-mmfcrf-mno-mfcrf-mpopcntb-mno-popcntb- 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.
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.
-mcpu=cpu_type- Set architecture type, register usage, and
instruction scheduling parameters for machine type cpu_type.
Supported values for cpu_type are ‘8540’, ‘8548’,
and ‘native’.
-mcpu=powerpc specifies pure 32-bit PowerPC (either
endian), 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:
-mhard-float -mmfcrf -mmultiple
-mpopcntb -mpopcntd
-msingle-float -mdouble-float
-mfloat128
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=8548.
-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.
-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.
-mspe-mno-spe- This switch enables or disables the generation of SPE simd
instructions.
-mspe=yes/no- This option has been deprecated. Use -mspe and
-mno-spe instead.
-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.
-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.
-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.
-maix32- Disables the 64-bit ABI. 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.
-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.
-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.
-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 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.
-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.
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.
-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.
-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.