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IBM RS/6000 and PowerPC Options
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IBM
RS/6000 and PowerPC Options
These -m
options are defined for the IBM RS/6000 and PowerPC.
-
-mpower
-
-mno-power
-
-mpower2
-
-mno-power2
-
-mpowerpc
-
-mno-powerpc
-
-mpowerpc-gpopt
-
-mno-powerpc-gpopt
-
-mpowerpc-gfxopt
-
-mno-powerpc-gfxopt
-
-mpowerpc64
-
-mno-powerpc64
GNU CC supports two related
instruction set architectures for the RS/6000 and PowerPC. The POWER
instruction set are those instructions supported by the rios
chip set used in the original RS/6000 systems and the PowerPC instruction
set is the architecture of the Motorola MPC5xx, MPC6xx, MCP8xx
and the IBM 4xx microprocessors.
Neither architecture is
a subset of the other. However there is a large common subset of instructions
supported by both. An MQ register is included in processors supporting
the POWER architecture.
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 GNU CC.
Specifying the -mcpu=cpu_type
overrides the specification of these options.
We recommend you use the
-mcpu=cpu_type
option rather than any of the above listed options.
The -mpower
option allows GNU CC to generate instructions that are found only in the
POWER architecture and to use the MQ register. Specifying -mpower2
implies -power
and also allows GNU CC to generate instructions tha
ffb
t are present in the
POWER2 architecture but not the original POWER architecture.
The -mpowerpc
option allows GNU CC to generate instructions that are found only in the
32-bit subset of the PowerPC architecture. Specifying -mpowerpc-gpopt
implies -mpowerpc
and also allows GNU CC to use the optional PowerPC architecture instructions
in the General Purpose group, including floating-point square root.
Specifying -mpowerpc-gfxopt
implies -mpowerpc
and also allows GNU CC to use the optional PowerPC architecture instructions
in the Graphics group, including floating-point select.
The -mpowerpc64
option allows GNU CC to generate the additional 64-bit instructions that
are found in the full PowerPC64 architecture and to treat GPRs as 64-bit,
doubleword quantities. GNU CC defaults to -mno-powerpc64.
If you specify both -mno-power
and -mno-powerpc,
GNU CC will use only the instructions in the common subset of both architectures
plus some special AIX common-mode calls, and will not use the MQ register.
Specifying both -mpower
and -mpowerpc
permits GNU CC to use any instruction from either architecture and to allow
use of the MQ register; specify this for the Motorola MPC601.
-
-mnew-mnemonics
-mold-mnemonics
Select which mnemonics to
use in the generated assembler code.
-mnew-mnemonics
requests output that uses the assembler mnemonics defined for the PowerPC
architecture, while -mold-mnemonics
requests the assembler mnemonics defined for the POWER architecture. Instructions
defined in only one architecture have only one mnemonic; GNU CC uses that
mnemonic irrespective of which of these options is specified.
PowerPC assemblers support
both the old and new mnemonics, as will later POWER assemblers. Current
POWER assemblers only support the old mnemonics. Specify -mnew-mnemonics
if you have an assembler that supports them, otherwise specify -mold-mnemonics.
The default value of these
options depends on how GNU CC was configured. Specifying -mcpu=cpu_type
sometimes overrides the value of these option. Unless you are building
a cross-compiler, you should normally not specify either -mnew-mnemonics
or -mold-mnemonics,
but should instead accept the default.
-
-mcpu=cpu_type
Set architecture type, register
usage, choice of mnemonics, and instruction scheduling parameters for machine
type, cpu_type.
Supported values for cpu_type
are rs6000,
rios1,
rios2,
rsc,
601,
602,
603,
603e,
604,
604e,
620,
power,
power2,
powerpc,
403,
505,
801,
821,
823,
860
and common.
The -mcpu=power,
-mcpu=power2,
and -mcpu=powerpc
options specify generic POWER, POWER2 and pure PowerPC (i.e., not MPC601)
architecture machine types, with an appropriate, generic processor model
assumed for scheduling purposes.
Specifying -mcpu=rios1,
-mcpu=rios2,
-mcpu=rsc,
-mcpu=power,
or -mcpu=power2
enables the -mpower
option and disables the -mpowerpc
option; -mcpu=601
enables both the -mpower
and -mpowerpc
options. All of the -mcpu=602,
-mcpu=603,
-mcpu=603e,
-mcpu=604,
and -mcpu=620
options enable the -mpowerpc
option and disable the -mpower
option.
Exactly similarly, -mcpu=403,
-mcpu=505,
-mcpu=821,
-mcpu=860
and -mcpu=powerpc
all enable the -mpowerpc
option and disable the -mpower
option. -mcpu=commondisables
both the -mpower
and -mpowerpc
options.
AIX versions 4 or greater
selects -mcpu=common
by default, so that code will operate on all members of the RS/6000 and
PowerPC families. In that case, GNU CC will use only the instructions in
the common subset of both architectures plus some special AIX common-mode
calls, and will not use the MQ register. GNU CC assumes a generic processor
model for scheduling purposes.
Specifying any of the -mcpu=rios1,
-mcpu=rios2,
-mcpu=rsc,
-mcpu=power,
or -mcpu=power2
options also disables the new-mnemonics
option. Specifying -mcpu=601,
-mcpu=602,
-mcpu=603,
-mcpu=603e,
-mcpu=604,
-mcpu=620,
-mcpu=403,
or -mcpu=powerpc
also enables the new-mnemonics
option.
Specifying -mcpu=403,
-mcpu=821,
or -mcpu=860
also enables the -msoft-float
option.
-
-mtune=cpu_type
Set the instruction scheduling
parameters for machine type cpu_type,
but do not set the architecture type, register usage, choice of mnemonics
like -mcpu=cpu_type
would. The
same values for cpu_type
are used for
-mtune=cpu_type
as for -mcpu=cpu_type.
The -mtune=cpu_typeoption
overrides the -mcpu=cpu_type
option in terms of instruction scheduling parameters.
-
-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, GNU CC will allocate at least
one TOC entry for each unique non-automatic variable reference in your
program. GNU CC will also place 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 GNU CC from putting floating-point constants in the TOC and -mno-sum-in-toc
forces GNU CC 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 GNU CC 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 GNU CC to make only one TOC entry for every
file. When you specify this option, GNU CC will produce 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 AIX 64-bit
ABI and calling convention: 64-bit pointers, 64-bit long type, and the
infrastructure needed to support them. Specifying -maix64
implies -mpowerpc64
and -mpowerpc,
while -maix32
disables the 64-bit ABI and implies -mno-powerpc64.
GNU CC defaults to -maix32.
-
-mxl-call
-
-mno-xl-call
On AIX, pass floating-point
arguments to prototyped functions beyond the register save area (RSA) on
the stack in addition to floating point register arguments. 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. AIX XL compilers assume that floating
point arguments which do not fit in the RSA are on the stack when they
compile a subroutine 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 AIX XL compilers without optimization.
-
-mthreads
Support AIX Threads.
Link an application written to use pthreads with special libraries
and startup code to enable the application to run.
-
-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 -mthreads
option are incompatible.
-
-msoft-float
-
-mhard-float
Generate code that does
not use (or uses) the floating-point register set. Software floating point
emulation is provided if you use the -msoft-float
option, and pass the option to GNU CC when linking.
-
<
ffb
FONT SIZE=+0>-mmultiple
-
-mno-multiple
Generate code that uses
(or 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.
-
-mstring
-
-mno-string
Generate code that uses
(or 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.
Warning:
Do not use -mstring
on little endian PowerPC systems, since those instructions do not work
when the processor is in little endian mode.
-
-mupdate
-
-mnoupdate
Generate code that
uses (or 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.
-
-mfused-madd
-
-mno-fused-madd
Generate code that
uses (or does not use) the oating point multiply and accumulate instructions.
These instructions are generated by default if hardware floating is used.
-
-mno-bit-align
-
-mbit-align
On System V.4 and embedded
PowerPC systems do not (or 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 bitfields of length
1 would be aligned to a 4 byte boundary and have a size of 4 bytes. By
using -mno-bit-align,
the structure would be aligned to a 1 byte boundary and be one byte in
size.
-
-mno-strict-align
-
-mstrict-align
On System V.4 and embedded
PowerPC systems do not (or do) ass
ffb
ume that unaligned memory references
will be handled by the system.
-
-mrelocatable
-
-mno-relocatable
On embedded PowerPC systems
generate code that allows (or does not allow) the program to be relocated
to a different address at runtime. If you use -mrelocatable
on any module, all objects linked together must be compiled with -mrelocatable
or -mrelocatable-lib.
-
-mrelocatable-lib
-
-mno-relocatable-lib
On embedded PowerPC systems
generate code that allows (or does not allow) the program to be relocated
to a different address at runtime. Modules compiled with -mreloctable-lib
can be linked with either modules compiled without -mrelocatable
and -mrelocatable-lib
or with modules compiled with the -mrelocatable
options.
-
-mno-toc
-
-mtoc
On System V.4 and embedded
PowerPC systems do not (or do) assume that register 2 contains a pointer
to a global area pointing to the addresses used in the program.
-
-mno-traceback
-
-mtraceback
On embedded PowerPC systems
do not (or do) generate a trace-back tag before the start of the function.
This tag can be used by the debugger to identify where the start of a function
is.
-
-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.
-
-mcall-sysv
On System V.4 and embedded
PowerPC systems compile code using calling conventions that adheres to
the March 1995 draft of the System V Application Binary Interface (ABI),
PowerPC processor supplement. This is the default unless you configured
GCC using powerpc-*-eabiaix.
-
-mcall-sysv-eabi
Specify both -mcall-sysv
and -meabi
options.
-
-mcall-sysv-noeabi
Specify both -mcall-sysv
and -mnoeabi
options.
-
-mcall-aix
On System V.4 and embedded
PowerPC systems compile code using calling conventions that are similar
to those used on AIX. This is the default if you configured GCC using powerpc-*-eabiaix.
-
-mcall-solaris
On System V.4 and embedded
PowerPC systems, compile code for the Solaris operating system.
-
-mcall-linux
On System V.4 and embedded
PowerPC systems, compile code for the Linux operating system.
-
-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 were passed in the floating point
registers in case the function takes a variable arguments.
-
With -mprototype,
only calls to prototyped variable argument functions will set or clear
the bit.
-
ffb
-
-msim
On embedded PowerPC systems,
assume that the startup module is called sim-crt0.o
and the standard
C libraries are libsim.a
and libc.a.
This is default for powerpc-*-eabisim
configurations.
-
-mmvme
On embedded PowerPC systems,
assume that the startup module is called mvme-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.
-
-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 (or do not) adhere to the Embedded Applications Bi
ffb
nary
Interface (hence, 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 to 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, and that there is
no call of an initialization function from main, and the -msdata
option will only use 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 and static data in the .sdata
section. Put small uninitialized global and static 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.
-
-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 in
4cf
stead 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 (or do not) emit register names in the assembly language
output using symbolic forms.
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