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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
-mtune=cpu_type,
although the only useful values for those that select a particular CPU
implementation: cypress,
supersparc,
f930,
f934,
tsc701,
and ultrasparc.
-
-malign-loops=num
Align loops to a 2 raised
to a num
byte boundary. If -malign-loops
is not specified, the default is 2.
-
-malign-jumps=num
Align instructions that
are only jumped to a 2 raised to a num
byte boundary. If -malign-jumps
is not specified, the default is 2.
-
-malign-functions=num
Align the start of functions
to a 2 raised to a num
byte boundary. If -malign-functions
is not specified, the default is 2 if compiling for a 32-bit SPARC processor,
and 5 if compiling for a 64-bit SPARC processor.
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.
-
-m32
-
-m64
Generate code for
a 32-bit or 64-bit environment. The 32-bit environment sets int,
long
and pointer
to 32-bits. The 64-bit environment sets int
to 32-bits and long
and pointer
to 64-bits.
-
-mcmodel=medlow
Generate code for the Medium/Low
code model: the program must be linked in the low 32 bits of the address
space. Pointers are still 64 bits. Programs can be statically or dynamically
linked.
-
-mcmodel=medmid
Generate code for the Medium/Middle
code model: the program must be linked in the low 44 bits of the address
space, the text segment must be less than 2G bytes, and data segment must
be within 2G of the text segment. Pointers are 64 bits.
-
-mcmodel=medany
Generate code for the Medium/Anywhere
code model: the program may be linked anywhere in the address space, the
text segment must be less than 2G bytes, and data segment must be within
2G of the text segment. Pointers are 64 bits.
-
-mcmodel=embmedany
Generate code for the Medium/Anywhere
code model for embedded systems: assume a 32-bit text and a 32-bit data
segment, both starting anywhere (determined at link time). Register %g4
points to the base of the data segment. Pointers still 64 bits. Programs
are statically linked, PIC is not supported.
-
-mstack-bias
-
-mno-stack-bias
With -mstack-bias,
GNU CC assumes 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.
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