Using and Porting GNU CC
-m' switches are supported on the SPARC:
-mapp-regs' to generate output using the global registers 2 through 4, which the SPARC SVR4 ABI reserves for applications. This is the default.
To be fully SVR4 ABI compliant at the cost of some performance loss,
-mno-app-regs'. You should compile libraries and system
software with this option.
-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 `
library that comes with GNU CC, with `
-msoft-float' in order for
this to work.
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.
-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.
-mno-epilogue', the compiler tries to emit exit code inline
at every function exit.
-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 although debugger support is still incomplete. 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.
-mno-flat' (the default), the compiler emits save/restore
instructions (except for leaf functions) and is the normal mode of operation.
-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.
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.
-mcypress' (the default), the compiler optimizes code for the
Cypress CY7C602 chip, as used in the SparcStation/SparcSever 3xx series.
This is also apropriate for the older SparcStation 1, 2, IPX etc.
-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.
In a future version of GCC, these options will very likely be
renamed to `
-mcpu=cypress' and `
-m' switches are supported in addition to the above
on SPARC V9 processors:
-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.