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MIPS
Options
The following -m
options are defined for the MIPS family of computers.
-mcpu=cpu type
Assume the
defaults for the machine type cpu
type
when scheduling instructions. The choices for cpu
type
are r2000,
r3000,
r4000,
r4400,
r4600,
and r6000.
While picking a specific cpu
type
will schedule things appropriately for that particular chip, the compiler
will not generate any code that does not meet level 1 of the MIPS ISA (instruction
set architecture) without the -mips2
or -mips3
switches being used.
-mips1
Issue instructions from level 1 of the MIPS ISA. This is the default. r3000
is the default cpu
type at
this ISA level.
-mips2
Issue instructions
from level 2 of the MIPS ISA (branch likely, square root instructions).
r6000
is the default CPU type at this ISA level.
-mips3
Issue instructions from level 3 of the MIPS ISA (64 bit instructions).
r4000
is the default cpu
type at this
ISA level. This option does not change the sizes of any of the C data types.
-mfp32
Assume that 32 32-bit floating point registers are available. This is the
default.
-mfp64
Assume that 32 64-bit floating point registers are available. This is the
default when the -mips3
option is used.
-mgp32
Assume that 32 32-bit general purpose registers are available. This is
the default.
-mgp64
Assume that 32 64-bit general purpose registers are available. This is
the default when the -mips3
option is used.
-mint64
Types long,
int,
and pointer
are 64 bits. This works only if -mips3
is also specified.
-mlong64
Types long
and pointer
are 64 bits, and type int
is 32 bits. This works only if -mips3
is also specified.
-mmips-as
Generate code for the MIPS assembler, and invoke mips-tfile
to add normal debug information. This is the default for all platforms
except for the OSF/1 reference platform, using the OSF/rose object format.
If the either of the -gstabs
or -gstabs+
switches are used, the mips-tfile
program will encapsulate the stabs
within MIPS ECOFF.
-mgas
Generate code for the GNU assembler. This is the default on the OSF/1 reference
platform, using the OSF/rose
object format.
-mrnames
-mno-rnames
The -mrnames
switch says to output code using the MIPS software names for the registers,
instead of the hardware names (i.e., a0
instead of
$4).
The only known assembler that supports this option is the Algorithmics
assembler.
-mgpopt
-mno-gpopt
The -mgpopt
switch says to write all of the data declarations before the instructions
in the text section, this allows the MIPS assembler to generate one word
memory references instead of using two words for short global or static
data items. This is on by default if optimization is selected.
-mstats
-mno-stats
For each non-inline function processed, the -mstats
switch causes the compiler to emit one line to the standard error file
to print statistics about the program (number of registers saved, stack
size, etc.).
-mmemcpy
-mno-memcpy
The -mmemcpy
switch makes all block moves call the appropriate string function (memcpy
or bcopy)
instead of possibly generating inline code.
-mmips-tfile
-mno-mips-tfile
The -mno-mips-tfile
switch causes the compiler not post-process the object file with the mips-tfile
program, after the MIPS assembler has generated it to add debug support.
If mips-tfile
is not run, then no local variables will be available to the debugger.
In addition, stage2
and stage3
objects will have the temporary filenames passed to the assembler embedded
in the object file, which means the objects will not compare the same.
The -mno-mips-tfile
switch should only be used when there are bugs in the mips-tfile
program that prevents compilation.
-msoft-float
Generate output containing library calls for floating point.
- Warning:
The requisite libraries are not part of GNU CC. Normally the facilities
of the machines usual C compiler are used, but this cant be done directly
in cross-compilation. You must make your own arrangements to provide suitable
library functions for cross-compilation.
-mhard-float
Generate output containing floating point instructions. This is the default
if you use the unmodified sources.
-mabicalls
-mno-abicalls
Emit (or do not emit) the pseudo operations .abicalls,
.cpload,
and .cprestore
that some System V.4 ports use for position independent code.
-mlong-calls
-mno-long-calls
Do all calls with the JALR
instruction, which requires loading up a functions address into a register
before the call. You need to use this switch, if you call outside of the
current 512 megabyte segment to functions that are not through pointers.
-mhalf-pic
-mno-half-pic
Put pointers to extern references into the data section and load them up,
rather than put the references in the text section.
-membedded-pic
-mno-embedded-pic
Generate PIC code suitable for some embedded systems. All calls are made
using PC relative address, and all data is addressed using the $gp
register. This requires GNU as
and GNU ld
which do most of the work.
-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.
-msingle-float
-mdouble-float
The -msingle-float
switch tells gcc
to assume that the floating point coprocessor only supports single precision
operations, as on the r4650
chip. The -mdouble-float
switch permits gcc
to use double precision operations. This is the default.
-mmad
-mno-mad
Permit use of the mad,
madu
and mul
instructions, as on the r4650
chip.
-m4650
Turns on -msingle-float,
-mmad,
and, at least for now, -mcpu=r4650.
-EL
Compile code for the processor in little endian mode. The requisite libraries
are assumed to exist.
-EB
Compile code for the processor in big endian mode. The requisite libraries
are assumed to exist.
-G
num
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. This allows the assembler to emit one word memory reference instructions
based on the global pointer (gp
or $28),
instead of the normal two words used. By default, num
is 8 when the MIPS assembler is used, and 0 when the GNU assembler is used.
The -G num
switch is also passed to the assembler and linker. All modules should be
compiled with the same -G
num
value.
-nocpp
Tell the MIPS
assembler to not run its preprocessor over user assembler files (with a
suffix, .s)
when assembling them.