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SPARC
Options
The following -m
switches 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 Application Binary Interface (ABI) reserves for applications. 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.
-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 GNU CC, 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-epilogue
-mepilogue
With -mepilogue
(the default), the compiler always emits code for function exit at the
end of each function. Any function exit in the middle of the function (such
as a return statement in C) will generate a jump to the exit code at the
end of the function.
With -mno-epilogue,
the compiler tries to emit exit code inline at every function exit.
-mno-flat
-mflat
With -mflat,
the compiler does not generate save/restore instructions and will use a
flat or single register window calling convention. This model uses
%i7
as the frame pointer and is compatible with the normal register window
model. Code from either may be intermixed. The local registers and the
input registers (0-5) are still treated as “call saved” registers and will
be saved on the stack as necessary.
With -mno-flat
(the default), the compiler emits save/restore instructions (except for
leaf functions) and is the normal mode of operation.
-mno-unaligned-doubles
-munaligned-doubles
Assume that doubles have 8 byte alignment. This is the default.
With -munaligned-doubles,
GNU CC 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.
-mv8
-msparclite
These two options
select variations on the SPARC architecture.
By default (unless specifically
configured for the Fujitsu SPARClite), GCC generates code for the v7 variant
of the SPARC architecture.
-mv8
will give you SPARC v8 code. 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.
-msparclite
will give you SPARClite code. This adds the integer
multiply, integer
divide step and
scan (ffs)
instructions which exist in SPARClite but not in SPARC v7.
These options are deprecated
and will be deleted in GNU CC 2.9. They have been replaced with -mcpu=xxx.
-mcypress
-msupersparc
These two options
select the processor for which the code is optimized.
With -mcypress
(the default), the compiler optimizes code 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 -msupersparc
the compiler optimizes code for the SuperSparc CPU, as used in the SparcStation
10, 1000 and 2000 series. This flag also enables use of the full SPARC
v8 instruction set. These options are deprecated and will be deleted in
GNU CC 2.9. They have been replaced with -mcpu=xxx.
-mcpu=cpu_type
Set architecture
type and instruction scheduling parameters for machine type cpu_type.
Supported values for cpu_type
are common,
cypress,
v8,
supersparc,
sparclite,
f930,
f934,
sparclet,
90c701,
v8plus,
v9,
and ultrasparc.
Specifying ‘v9’
is only supported on true 64 bit targets.
-mtune=cpu_type
Set the instruction
scheduling parameters for machine type cpu_type,
but do not set the architecture type like -mcpu=cpu_type
would. The same values for -mcpu=cpu_type
are used for
-tune=cpu_type.
The following -m
switches are supported in addition to the previous switches on SPARCLET
processor.
-mlittle-endian
Generate code for a processor running in little-endian mode.
-mlive-g0
Treat register %g0
as a normal register. GCC will continue to clobber it as necessary but
will not assume it always reads as 0.
-mbroken-saverestore
Generate code that does not use non-trivial forms of the save
and restore
instructions. Early versions of the SPARCLET processor do not correctly
handle save
and restore
instructions used with arguments. They correctly handle them used without
arguments. A save
instruction used without arguments increments the current window pointer
but does not allocate a new stack frame. It is assumed that the window
overflow trap handler will properly handle this case as will interrupt
handlers.
The following -m
switches are supported in addition to the previous switches on SPARC V9
processors in 64 bit environments.
-mlittle-endian
Generate code for a processor running in little-endian mode.
-mmedlow
Generate code
for the Medium/Low code model: assume a 32 bit address space. Programs
are statically linked, PIC is not supported. Pointers are still 64 bits.
It is very likely that a future version of GCC will rename this option.
-mmedany
Generate code
for the Medium/Anywhere code model: assume a 32 bit text and a 32 bit data
segment, both starting anywhere (determined at link time). Programs are
statically linked, PIC is not supported. Pointers are still 64 bits.
It is very likely that a
future version of GCC will rename this option.
-mfullany
Generate code
for the Full/Anywhere code model: assume a full 64 bit address space. PIC
is not supported.
It is very likely that a
future version of GCC will rename this option.
-mint64
Types long
and int
are 64 bits.
-mlong32
Types long
and int
are 32 bits.
-mlong64
-mint32
Type long
is 64 bits, and type int
is 32 bits.
-mstack-bias
-mno-stack-bias
With -mstack-bias,
assume that the stack pointer, and frame pointer if present, are offset
by -2047
which must be added back when making stack frame references. Otherwise,
assume no such offset is present.