different values of num may or may not work; if it
           doesn't the linker gives an error message---incorrect code is not
           generated.

       -mdebug
           Makes the M32R-specific code in the compiler display some
           statistics that might help in debugging programs.

       -malign-loops
           Align all loops to a 32-byte boundary.

       -mno-align-loops
           Do not enforce a 32-byte alignment for loops.  This is the
           default.

       -missue-rate=number
           Issue number instructions per cycle.  number can only be 1 or 2.

       -mbranch-cost=number
           number can only be 1 or 2.  If it is 1 then branches are
           preferred over conditional code, if it is 2, then the opposite
           applies.

       -mflush-trap=number
           Specifies the trap number to use to flush the cache.  The default
           is 12.  Valid numbers are between 0 and 15 inclusive.

       -mno-flush-trap
           Specifies that the cache cannot be flushed by using a trap.

       -mflush-func=name
           Specifies the name of the operating system function to call to
           flush the cache.  The default is _flush_cache, but a function
           call is only used if a trap is not available.

       -mno-flush-func
           Indicates that there is no OS function for flushing the cache.

       M680x0 Options

       These are the -m options defined for M680x0 and ColdFire processors.
       The default settings depend on which architecture was selected when
       the compiler was configured; the defaults for the most common choices
       are given below.

       -march=arch
           Generate code for a specific M680x0 or ColdFire instruction set
           architecture.  Permissible values of arch for M680x0
           architectures are: 68000, 68010, 68020, 68030, 68040, 68060 and
           cpu32.  ColdFire architectures are selected according to
           Freescale's ISA classification and the permissible values are:
           isaa, isaaplus, isab and isac.

           GCC defines a macro "__mcfarch__" whenever it is generating code
           for a ColdFire target.  The arch in this macro is one of the
           -march arguments given above.

           When used together, -march and -mtune select code that runs on a
           family of similar processors but that is optimized for a
           particular microarchitecture.

       -mcpu=cpu
           Generate code for a specific M680x0 or ColdFire processor.  The
           M680x0 cpus are: 68000, 68010, 68020, 68030, 68040, 68060, 68302,
           68332 and cpu32.  The ColdFire cpus are given by the table below,
           which also classifies the CPUs into families:

           Family : -mcpu arguments
           51 : 51 51ac 51ag 51cn 51em 51je 51jf 51jg 51jm 51mm 51qe 51qm
           5206 : 5202 5204 5206
           5206e : 5206e
           5208 : 5207 5208
           5211a : 5210a 5211a
           5213 : 5211 5212 5213
           5216 : 5214 5216
           52235 : 52230 52231 52232 52233 52234 52235
           5225 : 5224 5225
           52259 : 52252 52254 52255 52256 52258 52259
           5235 : 5232 5233 5234 5235 523x
           5249 : 5249
           5250 : 5250
           5271 : 5270 5271
           5272 : 5272
           5275 : 5274 5275
           5282 : 5280 5281 5282 528x
           53017 : 53011 53012 53013 53014 53015 53016 53017
           5307 : 5307
           5329 : 5327 5328 5329 532x
           5373 : 5372 5373 537x
           5407 : 5407
           5475 : 5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483
           5484 5485

           -mcpu=cpu overrides -march=arch if arch is compatible with cpu.
           Other combinations of -mcpu and -march are rejected.

           GCC defines the macro "__mcf_cpu_cpu" when ColdFire target cpu is
           selected.  It also defines "__mcf_family_family", where the value
           of family is given by the table above.

       -mtune=tune
           Tune the code for a particular microarchitecture within the
           constraints set by -march and -mcpu.  The M680x0
           microarchitectures are: 68000, 68010, 68020, 68030, 68040, 68060
           and cpu32.  The ColdFire microarchitectures are: cfv1, cfv2,
           cfv3, cfv4 and cfv4e.

           You can also use -mtune=68020-40 for code that needs to run
           relatively well on 68020, 68030 and 68040 targets.
           -mtune=68020-60 is similar but includes 68060 targets as well.
           These two options select the same tuning decisions as -m68020-40
           and -m68020-60 respectively.

           GCC defines the macros "__mcarch" and "__mcarch__" when tuning
           for 680x0 architecture arch.  It also defines "mcarch" unless
           either -ansi or a non-GNU -std option is used.  If GCC is tuning
           for a range of architectures, as selected by -mtune=68020-40 or
           -mtune=68020-60, it defines the macros for every architecture in
           the range.

           GCC also defines the macro "__muarch__" when tuning for ColdFire
           microarchitecture uarch, where uarch is one of the arguments
           given above.

       -m68000
       -mc68000
           Generate output for a 68000.  This is the default when the
           compiler is configured for 68000-based systems.  It is equivalent
           to -march=68000.

           Use this option for microcontrollers with a 68000 or EC000 core,
           including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.

       -m68010
           Generate output for a 68010.  This is the default when the
           compiler is configured for 68010-based systems.  It is equivalent
           to -march=68010.

       -m68020
       -mc68020
           Generate output for a 68020.  This is the default when the
           compiler is configured for 68020-based systems.  It is equivalent
           to -march=68020.

       -m68030
           Generate output for a 68030.  This is the default when the
           compiler is configured for 68030-based systems.  It is equivalent
           to -march=68030.

       -m68040
           Generate output for a 68040.  This is the default when the
           compiler is configured for 68040-based systems.  It is equivalent
           to -march=68040.

           This option inhibits the use of 68881/68882 instructions that
           have to be emulated by software on the 68040.  Use this option if
           your 68040 does not have code to emulate those instructions.

       -m68060
           Generate output for a 68060.  This is the default when the
           compiler is configured for 68060-based systems.  It is equivalent
           to -march=68060.

           This option inhibits the use of 68020 and 68881/68882
           instructions that have to be emulated by software on the 68060.
           Use this option if your 68060 does not have code to emulate those
           instructions.

       -mcpu32
           Generate output for a CPU32.  This is the default when the
           compiler is configured for CPU32-based systems.  It is equivalent
           to -march=cpu32.

           Use this option for microcontrollers with a CPU32 or CPU32+ core,
           including the 68330, 68331, 68332, 68333, 68334, 68336, 68340,
           68341, 68349 and 68360.

       -m5200
           Generate output for a 520X ColdFire CPU.  This is the default
           when the compiler is configured for 520X-based systems.  It is
           equivalent to -mcpu=5206, and is now deprecated in favor of that
           option.

           Use this option for microcontroller with a 5200 core, including
           the MCF5202, MCF5203, MCF5204 and MCF5206.

       -m5206e
           Generate output for a 5206e ColdFire CPU.  The option is now
           deprecated in favor of the equivalent -mcpu=5206e.

       -m528x
           Generate output for a member of the ColdFire 528X family.  The
           option is now deprecated in favor of the equivalent -mcpu=528x.

       -m5307
           Generate output for a ColdFire 5307 CPU.  The option is now
           deprecated in favor of the equivalent -mcpu=5307.

       -m5407
           Generate output for a ColdFire 5407 CPU.  The option is now
           deprecated in favor of the equivalent -mcpu=5407.

       -mcfv4e
           Generate output for a ColdFire V4e family CPU (e.g. 547x/548x).
           This includes use of hardware floating-point instructions.  The
           option is equivalent to -mcpu=547x, and is now deprecated in
           favor of that option.

       -m68020-40
           Generate output for a 68040, without using any of the new
           instructions.  This results in code that can run relatively
           efficiently on either a 68020/68881 or a 68030 or a 68040.  The
           generated code does use the 68881 instructions that are emulated
           on the 68040.

           The option is equivalent to -march=68020 -mtune=68020-40.

       -m68020-60
           Generate output for a 68060, without using any of the new
           instructions.  This results in code that can run relatively
           efficiently on either a 68020/68881 or a 68030 or a 68040.  The
           generated code does use the 68881 instructions that are emulated
           on the 68060.

           The option is equivalent to -march=68020 -mtune=68020-60.

       -mhard-float
       -m68881
           Generate floating-point instructions.  This is the default for
           68020 and above, and for ColdFire devices that have an FPU.  It
           defines the macro "__HAVE_68881__" on M680x0 targets and
           "__mcffpu__" on ColdFire targets.

       -msoft-float
           Do not generate floating-point instructions; use library calls
           instead.  This is the default for 68000, 68010, and 68832
           targets.  It is also the default for ColdFire devices that have
           no FPU.

       -mdiv
       -mno-div
           Generate (do not generate) ColdFire hardware divide and remainder
           instructions.  If -march is used without -mcpu, the default is
           "on" for ColdFire architectures and "off" for M680x0
           architectures.  Otherwise, the default is taken from the target
           CPU (either the default CPU, or the one specified by -mcpu).  For
           example, the default is "off" for -mcpu=5206 and "on" for
           -mcpu=5206e.

           GCC defines the macro "__mcfhwdiv__" when this option is enabled.

       -mshort
           Consider type "int" to be 16 bits wide, like "short int".
           Additionally, parameters passed on the stack are also aligned to
           a 16-bit boundary even on targets whose API mandates promotion to
           32-bit.

       -mno-short
           Do not consider type "int" to be 16 bits wide.  This is the
           default.

       -mnobitfield
       -mno-bitfield
           Do not use the bit-field instructions.  The -m68000, -mcpu32 and
           -m5200 options imply -mnobitfield.

       -mbitfield
           Do use the bit-field instructions.  The -m68020 option implies
           -mbitfield.  This is the default if you use a configuration
           designed for a 68020.

       -mrtd
           Use a different function-calling convention, in which functions
           that take a fixed number of arguments return with the "rtd"
           instruction, which pops their arguments while returning.  This
           saves one instruction in the caller since there is no need to pop
           the arguments there.

           This calling convention is incompatible with the one normally
           used on Unix, so you cannot use it if you need to call libraries
           compiled with the Unix compiler.

           Also, you must provide function prototypes for all functions that
           take variable numbers of arguments (including "printf");
           otherwise incorrect code is generated for calls to those
           functions.

           In addition, seriously incorrect code results if you call a
           function with too many arguments.  (Normally, extra arguments are
           harmlessly ignored.)

           The "rtd" instruction is supported by the 68010, 68020, 68030,
           68040, 68060 and CPU32 processors, but not by the 68000 or 5200.

       -mno-rtd
           Do not use the calling conventions selected by -mrtd.  This is
           the default.

       -malign-int
       -mno-align-int
           Control whether GCC aligns "int", "long", "long long", "float",
           "double", and "long double" variables on a 32-bit boundary
           (-malign-int) or a 16-bit boundary (-mno-align-int).  Aligning
           variables on 32-bit boundaries produces code that runs somewhat
           faster on processors with 32-bit busses at the expense of more
           memory.

           Warning: if you use the -malign-int switch, GCC aligns structures
           containing the above types differently than most published
           application binary interface specifications for the m68k.

       -mpcrel
           Use the pc-relative addressing mode of the 68000 directly,
           instead of using a global offset table.  At present, this option
           implies -fpic, allowing at most a 16-bit offset for pc-relative
           addressing.  -fPIC is not presently supported with -mpcrel,
           though this could be supported for 68020 and higher processors.

       -mno-strict-align
       -mstrict-align
           Do not (do) assume that unaligned memory references are handled
           by the system.

       -msep-data
           Generate code that allows the data segment to be located in a
           different area of memory from the text segment.  This allows for
           execute-in-place in an environment without virtual memory
           management.  This option implies -fPIC.

       -mno-sep-data
           Generate code that assumes that the data segment follows the text
           segment.  This is the default.

       -mid-shared-library
           Generate code that supports shared libraries via the library ID
           method.  This allows for execute-in-place and shared libraries in
           an environment without virtual memory management.  This option
           implies -fPIC.

       -mno-id-shared-library
           Generate code that doesn't assume ID-based shared libraries are
           being used.  This is the default.

       -mshared-library-id=n
           Specifies the identification number of the ID-based shared
           library being compiled.  Specifying a value of 0 generates more
           compact code; specifying other values forces the allocation of
           that number to the current library, but is no more space- or
           time-efficient than omitting this option.

       -mxgot
       -mno-xgot
           When generating position-independent code for ColdFire, generate
           code that works if the GOT has more than 8192 entries.  This code
           is larger and slower than code generated without this option.  On
           M680x0 processors, this option is not needed; -fPIC suffices.

           GCC normally uses a single instruction to load values from the
           GOT.  While this is relatively efficient, it only works if the
           GOT is smaller than about 64k.  Anything larger causes the linker
           to report an error such as:

                   relocation truncated to fit: R_68K_GOT16O foobar

           If this happens, you should recompile your code with -mxgot.  It
           should then work with very large GOTs.  However, code generated
           with -mxgot is less efficient, since it takes 4 instructions to
           fetch the value of a global symbol.

           Note that some linkers, including newer versions of the GNU
           linker, can create multiple GOTs and sort GOT entries.  If you
           have such a linker, you should only need to use -mxgot when
           compiling a single object file that accesses more than 8192 GOT
           entries.  Very few do.

           These options have no effect unless GCC is generating position-
           independent code.

       MCore Options

       These are the -m options defined for the Motorola M*Core processors.

       -mhardlit
       -mno-hardlit
           Inline constants into the code stream if it can be done in two
           instructions or less.

       -mdiv
       -mno-div
           Use the divide instruction.  (Enabled by default).

       -mrelax-immediate
       -mno-relax-immediate
           Allow arbitrary-sized immediates in bit operations.

       -mwide-bitfields
       -mno-wide-bitfields
           Always treat bit-fields as "int"-sized.

       -m4byte-functions
       -mno-4byte-functions
           Force all functions to be aligned to a 4-byte boundary.

       -mcallgraph-data
       -mno-callgraph-data
           Emit callgraph information.

       -mslow-bytes
       -mno-slow-bytes
           Prefer word access when reading byte quantities.

       -mlittle-endian
       -mbig-endian
           Generate code for a little-endian target.

       -m210
       -m340
           Generate code for the 210 processor.

       -mno-lsim
           Assume that runtime support has been provided and so omit the
           simulator library (libsim.a) from the linker command line.

       -mstack-increment=size
           Set the maximum amount for a single stack increment operation.
           Large values can increase the speed of programs that contain
           functions that need a large amount of stack space, but they can
           also trigger a segmentation fault if the stack is extended too
           much.  The default value is 0x1000.

       MeP Options

       -mabsdiff
           Enables the "abs" instruction, which is the absolute difference
           between two registers.

       -mall-opts
           Enables all the optional instructions---average, multiply,
           divide, bit operations, leading zero, absolute difference,
           min/max, clip, and saturation.

       -maverage
           Enables the "ave" instruction, which computes the average of two
           registers.

       -mbased=n
           Variables of size n bytes or smaller are placed in the ".based"
           section by default.  Based variables use the $tp register as a
           base register, and there is a 128-byte limit to the ".based"
           section.

       -mbitops
           Enables the bit operation instructions---bit test ("btstm"), set
           ("bsetm"), clear ("bclrm"), invert ("bnotm"), and test-and-set
           ("tas").

       -mc=name
           Selects which section constant data is placed in.  name may be
           tiny, near, or far.

       -mclip
           Enables the "clip" instruction.  Note that -mclip is not useful
           unless you also provide -mminmax.

       -mconfig=name
           Selects one of the built-in core configurations.  Each MeP chip
           has one or more modules in it; each module has a core CPU and a
           variety of coprocessors, optional instructions, and peripherals.
           The "MeP-Integrator" tool, not part of GCC, provides these
           configurations through this option; using this option is the same
           as using all the corresponding command-line options.  The default
           configuration is default.

       -mcop
           Enables the coprocessor instructions.  By default, this is a
           32-bit coprocessor.  Note that the coprocessor is normally
           enabled via the -mconfig= option.

       -mcop32
           Enables the 32-bit coprocessor's instructions.

       -mcop64
           Enables the 64-bit coprocessor's instructions.

       -mivc2
           Enables IVC2 scheduling.  IVC2 is a 64-bit VLIW coprocessor.

       -mdc
           Causes constant variables to be placed in the ".near" section.

       -mdiv
           Enables the "div" and "divu" instructions.

       -meb
           Generate big-endian code.

       -mel
           Generate little-endian code.

       -mio-volatile
           Tells the compiler that any variable marked with the "io"
           attribute is to be considered volatile.

       -ml Causes variables to be assigned to the ".far" section by default.

       -mleadz
           Enables the "leadz" (leading zero) instruction.

       -mm Causes variables to be assigned to the ".near" section by
           default.

       -mminmax
           Enables the "min" and "max" instructions.

       -mmult
           Enables the multiplication and multiply-accumulate instructions.

       -mno-opts
           Disables all the optional instructions enabled by -mall-opts.

       -mrepeat
           Enables the "repeat" and "erepeat" instructions, used for low-
           overhead looping.

       -ms Causes all variables to default to the ".tiny" section.  Note
           that there is a 65536-byte limit to this section.  Accesses to
           these variables use the %gp base register.

       -msatur
           Enables the saturation instructions.  Note that the compiler does
           not currently generate these itself, but this option is included
           for compatibility with other tools, like "as".

       -msdram
           Link the SDRAM-based runtime instead of the default ROM-based
           runtime.

       -msim
           Link the simulator run-time libraries.

       -msimnovec
           Link the simulator runtime libraries, excluding built-in support
           for reset and exception vectors and tables.

       -mtf
           Causes all functions to default to the ".far" section.  Without
           this option, functions default to the ".near" section.

       -mtiny=n
           Variables that are n bytes or smaller are allocated to the
           ".tiny" section.  These variables use the $gp base register.  The
           default for this option is 4, but note that there's a 65536-byte
           limit to the ".tiny" section.

       MicroBlaze Options

       -msoft-float
           Use software emulation for floating point (default).

       -mhard-float
           Use hardware floating-point instructions.

       -mmemcpy
           Do not optimize block moves, use "memcpy".

       -mno-clearbss
           This option is deprecated.  Use -fno-zero-initialized-in-bss
           instead.

       -mcpu=cpu-type
           Use features of, and schedule code for, the given CPU.  Supported
           values are in the format vX.YY.Z, where X is a major version, YY
           is the minor version, and Z is compatibility code.  Example
           values are v3.00.a, v4.00.b, v5.00.a, v5.00.b, v5.00.b, v6.00.a.

       -mxl-soft-mul
           Use software multiply emulation (default).

       -mxl-soft-div
           Use software emulation for divides (default).

       -mxl-barrel-shift
           Use the hardware barrel shifter.

       -mxl-pattern-compare
           Use pattern compare instructions.

       -msmall-divides
           Use table lookup optimization for small signed integer divisions.

       -mxl-stack-check
           This option is deprecated.  Use -fstack-check instead.

       -mxl-gp-opt
           Use GP-relative ".sdata"/".sbss" sections.

       -mxl-multiply-high
           Use multiply high instructions for high part of 32x32 multiply.

       -mxl-float-convert
           Use hardware floating-point conversion instructions.

       -mxl-float-sqrt
           Use hardware floating-point square root instruction.

       -mbig-endian
           Generate code for a big-endian target.

       -mlittle-endian
           Generate code for a little-endian target.

       -mxl-reorder
           Use reorder instructions (swap and byte reversed load/store).

       -mxl-mode-app-model
           Select application model app-model.  Valid models are

           executable
               normal executable (default), uses startup code crt0.o.

           xmdstub
               for use with Xilinx Microprocessor Debugger (XMD) based
               software intrusive debug agent called xmdstub. This uses
               startup file crt1.o and sets the start address of the program
               to 0x800.

           bootstrap
               for applications that are loaded using a bootloader.  This
               model uses startup file crt2.o which does not contain a
               processor reset vector handler. This is suitable for
               transferring control on a processor reset to the bootloader
               rather than the application.

           novectors
               for applications that do not require any of the MicroBlaze
               vectors. This option may be useful for applications running
               within a monitoring application. This model uses crt3.o as a
               startup file.

           Option -xl-mode-app-model is a deprecated alias for
           -mxl-mode-app-model.

       MIPS Options

       -EB Generate big-endian code.

       -EL Generate little-endian code.  This is the default for mips*el-*-*
           configurations.

       -march=arch
           Generate code that runs on arch, which can be the name of a
           generic MIPS ISA, or the name of a particular processor.  The ISA
           names are: mips1, mips2, mips3, mips4, mips32, mips32r2,
           mips32r3, mips32r5, mips32r6, mips64, mips64r2, mips64r3,
           mips64r5 and mips64r6.  The processor names are: 4kc, 4km, 4kp,
           4ksc, 4kec, 4kem, 4kep, 4ksd, 5kc, 5kf, 20kc, 24kc, 24kf2_1,
           24kf1_1, 24kec, 24kef2_1, 24kef1_1, 34kc, 34kf2_1, 34kf1_1, 34kn,
           74kc, 74kf2_1, 74kf1_1, 74kf3_2, 1004kc, 1004kf2_1, 1004kf1_1,
           i6400, interaptiv, loongson2e, loongson2f, loongson3a, m4k, m14k,
           m14kc, m14ke, m14kec, m5100, m5101, octeon, octeon+, octeon2,
           octeon3, orion, p5600, r2000, r3000, r3900, r4000, r4400, r4600,
           r4650, r4700, r6000, r8000, rm7000, rm9000, r10000, r12000,
           r14000, r16000, sb1, sr71000, vr4100, vr4111, vr4120, vr4130,
           vr4300, vr5000, vr5400, vr5500, xlr and xlp.  The special value
           from-abi selects the most compatible architecture for the
           selected ABI (that is, mips1 for 32-bit ABIs and mips3 for 64-bit
           ABIs).

           The native Linux/GNU toolchain also supports the value native,
           which selects the best architecture option for the host
           processor.  -march=native has no effect if GCC does not recognize
           the processor.

           In processor names, a final 000 can be abbreviated as k (for
           example, -march=r2k).  Prefixes are optional, and vr may be
           written r.

           Names of the form nf2_1 refer to processors with FPUs clocked at
           half the rate of the core, names of the form nf1_1 refer to
           processors with FPUs clocked at the same rate as the core, and
           names of the form nf3_2 refer to processors with FPUs clocked a
           ratio of 3:2 with respect to the core.  For compatibility
           reasons, nf is accepted as a synonym for nf2_1 while nx and bfx
           are accepted as synonyms for nf1_1.

           GCC defines two macros based on the value of this option.  The
           first is "_MIPS_ARCH", which gives the name of target
           architecture, as a string.  The second has the form
           "_MIPS_ARCH_foo", where foo is the capitalized value of
           "_MIPS_ARCH".  For example, -march=r2000 sets "_MIPS_ARCH" to
           "r2000" and defines the macro "_MIPS_ARCH_R2000".

           Note that the "_MIPS_ARCH" macro uses the processor names given
           above.  In other words, it has the full prefix and does not
           abbreviate 000 as k.  In the case of from-abi, the macro names
           the resolved architecture (either "mips1" or "mips3").  It names
           the default architecture when no -march option is given.

       -mtune=arch
           Optimize for arch.  Among other things, this option controls the
           way instructions are scheduled, and the perceived cost of
           arithmetic operations.  The list of arch values is the same as
           for -march.

           When this option is not used, GCC optimizes for the processor
           specified by -march.  By using -march and -mtune together, it is
           possible to generate code that runs on a family of processors,
           but optimize the code for one particular member of that family.

           -mtune defines the macros "_MIPS_TUNE" and "_MIPS_TUNE_foo",
           which work in the same way as the -march ones described above.

       -mips1
           Equivalent to -march=mips1.

       -mips2
           Equivalent to -march=mips2.

       -mips3
           Equivalent to -march=mips3.

       -mips4
           Equivalent to -march=mips4.

       -mips32
           Equivalent to -march=mips32.

       -mips32r3
           Equivalent to -march=mips32r3.

       -mips32r5
           Equivalent to -march=mips32r5.

       -mips32r6
           Equivalent to -march=mips32r6.

       -mips64
           Equivalent to -march=mips64.

       -mips64r2
           Equivalent to -march=mips64r2.

       -mips64r3
           Equivalent to -march=mips64r3.

       -mips64r5
           Equivalent to -march=mips64r5.

       -mips64r6
           Equivalent to -march=mips64r6.

       -mips16
       -mno-mips16
           Generate (do not generate) MIPS16 code.  If GCC is targeting a
           MIPS32 or MIPS64 architecture, it makes use of the MIPS16e ASE.

           MIPS16 code generation can also be controlled on a per-function
           basis by means of "mips16" and "nomips16" attributes.

       -mflip-mips16
           Generate MIPS16 code on alternating functions.  This option is
           provided for regression testing of mixed MIPS16/non-MIPS16 code
           generation, and is not intended for ordinary use in compiling
           user code.

       -minterlink-compressed
       -mno-interlink-compressed
           Require (do not require) that code using the standard
           (uncompressed) MIPS ISA be link-compatible with MIPS16 and
           microMIPS code, and vice versa.

           For example, code using the standard ISA encoding cannot jump
           directly to MIPS16 or microMIPS code; it must either use a call
           or an indirect jump.  -minterlink-compressed therefore disables
           direct jumps unless GCC knows that the target of the jump is not
           compressed.

       -minterlink-mips16
       -mno-interlink-mips16
           Aliases of -minterlink-compressed and -mno-interlink-compressed.
           These options predate the microMIPS ASE and are retained for
           backwards compatibility.

       -mabi=32
       -mabi=o64
       -mabi=n32
       -mabi=64
       -mabi=eabi
           Generate code for the given ABI.

           Note that the EABI has a 32-bit and a 64-bit variant.  GCC
           normally generates 64-bit code when you select a 64-bit
           architecture, but you can use -mgp32 to get 32-bit code instead.

           For information about the O64 ABI, see
           <http://gcc.gnu.org/projects/mipso64-abi.html >.

           GCC supports a variant of the o32 ABI in which floating-point
           registers are 64 rather than 32 bits wide.  You can select this
           combination with -mabi=32 -mfp64.  This ABI relies on the "mthc1"
           and "mfhc1" instructions and is therefore only supported for
           MIPS32R2, MIPS32R3 and MIPS32R5 processors.

           The register assignments for arguments and return values remain
           the same, but each scalar value is passed in a single 64-bit
           register rather than a pair of 32-bit registers.  For example,
           scalar floating-point values are returned in $f0 only, not a
           $f0/$f1 pair.  The set of call-saved registers also remains the
           same in that the even-numbered double-precision registers are
           saved.

           Two additional variants of the o32 ABI are supported to enable a
           transition from 32-bit to 64-bit registers.  These are FPXX
           (-mfpxx) and FP64A (-mfp64 -mno-odd-spreg).  The FPXX extension
           mandates that all code must execute correctly when run using
           32-bit or 64-bit registers.  The code can be interlinked with
           either FP32 or FP64, but not both.  The FP64A extension is
           similar to the FP64 extension but forbids the use of odd-numbered
           single-precision registers.  This can be used in conjunction with
           the "FRE" mode of FPUs in MIPS32R5 processors and allows both
           FP32 and FP64A code to interlink and run in the same process
           without changing FPU modes.

       -mabicalls
       -mno-abicalls
           Generate (do not generate) code that is suitable for SVR4-style
           dynamic objects.  -mabicalls is the default for SVR4-based
           systems.

       -mshared
       -mno-shared
           Generate (do not generate) code that is fully position-
           independent, and that can therefore be linked into shared
           libraries.  This option only affects -mabicalls.

           All -mabicalls code has traditionally been position-independent,
           regardless of options like -fPIC and -fpic.  However, as an
           extension, the GNU toolchain allows executables to use absolute
           accesses for locally-binding symbols.  It can also use shorter GP
           initialization sequences and generate direct calls to locally-
           defined functions.  This mode is selected by -mno-shared.

           -mno-shared depends on binutils 2.16 or higher and generates
           objects that can only be linked by the GNU linker.  However, the
           option does not affect the ABI of the final executable; it only
           affects the ABI of relocatable objects.  Using -mno-shared
           generally makes executables both smaller and quicker.

           -mshared is the default.

       -mplt
       -mno-plt
           Assume (do not assume) that the static and dynamic linkers
           support PLTs and copy relocations.  This option only affects
           -mno-shared -mabicalls.  For the n64 ABI, this option has no
           effect without -msym32.

           You can make -mplt the default by configuring GCC with
           --with-mips-plt.  The default is -mno-plt otherwise.

       -mxgot
       -mno-xgot
           Lift (do not lift) the usual restrictions on the size of the
           global offset table.

           GCC normally uses a single instruction to load values from the
           GOT.  While this is relatively efficient, it only works if the
           GOT is smaller than about 64k.  Anything larger causes the linker
           to report an error such as:

                   relocation truncated to fit: R_MIPS_GOT16 foobar

           If this happens, you should recompile your code with -mxgot.
           This works with very large GOTs, although the code is also less
           efficient, since it takes three instructions to fetch the value
           of a global symbol.

           Note that some linkers can create multiple GOTs.  If you have
           such a linker, you should only need to use -mxgot when a single
           object file accesses more than 64k's worth of GOT entries.  Very
           few do.

           These options have no effect unless GCC is generating position
           independent code.

       -mgp32
           Assume that general-purpose registers are 32 bits wide.

       -mgp64
           Assume that general-purpose registers are 64 bits wide.

       -mfp32
           Assume that floating-point registers are 32 bits wide.

       -mfp64
           Assume that floating-point registers are 64 bits wide.

       -mfpxx
           Do not assume the width of floating-point registers.

       -mhard-float
           Use floating-point coprocessor instructions.

       -msoft-float
           Do not use floating-point coprocessor instructions.  Implement
           floating-point calculations using library calls instead.

       -mno-float
           Equivalent to -msoft-float, but additionally asserts that the
           program being compiled does not perform any floating-point
           operations.  This option is presently supported only by some
           bare-metal MIPS configurations, where it may select a special set
           of libraries that lack all floating-point support (including, for
           example, the floating-point "printf" formats).  If code compiled
           with -mno-float accidentally contains floating-point operations,
           it is likely to suffer a link-time or run-time failure.

       -msingle-float
           Assume that the floating-point coprocessor only supports single-
           precision operations.

       -mdouble-float
           Assume that the floating-point coprocessor supports double-
           precision operations.  This is the default.

       -modd-spreg
       -mno-odd-spreg
           Enable the use of odd-numbered single-precision floating-point
           registers for the o32 ABI.  This is the default for processors
           that are known to support these registers.  When using the o32
           FPXX ABI, -mno-odd-spreg is set by default.

       -mabs=2008
       -mabs=legacy
           These options control the treatment of the special not-a-number
           (NaN) IEEE 754 floating-point data with the "abs.fmt" and
           "neg.fmt" machine instructions.

           By default or when -mabs=legacy is used the legacy treatment is
           selected.  In this case these instructions are considered
           arithmetic and avoided where correct operation is required and
           the input operand might be a NaN.  A longer sequence of
           instructions that manipulate the sign bit of floating-point datum
           manually is used instead unless the -ffinite-math-only option has
           also been specified.

           The -mabs=2008 option selects the IEEE 754-2008 treatment.  In
           this case these instructions are considered non-arithmetic and
           therefore operating correctly in all cases, including in
           particular where the input operand is a NaN.  These instructions
           are therefore always used for the respective operations.

       -mnan=2008
       -mnan=legacy
           These options control the encoding of the special not-a-number
           (NaN) IEEE 754 floating-point data.

           The -mnan=legacy option selects the legacy encoding.  In this
           case quiet NaNs (qNaNs) are denoted by the first bit of their
           trailing significand field being 0, whereas signalling NaNs
           (sNaNs) are denoted by the first bit of their trailing
           significand field being 1.

           The -mnan=2008 option selects the IEEE 754-2008 encoding.  In
           this case qNaNs are denoted by the first bit of their trailing
           significand field being 1, whereas sNaNs are denoted by the first
           bit of their trailing significand field being 0.

           The default is -mnan=legacy unless GCC has been configured with
           --with-nan=2008.

       -mllsc
       -mno-llsc
           Use (do not use) ll, sc, and sync instructions to implement
           atomic memory built-in functions.  When neither option is
           specified, GCC uses the instructions if the target architecture
           supports them.

           -mllsc is useful if the runtime environment can emulate the
           instructions and -mno-llsc can be useful when compiling for
           nonstandard ISAs.  You can make either option the default by
           configuring GCC with --with-llsc and --without-llsc respectively.
           --with-llsc is the default for some configurations; see the
           installation documentation for details.

       -mdsp
       -mno-dsp
           Use (do not use) revision 1 of the MIPS DSP ASE.
             This option defines the preprocessor macro "__mips_dsp".  It
           also defines "__mips_dsp_rev" to 1.

       -mdspr2
       -mno-dspr2
           Use (do not use) revision 2 of the MIPS DSP ASE.
             This option defines the preprocessor macros "__mips_dsp" and
           "__mips_dspr2".  It also defines "__mips_dsp_rev" to 2.

       -msmartmips
       -mno-smartmips
           Use (do not use) the MIPS SmartMIPS ASE.

       -mpaired-single
       -mno-paired-single
           Use (do not use) paired-single floating-point instructions.
             This option requires hardware floating-point support to be
           enabled.

       -mdmx
       -mno-mdmx
           Use (do not use) MIPS Digital Media Extension instructions.  This
           option can only be used when generating 64-bit code and requires
           hardware floating-point support to be enabled.

       -mips3d
       -mno-mips3d
           Use (do not use) the MIPS-3D ASE.  The option -mips3d implies
           -mpaired-single.

       -mmicromips
       -mno-micromips
           Generate (do not generate) microMIPS code.

           MicroMIPS code generation can also be controlled on a per-
           function basis by means of "micromips" and "nomicromips"
           attributes.

       -mmt
       -mno-mt
           Use (do not use) MT Multithreading instructions.

       -mmcu
       -mno-mcu
           Use (do not use) the MIPS MCU ASE instructions.

       -meva
       -mno-eva
           Use (do not use) the MIPS Enhanced Virtual Addressing
           instructions.

       -mvirt
       -mno-virt
           Use (do not use) the MIPS Virtualization Application Specific
           instructions.

       -mxpa
       -mno-xpa
           Use (do not use) the MIPS eXtended Physical Address (XPA)
           instructions.

       -mlong64
           Force "long" types to be 64 bits wide.  See -mlong32 for an
           explanation of the default and the way that the pointer size is
           determined.

       -mlong32
           Force "long", "int", and pointer types to be 32 bits wide.

           The default size of "int"s, "long"s and pointers depends on the
           ABI.  All the supported ABIs use 32-bit "int"s.  The n64 ABI uses
           64-bit "long"s, as does the 64-bit EABI; the others use 32-bit
           "long"s.  Pointers are the same size as "long"s, or the same size
           as integer registers, whichever is smaller.

       -msym32
       -mno-sym32
           Assume (do not assume) that all symbols have 32-bit values,
           regardless of the selected ABI.  This option is useful in
           combination with -mabi=64 and -mno-abicalls because it allows GCC
           to generate shorter and faster references to symbolic addresses.

       -G num
           Put definitions of externally-visible data in a small data
           section if that data is no bigger than num bytes.  GCC can then
           generate more efficient accesses to the data; see -mgpopt for
           details.

           The default -G option depends on the configuration.

       -mlocal-sdata
       -mno-local-sdata
           Extend (do not extend) the -G behavior to local data too, such as
           to static variables in C.  -mlocal-sdata is the default for all
           configurations.

           If the linker complains that an application is using too much
           small data, you might want to try rebuilding the less
           performance-critical parts with -mno-local-sdata.  You might also
           want to build large libraries with -mno-local-sdata, so that the
           libraries leave more room for the main program.

       -mextern-sdata
       -mno-extern-sdata
           Assume (do not assume) that externally-defined data is in a small
           data section if the size of that data is within the -G limit.
           -mextern-sdata is the default for all configurations.

           If you compile a module Mod with -mextern-sdata -G num -mgpopt,
           and Mod references a variable Var that is no bigger than num
           bytes, you must make sure that Var is placed in a small data
           section.  If Var is defined by another module, you must either
           compile that module with a high-enough -G setting or attach a
           "section" attribute to Var's definition.  If Var is common, you
           must link the application with a high-enough -G setting.

           The easiest way of satisfying these restrictions is to compile
           and link every module with the same -G option.  However, you may
           wish to build a library that supports several different small
           data limits.  You can do this by compiling the library with the
           highest supported -G setting and additionally using
           -mno-extern-sdata to stop the library from making assumptions
           about externally-defined data.

       -mgpopt
       -mno-gpopt
           Use (do not use) GP-relative accesses for symbols that are known
           to be in a small data section; see -G, -mlocal-sdata and
           -mextern-sdata.  -mgpopt is the default for all configurations.

           -mno-gpopt is useful for cases where the $gp register might not
           hold the value of "_gp".  For example, if the code is part of a
           library that might be used in a boot monitor, programs that call
           boot monitor routines pass an unknown value in $gp.  (In such
           situations, the boot monitor itself is usually compiled with
           -G0.)

           -mno-gpopt implies -mno-local-sdata and -mno-extern-sdata.

       -membedded-data
       -mno-embedded-data
           Allocate variables to the read-only data section first if
           possible, then next in the small data section if possible,
           otherwise in data.  This gives slightly slower code than the
           default, but reduces the amount of RAM required when executing,
           and thus may be preferred for some embedded systems.

       -muninit-const-in-rodata
       -mno-uninit-const-in-rodata
           Put uninitialized "const" variables in the read-only data
           section.  This option is only meaningful in conjunction with
           -membedded-data.

       -mcode-readable=setting
           Specify whether GCC may generate code that reads from executable
           sections.  There are three possible settings:

           -mcode-readable=yes
               Instructions may freely access executable sections.  This is
               the default setting.

           -mcode-readable=pcrel
               MIPS16 PC-relative load instructions can access executable
               sections, but other instructions must not do so.  This option
               is useful on 4KSc and 4KSd processors when the code TLBs have
               the Read Inhibit bit set.  It is also useful on processors
               that can be configured to have a dual instruction/data SRAM
               interface and that, like the M4K, automatically redirect PC-
               relative loads to the instruction RAM.

           -mcode-readable=no
               Instructions must not access executable sections.  This
               option can be useful on targets that are configured to have a
               dual instruction/data SRAM interface but that (unlike the
               M4K) do not automatically redirect PC-relative loads to the
               instruction RAM.

       -msplit-addresses
       -mno-split-addresses
           Enable (disable) use of the "%hi()" and "%lo()" assembler
           relocation operators.  This option has been superseded by
           -mexplicit-relocs but is retained for backwards compatibility.

       -mexplicit-relocs
       -mno-explicit-relocs
           Use (do not use) assembler relocation operators when dealing with
           symbolic addresses.  The alternative, selected by
           -mno-explicit-relocs, is to use assembler macros instead.

           -mexplicit-relocs is the default if GCC was configured to use an
           assembler that supports relocation operators.

       -mcheck-zero-division
       -mno-check-zero-division
           Trap (do not trap) on integer division by zero.

           The default is -mcheck-zero-division.

       -mdivide-traps
       -mdivide-breaks
           MIPS systems check for division by zero by generating either a
           conditional trap or a break instruction.  Using traps results in
           smaller code, but is only supported on MIPS II and later.  Also,
           some versions of the Linux kernel have a bug that prevents trap
           from generating the proper signal ("SIGFPE").  Use -mdivide-traps
           to allow conditional traps on architectures that support them and
           -mdivide-breaks to force the use of breaks.

           The default is usually -mdivide-traps, but this can be overridden
           at configure time using --with-divide=breaks.  Divide-by-zero
           checks can be completely disabled using -mno-check-zero-division.

       -mmemcpy
       -mno-memcpy
           Force (do not force) the use of "memcpy" for non-trivial block
           moves.  The default is -mno-memcpy, which allows GCC to inline
           most constant-sized copies.

       -mlong-calls
       -mno-long-calls
           Disable (do not disable) use of the "jal" instruction.  Calling
           functions using "jal" is more efficient but requires the caller
           and callee to be in the same 256 megabyte segment.

           This option has no effect on abicalls code.  The default is
           -mno-long-calls.

       -mmad
       -mno-mad
           Enable (disable) use of the "mad", "madu" and "mul" instructions,
           as provided by the R4650 ISA.

       -mimadd
       -mno-imadd
           Enable (disable) use of the "madd" and "msub" integer
           instructions.  The default is -mimadd on architectures that
           support "madd" and "msub" except for the 74k architecture where
           it was found to generate slower code.

       -mfused-madd
       -mno-fused-madd
           Enable (disable) use of the floating-point multiply-accumulate
           instructions, when they are available.  The default is
           -mfused-madd.

           On the R8000 CPU when multiply-accumulate instructions are used,
           the intermediate product is calculated to infinite precision and
           is not subject to the FCSR Flush to Zero bit.  This may be
           undesirable in some circumstances.  On other processors the
           result is numerically identical to the equivalent computation
           using separate multiply, add, subtract and negate instructions.

       -nocpp
           Tell the MIPS assembler to not run its preprocessor over user
           assembler files (with a .s suffix) when assembling them.

       -mfix-24k
       -mno-fix-24k
           Work around the 24K E48 (lost data on stores during refill)
           errata.  The workarounds are implemented by the assembler rather
           than by GCC.

       -mfix-r4000
       -mno-fix-r4000
           Work around certain R4000 CPU errata:

           -   A double-word or a variable shift may give an incorrect
               result if executed immediately after starting an integer
               division.

           -   A double-word or a variable shift may give an incorrect
               result if executed while an integer multiplication is in
               progress.

           -   An integer division may give an incorrect result if started
               in a delay slot of a taken branch or a jump.

       -mfix-r4400
       -mno-fix-r4400
           Work around certain R4400 CPU errata:

           -   A double-word or a variable shift may give an incorrect
               result if executed immediately after starting an integer
               division.

       -mfix-r10000
       -mno-fix-r10000
           Work around certain R10000 errata:

           -   "ll"/"sc" sequences may not behave atomically on revisions
               prior to 3.0.  They may deadlock on revisions 2.6 and
               earlier.

           This option can only be used if the target architecture supports
           branch-likely instructions.  -mfix-r10000 is the default when
           -march=r10000 is used; -mno-fix-r10000 is the default otherwise.

       -mfix-rm7000
       -mno-fix-rm7000
           Work around the RM7000 "dmult"/"dmultu" errata.  The workarounds
           are implemented by the assembler rather than by GCC.

       -mfix-vr4120
       -mno-fix-vr4120
           Work around certain VR4120 errata:

           -   "dmultu" does not always produce the correct result.

           -   "div" and "ddiv" do not always produce the correct result if
               one of the operands is negative.

           The workarounds for the division errata rely on special functions
           in libgcc.a.  At present, these functions are only provided by
           the "mips64vr*-elf" configurations.

           Other VR4120 errata require a NOP to be inserted between certain
           pairs of instructions.  These errata are handled by the
           assembler, not by GCC itself.

       -mfix-vr4130
           Work around the VR4130 "mflo"/"mfhi" errata.  The workarounds are
           implemented by the assembler rather than by GCC, although GCC
           avoids using "mflo" and "mfhi" if the VR4130 "macc", "macchi",
           "dmacc" and "dmacchi" instructions are available instead.

       -mfix-sb1
       -mno-fix-sb1
           Work around certain SB-1 CPU core errata.  (This flag currently
           works around the SB-1 revision 2 "F1" and "F2" floating-point
           errata.)

       -mr10k-cache-barrier=setting
           Specify whether GCC should insert cache barriers to avoid the
           side-effects of speculation on R10K processors.

           In common with many processors, the R10K tries to predict the
           outcome of a conditional branch and speculatively executes
           instructions from the "taken" branch.  It later aborts these
           instructions if the predicted outcome is wrong.  However, on the
           R10K, even aborted instructions can have side effects.

           This problem only affects kernel stores and, depending on the
           system, kernel loads.  As an example, a speculatively-executed
           store may load the target memory into cache and mark the cache
           line as dirty, even if the store itself is later aborted.  If a
           DMA operation writes to the same area of memory before the
           "dirty" line is flushed, the cached data overwrites the DMA-ed
           data.  See the R10K processor manual for a full description,
           including other potential problems.

           One workaround is to insert cache barrier instructions before
           every memory access that might be speculatively executed and that
           might have side effects even if aborted.
           -mr10k-cache-barrier=setting controls GCC's implementation of
           this workaround.  It assumes that aborted accesses to any byte in
           the following regions does not have side effects:

           1.  the memory occupied by the current function's stack frame;

           2.  the memory occupied by an incoming stack argument;

           3.  the memory occupied by an object with a link-time-constant
               address.

           It is the kernel's responsibility to ensure that speculative
           accesses to these regions are indeed safe.

           If the input program contains a function declaration such as:

                   void foo (void);

           then the implementation of "foo" must allow "j foo" and "jal foo"
           to be executed speculatively.  GCC honors this restriction for
           functions it compiles itself.  It expects non-GCC functions (such
           as hand-written assembly code) to do the same.

           The option has three forms:

           -mr10k-cache-barrier=load-store
               Insert a cache barrier before a load or store that might be
               speculatively executed and that might have side effects even
               if aborted.

           -mr10k-cache-barrier=store
               Insert a cache barrier before a store that might be
               speculatively executed and that might have side effects even
               if aborted.

           -mr10k-cache-barrier=none
               Disable the insertion of cache barriers.  This is the default
               setting.

       -mflush-func=func
       -mno-flush-func
           Specifies the function to call to flush the I and D caches, or to
           not call any such function.  If called, the function must take
           the same arguments as the common "_flush_func", that is, the
           address of the memory range for which the cache is being flushed,
           the size of the memory range, and the number 3 (to flush both
           caches).  The default depends on the target GCC was configured
           for, but commonly is either "_flush_func" or "__cpu_flush".

       mbranch-cost=num
           Set the cost of branches to roughly num "simple" instructions.
           This cost is only a heuristic and is not guaranteed to produce
           consistent results across releases.  A zero cost redundantly
           selects the default, which is based on the -mtune setting.

       -mbranch-likely
       -mno-branch-likely
           Enable or disable use of Branch Likely instructions, regardless
           of the default for the selected architecture.  By default, Branch
           Likely instructions may be generated if they are supported by the
           selected architecture.  An exception is for the MIPS32 and MIPS64
           architectures and processors that implement those architectures;
           for those, Branch Likely instructions are not be generated by
           default because the MIPS32 and MIPS64 architectures specifically
           deprecate their use.

       -mcompact-branches=never
       -mcompact-branches=optimal
       -mcompact-branches=always
           These options control which form of branches will be generated.
           The default is -mcompact-branches=optimal.

           The -mcompact-branches=never option ensures that compact branch
           instructions will never be generated.

           The -mcompact-branches=always option ensures that a compact
           branch instruction will be generated if available.  If a compact
           branch instruction is not available, a delay slot form of the
           branch will be used instead.

           This option is supported from MIPS Release 6 onwards.

           The -mcompact-branches=optimal option will cause a delay slot
           branch to be used if one is available in the current ISA and the
           delay slot is successfully filled.  If the delay slot is not
           filled, a compact branch will be chosen if one is available.

       -mfp-exceptions
       -mno-fp-exceptions
           Specifies whether FP exceptions are enabled.  This affects how FP
           instructions are scheduled for some processors.  The default is
           that FP exceptions are enabled.

           For instance, on the SB-1, if FP exceptions are disabled, and we
           are emitting 64-bit code, then we can use both FP pipes.
           Otherwise, we can only use one FP pipe.

       -mvr4130-align
       -mno-vr4130-align
           The VR4130 pipeline is two-way superscalar, but can only issue
           two instructions together if the first one is 8-byte aligned.
           When this option is enabled, GCC aligns pairs of instructions
           that it thinks should execute in parallel.

           This option only has an effect when optimizing for the VR4130.
           It normally makes code faster, but at the expense of making it
           bigger.  It is enabled by default at optimization level -O3.

       -msynci
       -mno-synci
           Enable (disable) generation of "synci" instructions on
           architectures that support it.  The "synci" instructions (if
           enabled) are generated when "__builtin___clear_cache" is
           compiled.

           This option defaults to -mno-synci, but the default can be
           overridden by configuring GCC with --with-synci.

           When compiling code for single processor systems, it is generally
           safe to use "synci".  However, on many multi-core (SMP) systems,
           it does not invalidate the instruction caches on all cores and
           may lead to undefined behavior.

       -mrelax-pic-calls
       -mno-relax-pic-calls
           Try to turn PIC calls that are normally dispatched via register
           $25 into direct calls.  This is only possible if the linker can
           resolve the destination at link time and if the destination is
           within range for a direct call.

           -mrelax-pic-calls is the default if GCC was configured to use an
           assembler and a linker that support the ".reloc" assembly
           directive and -mexplicit-relocs is in effect.  With
           -mno-explicit-relocs, this optimization can be performed by the
           assembler and the linker alone without help from the compiler.

       -mmcount-ra-address
       -mno-mcount-ra-address
           Emit (do not emit) code that allows "_mcount" to modify the
           calling function's return address.  When enabled, this option
           extends the usual "_mcount" interface with a new ra-address
           parameter, which has type "intptr_t *" and is passed in register
           $12.  "_mcount" can then modify the return address by doing both
           of the following:

           *   Returning the new address in register $31.

           *   Storing the new address in "*ra-address", if ra-address is
               nonnull.

           The default is -mno-mcount-ra-address.

       -mframe-header-opt
       -mno-frame-header-opt
           Enable (disable) frame header optimization in the o32 ABI.  When
           using the o32 ABI, calling functions will allocate 16 bytes on
           the stack for the called function to write out register
           arguments.  When enabled, this optimization will suppress the
           allocation of the frame header if it can be determined that it is
           unused.

           This optimization is off by default at all optimization levels.

       MMIX Options

       These options are defined for the MMIX:

       -mlibfuncs
       -mno-libfuncs
           Specify that intrinsic library functions are being compiled,
           passing all values in registers, no matter the size.

       -mepsilon
       -mno-epsilon
           Generate floating-point comparison instructions that compare with
           respect to the "rE" epsilon register.

       -mabi=mmixware
       -mabi=gnu
           Generate code that passes function parameters and return values
           that (in the called function) are seen as registers $0 and up, as
           opposed to the GNU ABI which uses global registers $231 and up.

       -mzero-extend
       -mno-zero-extend
           When reading data from memory in sizes shorter than 64 bits, use
           (do not use) zero-extending load instructions by default, rather
           than sign-extending ones.

       -mknuthdiv
       -mno-knuthdiv
           Make the result of a division yielding a remainder have the same
           sign as the divisor.  With the default, -mno-knuthdiv, the sign
           of the remainder follows the sign of the dividend.  Both methods
           are arithmetically valid, the latter being almost exclusively
           used.

       -mtoplevel-symbols
       -mno-toplevel-symbols
           Prepend (do not prepend) a : to all global symbols, so the
           assembly code can be used with the "PREFIX" assembly directive.

       -melf
           Generate an executable in the ELF format, rather than the default
           mmo format used by the mmix simulator.

       -mbranch-predict
       -mno-branch-predict
           Use (do not use) the probable-branch instructions, when static
           branch prediction indicates a probable branch.

       -mbase-addresses
       -mno-base-addresses
           Generate (do not generate) code that uses base addresses.  Using
           a base address automatically generates a request (handled by the
           assembler and the linker) for a constant to be set up in a global
           register.  The register is used for one or more base address
           requests within the range 0 to 255 from the value held in the
           register.  The generally leads to short and fast code, but the
           number of different data items that can be addressed is limited.
           This means that a program that uses lots of static data may
           require -mno-base-addresses.

       -msingle-exit
       -mno-single-exit
           Force (do not force) generated code to have a single exit point
           in each function.

       MN10300 Options

       These -m options are defined for Matsushita MN10300 architectures:

       -mmult-bug
           Generate code to avoid bugs in the multiply instructions for the
           MN10300 processors.  This is the default.

       -mno-mult-bug
           Do not generate code to avoid bugs in the multiply instructions
           for the MN10300 processors.

       -mam33
           Generate code using features specific to the AM33 processor.

       -mno-am33
           Do not generate code using features specific to the AM33
           processor.  This is the default.

       -mam33-2
           Generate code using features specific to the AM33/2.0 processor.

       -mam34
           Generate code using features specific to the AM34 processor.

       -mtune=cpu-type
           Use the timing characteristics of the indicated CPU type when
           scheduling instructions.  This does not change the targeted
           processor type.  The CPU type must be one of mn10300, am33,
           am33-2 or am34.

       -mreturn-pointer-on-d0
           When generating a function that returns a pointer, return the
           pointer in both "a0" and "d0".  Otherwise, the pointer is
           returned only in "a0", and attempts to call such functions
           without a prototype result in errors.  Note that this option is
           on by default; use -mno-return-pointer-on-d0 to disable it.

       -mno-crt0
           Do not link in the C run-time initialization object file.

       -mrelax
           Indicate to the linker that it should perform a relaxation
           optimization pass to shorten branches, calls and absolute memory
           addresses.  This option only has an effect when used on the
           command line for the final link step.

           This option makes symbolic debugging impossible.

       -mliw
           Allow the compiler to generate Long Instruction Word instructions
           if the target is the AM33 or later.  This is the default.  This
           option defines the preprocessor macro "__LIW__".

       -mnoliw
           Do not allow the compiler to generate Long Instruction Word
           instructions.  This option defines the preprocessor macro
           "__NO_LIW__".

       -msetlb
           Allow the compiler to generate the SETLB and Lcc instructions if
           the target is the AM33 or later.  This is the default.  This
           option defines the preprocessor macro "__SETLB__".

       -mnosetlb
           Do not allow the compiler to generate SETLB or Lcc instructions.
           This option defines the preprocessor macro "__NO_SETLB__".

       Moxie Options

       -meb
           Generate big-endian code.  This is the default for moxie-*-*
           configurations.

       -mel
           Generate little-endian code.

       -mmul.x
           Generate mul.x and umul.x instructions.  This is the default for
           moxiebox-*-* configurations.

       -mno-crt0
           Do not link in the C run-time initialization object file.

       MSP430 Options

       These options are defined for the MSP430:

       -masm-hex
           Force assembly output to always use hex constants.  Normally such
           constants are signed decimals, but this option is available for
           testsuite and/or aesthetic purposes.

       -mmcu=
           Select the MCU to target.  This is used to create a C
           preprocessor symbol based upon the MCU name, converted to upper
           case and pre- and post-fixed with __.  This in turn is used by
           the msp430.h header file to select an MCU-specific supplementary
           header file.

           The option also sets the ISA to use.  If the MCU name is one that
           is known to only support the 430 ISA then that is selected,
           otherwise the 430X ISA is selected.  A generic MCU name of msp430
           can also be used to select the 430 ISA.  Similarly the generic
           msp430x MCU name selects the 430X ISA.

           In addition an MCU-specific linker script is added to the linker
           command line.  The script's name is the name of the MCU with .ld
           appended.  Thus specifying -mmcu=xxx on the gcc command line
           defines the C preprocessor symbol "__XXX__" and cause the linker
           to search for a script called xxx.ld.

           This option is also passed on to the assembler.

       -mwarn-mcu
       -mno-warn-mcu
           This option enables or disables warnings about conflicts between
           the MCU name specified by the -mmcu option and the ISA set by the
           -mcpu option and/or the hardware multiply support set by the
           -mhwmult option.  It also toggles warnings about unrecognized MCU
           names.  This option is on by default.

       -mcpu=
           Specifies the ISA to use.  Accepted values are msp430, msp430x
           and msp430xv2.  This option is deprecated.  The -mmcu= option
           should be used to select the ISA.

       -msim
           Link to the simulator runtime libraries and linker script.
           Overrides any scripts that would be selected by the -mmcu=
           option.

       -mlarge
           Use large-model addressing (20-bit pointers, 32-bit "size_t").

       -msmall
           Use small-model addressing (16-bit pointers, 16-bit "size_t").

       -mrelax
           This option is passed to the assembler and linker, and allows the
           linker to perform certain optimizations that cannot be done until
           the final link.

       mhwmult=
           Describes the type of hardware multiply supported by the target.
           Accepted values are none for no hardware multiply, 16bit for the
           original 16-bit-only multiply supported by early MCUs.  32bit for
           the 16/32-bit multiply supported by later MCUs and f5series for
           the 16/32-bit multiply supported by F5-series MCUs.  A value of
           auto can also be given.  This tells GCC to deduce the hardware
           multiply support based upon the MCU name provided by the -mmcu
           option.  If no -mmcu option is specified or if the MCU name is
           not recognized then no hardware multiply support is assumed.
           "auto" is the default setting.

           Hardware multiplies are normally performed by calling a library
           routine.  This saves space in the generated code.  When compiling
           at -O3 or higher however the hardware multiplier is invoked
           inline.  This makes for bigger, but faster code.

           The hardware multiply routines disable interrupts whilst running
           and restore the previous interrupt state when they finish.  This
           makes them safe to use inside interrupt handlers as well as in
           normal code.

       -minrt
           Enable the use of a minimum runtime environment - no static
           initializers or constructors.  This is intended for memory-
           constrained devices.  The compiler includes special symbols in
           some objects that tell the linker and runtime which code
           fragments are required.

       -mcode-region=
       -mdata-region=
           These options tell the compiler where to place functions and data
           that do not have one of the "lower", "upper", "either" or
           "section" attributes.  Possible values are "lower", "upper",
           "either" or "any".  The first three behave like the corresponding
           attribute.  The fourth possible value - "any" - is the default.
           It leaves placement entirely up to the linker script and how it
           assigns the standard sections (".text", ".data", etc) to the
           memory regions.

       -msilicon-errata=
           This option passes on a request to assembler to enable the fixes
           for the named silicon errata.

       -msilicon-errata-warn=
           This option passes on a request to the assembler to enable
           warning messages when a silicon errata might need to be applied.

       NDS32 Options

       These options are defined for NDS32 implementations:

       -mbig-endian
           Generate code in big-endian mode.

       -mlittle-endian
           Generate code in little-endian mode.

       -mreduced-regs
           Use reduced-set registers for register allocation.

       -mfull-regs
           Use full-set registers for register allocation.

       -mcmov
           Generate conditional move instructions.

       -mno-cmov
           Do not generate conditional move instructions.

       -mperf-ext
           Generate performance extension instructions.

       -mno-perf-ext
           Do not generate performance extension instructions.

       -mv3push
           Generate v3 push25/pop25 instructions.

       -mno-v3push
           Do not generate v3 push25/pop25 instructions.

       -m16-bit
           Generate 16-bit instructions.

       -mno-16-bit
           Do not generate 16-bit instructions.

       -misr-vector-size=num
           Specify the size of each interrupt vector, which must be 4 or 16.

       -mcache-block-size=num
           Specify the size of each cache block, which must be a power of 2
           between 4 and 512.

       -march=arch
           Specify the name of the target architecture.

       -mcmodel=code-model
           Set the code model to one of

           small
               All the data and read-only data segments must be within 512KB
               addressing space.  The text segment must be within 16MB
               addressing space.

           medium
               The data segment must be within 512KB while the read-only
               data segment can be within 4GB addressing space.  The text
               segment should be still within 16MB addressing space.

           large
               All the text and data segments can be within 4GB addressing
               space.

       -mctor-dtor
           Enable constructor/destructor feature.

       -mrelax
           Guide linker to relax instructions.

       Nios II Options

       These are the options defined for the Altera Nios II processor.

       -G num
           Put global and static objects less than or equal to num bytes
           into the small data or BSS sections instead of the normal data or
           BSS sections.  The default value of num is 8.

       -mgpopt=option
       -mgpopt
       -mno-gpopt
           Generate (do not generate) GP-relative accesses.  The following
           option names are recognized:

           none
               Do not generate GP-relative accesses.

           local
               Generate GP-relative accesses for small data objects that are
               not external, weak, or uninitialized common symbols.  Also
               use GP-relative addressing for objects that have been
               explicitly placed in a small data section via a "section"
               attribute.

           global
               As for local, but also generate GP-relative accesses for
               small data objects that are external, weak, or common.  If
               you use this option, you must ensure that all parts of your
               program (including libraries) are compiled with the same -G
               setting.

           data
               Generate GP-relative accesses for all data objects in the
               program.  If you use this option, the entire data and BSS
               segments of your program must fit in 64K of memory and you
               must use an appropriate linker script to allocate them within
               the addressable range of the global pointer.

           all Generate GP-relative addresses for function pointers as well
               as data pointers.  If you use this option, the entire text,
               data, and BSS segments of your program must fit in 64K of
               memory and you must use an appropriate linker script to
               allocate them within the addressable range of the global
               pointer.

           -mgpopt is equivalent to -mgpopt=local, and -mno-gpopt is
           equivalent to -mgpopt=none.

           The default is -mgpopt except when -fpic or -fPIC is specified to
           generate position-independent code.  Note that the Nios II ABI
           does not permit GP-relative accesses from shared libraries.

           You may need to specify -mno-gpopt explicitly when building
           programs that include large amounts of small data, including
           large GOT data sections.  In this case, the 16-bit offset for GP-
           relative addressing may not be large enough to allow access to
           the entire small data section.

       -mel
       -meb
           Generate little-endian (default) or big-endian (experimental)
           code, respectively.

       -march=arch
           This specifies the name of the target Nios II architecture.  GCC
           uses this name to determine what kind of instructions it can emit
           when generating assembly code.  Permissible names are: r1, r2.

           The preprocessor macro "__nios2_arch__" is available to programs,
           with value 1 or 2, indicating the targeted ISA level.

       -mbypass-cache
       -mno-bypass-cache
           Force all load and store instructions to always bypass cache by
           using I/O variants of the instructions. The default is not to
           bypass the cache.

       -mno-cache-volatile
       -mcache-volatile
           Volatile memory access bypass the cache using the I/O variants of
           the load and store instructions. The default is not to bypass the
           cache.

       -mno-fast-sw-div
       -mfast-sw-div
           Do not use table-based fast divide for small numbers. The default
           is to use the fast divide at -O3 and above.

       -mno-hw-mul
       -mhw-mul
       -mno-hw-mulx
       -mhw-mulx
       -mno-hw-div
       -mhw-div
           Enable or disable emitting "mul", "mulx" and "div" family of
           instructions by the compiler. The default is to emit "mul" and
           not emit "div" and "mulx".

       -mbmx
       -mno-bmx
       -mcdx
       -mno-cdx
           Enable or disable generation of Nios II R2 BMX (bit manipulation)
           and CDX (code density) instructions.  Enabling these instructions
           also requires -march=r2.  Since these instructions are optional
           extensions to the R2 architecture, the default is not to emit
           them.

       -mcustom-insn=N
       -mno-custom-insn
           Each -mcustom-insn=N option enables use of a custom instruction
           with encoding N when generating code that uses insn.  For
           example, -mcustom-fadds=253 generates custom instruction 253 for
           single-precision floating-point add operations instead of the
           default behavior of using a library call.

           The following values of insn are supported.  Except as otherwise
           noted, floating-point operations are expected to be implemented
           with normal IEEE 754 semantics and correspond directly to the C
           operators or the equivalent GCC built-in functions.

           Single-precision floating point:

           fadds, fsubs, fdivs, fmuls
               Binary arithmetic operations.

           fnegs
               Unary negation.

           fabss
               Unary absolute value.

           fcmpeqs, fcmpges, fcmpgts, fcmples, fcmplts, fcmpnes
               Comparison operations.

           fmins, fmaxs
               Floating-point minimum and maximum.  These instructions are
               only generated if -ffinite-math-only is specified.

           fsqrts
               Unary square root operation.

           fcoss, fsins, ftans, fatans, fexps, flogs
               Floating-point trigonometric and exponential functions.
               These instructions are only generated if
               -funsafe-math-optimizations is also specified.

           Double-precision floating point:

           faddd, fsubd, fdivd, fmuld
               Binary arithmetic operations.

           fnegd
               Unary negation.

           fabsd
               Unary absolute value.

           fcmpeqd, fcmpged, fcmpgtd, fcmpled, fcmpltd, fcmpned
               Comparison operations.

           fmind, fmaxd
               Double-precision minimum and maximum.  These instructions are
               only generated if -ffinite-math-only is specified.

           fsqrtd
               Unary square root operation.

           fcosd, fsind, ftand, fatand, fexpd, flogd
               Double-precision trigonometric and exponential functions.
               These instructions are only generated if
               -funsafe-math-optimizations is also specified.

           Conversions:

           fextsd
               Conversion from single precision to double precision.

           ftruncds
               Conversion from double precision to single precision.

           fixsi, fixsu, fixdi, fixdu
               Conversion from floating point to signed or unsigned integer
               types, with truncation towards zero.

           round
               Conversion from single-precision floating point to signed
               integer, rounding to the nearest integer and ties away from
               zero.  This corresponds to the "__builtin_lroundf" function
               when -fno-math-errno is used.

           floatis, floatus, floatid, floatud
               Conversion from signed or unsigned integer types to floating-
               point types.

           In addition, all of the following transfer instructions for
           internal registers X and Y must be provided to use any of the
           double-precision floating-point instructions.  Custom
           instructions taking two double-precision source operands expect
           the first operand in the 64-bit register X.  The other operand
           (or only operand of a unary operation) is given to the custom
           arithmetic instruction with the least significant half in source
           register src1 and the most significant half in src2.  A custom
           instruction that returns a double-precision result returns the
           most significant 32 bits in the destination register and the
           other half in 32-bit register Y.  GCC automatically generates the
           necessary code sequences to write register X and/or read register
           Y when double-precision floating-point instructions are used.

           fwrx
               Write src1 into the least significant half of X and src2 into
               the most significant half of X.

           fwry
               Write src1 into Y.

           frdxhi, frdxlo
               Read the most or least (respectively) significant half of X
               and store it in dest.

           frdy
               Read the value of Y and store it into dest.

           Note that you can gain more local control over generation of Nios
           II custom instructions by using the "target("custom-insn=N")" and
           "target("no-custom-insn")" function attributes or pragmas.

       -mcustom-fpu-cfg=name
           This option enables a predefined, named set of custom instruction
           encodings (see -mcustom-insn above).  Currently, the following
           sets are defined:

           -mcustom-fpu-cfg=60-1 is equivalent to: -mcustom-fmuls=252
           -mcustom-fadds=253 -mcustom-fsubs=254 -fsingle-precision-constant

           -mcustom-fpu-cfg=60-2 is equivalent to: -mcustom-fmuls=252
           -mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255
           -fsingle-precision-constant

           -mcustom-fpu-cfg=72-3 is equivalent to: -mcustom-floatus=243
           -mcustom-fixsi=244 -mcustom-floatis=245 -mcustom-fcmpgts=246
           -mcustom-fcmples=249 -mcustom-fcmpeqs=250 -mcustom-fcmpnes=251
           -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254
           -mcustom-fdivs=255 -fsingle-precision-constant

           Custom instruction assignments given by individual -mcustom-insn=
           options override those given by -mcustom-fpu-cfg=, regardless of
           the order of the options on the command line.

           Note that you can gain more local control over selection of a FPU
           configuration by using the "target("custom-fpu-cfg=name")"
           function attribute or pragma.

       These additional -m options are available for the Altera Nios II ELF
       (bare-metal) target:

       -mhal
           Link with HAL BSP.  This suppresses linking with the GCC-provided
           C runtime startup and termination code, and is typically used in
           conjunction with -msys-crt0= to specify the location of the
           alternate startup code provided by the HAL BSP.

       -msmallc
           Link with a limited version of the C library, -lsmallc, rather
           than Newlib.

       -msys-crt0=startfile
           startfile is the file name of the startfile (crt0) to use when
           linking.  This option is only useful in conjunction with -mhal.

       -msys-lib=systemlib
           systemlib is the library name of the library that provides low-
           level system calls required by the C library, e.g. "read" and
           "write".  This option is typically used to link with a library
           provided by a HAL BSP.

       Nvidia PTX Options

       These options are defined for Nvidia PTX:

       -m32
       -m64
           Generate code for 32-bit or 64-bit ABI.

       -mmainkernel
           Link in code for a __main kernel.  This is for stand-alone
           instead of offloading execution.

       -moptimize
           Apply partitioned execution optimizations.  This is the default
           when any level of optimization is selected.

       PDP-11 Options

       These options are defined for the PDP-11:

       -mfpu
           Use hardware FPP floating point.  This is the default.  (FIS
           floating point on the PDP-11/40 is not supported.)

       -msoft-float
           Do not use hardware floating point.

       -mac0
           Return floating-point results in ac0 (fr0 in Unix assembler
           syntax).

       -mno-ac0
           Return floating-point results in memory.  This is the default.

       -m40
           Generate code for a PDP-11/40.

       -m45
           Generate code for a PDP-11/45.  This is the default.

       -m10
           Generate code for a PDP-11/10.

       -mbcopy-builtin
           Use inline "movmemhi" patterns for copying memory.  This is the
           default.

       -mbcopy
           Do not use inline "movmemhi" patterns for copying memory.

       -mint16
       -mno-int32
           Use 16-bit "int".  This is the default.

       -mint32
       -mno-int16
           Use 32-bit "int".

       -mfloat64
       -mno-float32
           Use 64-bit "float".  This is the default.

       -mfloat32
       -mno-float64
           Use 32-bit "float".

       -mabshi
           Use "abshi2" pattern.  This is the default.

       -mno-abshi
           Do not use "abshi2" pattern.

       -mbranch-expensive
           Pretend that branches are expensive.  This is for experimenting
           with code generation only.

       -mbranch-cheap
           Do not pretend that branches are expensive.  This is the default.

       -munix-asm
           Use Unix assembler syntax.  This is the default when configured
           for pdp11-*-bsd.

       -mdec-asm
           Use DEC assembler syntax.  This is the default when configured
           for any PDP-11 target other than pdp11-*-bsd.

       picoChip Options

       These -m options are defined for picoChip implementations:

       -mae=ae_type
           Set the instruction set, register set, and instruction scheduling
           parameters for array element type ae_type.  Supported values for
           ae_type are ANY, MUL, and MAC.

           -mae=ANY selects a completely generic AE type.  Code generated
           with this option runs on any of the other AE types.  The code is
           not as efficient as it would be if compiled for a specific AE
           type, and some types of operation (e.g., multiplication) do not
           work properly on all types of AE.

           -mae=MUL selects a MUL AE type.  This is the most useful AE type
           for compiled code, and is the default.

           -mae=MAC selects a DSP-style MAC AE.  Code compiled with this
           option may suffer from poor performance of byte (char)
           manipulation, since the DSP AE does not provide hardware support
           for byte load/stores.

       -msymbol-as-address
           Enable the compiler to directly use a symbol name as an address
           in a load/store instruction, without first loading it into a
           register.  Typically, the use of this option generates larger
           programs, which run faster than when the option isn't used.
           However, the results vary from program to program, so it is left
           as a user option, rather than being permanently enabled.

       -mno-inefficient-warnings
           Disables warnings about the generation of inefficient code.
           These warnings can be generated, for example, when compiling code
           that performs byte-level memory operations on the MAC AE type.
           The MAC AE has no hardware support for byte-level memory
           operations, so all byte load/stores must be synthesized from word
           load/store operations.  This is inefficient and a warning is
           generated to indicate that you should rewrite the code to avoid
           byte operations, or to target an AE type that has the necessary
           hardware support.  This option disables these warnings.

       PowerPC Options

       These are listed under

       RL78 Options

       -msim
           Links in additional target libraries to support operation within
           a simulator.

       -mmul=none
       -mmul=g10
       -mmul=g13
       -mmul=g14
       -mmul=rl78
           Specifies the type of hardware multiplication and division
           support to be used.  The simplest is "none", which uses software
           for both multiplication and division.  This is the default.  The
           "g13" value is for the hardware multiply/divide peripheral found
           on the RL78/G13 (S2 core) targets.  The "g14" value selects the
           use of the multiplication and division instructions supported by
           the RL78/G14 (S3 core) parts.  The value "rl78" is an alias for
           "g14" and the value "mg10" is an alias for "none".

           In addition a C preprocessor macro is defined, based upon the
           setting of this option.  Possible values are:
           "__RL78_MUL_NONE__", "__RL78_MUL_G13__" or "__RL78_MUL_G14__".

       -mcpu=g10
       -mcpu=g13
       -mcpu=g14
       -mcpu=rl78
           Specifies the RL78 core to target.  The default is the G14 core,
           also known as an S3 core or just RL78.  The G13 or S2 core does
           not have multiply or divide instructions, instead it uses a
           hardware peripheral for these operations.  The G10 or S1 core
           does not have register banks, so it uses a different calling
           convention.

           If this option is set it also selects the type of hardware
           multiply support to use, unless this is overridden by an explicit
           -mmul=none option on the command line.  Thus specifying -mcpu=g13
           enables the use of the G13 hardware multiply peripheral and
           specifying -mcpu=g10 disables the use of hardware multiplications
           altogether.

           Note, although the RL78/G14 core is the default target,
           specifying -mcpu=g14 or -mcpu=rl78 on the command line does
           change the behavior of the toolchain since it also enables G14
           hardware multiply support.  If these options are not specified on
           the command line then software multiplication routines will be
           used even though the code targets the RL78 core.  This is for
           backwards compatibility with older toolchains which did not have
           hardware multiply and divide support.

           In addition a C preprocessor macro is defined, based upon the
           setting of this option.  Possible values are: "__RL78_G10__",
           "__RL78_G13__" or "__RL78_G14__".

       -mg10
       -mg13
       -mg14
       -mrl78
           These are aliases for the corresponding -mcpu= option.  They are
           provided for backwards compatibility.

       -mallregs
           Allow the compiler to use all of the available registers.  By
           default registers "r24..r31" are reserved for use in interrupt
           handlers.  With this option enabled these registers can be used
           in ordinary functions as well.

       -m64bit-doubles
       -m32bit-doubles
           Make the "double" data type be 64 bits (-m64bit-doubles) or 32
           bits (-m32bit-doubles) in size.  The default is -m32bit-doubles.

       IBM RS/6000 and PowerPC Options

       These -m options are defined for the IBM RS/6000 and PowerPC:

       -mpowerpc-gpopt
       -mno-powerpc-gpopt
       -mpowerpc-gfxopt
       -mno-powerpc-gfxopt
       -mpowerpc64
       -mno-powerpc64
       -mmfcrf
       -mno-mfcrf
       -mpopcntb
       -mno-popcntb
       -mpopcntd
       -mno-popcntd
       -mfprnd
       -mno-fprnd
       -mcmpb
       -mno-cmpb
       -mmfpgpr
       -mno-mfpgpr
       -mhard-dfp
       -mno-hard-dfp
           You use these options to specify which instructions are available
           on the processor you are using.  The default value of these
           options is determined when configuring GCC.  Specifying the
           -mcpu=cpu_type overrides the specification of these options.  We
           recommend you use the -mcpu=cpu_type option rather than the
           options listed above.

           Specifying -mpowerpc-gpopt allows GCC to use the optional PowerPC
           architecture instructions in the General Purpose group, including
           floating-point square root.  Specifying -mpowerpc-gfxopt allows
           GCC to use the optional PowerPC architecture instructions in the
           Graphics group, including floating-point select.

           The -mmfcrf option allows GCC to generate the move from condition
           register field instruction implemented on the POWER4 processor
           and other processors that support the PowerPC V2.01 architecture.
           The -mpopcntb option allows GCC to generate the popcount and
           double-precision FP reciprocal estimate instruction implemented
           on the POWER5 processor and other processors that support the
           PowerPC V2.02 architecture.  The -mpopcntd option allows GCC to
           generate the popcount instruction implemented on the POWER7
           processor and other processors that support the PowerPC V2.06
           architecture.  The -mfprnd option allows GCC to generate the FP
           round to integer instructions implemented on the POWER5+
           processor and other processors that support the PowerPC V2.03
           architecture.  The -mcmpb option allows GCC to generate the
           compare bytes instruction implemented on the POWER6 processor and
           other processors that support the PowerPC V2.05 architecture.
           The -mmfpgpr option allows GCC to generate the FP move to/from
           general-purpose register instructions implemented on the POWER6X
           processor and other processors that support the extended PowerPC
           V2.05 architecture.  The -mhard-dfp option allows GCC to generate
           the decimal floating-point instructions implemented on some POWER
           processors.

           The -mpowerpc64 option allows GCC to generate the additional
           64-bit instructions that are found in the full PowerPC64
           architecture and to treat GPRs as 64-bit, doubleword quantities.
           GCC defaults to -mno-powerpc64.

       -mcpu=cpu_type
           Set architecture type, register usage, and instruction scheduling
           parameters for machine type cpu_type.  Supported values for
           cpu_type are 401, 403, 405, 405fp, 440, 440fp, 464, 464fp, 476,
           476fp, 505, 601, 602, 603, 603e, 604, 604e, 620, 630, 740, 7400,
           7450, 750, 801, 821, 823, 860, 970, 8540, a2, e300c2, e300c3,
           e500mc, e500mc64, e5500, e6500, ec603e, G3, G4, G5, titan,
           power3, power4, power5, power5+, power6, power6x, power7, power8,
           power9, powerpc, powerpc64, powerpc64le, and rs64.

           -mcpu=powerpc, -mcpu=powerpc64, and -mcpu=powerpc64le specify
           pure 32-bit PowerPC (either endian), 64-bit big endian PowerPC
           and 64-bit little endian PowerPC architecture machine types, with
           an appropriate, generic processor model assumed for scheduling
           purposes.

           The other options specify a specific processor.  Code generated
           under those options runs best on that processor, and may not run
           at all on others.

           The -mcpu options automatically enable or disable the following
           options:

           -maltivec  -mfprnd  -mhard-float  -mmfcrf  -mmultiple -mpopcntb
           -mpopcntd  -mpowerpc64 -mpowerpc-gpopt  -mpowerpc-gfxopt
           -msingle-float -mdouble-float -msimple-fpu -mstring  -mmulhw
           -mdlmzb  -mmfpgpr -mvsx -mcrypto -mdirect-move -mhtm
           -mpower8-fusion -mpower8-vector -mquad-memory
           -mquad-memory-atomic -mmodulo -mfloat128 -mfloat128-hardware
           -mpower9-fusion -mpower9-vector -mpower9-dform

           The particular options set for any particular CPU varies between
           compiler versions, depending on what setting seems to produce
           optimal code for that CPU; it doesn't necessarily reflect the
           actual hardware's capabilities.  If you wish to set an individual
           option to a particular value, you may specify it after the -mcpu
           option, like -mcpu=970 -mno-altivec.

           On AIX, the -maltivec and -mpowerpc64 options are not enabled or
           disabled by the -mcpu option at present because AIX does not have
           full support for these options.  You may still enable or disable
           them individually if you're sure it'll work in your environment.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type
           cpu_type, but do not set the architecture type or register usage,
           as -mcpu=cpu_type does.  The same values for cpu_type are used
           for -mtune as for -mcpu.  If both are specified, the code
           generated uses the architecture and registers set by -mcpu, but
           the scheduling parameters set by -mtune.

       -mcmodel=small
           Generate PowerPC64 code for the small model: The TOC is limited
           to 64k.

       -mcmodel=medium
           Generate PowerPC64 code for the medium model: The TOC and other
           static data may be up to a total of 4G in size.

       -mcmodel=large
           Generate PowerPC64 code for the large model: The TOC may be up to
           4G in size.  Other data and code is only limited by the 64-bit
           address space.

       -maltivec
       -mno-altivec
           Generate code that uses (does not use) AltiVec instructions, and
           also enable the use of built-in functions that allow more direct
           access to the AltiVec instruction set.  You may also need to set
           -mabi=altivec to adjust the current ABI with AltiVec ABI
           enhancements.

           When -maltivec is used, rather than -maltivec=le or -maltivec=be,
           the element order for AltiVec intrinsics such as "vec_splat",
           "vec_extract", and "vec_insert" match array element order
           corresponding to the endianness of the target.  That is, element
           zero identifies the leftmost element in a vector register when
           targeting a big-endian platform, and identifies the rightmost
           element in a vector register when targeting a little-endian
           platform.

       -maltivec=be
           Generate AltiVec instructions using big-endian element order,
           regardless of whether the target is big- or little-endian.  This
           is the default when targeting a big-endian platform.

           The element order is used to interpret element numbers in AltiVec
           intrinsics such as "vec_splat", "vec_extract", and "vec_insert".
           By default, these match array element order corresponding to the
           endianness for the target.

       -maltivec=le
           Generate AltiVec instructions using little-endian element order,
           regardless of whether the target is big- or little-endian.  This
           is the default when targeting a little-endian platform.  This
           option is currently ignored when targeting a big-endian platform.

           The element order is used to interpret element numbers in AltiVec
           intrinsics such as "vec_splat", "vec_extract", and "vec_insert".
           By default, these match array element order corresponding to the
           endianness for the target.

       -mvrsave
       -mno-vrsave
           Generate VRSAVE instructions when generating AltiVec code.

       -mgen-cell-microcode
           Generate Cell microcode instructions.

       -mwarn-cell-microcode
           Warn when a Cell microcode instruction is emitted.  An example of
           a Cell microcode instruction is a variable shift.

       -msecure-plt
           Generate code that allows ld and ld.so to build executables and
           shared libraries with non-executable ".plt" and ".got" sections.
           This is a PowerPC 32-bit SYSV ABI option.

       -mbss-plt
           Generate code that uses a BSS ".plt" section that ld.so fills in,
           and requires ".plt" and ".got" sections that are both writable
           and executable.  This is a PowerPC 32-bit SYSV ABI option.

       -misel
       -mno-isel
           This switch enables or disables the generation of ISEL
           instructions.

       -misel=yes/no
           This switch has been deprecated.  Use -misel and -mno-isel
           instead.

       -mlra
           Enable Local Register Allocation.  This is still experimental for
           PowerPC, so by default the compiler uses standard reload (i.e.
           -mno-lra).

       -mspe
       -mno-spe
           This switch enables or disables the generation of SPE simd
           instructions.

       -mpaired
       -mno-paired
           This switch enables or disables the generation of PAIRED simd
           instructions.

       -mspe=yes/no
           This option has been deprecated.  Use -mspe and -mno-spe instead.

       -mvsx
       -mno-vsx
           Generate code that uses (does not use) vector/scalar (VSX)
           instructions, and also enable the use of built-in functions that
           allow more direct access to the VSX instruction set.

       -mcrypto
       -mno-crypto
           Enable the use (disable) of the built-in functions that allow
           direct access to the cryptographic instructions that were added
           in version 2.07 of the PowerPC ISA.

       -mdirect-move
       -mno-direct-move
           Generate code that uses (does not use) the instructions to move
           data between the general purpose registers and the vector/scalar
           (VSX) registers that were added in version 2.07 of the PowerPC
           ISA.

       -mhtm
       -mno-htm
           Enable (disable) the use of the built-in functions that allow
           direct access to the Hardware Transactional Memory (HTM)
           instructions that were added in version 2.07 of the PowerPC ISA.

       -mpower8-fusion
       -mno-power8-fusion
           Generate code that keeps (does not keeps) some integer operations
           adjacent so that the instructions can be fused together on power8
           and later processors.

       -mpower8-vector
       -mno-power8-vector
           Generate code that uses (does not use) the vector and scalar
           instructions that were added in version 2.07 of the PowerPC ISA.
           Also enable the use of built-in functions that allow more direct
           access to the vector instructions.

       -mquad-memory
       -mno-quad-memory
           Generate code that uses (does not use) the non-atomic quad word
           memory instructions.  The -mquad-memory option requires use of
           64-bit mode.

       -mquad-memory-atomic
       -mno-quad-memory-atomic
           Generate code that uses (does not use) the atomic quad word
           memory instructions.  The -mquad-memory-atomic option requires
           use of 64-bit mode.

       -mupper-regs-df
       -mno-upper-regs-df
           Generate code that uses (does not use) the scalar double
           precision instructions that target all 64 registers in the
           vector/scalar floating point register set that were added in
           version 2.06 of the PowerPC ISA.  -mupper-regs-df is turned on by
           default if you use any of the -mcpu=power7, -mcpu=power8, or
           -mvsx options.

       -mupper-regs-sf
       -mno-upper-regs-sf
           Generate code that uses (does not use) the scalar single
           precision instructions that target all 64 registers in the
           vector/scalar floating point register set that were added in
           version 2.07 of the PowerPC ISA.  -mupper-regs-sf is turned on by
           default if you use either of the -mcpu=power8 or -mpower8-vector
           options.

       -mupper-regs
       -mno-upper-regs
           Generate code that uses (does not use) the scalar instructions
           that target all 64 registers in the vector/scalar floating point
           register set, depending on the model of the machine.

           If the -mno-upper-regs option is used, it turns off both
           -mupper-regs-sf and -mupper-regs-df options.

       -mfloat128
       -mno-float128
           Enable/disable the __float128 keyword for IEEE 128-bit floating
           point and use either software emulation for IEEE 128-bit floating
           point or hardware instructions.

           The VSX instruction set (-mvsx, -mcpu=power7, or -mcpu=power8)
           must be enabled to use the -mfloat128 option.  The -mfloat128
           option only works on PowerPC 64-bit Linux systems.

           If you use the ISA 3.0 instruction set (-mcpu=power9), the
           -mfloat128 option will also enable the generation of ISA 3.0 IEEE
           128-bit floating point instructions.  Otherwise, IEEE 128-bit
           floating point will be done with software emulation.

       -mfloat128-hardware
       -mno-float128-hardware
           Enable/disable using ISA 3.0 hardware instructions to support the
           __float128 data type.

           If you use -mfloat128-hardware, it will enable the option
           -mfloat128 as well.

           If you select ISA 3.0 instructions with -mcpu=power9, but do not
           use either -mfloat128 or -mfloat128-hardware, the IEEE 128-bit
           floating point support will not be enabled.

       -mmodulo
       -mno-modulo
           Generate code that uses (does not use) the ISA 3.0 integer modulo
           instructions.  The -mmodulo option is enabled by default with the
           -mcpu=power9 option.

       -mpower9-fusion
       -mno-power9-fusion
           Generate code that keeps (does not keeps) some operations
           adjacent so that the instructions can be fused together on power9
           and later processors.

       -mpower9-vector
       -mno-power9-vector
           Generate code that uses (does not use) the vector and scalar
           instructions that were added in version 3.0 of the PowerPC ISA.
           Also enable the use of built-in functions that allow more direct
           access to the vector instructions.

       -mpower9-dform
       -mno-power9-dform
           Enable (disable) scalar d-form (register + offset) memory
           instructions to load/store traditional Altivec registers. If the
           LRA register allocator is enabled, also enable (disable) vector
           d-form memory instructions.

       -mfloat-gprs=yes/single/double/no
       -mfloat-gprs
           This switch enables or disables the generation of floating-point
           operations on the general-purpose registers for architectures
           that support it.

           The argument yes or single enables the use of single-precision
           floating-point operations.

           The argument double enables the use of single and double-
           precision floating-point operations.

           The argument no disables floating-point operations on the
           general-purpose registers.

           This option is currently only available on the MPC854x.

       -m32
       -m64
           Generate code for 32-bit or 64-bit environments of Darwin and
           SVR4 targets (including GNU/Linux).  The 32-bit environment sets
           int, long and pointer to 32 bits and generates code that runs on
           any PowerPC variant.  The 64-bit environment sets int to 32 bits
           and long and pointer to 64 bits, and generates code for
           PowerPC64, as for -mpowerpc64.

       -mfull-toc
       -mno-fp-in-toc
       -mno-sum-in-toc
       -mminimal-toc
           Modify generation of the TOC (Table Of Contents), which is
           created for every executable file.  The -mfull-toc option is
           selected by default.  In that case, GCC allocates at least one
           TOC entry for each unique non-automatic variable reference in
           your program.  GCC also places floating-point constants in the
           TOC.  However, only 16,384 entries are available in the TOC.

           If you receive a linker error message that saying you have
           overflowed the available TOC space, you can reduce the amount of
           TOC space used with the -mno-fp-in-toc and -mno-sum-in-toc
           options.  -mno-fp-in-toc prevents GCC from putting floating-point
           constants in the TOC and -mno-sum-in-toc forces GCC to generate
           code to calculate the sum of an address and a constant at run
           time instead of putting that sum into the TOC.  You may specify
           one or both of these options.  Each causes GCC to produce very
           slightly slower and larger code at the expense of conserving TOC
           space.

           If you still run out of space in the TOC even when you specify
           both of these options, specify -mminimal-toc instead.  This
           option causes GCC to make only one TOC entry for every file.
           When you specify this option, GCC produces code that is slower
           and larger but which uses extremely little TOC space.  You may
           wish to use this option only on files that contain less
           frequently-executed code.

       -maix64
       -maix32
           Enable 64-bit AIX ABI and calling convention: 64-bit pointers,
           64-bit "long" type, and the infrastructure needed to support
           them.  Specifying -maix64 implies -mpowerpc64, while -maix32
           disables the 64-bit ABI and implies -mno-powerpc64.  GCC defaults
           to -maix32.

       -mxl-compat
       -mno-xl-compat
           Produce code that conforms more closely to IBM XL compiler
           semantics when using AIX-compatible ABI.  Pass floating-point
           arguments to prototyped functions beyond the register save area
           (RSA) on the stack in addition to argument FPRs.  Do not assume
           that most significant double in 128-bit long double value is
           properly rounded when comparing values and converting to double.
           Use XL symbol names for long double support routines.

           The AIX calling convention was extended but not initially
           documented to handle an obscure K&R C case of calling a function
           that takes the address of its arguments with fewer arguments than
           declared.  IBM XL compilers access floating-point arguments that
           do not fit in the RSA from the stack when a subroutine is
           compiled without optimization.  Because always storing floating-
           point arguments on the stack is inefficient and rarely needed,
           this option is not enabled by default and only is necessary when
           calling subroutines compiled by IBM XL compilers without
           optimization.

       -mpe
           Support IBM RS/6000 SP Parallel Environment (PE).  Link an
           application written to use message passing with special startup
           code to enable the application to run.  The system must have PE
           installed in the standard location (/usr/lpp/ppe.poe/), or the
           specs file must be overridden with the -specs= option to specify
           the appropriate directory location.  The Parallel Environment
           does not support threads, so the -mpe option and the -pthread
           option are incompatible.

       -malign-natural
       -malign-power
           On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option
           -malign-natural overrides the ABI-defined alignment of larger
           types, such as floating-point doubles, on their natural size-
           based boundary.  The option -malign-power instructs GCC to follow
           the ABI-specified alignment rules.  GCC defaults to the standard
           alignment defined in the ABI.

           On 64-bit Darwin, natural alignment is the default, and
           -malign-power is not supported.

       -msoft-float
       -mhard-float
           Generate code that does not use (uses) the floating-point
           register set.  Software floating-point emulation is provided if
           you use the -msoft-float option, and pass the option to GCC when
           linking.

       -msingle-float
       -mdouble-float
           Generate code for single- or double-precision floating-point
           operations.  -mdouble-float implies -msingle-float.

       -msimple-fpu
           Do not generate "sqrt" and "div" instructions for hardware
           floating-point unit.

       -mfpu=name
           Specify type of floating-point unit.  Valid values for name are
           sp_lite (equivalent to -msingle-float -msimple-fpu), dp_lite
           (equivalent to -mdouble-float -msimple-fpu), sp_full (equivalent
           to -msingle-float), and dp_full (equivalent to -mdouble-float).

       -mxilinx-fpu
           Perform optimizations for the floating-point unit on Xilinx PPC
           405/440.

       -mmultiple
       -mno-multiple
           Generate code that uses (does not use) the load multiple word
           instructions and the store multiple word instructions.  These
           instructions are generated by default on POWER systems, and not
           generated on PowerPC systems.  Do not use -mmultiple on little-
           endian PowerPC systems, since those instructions do not work when
           the processor is in little-endian mode.  The exceptions are
           PPC740 and PPC750 which permit these instructions in little-
           endian mode.

       -mstring
       -mno-string
           Generate code that uses (does not use) the load string
           instructions and the store string word instructions to save
           multiple registers and do small block moves.  These instructions
           are generated by default on POWER systems, and not generated on
           PowerPC systems.  Do not use -mstring on little-endian PowerPC
           systems, since those instructions do not work when the processor
           is in little-endian mode.  The exceptions are PPC740 and PPC750
           which permit these instructions in little-endian mode.

       -mupdate
       -mno-update
           Generate code that uses (does not use) the load or store
           instructions that update the base register to the address of the
           calculated memory location.  These instructions are generated by
           default.  If you use -mno-update, there is a small window between
           the time that the stack pointer is updated and the address of the
           previous frame is stored, which means code that walks the stack
           frame across interrupts or signals may get corrupted data.

       -mavoid-indexed-addresses
       -mno-avoid-indexed-addresses
           Generate code that tries to avoid (not avoid) the use of indexed
           load or store instructions. These instructions can incur a
           performance penalty on Power6 processors in certain situations,
           such as when stepping through large arrays that cross a 16M
           boundary.  This option is enabled by default when targeting
           Power6 and disabled otherwise.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating-point
           multiply and accumulate instructions.  These instructions are
           generated by default if hardware floating point is used.  The
           machine-dependent -mfused-madd option is now mapped to the
           machine-independent -ffp-contract=fast option, and
           -mno-fused-madd is mapped to -ffp-contract=off.

       -mmulhw
       -mno-mulhw
           Generate code that uses (does not use) the half-word multiply and
           multiply-accumulate instructions on the IBM 405, 440, 464 and 476
           processors.  These instructions are generated by default when
           targeting those processors.

       -mdlmzb
       -mno-dlmzb
           Generate code that uses (does not use) the string-search dlmzb
           instruction on the IBM 405, 440, 464 and 476 processors.  This
           instruction is generated by default when targeting those
           processors.

       -mno-bit-align
       -mbit-align
           On System V.4 and embedded PowerPC systems do not (do) force
           structures and unions that contain bit-fields to be aligned to
           the base type of the bit-field.

           For example, by default a structure containing nothing but 8
           "unsigned" bit-fields of length 1 is aligned to a 4-byte boundary
           and has a size of 4 bytes.  By using -mno-bit-align, the
           structure is aligned to a 1-byte boundary and is 1 byte in size.

       -mno-strict-align
       -mstrict-align
           On System V.4 and embedded PowerPC systems do not (do) assume
           that unaligned memory references are handled by the system.

       -mrelocatable
       -mno-relocatable
           Generate code that allows (does not allow) a static executable to
           be relocated to a different address at run time.  A simple
           embedded PowerPC system loader should relocate the entire
           contents of ".got2" and 4-byte locations listed in the ".fixup"
           section, a table of 32-bit addresses generated by this option.
           For this to work, all objects linked together must be compiled
           with -mrelocatable or -mrelocatable-lib.  -mrelocatable code
           aligns the stack to an 8-byte boundary.

       -mrelocatable-lib
       -mno-relocatable-lib
           Like -mrelocatable, -mrelocatable-lib generates a ".fixup"
           section to allow static executables to be relocated at run time,
           but -mrelocatable-lib does not use the smaller stack alignment of
           -mrelocatable.  Objects compiled with -mrelocatable-lib may be
           linked with objects compiled with any combination of the
           -mrelocatable options.

       -mno-toc
       -mtoc
           On System V.4 and embedded PowerPC systems do not (do) assume
           that register 2 contains a pointer to a global area pointing to
           the addresses used in the program.

       -mlittle
       -mlittle-endian
           On System V.4 and embedded PowerPC systems compile code for the
           processor in little-endian mode.  The -mlittle-endian option is
           the same as -mlittle.

       -mbig
       -mbig-endian
           On System V.4 and embedded PowerPC systems compile code for the
           processor in big-endian mode.  The -mbig-endian option is the
           same as -mbig.

       -mdynamic-no-pic
           On Darwin and Mac OS X systems, compile code so that it is not
           relocatable, but that its external references are relocatable.
           The resulting code is suitable for applications, but not shared
           libraries.

       -msingle-pic-base
           Treat the register used for PIC addressing as read-only, rather
           than loading it in the prologue for each function.  The runtime
           system is responsible for initializing this register with an
           appropriate value before execution begins.

       -mprioritize-restricted-insns=priority
           This option controls the priority that is assigned to dispatch-
           slot restricted instructions during the second scheduling pass.
           The argument priority takes the value 0, 1, or 2 to assign no,
           highest, or second-highest (respectively) priority to dispatch-
           slot restricted instructions.

       -msched-costly-dep=dependence_type
           This option controls which dependences are considered costly by
           the target during instruction scheduling.  The argument
           dependence_type takes one of the following values:

           no  No dependence is costly.

           all All dependences are costly.

           true_store_to_load
               A true dependence from store to load is costly.

           store_to_load
               Any dependence from store to load is costly.

           number
               Any dependence for which the latency is greater than or equal
               to number is costly.

       -minsert-sched-nops=scheme
           This option controls which NOP insertion scheme is used during
           the second scheduling pass.  The argument scheme takes one of the
           following values:

           no  Don't insert NOPs.

           pad Pad with NOPs any dispatch group that has vacant issue slots,
               according to the scheduler's grouping.

           regroup_exact
               Insert NOPs to force costly dependent insns into separate
               groups.  Insert exactly as many NOPs as needed to force an
               insn to a new group, according to the estimated processor
               grouping.

           number
               Insert NOPs to force costly dependent insns into separate
               groups.  Insert number NOPs to force an insn to a new group.

       -mcall-sysv
           On System V.4 and embedded PowerPC systems compile code using
           calling conventions that adhere to the March 1995 draft of the
           System V Application Binary Interface, PowerPC processor
           supplement.  This is the default unless you configured GCC using
           powerpc-*-eabiaix.

       -mcall-sysv-eabi
       -mcall-eabi
           Specify both -mcall-sysv and -meabi options.

       -mcall-sysv-noeabi
           Specify both -mcall-sysv and -mno-eabi options.

       -mcall-aixdesc
           On System V.4 and embedded PowerPC systems compile code for the
           AIX operating system.

       -mcall-linux
           On System V.4 and embedded PowerPC systems compile code for the
           Linux-based GNU system.

       -mcall-freebsd
           On System V.4 and embedded PowerPC systems compile code for the
           FreeBSD operating system.

       -mcall-netbsd
           On System V.4 and embedded PowerPC systems compile code for the
           NetBSD operating system.

       -mcall-openbsd
           On System V.4 and embedded PowerPC systems compile code for the
           OpenBSD operating system.

       -maix-struct-return
           Return all structures in memory (as specified by the AIX ABI).

       -msvr4-struct-return
           Return structures smaller than 8 bytes in registers (as specified
           by the SVR4 ABI).

       -mabi=abi-type
           Extend the current ABI with a particular extension, or remove
           such extension.  Valid values are altivec, no-altivec, spe, no-
           spe, ibmlongdouble, ieeelongdouble, elfv1, elfv2.

       -mabi=spe
           Extend the current ABI with SPE ABI extensions.  This does not
           change the default ABI, instead it adds the SPE ABI extensions to
           the current ABI.

       -mabi=no-spe
           Disable Book-E SPE ABI extensions for the current ABI.

       -mabi=ibmlongdouble
           Change the current ABI to use IBM extended-precision long double.
           This is a PowerPC 32-bit SYSV ABI option.

       -mabi=ieeelongdouble
           Change the current ABI to use IEEE extended-precision long
           double.  This is a PowerPC 32-bit Linux ABI option.

       -mabi=elfv1
           Change the current ABI to use the ELFv1 ABI.  This is the default
           ABI for big-endian PowerPC 64-bit Linux.  Overriding the default
           ABI requires special system support and is likely to fail in
           spectacular ways.

       -mabi=elfv2
           Change the current ABI to use the ELFv2 ABI.  This is the default
           ABI for little-endian PowerPC 64-bit Linux.  Overriding the
           default ABI requires special system support and is likely to fail
           in spectacular ways.

       -mprototype
       -mno-prototype
           On System V.4 and embedded PowerPC systems assume that all calls
           to variable argument functions are properly prototyped.
           Otherwise, the compiler must insert an instruction before every
           non-prototyped call to set or clear bit 6 of the condition code
           register ("CR") to indicate whether floating-point values are
           passed in the floating-point registers in case the function takes
           variable arguments.  With -mprototype, only calls to prototyped
           variable argument functions set or clear the bit.

       -msim
           On embedded PowerPC systems, assume that the startup module is
           called sim-crt0.o and that the standard C libraries are libsim.a
           and libc.a.  This is the default for powerpc-*-eabisim
           configurations.

       -mmvme
           On embedded PowerPC systems, assume that the startup module is
           called crt0.o and the standard C libraries are libmvme.a and
           libc.a.

       -mads
           On embedded PowerPC systems, assume that the startup module is
           called crt0.o and the standard C libraries are libads.a and
           libc.a.

       -myellowknife
           On embedded PowerPC systems, assume that the startup module is
           called crt0.o and the standard C libraries are libyk.a and
           libc.a.

       -mvxworks
           On System V.4 and embedded PowerPC systems, specify that you are
           compiling for a VxWorks system.

       -memb
           On embedded PowerPC systems, set the "PPC_EMB" bit in the ELF
           flags header to indicate that eabi extended relocations are used.

       -meabi
       -mno-eabi
           On System V.4 and embedded PowerPC systems do (do not) adhere to
           the Embedded Applications Binary Interface (EABI), which is a set
           of modifications to the System V.4 specifications.  Selecting
           -meabi means that the stack is aligned to an 8-byte boundary, a
           function "__eabi" is called from "main" to set up the EABI
           environment, and the -msdata option can use both "r2" and "r13"
           to point to two separate small data areas.  Selecting -mno-eabi
           means that the stack is aligned to a 16-byte boundary, no EABI
           initialization function is called from "main", and the -msdata
           option only uses "r13" to point to a single small data area.  The
           -meabi option is on by default if you configured GCC using one of
           the powerpc*-*-eabi* options.

       -msdata=eabi
           On System V.4 and embedded PowerPC systems, put small initialized
           "const" global and static data in the ".sdata2" section, which is
           pointed to by register "r2".  Put small initialized non-"const"
           global and static data in the ".sdata" section, which is pointed
           to by register "r13".  Put small uninitialized global and static
           data in the ".sbss" section, which is adjacent to the ".sdata"
           section.  The -msdata=eabi option is incompatible with the
           -mrelocatable option.  The -msdata=eabi option also sets the
           -memb option.

       -msdata=sysv
           On System V.4 and embedded PowerPC systems, put small global and
           static data in the ".sdata" section, which is pointed to by
           register "r13".  Put small uninitialized global and static data
           in the ".sbss" section, which is adjacent to the ".sdata"
           section.  The -msdata=sysv option is incompatible with the
           -mrelocatable option.

       -msdata=default
       -msdata
           On System V.4 and embedded PowerPC systems, if -meabi is used,
           compile code the same as -msdata=eabi, otherwise compile code the
           same as -msdata=sysv.

       -msdata=data
           On System V.4 and embedded PowerPC systems, put small global data
           in the ".sdata" section.  Put small uninitialized global data in
           the ".sbss" section.  Do not use register "r13" to address small
           data however.  This is the default behavior unless other -msdata
           options are used.

       -msdata=none
       -mno-sdata
           On embedded PowerPC systems, put all initialized global and
           static data in the ".data" section, and all uninitialized data in
           the ".bss" section.

       -mblock-move-inline-limit=num
           Inline all block moves (such as calls to "memcpy" or structure
           copies) less than or equal to num bytes.  The minimum value for
           num is 32 bytes on 32-bit targets and 64 bytes on 64-bit targets.
           The default value is target-specific.

       -G num
           On embedded PowerPC systems, put global and static items less
           than or equal to num bytes into the small data or BSS sections
           instead of the normal data or BSS section.  By default, num is 8.
           The -G num switch is also passed to the linker.  All modules
           should be compiled with the same -G num value.

       -mregnames
       -mno-regnames
           On System V.4 and embedded PowerPC systems do (do not) emit
           register names in the assembly language output using symbolic
           forms.

       -mlongcall
       -mno-longcall
           By default assume that all calls are far away so that a longer
           and more expensive calling sequence is required.  This is
           required for calls farther than 32 megabytes (33,554,432 bytes)
           from the current location.  A short call is generated if the
           compiler knows the call cannot be that far away.  This setting
           can be overridden by the "shortcall" function attribute, or by
           "#pragma longcall(0)".

           Some linkers are capable of detecting out-of-range calls and
           generating glue code on the fly.  On these systems, long calls
           are unnecessary and generate slower code.  As of this writing,
           the AIX linker can do this, as can the GNU linker for PowerPC/64.
           It is planned to add this feature to the GNU linker for 32-bit
           PowerPC systems as well.

           On Darwin/PPC systems, "#pragma longcall" generates "jbsr callee,
           L42", plus a branch island (glue code).  The two target addresses
           represent the callee and the branch island.  The Darwin/PPC
           linker prefers the first address and generates a "bl callee" if
           the PPC "bl" instruction reaches the callee directly; otherwise,
           the linker generates "bl L42" to call the branch island.  The
           branch island is appended to the body of the calling function; it
           computes the full 32-bit address of the callee and jumps to it.

           On Mach-O (Darwin) systems, this option directs the compiler emit
           to the glue for every direct call, and the Darwin linker decides
           whether to use or discard it.

           In the future, GCC may ignore all longcall specifications when
           the linker is known to generate glue.

       -mtls-markers
       -mno-tls-markers
           Mark (do not mark) calls to "__tls_get_addr" with a relocation
           specifying the function argument.  The relocation allows the
           linker to reliably associate function call with argument setup
           instructions for TLS optimization, which in turn allows GCC to
           better schedule the sequence.

       -pthread
           Adds support for multithreading with the pthreads library.  This
           option sets flags for both the preprocessor and linker.

       -mrecip
       -mno-recip
           This option enables use of the reciprocal estimate and reciprocal
           square root estimate instructions with additional Newton-Raphson
           steps to increase precision instead of doing a divide or square
           root and divide for floating-point arguments.  You should use the
           -ffast-math option when using -mrecip (or at least
           -funsafe-math-optimizations, -ffinite-math-only,
           -freciprocal-math and -fno-trapping-math).  Note that while the
           throughput of the sequence is generally higher than the
           throughput of the non-reciprocal instruction, the precision of
           the sequence can be decreased by up to 2 ulp (i.e. the inverse of
           1.0 equals 0.99999994) for reciprocal square roots.

       -mrecip=opt
           This option controls which reciprocal estimate instructions may
           be used.  opt is a comma-separated list of options, which may be
           preceded by a "!" to invert the option:

           all Enable all estimate instructions.

           default
               Enable the default instructions, equivalent to -mrecip.

           none
               Disable all estimate instructions, equivalent to -mno-recip.

           div Enable the reciprocal approximation instructions for both
               single and double precision.

           divf
               Enable the single-precision reciprocal approximation
               instructions.

           divd
               Enable the double-precision reciprocal approximation
               instructions.

           rsqrt
               Enable the reciprocal square root approximation instructions
               for both single and double precision.

           rsqrtf
               Enable the single-precision reciprocal square root
               approximation instructions.

           rsqrtd
               Enable the double-precision reciprocal square root
               approximation instructions.

           So, for example, -mrecip=all,!rsqrtd enables all of the
           reciprocal estimate instructions, except for the "FRSQRTE",
           "XSRSQRTEDP", and "XVRSQRTEDP" instructions which handle the
           double-precision reciprocal square root calculations.

       -mrecip-precision
       -mno-recip-precision
           Assume (do not assume) that the reciprocal estimate instructions
           provide higher-precision estimates than is mandated by the
           PowerPC ABI.  Selecting -mcpu=power6, -mcpu=power7 or
           -mcpu=power8 automatically selects -mrecip-precision.  The
           double-precision square root estimate instructions are not
           generated by default on low-precision machines, since they do not
           provide an estimate that converges after three steps.

       -mveclibabi=type
           Specifies the ABI type to use for vectorizing intrinsics using an
           external library.  The only type supported at present is mass,
           which specifies to use IBM's Mathematical Acceleration Subsystem
           (MASS) libraries for vectorizing intrinsics using external
           libraries.  GCC currently emits calls to "acosd2", "acosf4",
           "acoshd2", "acoshf4", "asind2", "asinf4", "asinhd2", "asinhf4",
           "atan2d2", "atan2f4", "atand2", "atanf4", "atanhd2", "atanhf4",
           "cbrtd2", "cbrtf4", "cosd2", "cosf4", "coshd2", "coshf4",
           "erfcd2", "erfcf4", "erfd2", "erff4", "exp2d2", "exp2f4",
           "expd2", "expf4", "expm1d2", "expm1f4", "hypotd2", "hypotf4",
           "lgammad2", "lgammaf4", "log10d2", "log10f4", "log1pd2",
           "log1pf4", "log2d2", "log2f4", "logd2", "logf4", "powd2",
           "powf4", "sind2", "sinf4", "sinhd2", "sinhf4", "sqrtd2",
           "sqrtf4", "tand2", "tanf4", "tanhd2", and "tanhf4" when
           generating code for power7.  Both -ftree-vectorize and
           -funsafe-math-optimizations must also be enabled.  The MASS
           libraries must be specified at link time.

       -mfriz
       -mno-friz
           Generate (do not generate) the "friz" instruction when the
           -funsafe-math-optimizations option is used to optimize rounding
           of floating-point values to 64-bit integer and back to floating
           point.  The "friz" instruction does not return the same value if
           the floating-point number is too large to fit in an integer.

       -mpointers-to-nested-functions
       -mno-pointers-to-nested-functions
           Generate (do not generate) code to load up the static chain
           register ("r11") when calling through a pointer on AIX and 64-bit
           Linux systems where a function pointer points to a 3-word
           descriptor giving the function address, TOC value to be loaded in
           register "r2", and static chain value to be loaded in register
           "r11".  The -mpointers-to-nested-functions is on by default.  You
           cannot call through pointers to nested functions or pointers to
           functions compiled in other languages that use the static chain
           if you use -mno-pointers-to-nested-functions.

       -msave-toc-indirect
       -mno-save-toc-indirect
           Generate (do not generate) code to save the TOC value in the
           reserved stack location in the function prologue if the function
           calls through a pointer on AIX and 64-bit Linux systems.  If the
           TOC value is not saved in the prologue, it is saved just before
           the call through the pointer.  The -mno-save-toc-indirect option
           is the default.

       -mcompat-align-parm
       -mno-compat-align-parm
           Generate (do not generate) code to pass structure parameters with
           a maximum alignment of 64 bits, for compatibility with older
           versions of GCC.

           Older versions of GCC (prior to 4.9.0) incorrectly did not align
           a structure parameter on a 128-bit boundary when that structure
           contained a member requiring 128-bit alignment.  This is
           corrected in more recent versions of GCC.  This option may be
           used to generate code that is compatible with functions compiled
           with older versions of GCC.

           The -mno-compat-align-parm option is the default.

       RX Options

       These command-line options are defined for RX targets:

       -m64bit-doubles
       -m32bit-doubles
           Make the "double" data type be 64 bits (-m64bit-doubles) or 32
           bits (-m32bit-doubles) in size.  The default is -m32bit-doubles.
           Note RX floating-point hardware only works on 32-bit values,
           which is why the default is -m32bit-doubles.

       -fpu
       -nofpu
           Enables (-fpu) or disables (-nofpu) the use of RX floating-point
           hardware.  The default is enabled for the RX600 series and
           disabled for the RX200 series.

           Floating-point instructions are only generated for 32-bit
           floating-point values, however, so the FPU hardware is not used
           for doubles if the -m64bit-doubles option is used.

           Note If the -fpu option is enabled then
           -funsafe-math-optimizations is also enabled automatically.  This
           is because the RX FPU instructions are themselves unsafe.

       -mcpu=name
           Selects the type of RX CPU to be targeted.  Currently three types
           are supported, the generic RX600 and RX200 series hardware and
           the specific RX610 CPU.  The default is RX600.

           The only difference between RX600 and RX610 is that the RX610
           does not support the "MVTIPL" instruction.

           The RX200 series does not have a hardware floating-point unit and
           so -nofpu is enabled by default when this type is selected.

       -mbig-endian-data
       -mlittle-endian-data
           Store data (but not code) in the big-endian format.  The default
           is -mlittle-endian-data, i.e. to store data in the little-endian
           format.

       -msmall-data-limit=N
           Specifies the maximum size in bytes of global and static
           variables which can be placed into the small data area.  Using
           the small data area can lead to smaller and faster code, but the
           size of area is limited and it is up to the programmer to ensure
           that the area does not overflow.  Also when the small data area
           is used one of the RX's registers (usually "r13") is reserved for
           use pointing to this area, so it is no longer available for use
           by the compiler.  This could result in slower and/or larger code
           if variables are pushed onto the stack instead of being held in
           this register.

           Note, common variables (variables that have not been initialized)
           and constants are not placed into the small data area as they are
           assigned to other sections in the output executable.

           The default value is zero, which disables this feature.  Note,
           this feature is not enabled by default with higher optimization
           levels (-O2 etc) because of the potentially detrimental effects
           of reserving a register.  It is up to the programmer to
           experiment and discover whether this feature is of benefit to
           their program.  See the description of the -mpid option for a
           description of how the actual register to hold the small data
           area pointer is chosen.

       -msim
       -mno-sim
           Use the simulator runtime.  The default is to use the libgloss
           board-specific runtime.

       -mas100-syntax
       -mno-as100-syntax
           When generating assembler output use a syntax that is compatible
           with Renesas's AS100 assembler.  This syntax can also be handled
           by the GAS assembler, but it has some restrictions so it is not
           generated by default.

       -mmax-constant-size=N
           Specifies the maximum size, in bytes, of a constant that can be
           used as an operand in a RX instruction.  Although the RX
           instruction set does allow constants of up to 4 bytes in length
           to be used in instructions, a longer value equates to a longer
           instruction.  Thus in some circumstances it can be beneficial to
           restrict the size of constants that are used in instructions.
           Constants that are too big are instead placed into a constant
           pool and referenced via register indirection.

           The value N can be between 0 and 4.  A value of 0 (the default)
           or 4 means that constants of any size are allowed.

       -mrelax
           Enable linker relaxation.  Linker relaxation is a process whereby
           the linker attempts to reduce the size of a program by finding
           shorter versions of various instructions.  Disabled by default.

       -mint-register=N
           Specify the number of registers to reserve for fast interrupt
           handler functions.  The value N can be between 0 and 4.  A value
           of 1 means that register "r13" is reserved for the exclusive use
           of fast interrupt handlers.  A value of 2 reserves "r13" and
           "r12".  A value of 3 reserves "r13", "r12" and "r11", and a value
           of 4 reserves "r13" through "r10".  A value of 0, the default,
           does not reserve any registers.

       -msave-acc-in-interrupts
           Specifies that interrupt handler functions should preserve the
           accumulator register.  This is only necessary if normal code
           might use the accumulator register, for example because it
           performs 64-bit multiplications.  The default is to ignore the
           accumulator as this makes the interrupt handlers faster.

       -mpid
       -mno-pid
           Enables the generation of position independent data.  When
           enabled any access to constant data is done via an offset from a
           base address held in a register.  This allows the location of
           constant data to be determined at run time without requiring the
           executable to be relocated, which is a benefit to embedded
           applications with tight memory constraints.  Data that can be
           modified is not affected by this option.

           Note, using this feature reserves a register, usually "r13", for
           the constant data base address.  This can result in slower and/or
           larger code, especially in complicated functions.

           The actual register chosen to hold the constant data base address
           depends upon whether the -msmall-data-limit and/or the
           -mint-register command-line options are enabled.  Starting with
           register "r13" and proceeding downwards, registers are allocated
           first to satisfy the requirements of -mint-register, then -mpid
           and finally -msmall-data-limit.  Thus it is possible for the
           small data area register to be "r8" if both -mint-register=4 and
           -mpid are specified on the command line.

           By default this feature is not enabled.  The default can be
           restored via the -mno-pid command-line option.

       -mno-warn-multiple-fast-interrupts
       -mwarn-multiple-fast-interrupts
           Prevents GCC from issuing a warning message if it finds more than
           one fast interrupt handler when it is compiling a file.  The
           default is to issue a warning for each extra fast interrupt
           handler found, as the RX only supports one such interrupt.

       -mallow-string-insns
       -mno-allow-string-insns
           Enables or disables the use of the string manipulation
           instructions "SMOVF", "SCMPU", "SMOVB", "SMOVU", "SUNTIL"
           "SWHILE" and also the "RMPA" instruction.  These instructions may
           prefetch data, which is not safe to do if accessing an I/O
           register.  (See section 12.2.7 of the RX62N Group User's Manual
           for more information).

           The default is to allow these instructions, but it is not
           possible for GCC to reliably detect all circumstances where a
           string instruction might be used to access an I/O register, so
           their use cannot be disabled automatically.  Instead it is
           reliant upon the programmer to use the -mno-allow-string-insns
           option if their program accesses I/O space.

           When the instructions are enabled GCC defines the C preprocessor
           symbol "__RX_ALLOW_STRING_INSNS__", otherwise it defines the
           symbol "__RX_DISALLOW_STRING_INSNS__".

       -mjsr
       -mno-jsr
           Use only (or not only) "JSR" instructions to access functions.
           This option can be used when code size exceeds the range of "BSR"
           instructions.  Note that -mno-jsr does not mean to not use "JSR"
           but instead means that any type of branch may be used.

       Note: The generic GCC command-line option -ffixed-reg has special
       significance to the RX port when used with the "interrupt" function
       attribute.  This attribute indicates a function intended to process
       fast interrupts.  GCC ensures that it only uses the registers "r10",
       "r11", "r12" and/or "r13" and only provided that the normal use of
       the corresponding registers have been restricted via the -ffixed-reg
       or -mint-register command-line options.

       S/390 and zSeries Options

       These are the -m options defined for the S/390 and zSeries
       architecture.

       -mhard-float
       -msoft-float
           Use (do not use) the hardware floating-point instructions and
           registers for floating-point operations.  When -msoft-float is
           specified, functions in libgcc.a are used to perform floating-
           point operations.  When -mhard-float is specified, the compiler
           generates IEEE floating-point instructions.  This is the default.

       -mhard-dfp
       -mno-hard-dfp
           Use (do not use) the hardware decimal-floating-point instructions
           for decimal-floating-point operations.  When -mno-hard-dfp is
           specified, functions in libgcc.a are used to perform decimal-
           floating-point operations.  When -mhard-dfp is specified, the
           compiler generates decimal-floating-point hardware instructions.
           This is the default for -march=z9-ec or higher.

       -mlong-double-64
       -mlong-double-128
           These switches control the size of "long double" type. A size of
           64 bits makes the "long double" type equivalent to the "double"
           type. This is the default.

       -mbackchain
       -mno-backchain
           Store (do not store) the address of the caller's frame as
           backchain pointer into the callee's stack frame.  A backchain may
           be needed to allow debugging using tools that do not understand
           DWARF call frame information.  When -mno-packed-stack is in
           effect, the backchain pointer is stored at the bottom of the
           stack frame; when -mpacked-stack is in effect, the backchain is
           placed into the topmost word of the 96/160 byte register save
           area.

           In general, code compiled with -mbackchain is call-compatible
           with code compiled with -mmo-backchain; however, use of the
           backchain for debugging purposes usually requires that the whole
           binary is built with -mbackchain.  Note that the combination of
           -mbackchain, -mpacked-stack and -mhard-float is not supported.
           In order to build a linux kernel use -msoft-float.

           The default is to not maintain the backchain.

       -mpacked-stack
       -mno-packed-stack
           Use (do not use) the packed stack layout.  When -mno-packed-stack
           is specified, the compiler uses the all fields of the 96/160 byte
           register save area only for their default purpose; unused fields
           still take up stack space.  When -mpacked-stack is specified,
           register save slots are densely packed at the top of the register
           save area; unused space is reused for other purposes, allowing
           for more efficient use of the available stack space.  However,
           when -mbackchain is also in effect, the topmost word of the save
           area is always used to store the backchain, and the return
           address register is always saved two words below the backchain.

           As long as the stack frame backchain is not used, code generated
           with -mpacked-stack is call-compatible with code generated with
           -mno-packed-stack.  Note that some non-FSF releases of GCC 2.95
           for S/390 or zSeries generated code that uses the stack frame
           backchain at run time, not just for debugging purposes.  Such
           code is not call-compatible with code compiled with
           -mpacked-stack.  Also, note that the combination of -mbackchain,
           -mpacked-stack and -mhard-float is not supported.  In order to
           build a linux kernel use -msoft-float.

           The default is to not use the packed stack layout.

       -msmall-exec
       -mno-small-exec
           Generate (or do not generate) code using the "bras" instruction
           to do subroutine calls.  This only works reliably if the total
           executable size does not exceed 64k.  The default is to use the
           "basr" instruction instead, which does not have this limitation.

       -m64
       -m31
           When -m31 is specified, generate code compliant to the GNU/Linux
           for S/390 ABI.  When -m64 is specified, generate code compliant
           to the GNU/Linux for zSeries ABI.  This allows GCC in particular
           to generate 64-bit instructions.  For the s390 targets, the
           default is -m31, while the s390x targets default to -m64.

       -mzarch
       -mesa
           When -mzarch is specified, generate code using the instructions
           available on z/Architecture.  When -mesa is specified, generate
           code using the instructions available on ESA/390.  Note that
           -mesa is not possible with -m64.  When generating code compliant
           to the GNU/Linux for S/390 ABI, the default is -mesa.  When
           generating code compliant to the GNU/Linux for zSeries ABI, the
           default is -mzarch.

       -mhtm
       -mno-htm
           The -mhtm option enables a set of builtins making use of
           instructions available with the transactional execution facility
           introduced with the IBM zEnterprise EC12 machine generation S/390
           System z Built-in Functions.  -mhtm is enabled by default when
           using -march=zEC12.

       -mvx
       -mno-vx
           When -mvx is specified, generate code using the instructions
           available with the vector extension facility introduced with the
           IBM z13 machine generation.  This option changes the ABI for some
           vector type values with regard to alignment and calling
           conventions.  In case vector type values are being used in an
           ABI-relevant context a GAS .gnu_attribute command will be added
           to mark the resulting binary with the ABI used.  -mvx is enabled
           by default when using -march=z13.

       -mzvector
       -mno-zvector
           The -mzvector option enables vector language extensions and
           builtins using instructions available with the vector extension
           facility introduced with the IBM z13 machine generation.  This
           option adds support for vector to be used as a keyword to define
           vector type variables and arguments.  vector is only available
           when GNU extensions are enabled.  It will not be expanded when
           requesting strict standard compliance e.g. with -std=c99.  In
           addition to the GCC low-level builtins -mzvector enables a set of
           builtins added for compatibility with AltiVec-style
           implementations like Power and Cell.  In order to make use of
           these builtins the header file vecintrin.h needs to be included.
           -mzvector is disabled by default.

       -mmvcle
       -mno-mvcle
           Generate (or do not generate) code using the "mvcle" instruction
           to perform block moves.  When -mno-mvcle is specified, use a
           "mvc" loop instead.  This is the default unless optimizing for
           size.

       -mdebug
       -mno-debug
           Print (or do not print) additional debug information when
           compiling.  The default is to not print debug information.

       -march=cpu-type
           Generate code that runs on cpu-type, which is the name of a
           system representing a certain processor type.  Possible values
           for cpu-type are z900, z990, z9-109, z9-ec, z10, z196, zEC12, and
           z13.  The default is -march=z900.  g5 and g6 are deprecated and
           will be removed with future releases.

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code,
           except for the ABI and the set of available instructions.  The
           list of cpu-type values is the same as for -march.  The default
           is the value used for -march.

       -mtpf-trace
       -mno-tpf-trace
           Generate code that adds (does not add) in TPF OS specific
           branches to trace routines in the operating system.  This option
           is off by default, even when compiling for the TPF OS.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating-point
           multiply and accumulate instructions.  These instructions are
           generated by default if hardware floating point is used.

       -mwarn-framesize=framesize
           Emit a warning if the current function exceeds the given frame
           size.  Because this is a compile-time check it doesn't need to be
           a real problem when the program runs.  It is intended to identify
           functions that most probably cause a stack overflow.  It is
           useful to be used in an environment with limited stack size e.g.
           the linux kernel.

       -mwarn-dynamicstack
           Emit a warning if the function calls "alloca" or uses
           dynamically-sized arrays.  This is generally a bad idea with a
           limited stack size.

       -mstack-guard=stack-guard
       -mstack-size=stack-size
           If these options are provided the S/390 back end emits additional
           instructions in the function prologue that trigger a trap if the
           stack size is stack-guard bytes above the stack-size (remember
           that the stack on S/390 grows downward).  If the stack-guard
           option is omitted the smallest power of 2 larger than the frame
           size of the compiled function is chosen.  These options are
           intended to be used to help debugging stack overflow problems.
           The additionally emitted code causes only little overhead and
           hence can also be used in production-like systems without greater
           performance degradation.  The given values have to be exact
           powers of 2 and stack-size has to be greater than stack-guard
           without exceeding 64k.  In order to be efficient the extra code
           makes the assumption that the stack starts at an address aligned
           to the value given by stack-size.  The stack-guard option can
           only be used in conjunction with stack-size.

       -mhotpatch=pre-halfwords,post-halfwords
           If the hotpatch option is enabled, a "hot-patching" function
           prologue is generated for all functions in the compilation unit.
           The funtion label is prepended with the given number of two-byte
           NOP instructions (pre-halfwords, maximum 1000000).  After the
           label, 2 * post-halfwords bytes are appended, using the largest
           NOP like instructions the architecture allows (maximum 1000000).

           If both arguments are zero, hotpatching is disabled.

           This option can be overridden for individual functions with the
           "hotpatch" attribute.

       Score Options

       These options are defined for Score implementations:

       -meb
           Compile code for big-endian mode.  This is the default.

       -mel
           Compile code for little-endian mode.

       -mnhwloop
           Disable generation of "bcnz" instructions.

       -muls
           Enable generation of unaligned load and store instructions.

       -mmac
           Enable the use of multiply-accumulate instructions. Disabled by
           default.

       -mscore5
           Specify the SCORE5 as the target architecture.

       -mscore5u
           Specify the SCORE5U of the target architecture.

       -mscore7
           Specify the SCORE7 as the target architecture. This is the
           default.

       -mscore7d
           Specify the SCORE7D as the target architecture.

       SH Options

       These -m options are defined for the SH implementations:

       -m1 Generate code for the SH1.

       -m2 Generate code for the SH2.

       -m2e
           Generate code for the SH2e.

       -m2a-nofpu
           Generate code for the SH2a without FPU, or for a SH2a-FPU in such
           a way that the floating-point unit is not used.

       -m2a-single-only
           Generate code for the SH2a-FPU, in such a way that no double-
           precision floating-point operations are used.

       -m2a-single
           Generate code for the SH2a-FPU assuming the floating-point unit
           is in single-precision mode by default.

       -m2a
           Generate code for the SH2a-FPU assuming the floating-point unit
           is in double-precision mode by default.

       -m3 Generate code for the SH3.

       -m3e
           Generate code for the SH3e.

       -m4-nofpu
           Generate code for the SH4 without a floating-point unit.

       -m4-single-only
           Generate code for the SH4 with a floating-point unit that only
           supports single-precision arithmetic.

       -m4-single
           Generate code for the SH4 assuming the floating-point unit is in
           single-precision mode by default.

       -m4 Generate code for the SH4.

       -m4-100
           Generate code for SH4-100.

       -m4-100-nofpu
           Generate code for SH4-100 in such a way that the floating-point
           unit is not used.

       -m4-100-single
           Generate code for SH4-100 assuming the floating-point unit is in
           single-precision mode by default.

       -m4-100-single-only
           Generate code for SH4-100 in such a way that no double-precision
           floating-point operations are used.

       -m4-200
           Generate code for SH4-200.

       -m4-200-nofpu
           Generate code for SH4-200 without in such a way that the
           floating-point unit is not used.

       -m4-200-single
           Generate code for SH4-200 assuming the floating-point unit is in
           single-precision mode by default.

       -m4-200-single-only
           Generate code for SH4-200 in such a way that no double-precision
           floating-point operations are used.

       -m4-300
           Generate code for SH4-300.

       -m4-300-nofpu
           Generate code for SH4-300 without in such a way that the
           floating-point unit is not used.

       -m4-300-single
           Generate code for SH4-300 in such a way that no double-precision
           floating-point operations are used.

       -m4-300-single-only
           Generate code for SH4-300 in such a way that no double-precision
           floating-point operations are used.

       -m4-340
           Generate code for SH4-340 (no MMU, no FPU).

       -m4-500
           Generate code for SH4-500 (no FPU).  Passes -isa=sh4-nofpu to the
           assembler.

       -m4a-nofpu
           Generate code for the SH4al-dsp, or for a SH4a in such a way that
           the floating-point unit is not used.

       -m4a-single-only
           Generate code for the SH4a, in such a way that no double-
           precision floating-point operations are used.

       -m4a-single
           Generate code for the SH4a assuming the floating-point unit is in
           single-precision mode by default.

       -m4a
           Generate code for the SH4a.

       -m4al
           Same as -m4a-nofpu, except that it implicitly passes -dsp to the
           assembler.  GCC doesn't generate any DSP instructions at the
           moment.

       -mb Compile code for the processor in big-endian mode.

       -ml Compile code for the processor in little-endian mode.

       -mdalign
           Align doubles at 64-bit boundaries.  Note that this changes the
           calling conventions, and thus some functions from the standard C
           library do not work unless you recompile it first with -mdalign.

       -mrelax
           Shorten some address references at link time, when possible; uses
           the linker option -relax.

       -mbigtable
           Use 32-bit offsets in "switch" tables.  The default is to use
           16-bit offsets.

       -mbitops
           Enable the use of bit manipulation instructions on SH2A.

       -mfmovd
           Enable the use of the instruction "fmovd".  Check -mdalign for
           alignment constraints.

       -mrenesas
           Comply with the calling conventions defined by Renesas.

       -mno-renesas
           Comply with the calling conventions defined for GCC before the
           Renesas conventions were available.  This option is the default
           for all targets of the SH toolchain.

       -mnomacsave
           Mark the "MAC" register as call-clobbered, even if -mrenesas is
           given.

       -mieee
       -mno-ieee
           Control the IEEE compliance of floating-point comparisons, which
           affects the handling of cases where the result of a comparison is
           unordered.  By default -mieee is implicitly enabled.  If
           -ffinite-math-only is enabled -mno-ieee is implicitly set, which
           results in faster floating-point greater-equal and less-equal
           comparisons.  The implicit settings can be overridden by
           specifying either -mieee or -mno-ieee.

       -minline-ic_invalidate
           Inline code to invalidate instruction cache entries after setting
           up nested function trampolines.  This option has no effect if
           -musermode is in effect and the selected code generation option
           (e.g. -m4) does not allow the use of the "icbi" instruction.  If
           the selected code generation option does not allow the use of the
           "icbi" instruction, and -musermode is not in effect, the inlined
           code manipulates the instruction cache address array directly
           with an associative write.  This not only requires privileged
           mode at run time, but it also fails if the cache line had been
           mapped via the TLB and has become unmapped.

       -misize
           Dump instruction size and location in the assembly code.

       -mpadstruct
           This option is deprecated.  It pads structures to multiple of 4
           bytes, which is incompatible with the SH ABI.

       -matomic-model=model
           Sets the model of atomic operations and additional parameters as
           a comma separated list.  For details on the atomic built-in
           functions see __atomic Builtins.  The following models and
           parameters are supported:

           none
               Disable compiler generated atomic sequences and emit library
               calls for atomic operations.  This is the default if the
               target is not "sh*-*-linux*".

           soft-gusa
               Generate GNU/Linux compatible gUSA software atomic sequences
               for the atomic built-in functions.  The generated atomic
               sequences require additional support from the
               interrupt/exception handling code of the system and are only
               suitable for SH3* and SH4* single-core systems.  This option
               is enabled by default when the target is "sh*-*-linux*" and
               SH3* or SH4*.  When the target is SH4A, this option also
               partially utilizes the hardware atomic instructions "movli.l"
               and "movco.l" to create more efficient code, unless strict is
               specified.

           soft-tcb
               Generate software atomic sequences that use a variable in the
               thread control block.  This is a variation of the gUSA
               sequences which can also be used on SH1* and SH2* targets.
               The generated atomic sequences require additional support
               from the interrupt/exception handling code of the system and
               are only suitable for single-core systems.  When using this
               model, the gbr-offset= parameter has to be specified as well.

           soft-imask
               Generate software atomic sequences that temporarily disable
               interrupts by setting "SR.IMASK = 1111".  This model works
               only when the program runs in privileged mode and is only
               suitable for single-core systems.  Additional support from
               the interrupt/exception handling code of the system is not
               required.  This model is enabled by default when the target
               is "sh*-*-linux*" and SH1* or SH2*.

           hard-llcs
               Generate hardware atomic sequences using the "movli.l" and
               "movco.l" instructions only.  This is only available on SH4A
               and is suitable for multi-core systems.  Since the hardware
               instructions support only 32 bit atomic variables access to 8
               or 16 bit variables is emulated with 32 bit accesses.  Code
               compiled with this option is also compatible with other
               software atomic model interrupt/exception handling systems if
               executed on an SH4A system.  Additional support from the
               interrupt/exception handling code of the system is not
               required for this model.

           gbr-offset=
               This parameter specifies the offset in bytes of the variable
               in the thread control block structure that should be used by
               the generated atomic sequences when the soft-tcb model has
               been selected.  For other models this parameter is ignored.
               The specified value must be an integer multiple of four and
               in the range 0-1020.

           strict
               This parameter prevents mixed usage of multiple atomic
               models, even if they are compatible, and makes the compiler
               generate atomic sequences of the specified model only.

       -mtas
           Generate the "tas.b" opcode for "__atomic_test_and_set".  Notice
           that depending on the particular hardware and software
           configuration this can degrade overall performance due to the
           operand cache line flushes that are implied by the "tas.b"
           instruction.  On multi-core SH4A processors the "tas.b"
           instruction must be used with caution since it can result in data
           corruption for certain cache configurations.

       -mprefergot
           When generating position-independent code, emit function calls
           using the Global Offset Table instead of the Procedure Linkage
           Table.

       -musermode
       -mno-usermode
           Don't allow (allow) the compiler generating privileged mode code.
           Specifying -musermode also implies -mno-inline-ic_invalidate if
           the inlined code would not work in user mode.  -musermode is the
           default when the target is "sh*-*-linux*".  If the target is SH1*
           or SH2* -musermode has no effect, since there is no user mode.

       -multcost=number
           Set the cost to assume for a multiply insn.

       -mdiv=strategy
           Set the division strategy to be used for integer division
           operations.  strategy can be one of:

           call-div1
               Calls a library function that uses the single-step division
               instruction "div1" to perform the operation.  Division by
               zero calculates an unspecified result and does not trap.
               This is the default except for SH4, SH2A and SHcompact.

           call-fp
               Calls a library function that performs the operation in
               double precision floating point.  Division by zero causes a
               floating-point exception.  This is the default for SHcompact
               with FPU.  Specifying this for targets that do not have a
               double precision FPU defaults to "call-div1".

           call-table
               Calls a library function that uses a lookup table for small
               divisors and the "div1" instruction with case distinction for
               larger divisors.  Division by zero calculates an unspecified
               result and does not trap.  This is the default for SH4.
               Specifying this for targets that do not have dynamic shift
               instructions defaults to "call-div1".

           When a division strategy has not been specified the default
           strategy is selected based on the current target.  For SH2A the
           default strategy is to use the "divs" and "divu" instructions
           instead of library function calls.

       -maccumulate-outgoing-args
           Reserve space once for outgoing arguments in the function
           prologue rather than around each call.  Generally beneficial for
           performance and size.  Also needed for unwinding to avoid
           changing the stack frame around conditional code.

       -mdivsi3_libfunc=name
           Set the name of the library function used for 32-bit signed
           division to name.  This only affects the name used in the call
           division strategies, and the compiler still expects the same sets
           of input/output/clobbered registers as if this option were not
           present.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed
           registers.  A fixed register is one that the register allocator
           can not use.  This is useful when compiling kernel code.  A
           register range is specified as two registers separated by a dash.
           Multiple register ranges can be specified separated by a comma.

       -mbranch-cost=num
           Assume num to be the cost for a branch instruction.  Higher
           numbers make the compiler try to generate more branch-free code
           if possible.  If not specified the value is selected depending on
           the processor type that is being compiled for.

       -mzdcbranch
       -mno-zdcbranch
           Assume (do not assume) that zero displacement conditional branch
           instructions "bt" and "bf" are fast.  If -mzdcbranch is
           specified, the compiler prefers zero displacement branch code
           sequences.  This is enabled by default when generating code for
           SH4 and SH4A.  It can be explicitly disabled by specifying
           -mno-zdcbranch.

       -mcbranch-force-delay-slot
           Force the usage of delay slots for conditional branches, which
           stuffs the delay slot with a "nop" if a suitable instruction
           can't be found.  By default this option is disabled.  It can be
           enabled to work around hardware bugs as found in the original
           SH7055.

       -mfused-madd
       -mno-fused-madd
           Generate code that uses (does not use) the floating-point
           multiply and accumulate instructions.  These instructions are
           generated by default if hardware floating point is used.  The
           machine-dependent -mfused-madd option is now mapped to the
           machine-independent -ffp-contract=fast option, and
           -mno-fused-madd is mapped to -ffp-contract=off.

       -mfsca
       -mno-fsca
           Allow or disallow the compiler to emit the "fsca" instruction for
           sine and cosine approximations.  The option -mfsca must be used
           in combination with -funsafe-math-optimizations.  It is enabled
           by default when generating code for SH4A.  Using -mno-fsca
           disables sine and cosine approximations even if
           -funsafe-math-optimizations is in effect.

       -mfsrra
       -mno-fsrra
           Allow or disallow the compiler to emit the "fsrra" instruction
           for reciprocal square root approximations.  The option -mfsrra
           must be used in combination with -funsafe-math-optimizations and
           -ffinite-math-only.  It is enabled by default when generating
           code for SH4A.  Using -mno-fsrra disables reciprocal square root
           approximations even if -funsafe-math-optimizations and
           -ffinite-math-only are in effect.

       -mpretend-cmove
           Prefer zero-displacement conditional branches for conditional
           move instruction patterns.  This can result in faster code on the
           SH4 processor.

       -mfdpic
           Generate code using the FDPIC ABI.

       Solaris 2 Options

       These -m options are supported on Solaris 2:

       -mclear-hwcap
           -mclear-hwcap tells the compiler to remove the hardware
           capabilities generated by the Solaris assembler.  This is only
           necessary when object files use ISA extensions not supported by
           the current machine, but check at runtime whether or not to use
           them.

       -mimpure-text
           -mimpure-text, used in addition to -shared, tells the compiler to
           not pass -z text to the linker when linking a shared object.
           Using this option, you can link position-dependent code into a
           shared object.

           -mimpure-text suppresses the "relocations remain against
           allocatable but non-writable sections" linker error message.
           However, the necessary relocations trigger copy-on-write, and the
           shared object is not actually shared across processes.  Instead
           of using -mimpure-text, you should compile all source code with
           -fpic or -fPIC.

       These switches are supported in addition to the above on Solaris 2:

       -pthreads
           Add support for multithreading using the POSIX threads library.
           This option sets flags for both the preprocessor and linker.
           This option does not affect the thread safety of object code
           produced  by the compiler or that of libraries supplied with it.

       -pthread
           This is a synonym for -pthreads.

       SPARC Options

       These -m options are supported on the SPARC:

       -mno-app-regs
       -mapp-regs
           Specify -mapp-regs to generate output using the global registers
           2 through 4, which the SPARC SVR4 ABI reserves for applications.
           Like the global register 1, each global register 2 through 4 is
           then treated as an allocable register that is clobbered by
           function calls.  This is the default.

           To be fully SVR4 ABI-compliant at the cost of some performance
           loss, specify -mno-app-regs.  You should compile libraries and
           system software with this option.

       -mflat
       -mno-flat
           With -mflat, the compiler does not generate save/restore
           instructions and uses a "flat" or single register window model.
           This model is compatible with the regular register window model.
           The local registers and the input registers (0--5) are still
           treated as "call-saved" registers and are saved on the stack as
           needed.

           With -mno-flat (the default), the compiler generates save/restore
           instructions (except for leaf functions).  This is the normal
           operating mode.

       -mfpu
       -mhard-float
           Generate output containing floating-point instructions.  This is
           the default.

       -mno-fpu
       -msoft-float
           Generate output containing library calls for floating point.
           Warning: the requisite libraries are not available for all SPARC
           targets.  Normally the facilities of the machine's usual C
           compiler are used, but this cannot be done directly in cross-
           compilation.  You must make your own arrangements to provide
           suitable library functions for cross-compilation.  The embedded
           targets sparc-*-aout and sparclite-*-* do provide software
           floating-point support.

           -msoft-float changes the calling convention in the output file;
           therefore, it is only useful if you compile all of a program with
           this option.  In particular, you need to compile libgcc.a, the
           library that comes with GCC, with -msoft-float in order for this
           to work.

       -mhard-quad-float
           Generate output containing quad-word (long double) floating-point
           instructions.

       -msoft-quad-float
           Generate output containing library calls for quad-word (long
           double) floating-point instructions.  The functions called are
           those specified in the SPARC ABI.  This is the default.

           As of this writing, there are no SPARC implementations that have
           hardware support for the quad-word floating-point instructions.
           They all invoke a trap handler for one of these instructions, and
           then the trap handler emulates the effect of the instruction.
           Because of the trap handler overhead, this is much slower than
           calling the ABI library routines.  Thus the -msoft-quad-float
           option is the default.

       -mno-unaligned-doubles
       -munaligned-doubles
           Assume that doubles have 8-byte alignment.  This is the default.

           With -munaligned-doubles, GCC assumes that doubles have 8-byte
           alignment only if they are contained in another type, or if they
           have an absolute address.  Otherwise, it assumes they have 4-byte
           alignment.  Specifying this option avoids some rare compatibility
           problems with code generated by other compilers.  It is not the
           default because it results in a performance loss, especially for
           floating-point code.

       -muser-mode
       -mno-user-mode
           Do not generate code that can only run in supervisor mode.  This
           is relevant only for the "casa" instruction emitted for the LEON3
           processor.  This is the default.

       -mfaster-structs
       -mno-faster-structs
           With -mfaster-structs, the compiler assumes that structures
           should have 8-byte alignment.  This enables the use of pairs of
           "ldd" and "std" instructions for copies in structure assignment,
           in place of twice as many "ld" and "st" pairs.  However, the use
           of this changed alignment directly violates the SPARC ABI.  Thus,
           it's intended only for use on targets where the developer
           acknowledges that their resulting code is not directly in line
           with the rules of the ABI.

       -mstd-struct-return
       -mno-std-struct-return
           With -mstd-struct-return, the compiler generates checking code in
           functions returning structures or unions to detect size
           mismatches between the two sides of function calls, as per the
           32-bit ABI.

           The default is -mno-std-struct-return.  This option has no effect
           in 64-bit mode.

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling
           parameters for machine type cpu_type.  Supported values for
           cpu_type are v7, cypress, v8, supersparc, hypersparc, leon,
           leon3, leon3v7, sparclite, f930, f934, sparclite86x, sparclet,
           tsc701, v9, ultrasparc, ultrasparc3, niagara, niagara2, niagara3,
           niagara4 and niagara7.

           Native Solaris and GNU/Linux toolchains also support the value
           native, which selects the best architecture option for the host
           processor.  -mcpu=native has no effect if GCC does not recognize
           the processor.

           Default instruction scheduling parameters are used for values
           that select an architecture and not an implementation.  These are
           v7, v8, sparclite, sparclet, v9.

           Here is a list of each supported architecture and their supported
           implementations.

           v7  cypress, leon3v7

           v8  supersparc, hypersparc, leon, leon3

           sparclite
               f930, f934, sparclite86x

           sparclet
               tsc701

           v9  ultrasparc, ultrasparc3, niagara, niagara2, niagara3,
               niagara4, niagara7

           By default (unless configured otherwise), GCC generates code for
           the V7 variant of the SPARC architecture.  With -mcpu=cypress,
           the compiler additionally optimizes it for the Cypress CY7C602
           chip, as used in the SPARCStation/SPARCServer 3xx series.  This
           is also appropriate for the older SPARCStation 1, 2, IPX etc.

           With -mcpu=v8, GCC generates code for the V8 variant of the SPARC
           architecture.  The only difference from V7 code is that the
           compiler emits the integer multiply and integer divide
           instructions which exist in SPARC-V8 but not in SPARC-V7.  With
           -mcpu=supersparc, the compiler additionally optimizes it for the
           SuperSPARC chip, as used in the SPARCStation 10, 1000 and 2000
           series.

           With -mcpu=sparclite, GCC generates code for the SPARClite
           variant of the SPARC architecture.  This adds the integer
           multiply, integer divide step and scan ("ffs") instructions which
           exist in SPARClite but not in SPARC-V7.  With -mcpu=f930, the
           compiler additionally optimizes it for the Fujitsu MB86930 chip,
           which is the original SPARClite, with no FPU.  With -mcpu=f934,
           the compiler additionally optimizes it for the Fujitsu MB86934
           chip, which is the more recent SPARClite with FPU.

           With -mcpu=sparclet, GCC generates code for the SPARClet variant
           of the SPARC architecture.  This adds the integer multiply,
           multiply/accumulate, integer divide step and scan ("ffs")
           instructions which exist in SPARClet but not in SPARC-V7.  With
           -mcpu=tsc701, the compiler additionally optimizes it for the
           TEMIC SPARClet chip.

           With -mcpu=v9, GCC generates code for the V9 variant of the SPARC
           architecture.  This adds 64-bit integer and floating-point move
           instructions, 3 additional floating-point condition code
           registers and conditional move instructions.  With
           -mcpu=ultrasparc, the compiler additionally optimizes it for the
           Sun UltraSPARC I/II/IIi chips.  With -mcpu=ultrasparc3, the
           compiler additionally optimizes it for the Sun UltraSPARC
           III/III+/IIIi/IIIi+/IV/IV+ chips.  With -mcpu=niagara, the
           compiler additionally optimizes it for Sun UltraSPARC T1 chips.
           With -mcpu=niagara2, the compiler additionally optimizes it for
           Sun UltraSPARC T2 chips. With -mcpu=niagara3, the compiler
           additionally optimizes it for Sun UltraSPARC T3 chips.  With
           -mcpu=niagara4, the compiler additionally optimizes it for Sun
           UltraSPARC T4 chips.  With -mcpu=niagara7, the compiler
           additionally optimizes it for Oracle SPARC M7 chips.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type
           cpu_type, but do not set the instruction set or register set that
           the option -mcpu=cpu_type does.

           The same values for -mcpu=cpu_type can be used for
           -mtune=cpu_type, but the only useful values are those that select
           a particular CPU implementation.  Those are cypress, supersparc,
           hypersparc, leon, leon3, leon3v7, f930, f934, sparclite86x,
           tsc701, ultrasparc, ultrasparc3, niagara, niagara2, niagara3,
           niagara4 and niagara7.  With native Solaris and GNU/Linux
           toolchains, native can also be used.

       -mv8plus
       -mno-v8plus
           With -mv8plus, GCC generates code for the SPARC-V8+ ABI.  The
           difference from the V8 ABI is that the global and out registers
           are considered 64 bits wide.  This is enabled by default on
           Solaris in 32-bit mode for all SPARC-V9 processors.

       -mvis
       -mno-vis
           With -mvis, GCC generates code that takes advantage of the
           UltraSPARC Visual Instruction Set extensions.  The default is
           -mno-vis.

       -mvis2
       -mno-vis2
           With -mvis2, GCC generates code that takes advantage of version
           2.0 of the UltraSPARC Visual Instruction Set extensions.  The
           default is -mvis2 when targeting a cpu that supports such
           instructions, such as UltraSPARC-III and later.  Setting -mvis2
           also sets -mvis.

       -mvis3
       -mno-vis3
           With -mvis3, GCC generates code that takes advantage of version
           3.0 of the UltraSPARC Visual Instruction Set extensions.  The
           default is -mvis3 when targeting a cpu that supports such
           instructions, such as niagara-3 and later.  Setting -mvis3 also
           sets -mvis2 and -mvis.

       -mvis4
       -mno-vis4
           With -mvis4, GCC generates code that takes advantage of version
           4.0 of the UltraSPARC Visual Instruction Set extensions.  The
           default is -mvis4 when targeting a cpu that supports such
           instructions, such as niagara-7 and later.  Setting -mvis4 also
           sets -mvis3, -mvis2 and -mvis.

       -mcbcond
       -mno-cbcond
           With -mcbcond, GCC generates code that takes advantage of
           compare-and-branch instructions, as defined in the Sparc
           Architecture 2011.  The default is -mcbcond when targeting a cpu
           that supports such instructions, such as niagara-4 and later.

       -mpopc
       -mno-popc
           With -mpopc, GCC generates code that takes advantage of the
           UltraSPARC population count instruction.  The default is -mpopc
           when targeting a cpu that supports such instructions, such as
           Niagara-2 and later.

       -mfmaf
       -mno-fmaf
           With -mfmaf, GCC generates code that takes advantage of the
           UltraSPARC Fused Multiply-Add Floating-point extensions.  The
           default is -mfmaf when targeting a cpu that supports such
           instructions, such as Niagara-3 and later.

       -mfix-at697f
           Enable the documented workaround for the single erratum of the
           Atmel AT697F processor (which corresponds to erratum #13 of the
           AT697E processor).

       -mfix-ut699
           Enable the documented workarounds for the floating-point errata
           and the data cache nullify errata of the UT699 processor.

       These -m options are supported in addition to the above on SPARC-V9
       processors in 64-bit environments:

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit
           environment sets int, long and pointer to 32 bits.  The 64-bit
           environment sets int to 32 bits and long and pointer to 64 bits.

       -mcmodel=which
           Set the code model to one of

           medlow
               The Medium/Low code model: 64-bit addresses, programs must be
               linked in the low 32 bits of memory.  Programs can be
               statically or dynamically linked.

           medmid
               The Medium/Middle code model: 64-bit addresses, programs must
               be linked in the low 44 bits of memory, the text and data
               segments must be less than 2GB in size and the data segment
               must be located within 2GB of the text segment.

           medany
               The Medium/Anywhere code model: 64-bit addresses, programs
               may be linked anywhere in memory, the text and data segments
               must be less than 2GB in size and the data segment must be
               located within 2GB of the text segment.

           embmedany
               The Medium/Anywhere code model for embedded systems: 64-bit
               addresses, the text and data segments must be less than 2GB
               in size, both starting anywhere in memory (determined at link
               time).  The global register %g4 points to the base of the
               data segment.  Programs are statically linked and PIC is not
               supported.

       -mmemory-model=mem-model
           Set the memory model in force on the processor to one of

           default
               The default memory model for the processor and operating
               system.

           rmo Relaxed Memory Order

           pso Partial Store Order

           tso Total Store Order

           sc  Sequential Consistency

           These memory models are formally defined in Appendix D of the
           Sparc V9 architecture manual, as set in the processor's
           "PSTATE.MM" field.

       -mstack-bias
       -mno-stack-bias
           With -mstack-bias, GCC assumes that the stack pointer, and frame
           pointer if present, are offset by -2047 which must be added back
           when making stack frame references.  This is the default in
           64-bit mode.  Otherwise, assume no such offset is present.

       SPU Options

       These -m options are supported on the SPU:

       -mwarn-reloc
       -merror-reloc
           The loader for SPU does not handle dynamic relocations.  By
           default, GCC gives an error when it generates code that requires
           a dynamic relocation.  -mno-error-reloc disables the error,
           -mwarn-reloc generates a warning instead.

       -msafe-dma
       -munsafe-dma
           Instructions that initiate or test completion of DMA must not be
           reordered with respect to loads and stores of the memory that is
           being accessed.  With -munsafe-dma you must use the "volatile"
           keyword to protect memory accesses, but that can lead to
           inefficient code in places where the memory is known to not
           change.  Rather than mark the memory as volatile, you can use
           -msafe-dma to tell the compiler to treat the DMA instructions as
           potentially affecting all memory.

       -mbranch-hints
           By default, GCC generates a branch hint instruction to avoid
           pipeline stalls for always-taken or probably-taken branches.  A
           hint is not generated closer than 8 instructions away from its
           branch.  There is little reason to disable them, except for
           debugging purposes, or to make an object a little bit smaller.

       -msmall-mem
       -mlarge-mem
           By default, GCC generates code assuming that addresses are never
           larger than 18 bits.  With -mlarge-mem code is generated that
           assumes a full 32-bit address.

       -mstdmain
           By default, GCC links against startup code that assumes the SPU-
           style main function interface (which has an unconventional
           parameter list).  With -mstdmain, GCC links your program against
           startup code that assumes a C99-style interface to "main",
           including a local copy of "argv" strings.

       -mfixed-range=register-range
           Generate code treating the given register range as fixed
           registers.  A fixed register is one that the register allocator
           cannot use.  This is useful when compiling kernel code.  A
           register range is specified as two registers separated by a dash.
           Multiple register ranges can be specified separated by a comma.

       -mea32
       -mea64
           Compile code assuming that pointers to the PPU address space
           accessed via the "__ea" named address space qualifier are either
           32 or 64 bits wide.  The default is 32 bits.  As this is an ABI-
           changing option, all object code in an executable must be
           compiled with the same setting.

       -maddress-space-conversion
       -mno-address-space-conversion
           Allow/disallow treating the "__ea" address space as superset of
           the generic address space.  This enables explicit type casts
           between "__ea" and generic pointer as well as implicit
           conversions of generic pointers to "__ea" pointers.  The default
           is to allow address space pointer conversions.

       -mcache-size=cache-size
           This option controls the version of libgcc that the compiler
           links to an executable and selects a software-managed cache for
           accessing variables in the "__ea" address space with a particular
           cache size.  Possible options for cache-size are 8, 16, 32, 64
           and 128.  The default cache size is 64KB.

       -matomic-updates
       -mno-atomic-updates
           This option controls the version of libgcc that the compiler
           links to an executable and selects whether atomic updates to the
           software-managed cache of PPU-side variables are used.  If you
           use atomic updates, changes to a PPU variable from SPU code using
           the "__ea" named address space qualifier do not interfere with
           changes to other PPU variables residing in the same cache line
           from PPU code.  If you do not use atomic updates, such
           interference may occur; however, writing back cache lines is more
           efficient.  The default behavior is to use atomic updates.

       -mdual-nops
       -mdual-nops=n
           By default, GCC inserts nops to increase dual issue when it
           expects it to increase performance.  n can be a value from 0 to
           10.  A smaller n inserts fewer nops.  10 is the default, 0 is the
           same as -mno-dual-nops.  Disabled with -Os.

       -mhint-max-nops=n
           Maximum number of nops to insert for a branch hint.  A branch
           hint must be at least 8 instructions away from the branch it is
           affecting.  GCC inserts up to n nops to enforce this, otherwise
           it does not generate the branch hint.

       -mhint-max-distance=n
           The encoding of the branch hint instruction limits the hint to be
           within 256 instructions of the branch it is affecting.  By
           default, GCC makes sure it is within 125.

       -msafe-hints
           Work around a hardware bug that causes the SPU to stall
           indefinitely.  By default, GCC inserts the "hbrp" instruction to
           make sure this stall won't happen.

       Options for System V

       These additional options are available on System V Release 4 for
       compatibility with other compilers on those systems:

       -G  Create a shared object.  It is recommended that -symbolic or
           -shared be used instead.

       -Qy Identify the versions of each tool used by the compiler, in a
           ".ident" assembler directive in the output.

       -Qn Refrain from adding ".ident" directives to the output file (this
           is the default).

       -YP,dirs
           Search the directories dirs, and no others, for libraries
           specified with -l.

       -Ym,dir
           Look in the directory dir to find the M4 preprocessor.  The
           assembler uses this option.

       TILE-Gx Options

       These -m options are supported on the TILE-Gx:

       -mcmodel=small
           Generate code for the small model.  The distance for direct calls
           is limited to 500M in either direction.  PC-relative addresses
           are 32 bits.  Absolute addresses support the full address range.

       -mcmodel=large
           Generate code for the large model.  There is no limitation on
           call distance, pc-relative addresses, or absolute addresses.

       -mcpu=name
           Selects the type of CPU to be targeted.  Currently the only
           supported type is tilegx.

       -m32
       -m64
           Generate code for a 32-bit or 64-bit environment.  The 32-bit
           environment sets int, long, and pointer to 32 bits.  The 64-bit
           environment sets int to 32 bits and long and pointer to 64 bits.

       -mbig-endian
       -mlittle-endian
           Generate code in big/little endian mode, respectively.

       TILEPro Options

       These -m options are supported on the TILEPro:

       -mcpu=name
           Selects the type of CPU to be targeted.  Currently the only
           supported type is tilepro.

       -m32
           Generate code for a 32-bit environment, which sets int, long, and
           pointer to 32 bits.  This is the only supported behavior so the
           flag is essentially ignored.

       V850 Options

       These -m options are defined for V850 implementations:

       -mlong-calls
       -mno-long-calls
           Treat all calls as being far away (near).  If calls are assumed
           to be far away, the compiler always loads the function's address
           into a register, and calls indirect through the pointer.

       -mno-ep
       -mep
           Do not optimize (do optimize) basic blocks that use the same
           index pointer 4 or more times to copy pointer into the "ep"
           register, and use the shorter "sld" and "sst" instructions.  The
           -mep option is on by default if you optimize.

       -mno-prolog-function
       -mprolog-function
           Do not use (do use) external functions to save and restore
           registers at the prologue and epilogue of a function.  The
           external functions are slower, but use less code space if more
           than one function saves the same number of registers.  The
           -mprolog-function option is on by default if you optimize.

       -mspace
           Try to make the code as small as possible.  At present, this just
           turns on the -mep and -mprolog-function options.

       -mtda=n
           Put static or global variables whose size is n bytes or less into
           the tiny data area that register "ep" points to.  The tiny data
           area can hold up to 256 bytes in total (128 bytes for byte
           references).

       -msda=n
           Put static or global variables whose size is n bytes or less into
           the small data area that register "gp" points to.  The small data
           area can hold up to 64 kilobytes.

       -mzda=n
           Put static or global variables whose size is n bytes or less into
           the first 32 kilobytes of memory.

       -mv850
           Specify that the target processor is the V850.

       -mv850e3v5
           Specify that the target processor is the V850E3V5.  The
           preprocessor constant "__v850e3v5__" is defined if this option is
           used.

       -mv850e2v4
           Specify that the target processor is the V850E3V5.  This is an
           alias for the -mv850e3v5 option.

       -mv850e2v3
           Specify that the target processor is the V850E2V3.  The
           preprocessor constant "__v850e2v3__" is defined if this option is
           used.

       -mv850e2
           Specify that the target processor is the V850E2.  The
           preprocessor constant "__v850e2__" is defined if this option is
           used.

       -mv850e1
           Specify that the target processor is the V850E1.  The
           preprocessor constants "__v850e1__" and "__v850e__" are defined
           if this option is used.

       -mv850es
           Specify that the target processor is the V850ES.  This is an
           alias for the -mv850e1 option.

       -mv850e
           Specify that the target processor is the V850E.  The preprocessor
           constant "__v850e__" is defined if this option is used.

           If neither -mv850 nor -mv850e nor -mv850e1 nor -mv850e2 nor
           -mv850e2v3 nor -mv850e3v5 are defined then a default target
           processor is chosen and the relevant __v850*__ preprocessor
           constant is defined.

           The preprocessor constants "__v850" and "__v851__" are always
           defined, regardless of which processor variant is the target.

       -mdisable-callt
       -mno-disable-callt
           This option suppresses generation of the "CALLT" instruction for
           the v850e, v850e1, v850e2, v850e2v3 and v850e3v5 flavors of the
           v850 architecture.

           This option is enabled by default when the RH850 ABI is in use
           (see -mrh850-abi), and disabled by default when the GCC ABI is in
           use.  If "CALLT" instructions are being generated then the C
           preprocessor symbol "__V850_CALLT__" is defined.

       -mrelax
       -mno-relax
           Pass on (or do not pass on) the -mrelax command-line option to
           the assembler.

       -mlong-jumps
       -mno-long-jumps
           Disable (or re-enable) the generation of PC-relative jump
           instructions.

       -msoft-float
       -mhard-float
           Disable (or re-enable) the generation of hardware floating point
           instructions.  This option is only significant when the target
           architecture is V850E2V3 or higher.  If hardware floating point
           instructions are being generated then the C preprocessor symbol
           "__FPU_OK__" is defined, otherwise the symbol "__NO_FPU__" is
           defined.

       -mloop
           Enables the use of the e3v5 LOOP instruction.  The use of this
           instruction is not enabled by default when the e3v5 architecture
           is selected because its use is still experimental.

       -mrh850-abi
       -mghs
           Enables support for the RH850 version of the V850 ABI.  This is
           the default.  With this version of the ABI the following rules
           apply:

           *   Integer sized structures and unions are returned via a memory
               pointer rather than a register.

           *   Large structures and unions (more than 8 bytes in size) are
               passed by value.

           *   Functions are aligned to 16-bit boundaries.

           *   The -m8byte-align command-line option is supported.

           *   The -mdisable-callt command-line option is enabled by
               default.  The -mno-disable-callt command-line option is not
               supported.

           When this version of the ABI is enabled the C preprocessor symbol
           "__V850_RH850_ABI__" is defined.

       -mgcc-abi
           Enables support for the old GCC version of the V850 ABI.  With
           this version of the ABI the following rules apply:

           *   Integer sized structures and unions are returned in register
               "r10".

           *   Large structures and unions (more than 8 bytes in size) are
               passed by reference.

           *   Functions are aligned to 32-bit boundaries, unless optimizing
               for size.

           *   The -m8byte-align command-line option is not supported.

           *   The -mdisable-callt command-line option is supported but not
               enabled by default.

           When this version of the ABI is enabled the C preprocessor symbol
           "__V850_GCC_ABI__" is defined.

       -m8byte-align
       -mno-8byte-align
           Enables support for "double" and "long long" types to be aligned
           on 8-byte boundaries.  The default is to restrict the alignment
           of all objects to at most 4-bytes.  When -m8byte-align is in
           effect the C preprocessor symbol "__V850_8BYTE_ALIGN__" is
           defined.

       -mbig-switch
           Generate code suitable for big switch tables.  Use this option
           only if the assembler/linker complain about out of range branches
           within a switch table.

       -mapp-regs
           This option causes r2 and r5 to be used in the code generated by
           the compiler.  This setting is the default.

       -mno-app-regs
           This option causes r2 and r5 to be treated as fixed registers.

       VAX Options

       These -m options are defined for the VAX:

       -munix
           Do not output certain jump instructions ("aobleq" and so on) that
           the Unix assembler for the VAX cannot handle across long ranges.

       -mgnu
           Do output those jump instructions, on the assumption that the GNU
           assembler is being used.

       -mg Output code for G-format floating-point numbers instead of
           D-format.

       Visium Options

       -mdebug
           A program which performs file I/O and is destined to run on an
           MCM target should be linked with this option.  It causes the
           libraries libc.a and libdebug.a to be linked.  The program should
           be run on the target under the control of the GDB remote
           debugging stub.

       -msim
           A program which performs file I/O and is destined to run on the
           simulator should be linked with option.  This causes libraries
           libc.a and libsim.a to be linked.

       -mfpu
       -mhard-float
           Generate code containing floating-point instructions.  This is
           the default.

       -mno-fpu
       -msoft-float
           Generate code containing library calls for floating-point.

           -msoft-float changes the calling convention in the output file;
           therefore, it is only useful if you compile all of a program with
           this option.  In particular, you need to compile libgcc.a, the
           library that comes with GCC, with -msoft-float in order for this
           to work.

       -mcpu=cpu_type
           Set the instruction set, register set, and instruction scheduling
           parameters for machine type cpu_type.  Supported values for
           cpu_type are mcm, gr5 and gr6.

           mcm is a synonym of gr5 present for backward compatibility.

           By default (unless configured otherwise), GCC generates code for
           the GR5 variant of the Visium architecture.

           With -mcpu=gr6, GCC generates code for the GR6 variant of the
           Visium architecture.  The only difference from GR5 code is that
           the compiler will generate block move instructions.

       -mtune=cpu_type
           Set the instruction scheduling parameters for machine type
           cpu_type, but do not set the instruction set or register set that
           the option -mcpu=cpu_type would.

       -msv-mode
           Generate code for the supervisor mode, where there are no
           restrictions on the access to general registers.  This is the
           default.

       -muser-mode
           Generate code for the user mode, where the access to some general
           registers is forbidden: on the GR5, registers r24 to r31 cannot
           be accessed in this mode; on the GR6, only registers r29 to r31
           are affected.

       VMS Options

       These -m options are defined for the VMS implementations:

       -mvms-return-codes
           Return VMS condition codes from "main". The default is to return
           POSIX-style condition (e.g. error) codes.

       -mdebug-main=prefix
           Flag the first routine whose name starts with prefix as the main
           routine for the debugger.

       -mmalloc64
           Default to 64-bit memory allocation routines.

       -mpointer-size=size
           Set the default size of pointers. Possible options for size are
           32 or short for 32 bit pointers, 64 or long for 64 bit pointers,
           and no for supporting only 32 bit pointers.  The later option
           disables "pragma pointer_size".

       VxWorks Options

       The options in this section are defined for all VxWorks targets.
       Options specific to the target hardware are listed with the other
       options for that target.

       -mrtp
           GCC can generate code for both VxWorks kernels and real time
           processes (RTPs).  This option switches from the former to the
           latter.  It also defines the preprocessor macro "__RTP__".

       -non-static
           Link an RTP executable against shared libraries rather than
           static libraries.  The options -static and -shared can also be
           used for RTPs; -static is the default.

       -Bstatic
       -Bdynamic
           These options are passed down to the linker.  They are defined
           for compatibility with Diab.

       -Xbind-lazy
           Enable lazy binding of function calls.  This option is equivalent
           to -Wl,-z,now and is defined for compatibility with Diab.

       -Xbind-now
           Disable lazy binding of function calls.  This option is the
           default and is defined for compatibility with Diab.

       x86 Options

       These -m options are defined for the x86 family of computers.

       -march=cpu-type
           Generate instructions for the machine type cpu-type.  In contrast
           to -mtune=cpu-type, which merely tunes the generated code for the
           specified cpu-type, -march=cpu-type allows GCC to generate code
           that may not run at all on processors other than the one
           indicated.  Specifying -march=cpu-type implies -mtune=cpu-type.

           The choices for cpu-type are:

           native
               This selects the CPU to generate code for at compilation time
               by determining the processor type of the compiling machine.
               Using -march=native enables all instruction subsets supported
               by the local machine (hence the result might not run on
               different machines).  Using -mtune=native produces code
               optimized for the local machine under the constraints of the
               selected instruction set.

           i386
               Original Intel i386 CPU.

           i486
               Intel i486 CPU.  (No scheduling is implemented for this
               chip.)

           i586
           pentium
               Intel Pentium CPU with no MMX support.

           lakemont
               Intel Lakemont MCU, based on Intel Pentium CPU.

           pentium-mmx
               Intel Pentium MMX CPU, based on Pentium core with MMX
               instruction set support.

           pentiumpro
               Intel Pentium Pro CPU.

           i686
               When used with -march, the Pentium Pro instruction set is
               used, so the code runs on all i686 family chips.  When used
               with -mtune, it has the same meaning as generic.

           pentium2
               Intel Pentium II CPU, based on Pentium Pro core with MMX
               instruction set support.

           pentium3
           pentium3m
               Intel Pentium III CPU, based on Pentium Pro core with MMX and
               SSE instruction set support.

           pentium-m
               Intel Pentium M; low-power version of Intel Pentium III CPU
               with MMX, SSE and SSE2 instruction set support.  Used by
               Centrino notebooks.

           pentium4
           pentium4m
               Intel Pentium 4 CPU with MMX, SSE and SSE2 instruction set
               support.

           prescott
               Improved version of Intel Pentium 4 CPU with MMX, SSE, SSE2
               and SSE3 instruction set support.

           nocona
               Improved version of Intel Pentium 4 CPU with 64-bit
               extensions, MMX, SSE, SSE2 and SSE3 instruction set support.

           core2
               Intel Core 2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3
               and SSSE3 instruction set support.

           nehalem
               Intel Nehalem CPU with 64-bit extensions, MMX, SSE, SSE2,
               SSE3, SSSE3, SSE4.1, SSE4.2 and POPCNT instruction set
               support.

           westmere
               Intel Westmere CPU with 64-bit extensions, MMX, SSE, SSE2,
               SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES and PCLMUL
               instruction set support.

           sandybridge
               Intel Sandy Bridge CPU with 64-bit extensions, MMX, SSE,
               SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AES and
               PCLMUL instruction set support.

           ivybridge
               Intel Ivy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2,
               SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AES, PCLMUL,
               FSGSBASE, RDRND and F16C instruction set support.

           haswell
               Intel Haswell CPU with 64-bit extensions, MOVBE, MMX, SSE,
               SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
               PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2 and F16C instruction
               set support.

           broadwell
               Intel Broadwell CPU with 64-bit extensions, MOVBE, MMX, SSE,
               SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
               PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C, RDSEED, ADCX
               and PREFETCHW instruction set support.

           skylake
               Intel Skylake CPU with 64-bit extensions, MOVBE, MMX, SSE,
               SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
               PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C, RDSEED, ADCX,
               PREFETCHW, CLFLUSHOPT, XSAVEC and XSAVES instruction set
               support.

           bonnell
               Intel Bonnell CPU with 64-bit extensions, MOVBE, MMX, SSE,
               SSE2, SSE3 and SSSE3 instruction set support.

           silvermont
               Intel Silvermont CPU with 64-bit extensions, MOVBE, MMX, SSE,
               SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES, PCLMUL and
               RDRND instruction set support.

           knl Intel Knight's Landing CPU with 64-bit extensions, MOVBE,
               MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX,
               AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C,
               RDSEED, ADCX, PREFETCHW, AVX512F, AVX512PF, AVX512ER and
               AVX512CD instruction set support.

           skylake-avx512
               Intel Skylake Server CPU with 64-bit extensions, MOVBE, MMX,
               SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX,
               AVX2, AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C,
               RDSEED, ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F,
               AVX512VL, AVX512BW, AVX512DQ and AVX512CD instruction set
               support.

           k6  AMD K6 CPU with MMX instruction set support.

           k6-2
           k6-3
               Improved versions of AMD K6 CPU with MMX and 3DNow!
               instruction set support.

           athlon
           athlon-tbird
               AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow! and SSE
               prefetch instructions support.

           athlon-4
           athlon-xp
           athlon-mp
               Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow! and
               full SSE instruction set support.

           k8
           opteron
           athlon64
           athlon-fx
               Processors based on the AMD K8 core with x86-64 instruction
               set support, including the AMD Opteron, Athlon 64, and Athlon
               64 FX processors.  (This supersets MMX, SSE, SSE2, 3DNow!,
               enhanced 3DNow! and 64-bit instruction set extensions.)

           k8-sse3
           opteron-sse3
           athlon64-sse3
               Improved versions of AMD K8 cores with SSE3 instruction set
               support.

           amdfam10
           barcelona
               CPUs based on AMD Family 10h cores with x86-64 instruction
               set support.  (This supersets MMX, SSE, SSE2, SSE3, SSE4A,
               3DNow!, enhanced 3DNow!, ABM and 64-bit instruction set
               extensions.)

           bdver1
               CPUs based on AMD Family 15h cores with x86-64 instruction
               set support.  (This supersets FMA4, AVX, XOP, LWP, AES,
               PCL_MUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1,
               SSE4.2, ABM and 64-bit instruction set extensions.)

           bdver2
               AMD Family 15h core based CPUs with x86-64 instruction set
               support.  (This supersets BMI, TBM, F16C, FMA, FMA4, AVX,
               XOP, LWP, AES, PCL_MUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A,
               SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set
               extensions.)

           bdver3
               AMD Family 15h core based CPUs with x86-64 instruction set
               support.  (This supersets BMI, TBM, F16C, FMA, FMA4,
               FSGSBASE, AVX, XOP, LWP, AES, PCL_MUL, CX16, MMX, SSE, SSE2,
               SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit
               instruction set extensions.

           bdver4
               AMD Family 15h core based CPUs with x86-64 instruction set
               support.  (This supersets BMI, BMI2, TBM, F16C, FMA, FMA4,
               FSGSBASE, AVX, AVX2, XOP, LWP, AES, PCL_MUL, CX16, MOVBE,
               MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and
               64-bit instruction set extensions.

           znver1
               AMD Family 17h core based CPUs with x86-64 instruction set
               support.  (This supersets BMI, BMI2, F16C, FMA, FSGSBASE,
               AVX, AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO, AES, PCL_MUL,
               CX16, MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1,
               SSE4.2, ABM, XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, and 64-bit
               instruction set extensions.

           btver1
               CPUs based on AMD Family 14h cores with x86-64 instruction
               set support.  (This supersets MMX, SSE, SSE2, SSE3, SSSE3,
               SSE4A, CX16, ABM and 64-bit instruction set extensions.)

           btver2
               CPUs based on AMD Family 16h cores with x86-64 instruction
               set support. This includes MOVBE, F16C, BMI, AVX, PCL_MUL,
               AES, SSE4.2, SSE4.1, CX16, ABM, SSE4A, SSSE3, SSE3, SSE2,
               SSE, MMX and 64-bit instruction set extensions.

           winchip-c6
               IDT WinChip C6 CPU, dealt in same way as i486 with additional
               MMX instruction set support.

           winchip2
               IDT WinChip 2 CPU, dealt in same way as i486 with additional
               MMX and 3DNow!  instruction set support.

           c3  VIA C3 CPU with MMX and 3DNow! instruction set support.  (No
               scheduling is implemented for this chip.)

           c3-2
               VIA C3-2 (Nehemiah/C5XL) CPU with MMX and SSE instruction set
               support.  (No scheduling is implemented for this chip.)

           geode
               AMD Geode embedded processor with MMX and 3DNow! instruction
               set support.

       -mtune=cpu-type
           Tune to cpu-type everything applicable about the generated code,
           except for the ABI and the set of available instructions.  While
           picking a specific cpu-type schedules things appropriately for
           that particular chip, the compiler does not generate any code
           that cannot run on the default machine type unless you use a
           -march=cpu-type option.  For example, if GCC is configured for
           i686-pc-linux-gnu then -mtune=pentium4 generates code that is
           tuned for Pentium 4 but still runs on i686 machines.

           The choices for cpu-type are the same as for -march.  In
           addition, -mtune supports 2 extra choices for cpu-type:

           generic
               Produce code optimized for the most common IA32/AMD64/EM64T
               processors.  If you know the CPU on which your code will run,
               then you should use the corresponding -mtune or -march option
               instead of -mtune=generic.  But, if you do not know exactly
               what CPU users of your application will have, then you should
               use this option.

               As new processors are deployed in the marketplace, the
               behavior of this option will change.  Therefore, if you
               upgrade to a newer version of GCC, code generation controlled
               by this option will change to reflect the processors that are
               most common at the time that version of GCC is released.

               There is no -march=generic option because -march indicates
               the instruction set the compiler can use, and there is no
               generic instruction set applicable to all processors.  In
               contrast, -mtune indicates the processor (or, in this case,
               collection of processors) for which the code is optimized.

           intel
               Produce code optimized for the most current Intel processors,
               which are Haswell and Silvermont for this version of GCC.  If
               you know the CPU on which your code will run, then you should
               use the corresponding -mtune or -march option instead of
               -mtune=intel.  But, if you want your application performs
               better on both Haswell and Silvermont, then you should use
               this option.

               As new Intel processors are deployed in the marketplace, the
               behavior of this option will change.  Therefore, if you
               upgrade to a newer version of GCC, code generation controlled
               by this option will change to reflect the most current Intel
               processors at the time that version of GCC is released.

               There is no -march=intel option because -march indicates the
               instruction set the compiler can use, and there is no common
               instruction set applicable to all processors.  In contrast,
               -mtune indicates the processor (or, in this case, collection
               of processors) for which the code is optimized.

       -mcpu=cpu-type
           A deprecated synonym for -mtune.

       -mfpmath=unit
           Generate floating-point arithmetic for selected unit unit.  The
           choices for unit are:

           387 Use the standard 387 floating-point coprocessor present on
               the majority of chips and emulated otherwise.  Code compiled
               with this option runs almost everywhere.  The temporary
               results are computed in 80-bit precision instead of the
               precision specified by the type, resulting in slightly
               different results compared to most of other chips.  See
               -ffloat-store for more detailed description.

               This is the default choice for x86-32 targets.

           sse Use scalar floating-point instructions present in the SSE
               instruction set.  This instruction set is supported by
               Pentium III and newer chips, and in the AMD line by Athlon-4,
               Athlon XP and Athlon MP chips.  The earlier version of the
               SSE instruction set supports only single-precision
               arithmetic, thus the double and extended-precision arithmetic
               are still done using 387.  A later version, present only in
               Pentium 4 and AMD x86-64 chips, supports double-precision
               arithmetic too.

               For the x86-32 compiler, you must use -march=cpu-type, -msse
               or -msse2 switches to enable SSE extensions and make this
               option effective.  For the x86-64 compiler, these extensions
               are enabled by default.

               The resulting code should be considerably faster in the
               majority of cases and avoid the numerical instability
               problems of 387 code, but may break some existing code that
               expects temporaries to be 80 bits.

               This is the default choice for the x86-64 compiler.

           sse,387
           sse+387
           both
               Attempt to utilize both instruction sets at once.  This
               effectively doubles the amount of available registers, and on
               chips with separate execution units for 387 and SSE the
               execution resources too.  Use this option with care, as it is
               still experimental, because the GCC register allocator does
               not model separate functional units well, resulting in
               unstable performance.

       -masm=dialect
           Output assembly instructions using selected dialect.  Also
           affects which dialect is used for basic "asm" and extended "asm".
           Supported choices (in dialect order) are att or intel. The
           default is att. Darwin does not support intel.

       -mieee-fp
       -mno-ieee-fp
           Control whether or not the compiler uses IEEE floating-point
           comparisons.  These correctly handle the case where the result of
           a comparison is unordered.

       -msoft-float
           Generate output containing library calls for floating point.

           Warning: the requisite libraries are not part of GCC.  Normally
           the facilities of the machine's usual C compiler are used, but
           this can't be done directly in cross-compilation.  You must make
           your own arrangements to provide suitable library functions for
           cross-compilation.

           On machines where a function returns floating-point results in
           the 80387 register stack, some floating-point opcodes may be
           emitted even if -msoft-float is used.

       -mno-fp-ret-in-387
           Do not use the FPU registers for return values of functions.

           The usual calling convention has functions return values of types
           "float" and "double" in an FPU register, even if there is no FPU.
           The idea is that the operating system should emulate an FPU.

           The option -mno-fp-ret-in-387 causes such values to be returned
           in ordinary CPU registers instead.

       -mno-fancy-math-387
           Some 387 emulators do not support the "sin", "cos" and "sqrt"
           instructions for the 387.  Specify this option to avoid
           generating those instructions.  This option is the default on
           OpenBSD and NetBSD.  This option is overridden when -march
           indicates that the target CPU always has an FPU and so the
           instruction does not need emulation.  These instructions are not
           generated unless you also use the -funsafe-math-optimizations
           switch.

       -malign-double
       -mno-align-double
           Control whether GCC aligns "double", "long double", and "long
           long" variables on a two-word boundary or a one-word boundary.
           Aligning "double" variables on a two-word boundary produces code
           that runs somewhat faster on a Pentium at the expense of more
           memory.

           On x86-64, -malign-double is enabled by default.

           Warning: if you use the -malign-double switch, structures
           containing the above types are aligned differently than the
           published application binary interface specifications for the
           x86-32 and are not binary compatible with structures in code
           compiled without that switch.

       -m96bit-long-double
       -m128bit-long-double
           These switches control the size of "long double" type.  The
           x86-32 application binary interface specifies the size to be 96
           bits, so -m96bit-long-double is the default in 32-bit mode.

           Modern architectures (Pentium and newer) prefer "long double" to
           be aligned to an 8- or 16-byte boundary.  In arrays or structures
           conforming to the ABI, this is not possible.  So specifying
           -m128bit-long-double aligns "long double" to a 16-byte boundary
           by padding the "long double" with an additional 32-bit zero.

           In the x86-64 compiler, -m128bit-long-double is the default
           choice as its ABI specifies that "long double" is aligned on
           16-byte boundary.

           Notice that neither of these options enable any extra precision
           over the x87 standard of 80 bits for a "long double".

           Warning: if you override the default value for your target ABI,
           this changes the size of structures and arrays containing "long
           double" variables, as well as modifying the function calling
           convention for functions taking "long double".  Hence they are
           not binary-compatible with code compiled without that switch.

       -mlong-double-64
       -mlong-double-80
       -mlong-double-128
           These switches control the size of "long double" type. A size of
           64 bits makes the "long double" type equivalent to the "double"
           type. This is the default for 32-bit Bionic C library.  A size of
           128 bits makes the "long double" type equivalent to the
           "__float128" type. This is the default for 64-bit Bionic C
           library.

           Warning: if you override the default value for your target ABI,
           this changes the size of structures and arrays containing "long
           double" variables, as well as modifying the function calling
           convention for functions taking "long double".  Hence they are
           not binary-compatible with code compiled without that switch.

       -malign-data=type
           Control how GCC aligns variables.  Supported values for type are
           compat uses increased alignment value compatible uses GCC 4.8 and
           earlier, abi uses alignment value as specified by the psABI, and
           cacheline uses increased alignment value to match the cache line
           size.  compat is the default.

       -mlarge-data-threshold=threshold
           When -mcmodel=medium is specified, data objects larger than
           threshold are placed in the large data section.  This value must
           be the same across all objects linked into the binary, and
           defaults to 65535.

       -mrtd
           Use a different function-calling convention, in which functions
           that take a fixed number of arguments return with the "ret num"
           instruction, which pops their arguments while returning.  This
           saves one instruction in the caller since there is no need to pop
           the arguments there.

           You can specify that an individual function is called with this
           calling sequence with the function attribute "stdcall".  You can
           also override the -mrtd option by using the function attribute
           "cdecl".

           Warning: this calling convention is incompatible with the one
           normally used on Unix, so you cannot use it if you need to call
           libraries compiled with the Unix compiler.

           Also, you must provide function prototypes for all functions that
           take variable numbers of arguments (including "printf");
           otherwise incorrect code is generated for calls to those
           functions.

           In addition, seriously incorrect code results if you call a
           function with too many arguments.  (Normally, extra arguments are
           harmlessly ignored.)

       -mregparm=num
           Control how many registers are used to pass integer arguments.
           By default, no registers are used to pass arguments, and at most
           3 registers can be used.  You can control this behavior for a
           specific function by using the function attribute "regparm".

           Warning: if you use this switch, and num is nonzero, then you
           must build all modules with the same value, including any
           libraries.  This includes the system libraries and startup
           modules.

       -msseregparm
           Use SSE register passing conventions for float and double
           arguments and return values.  You can control this behavior for a
           specific function by using the function attribute "sseregparm".

           Warning: if you use this switch then you must build all modules
           with the same value, including any libraries.  This includes the
           system libraries and startup modules.

       -mvect8-ret-in-mem
           Return 8-byte vectors in memory instead of MMX registers.  This
           is the default on Solaris@tie{}8 and 9 and VxWorks to match the
           ABI of the Sun Studio compilers until version 12.  Later compiler
           versions (starting with Studio 12 Update@tie{}1) follow the ABI
           used by other x86 targets, which is the default on
           Solaris@tie{}10 and later.  Only use this option if you need to
           remain compatible with existing code produced by those previous
           compiler versions or older versions of GCC.

       -mpc32
       -mpc64
       -mpc80
           Set 80387 floating-point precision to 32, 64 or 80 bits.  When
           -mpc32 is specified, the significands of results of floating-
           point operations are rounded to 24 bits (single precision);
           -mpc64 rounds the significands of results of floating-point
           operations to 53 bits (double precision) and -mpc80 rounds the
           significands of results of floating-point operations to 64 bits
           (extended double precision), which is the default.  When this
           option is used, floating-point operations in higher precisions
           are not available to the programmer without setting the FPU
           control word explicitly.

           Setting the rounding of floating-point operations to less than
           the default 80 bits can speed some programs by 2% or more.  Note
           that some mathematical libraries assume that extended-precision
           (80-bit) floating-point operations are enabled by default;
           routines in such libraries could suffer significant loss of
           accuracy, typically through so-called "catastrophic
           cancellation", when this option is used to set the precision to
           less than extended precision.

       -mstackrealign
           Realign the stack at entry.  On the x86, the -mstackrealign
           option generates an alternate prologue and epilogue that realigns
           the run-time stack if necessary.  This supports mixing legacy
           codes that keep 4-byte stack alignment with modern codes that
           keep 16-byte stack alignment for SSE compatibility.  See also the
           attribute "force_align_arg_pointer", applicable to individual
           functions.

       -mpreferred-stack-boundary=num
           Attempt to keep the stack boundary aligned to a 2 raised to num
           byte boundary.  If -mpreferred-stack-boundary is not specified,
           the default is 4 (16 bytes or 128 bits).

           Warning: When generating code for the x86-64 architecture with
           SSE extensions disabled, -mpreferred-stack-boundary=3 can be used
           to keep the stack boundary aligned to 8 byte boundary.  Since
           x86-64 ABI require 16 byte stack alignment, this is ABI
           incompatible and intended to be used in controlled environment
           where stack space is important limitation.  This option leads to
           wrong code when functions compiled with 16 byte stack alignment
           (such as functions from a standard library) are called with
           misaligned stack.  In this case, SSE instructions may lead to
           misaligned memory access traps.  In addition, variable arguments
           are handled incorrectly for 16 byte aligned objects (including
           x87 long double and __int128), leading to wrong results.  You
           must build all modules with -mpreferred-stack-boundary=3,
           including any libraries.  This includes the system libraries and
           startup modules.

       -mincoming-stack-boundary=num
           Assume the incoming stack is aligned to a 2 raised to num byte
           boundary.  If -mincoming-stack-boundary is not specified, the one
           specified by -mpreferred-stack-boundary is used.

           On Pentium and Pentium Pro, "double" and "long double" values
           should be aligned to an 8-byte boundary (see -malign-double) or
           suffer significant run time performance penalties.  On Pentium
           III, the Streaming SIMD Extension (SSE) data type "__m128" may
           not work properly if it is not 16-byte aligned.

           To ensure proper alignment of this values on the stack, the stack
           boundary must be as aligned as that required by any value stored
           on the stack.  Further, every function must be generated such
           that it keeps the stack aligned.  Thus calling a function
           compiled with a higher preferred stack boundary from a function
           compiled with a lower preferred stack boundary most likely
           misaligns the stack.  It is recommended that libraries that use
           callbacks always use the default setting.

           This extra alignment does consume extra stack space, and
           generally increases code size.  Code that is sensitive to stack
           space usage, such as embedded systems and operating system
           kernels, may want to reduce the preferred alignment to
           -mpreferred-stack-boundary=2.

       -mmmx
       -msse
       -msse2
       -msse3
       -mssse3
       -msse4
       -msse4a
       -msse4.1
       -msse4.2
       -mavx
       -mavx2
       -mavx512f
       -mavx512pf
       -mavx512er
       -mavx512cd
       -mavx512vl
       -mavx512bw
       -mavx512dq
       -mavx512ifma
       -mavx512vbmi
       -msha
       -maes
       -mpclmul
       -mclfushopt
       -mfsgsbase
       -mrdrnd
       -mf16c
       -mfma
       -mfma4
       -mprefetchwt1
       -mxop
       -mlwp
       -m3dnow
       -mpopcnt
       -mabm
       -mbmi
       -mbmi2
       -mlzcnt
       -mfxsr
       -mxsave
       -mxsaveopt
       -mxsavec
       -mxsaves
       -mrtm
       -mtbm
       -mmpx
       -mmwaitx
       -mclzero
       -mpku
           These switches enable the use of instructions in the MMX, SSE,
           SSE2, SSE3, SSSE3, SSE4.1, AVX, AVX2, AVX512F, AVX512PF,
           AVX512ER, AVX512CD, SHA, AES, PCLMUL, FSGSBASE, RDRND, F16C, FMA,
           SSE4A, FMA4, XOP, LWP, ABM, AVX512VL, AVX512BW, AVX512DQ,
           AVX512IFMA AVX512VBMI, BMI, BMI2, FXSR, XSAVE, XSAVEOPT, LZCNT,
           RTM, MPX, MWAITX, PKU or 3DNow!  extended instruction sets.  Each
           has a corresponding -mno- option to disable use of these
           instructions.

           These extensions are also available as built-in functions: see
           x86 Built-in Functions, for details of the functions enabled and
           disabled by these switches.

           To generate SSE/SSE2 instructions automatically from floating-
           point code (as opposed to 387 instructions), see -mfpmath=sse.

           GCC depresses SSEx instructions when -mavx is used. Instead, it
           generates new AVX instructions or AVX equivalence for all SSEx
           instructions when needed.

           These options enable GCC to use these extended instructions in
           generated code, even without -mfpmath=sse.  Applications that
           perform run-time CPU detection must compile separate files for
           each supported architecture, using the appropriate flags.  In
           particular, the file containing the CPU detection code should be
           compiled without these options.

       -mdump-tune-features
           This option instructs GCC to dump the names of the x86
           performance tuning features and default settings. The names can
           be used in -mtune-ctrl=feature-list.

       -mtune-ctrl=feature-list
           This option is used to do fine grain control of x86 code
           generation features.  feature-list is a comma separated list of
           feature names. See also -mdump-tune-features. When specified, the
           feature is turned on if it is not preceded with ^, otherwise, it
           is turned off.  -mtune-ctrl=feature-list is intended to be used
           by GCC developers. Using it may lead to code paths not covered by
           testing and can potentially result in compiler ICEs or runtime
           errors.

       -mno-default
           This option instructs GCC to turn off all tunable features. See
           also -mtune-ctrl=feature-list and -mdump-tune-features.

       -mcld
           This option instructs GCC to emit a "cld" instruction in the
           prologue of functions that use string instructions.  String
           instructions depend on the DF flag to select between
           autoincrement or autodecrement mode.  While the ABI specifies the
           DF flag to be cleared on function entry, some operating systems
           violate this specification by not clearing the DF flag in their
           exception dispatchers.  The exception handler can be invoked with
           the DF flag set, which leads to wrong direction mode when string
           instructions are used.  This option can be enabled by default on
           32-bit x86 targets by configuring GCC with the --enable-cld
           configure option.  Generation of "cld" instructions can be
           suppressed with the -mno-cld compiler option in this case.

       -mvzeroupper
           This option instructs GCC to emit a "vzeroupper" instruction
           before a transfer of control flow out of the function to minimize
           the AVX to SSE transition penalty as well as remove unnecessary
           "zeroupper" intrinsics.

       -mprefer-avx128
           This option instructs GCC to use 128-bit AVX instructions instead
           of 256-bit AVX instructions in the auto-vectorizer.

       -mcx16
           This option enables GCC to generate "CMPXCHG16B" instructions.
           "CMPXCHG16B" allows for atomic operations on 128-bit double
           quadword (or oword) data types.  This is useful for high-
           resolution counters that can be updated by multiple processors
           (or cores).  This instruction is generated as part of atomic
           built-in functions: see __sync Builtins or __atomic Builtins for
           details.

       -msahf
           This option enables generation of "SAHF" instructions in 64-bit
           code.  Early Intel Pentium 4 CPUs with Intel 64 support, prior to
           the introduction of Pentium 4 G1 step in December 2005, lacked
           the "LAHF" and "SAHF" instructions which are supported by AMD64.
           These are load and store instructions, respectively, for certain
           status flags.  In 64-bit mode, the "SAHF" instruction is used to
           optimize "fmod", "drem", and "remainder" built-in functions; see
           Other Builtins for details.

       -mmovbe
           This option enables use of the "movbe" instruction to implement
           "__builtin_bswap32" and "__builtin_bswap64".

       -mcrc32
           This option enables built-in functions "__builtin_ia32_crc32qi",
           "__builtin_ia32_crc32hi", "__builtin_ia32_crc32si" and
           "__builtin_ia32_crc32di" to generate the "crc32" machine
           instruction.

       -mrecip
           This option enables use of "RCPSS" and "RSQRTSS" instructions
           (and their vectorized variants "RCPPS" and "RSQRTPS") with an
           additional Newton-Raphson step to increase precision instead of
           "DIVSS" and "SQRTSS" (and their vectorized variants) for single-
           precision floating-point arguments.  These instructions are
           generated only when -funsafe-math-optimizations is enabled
           together with -ffinite-math-only and -fno-trapping-math.  Note
           that while the throughput of the sequence is higher than the
           throughput of the non-reciprocal instruction, the precision of
           the sequence can be decreased by up to 2 ulp (i.e. the inverse of
           1.0 equals 0.99999994).

           Note that GCC implements "1.0f/sqrtf(x)" in terms of "RSQRTSS"
           (or "RSQRTPS") already with -ffast-math (or the above option
           combination), and doesn't need -mrecip.

           Also note that GCC emits the above sequence with additional
           Newton-Raphson step for vectorized single-float division and
           vectorized "sqrtf(x)" already with -ffast-math (or the above
           option combination), and doesn't need -mrecip.

       -mrecip=opt
           This option controls which reciprocal estimate instructions may
           be used.  opt is a comma-separated list of options, which may be
           preceded by a ! to invert the option:

           all Enable all estimate instructions.

           default
               Enable the default instructions, equivalent to -mrecip.

           none
               Disable all estimate instructions, equivalent to -mno-recip.

           div Enable the approximation for scalar division.

           vec-div
               Enable the approximation for vectorized division.

           sqrt
               Enable the approximation for scalar square root.

           vec-sqrt
               Enable the approximation for vectorized square root.

           So, for example, -mrecip=all,!sqrt enables all of the reciprocal
           approximations, except for square root.

       -mveclibabi=type
           Specifies the ABI type to use for vectorizing intrinsics using an
           external library.  Supported values for type are svml for the
           Intel short vector math library and acml for the AMD math core
           library.  To use this option, both -ftree-vectorize and
           -funsafe-math-optimizations have to be enabled, and an SVML or
           ACML ABI-compatible library must be specified at link time.

           GCC currently emits calls to "vmldExp2", "vmldLn2", "vmldLog102",
           "vmldLog102", "vmldPow2", "vmldTanh2", "vmldTan2", "vmldAtan2",
           "vmldAtanh2", "vmldCbrt2", "vmldSinh2", "vmldSin2", "vmldAsinh2",
           "vmldAsin2", "vmldCosh2", "vmldCos2", "vmldAcosh2", "vmldAcos2",
           "vmlsExp4", "vmlsLn4", "vmlsLog104", "vmlsLog104", "vmlsPow4",
           "vmlsTanh4", "vmlsTan4", "vmlsAtan4", "vmlsAtanh4", "vmlsCbrt4",
           "vmlsSinh4", "vmlsSin4", "vmlsAsinh4", "vmlsAsin4", "vmlsCosh4",
           "vmlsCos4", "vmlsAcosh4" and "vmlsAcos4" for corresponding
           function type when -mveclibabi=svml is used, and "__vrd2_sin",
           "__vrd2_cos", "__vrd2_exp", "__vrd2_log", "__vrd2_log2",
           "__vrd2_log10", "__vrs4_sinf", "__vrs4_cosf", "__vrs4_expf",
           "__vrs4_logf", "__vrs4_log2f", "__vrs4_log10f" and "__vrs4_powf"
           for the corresponding function type when -mveclibabi=acml is
           used.

       -mabi=name
           Generate code for the specified calling convention.  Permissible
           values are sysv for the ABI used on GNU/Linux and other systems,
           and ms for the Microsoft ABI.  The default is to use the
           Microsoft ABI when targeting Microsoft Windows and the SysV ABI
           on all other systems.  You can control this behavior for specific
           functions by using the function attributes "ms_abi" and
           "sysv_abi".

       -mtls-dialect=type
           Generate code to access thread-local storage using the gnu or
           gnu2 conventions.  gnu is the conservative default; gnu2 is more
           efficient, but it may add compile- and run-time requirements that
           cannot be satisfied on all systems.

       -mpush-args
       -mno-push-args
           Use PUSH operations to store outgoing parameters.  This method is
           shorter and usually equally fast as method using SUB/MOV
           operations and is enabled by default.  In some cases disabling it
           may improve performance because of improved scheduling and
           reduced dependencies.

       -maccumulate-outgoing-args
           If enabled, the maximum amount of space required for outgoing
           arguments is computed in the function prologue.  This is faster
           on most modern CPUs because of reduced dependencies, improved
           scheduling and reduced stack usage when the preferred stack
           boundary is not equal to 2.  The drawback is a notable increase
           in code size.  This switch implies -mno-push-args.

       -mthreads
           Support thread-safe exception handling on MinGW.  Programs that
           rely on thread-safe exception handling must compile and link all
           code with the -mthreads option.  When compiling, -mthreads
           defines -D_MT; when linking, it links in a special thread helper
           library -lmingwthrd which cleans up per-thread exception-handling
           data.

       -mms-bitfields
       -mno-ms-bitfields
           Enable/disable bit-field layout compatible with the native
           Microsoft Windows compiler.

           If "packed" is used on a structure, or if bit-fields are used, it
           may be that the Microsoft ABI lays out the structure differently
           than the way GCC normally does.  Particularly when moving packed
           data between functions compiled with GCC and the native Microsoft
           compiler (either via function call or as data in a file), it may
           be necessary to access either format.

           This option is enabled by default for Microsoft Windows targets.
           This behavior can also be controlled locally by use of variable
           or type attributes.  For more information, see x86 Variable
           Attributes and x86 Type Attributes.

           The Microsoft structure layout algorithm is fairly simple with
           the exception of the bit-field packing.  The padding and
           alignment of members of structures and whether a bit-field can
           straddle a storage-unit boundary are determine by these rules:

           1. Structure members are stored sequentially in the order in
           which they are
               declared: the first member has the lowest memory address and
               the last member the highest.

           2. Every data object has an alignment requirement.  The alignment
           requirement
               for all data except structures, unions, and arrays is either
               the size of the object or the current packing size (specified
               with either the "aligned" attribute or the "pack" pragma),
               whichever is less.  For structures, unions, and arrays, the
               alignment requirement is the largest alignment requirement of
               its members.  Every object is allocated an offset so that:

                       offset % alignment_requirement == 0

           3. Adjacent bit-fields are packed into the same 1-, 2-, or 4-byte
           allocation
               unit if the integral types are the same size and if the next
               bit-field fits into the current allocation unit without
               crossing the boundary imposed by the common alignment
               requirements of the bit-fields.

           MSVC interprets zero-length bit-fields in the following ways:

           1. If a zero-length bit-field is inserted between two bit-fields
           that
               are normally coalesced, the bit-fields are not coalesced.

               For example:

                       struct
                        {
                          unsigned long bf_1 : 12;
                          unsigned long : 0;
                          unsigned long bf_2 : 12;
                        } t1;

               The size of "t1" is 8 bytes with the zero-length bit-field.
               If the zero-length bit-field were removed, "t1"'s size would
               be 4 bytes.

           2. If a zero-length bit-field is inserted after a bit-field,
           "foo", and the
               alignment of the zero-length bit-field is greater than the
               member that follows it, "bar", "bar" is aligned as the type
               of the zero-length bit-field.

               For example: