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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-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 -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’, ‘future’, ‘powerpc’, ‘powerpc64’,
‘powerpc64le’, ‘rs64’, and ‘native’.
-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.
Specifying ‘native’ as cpu type detects and selects the
architecture option that corresponds to the host processor of the
system performing the compilation.
-mcpu=native has no effect if GCC does not recognize the
processor.
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 -mmulhw -mdlmzb -mmfpgpr -mvsx -mcrypto -mhtm -mpower8-fusion -mpower8-vector -mquad-memory -mquad-memory-atomic -mfloat128 -mfloat128-hardware -mprefixed -mpcrel -mmma
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. This is the default for 64-bit Linux.
-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, 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.
-mvrsave-mno-vrsave
Generate VRSAVE instructions when generating AltiVec code.
-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.
-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.
-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.
-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,
-mcpu=power8), or -mcpu=power9 must be enabled to
use the IEEE 128-bit floating point support. The IEEE 128-bit
floating point support only works on PowerPC Linux systems.
The default for -mfloat128 is enabled on PowerPC Linux
systems using the VSX instruction set, and disabled on other systems.
If you use the ISA 3.0 instruction set (-mpower9-vector or
-mcpu=power9) on a 64-bit system, the IEEE 128-bit floating
point support will also enable the generation of ISA 3.0 IEEE 128-bit
floating point instructions. Otherwise, if you do not specify to
generate ISA 3.0 instructions or you are targeting a 32-bit big endian
system, 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.
The default for -mfloat128-hardware is enabled on PowerPC
Linux systems using the ISA 3.0 instruction set, and disabled on other
systems.
-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.
-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.
-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.
numberAny 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.
numberInsert 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.
-mtraceback=traceback_type
Select the type of traceback table. Valid values for traceback_type
are ‘full’, ‘part’, and ‘no’.
-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’,
‘ibmlongdouble’, ‘ieeelongdouble’,
‘elfv1’, ‘elfv2’.
-mabi=ibmlongdouble
Change the current ABI to use IBM extended-precision long double.
This is not likely to work if your system defaults to using IEEE
extended-precision long double. If you change the long double type
from IEEE extended-precision, the compiler will issue a warning unless
you use the -Wno-psabi option. Requires -mlong-double-128
to be enabled.
-mabi=ieeelongdouble
Change the current ABI to use IEEE extended-precision long double.
This is not likely to work if your system defaults to using IBM
extended-precision long double. If you change the long double type
from IBM extended-precision, the compiler will issue a warning unless
you use the -Wno-psabi option. Requires -mlong-double-128
to be enabled.
-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.
-mgnu-attribute-mno-gnu-attribute
Emit .gnu_attribute assembly directives to set tag/value pairs in a .gnu.attributes section that specify ABI variations in function parameters or return values.
-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.
-mreadonly-in-sdata
Put read-only objects in the .sdata section as well. This is the
default.
-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.
-mblock-compare-inline-limit=num
Generate non-looping inline code for all block compares (such as calls
to memcmp or structure compares) less than or equal to num
bytes. If num is 0, all inline expansion (non-loop and loop) of
block compare is disabled. The default value is target-specific.
-mblock-compare-inline-loop-limit=num
Generate an inline expansion using loop code for all block compares that
are less than or equal to num bytes, but greater than the limit
for non-loop inline block compare expansion. If the block length is not
constant, at most num bytes will be compared before memcmp
is called to compare the remainder of the block. The default value is
target-specific.
-mstring-compare-inline-limit=num
Compare at most num string bytes with inline code.
If the difference or end of string is not found at the
end of the inline compare a call to strcmp or strncmp will
take care of the rest of the comparison. The default is 64 bytes.
-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 PowerPC64 ELFv2 and 32-bit PowerPC systems with newer GNU linkers,
GCC can generate long calls using an inline PLT call sequence (see
-mpltseq). PowerPC with -mbss-plt and PowerPC64
ELFv1 (big-endian) do not support inline PLT calls.
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.
-mpltseq-mno-pltseq
Implement (do not implement) -fno-plt and long calls using an inline
PLT call sequence that supports lazy linking and long calls to
functions in dlopen’d shared libraries. Inline PLT calls are only
supported on PowerPC64 ELFv2 and 32-bit PowerPC systems with newer GNU
linkers, and are enabled by default if the support is detected when
configuring GCC, and, in the case of 32-bit PowerPC, if GCC is
configured with --enable-secureplt. -mpltseq code
and -mbss-plt 32-bit PowerPC relocatable objects may not be
linked together.
-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.
-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.
-mstack-protector-guard=guard-mstack-protector-guard-reg=reg-mstack-protector-guard-offset=offset-mstack-protector-guard-symbol=symbol
Generate stack protection code using canary at guard. Supported
locations are ‘global’ for global canary or ‘tls’ for per-thread
canary in the TLS block (the default with GNU libc version 2.4 or later).
With the latter choice the options
-mstack-protector-guard-reg=reg and
-mstack-protector-guard-offset=offset furthermore specify
which register to use as base register for reading the canary, and from what
offset from that base register. The default for those is as specified in the
relevant ABI. -mstack-protector-guard-symbol=symbol overrides
the offset with a symbol reference to a canary in the TLS block.
-mpcrel-mno-pcrel
Generate (do not generate) pc-relative addressing when the option
-mcpu=future is used. The -mpcrel option requires
that the medium code model (-mcmodel=medium) and prefixed
addressing (-mprefixed) options are enabled.
-mprefixed-mno-prefixed
Generate (do not generate) addressing modes using prefixed load and
store instructions when the option -mcpu=future is used.
-mmma-mno-mma
Generate (do not generate) the MMA instructions when the option
-mcpu=future is used.
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