These function attributes are supported by the x86 back end:
cdeclcdecl attribute causes the compiler to
assume that the calling function pops off the stack space used to
pass arguments. This is
useful to override the effects of the -mrtd switch.
fastcallfastcall attribute causes the compiler to
pass the first argument (if of integral type) in the register ECX and
the second argument (if of integral type) in the register EDX. Subsequent
and other typed arguments are passed on the stack. The called function
pops the arguments off the stack. If the number of arguments is variable all
arguments are pushed on the stack.
thiscallthiscall attribute causes the compiler to
pass the first argument (if of integral type) in the register ECX.
Subsequent and other typed arguments are passed on the stack. The called
function pops the arguments off the stack.
If the number of arguments is variable all arguments are pushed on the
stack.
The thiscall attribute is intended for C++ non-static member functions.
As a GCC extension, this calling convention can be used for C functions
and for static member methods.
ms_abisysv_abims_abi attribute tells the compiler to use the Microsoft ABI,
while the sysv_abi attribute tells the compiler to use the ABI
used on GNU/Linux and other systems. The default is to use the Microsoft ABI
when targeting Windows. On all other systems, the default is the x86/AMD ABI.
Note, the ms_abi attribute for Microsoft Windows 64-bit targets currently
requires the -maccumulate-outgoing-args option.
callee_pop_aggregate_return (number)The default x86-32 ABI assumes that the callee pops the
stack for hidden pointer. However, on x86-32 Microsoft Windows targets,
the compiler assumes that the
caller pops the stack for hidden pointer.
ms_hook_prologueregparm (number)regparm attribute causes the compiler to
pass arguments number one to number if they are of integral type
in registers EAX, EDX, and ECX instead of on the stack. Functions that
take a variable number of arguments continue to be passed all of their
arguments on the stack.
Beware that on some ELF systems this attribute is unsuitable for
global functions in shared libraries with lazy binding (which is the
default). Lazy binding sends the first call via resolving code in
the loader, which might assume EAX, EDX and ECX can be clobbered, as
per the standard calling conventions. Solaris 8 is affected by this.
Systems with the GNU C Library version 2.1 or higher
and FreeBSD are believed to be
safe since the loaders there save EAX, EDX and ECX. (Lazy binding can be
disabled with the linker or the loader if desired, to avoid the
problem.)
sseregparmsseregparm attribute
causes the compiler to pass up to 3 floating-point arguments in
SSE registers instead of on the stack. Functions that take a
variable number of arguments continue to pass all of their
floating-point arguments on the stack.
force_align_arg_pointerforce_align_arg_pointer attribute may be
applied to individual function definitions, generating an alternate
prologue and epilogue that realigns the run-time stack if necessary.
This supports mixing legacy codes that run with a 4-byte aligned stack
with modern codes that keep a 16-byte stack for SSE compatibility.
stdcallstdcall attribute causes the compiler to
assume that the called function pops off the stack space used to
pass arguments, unless it takes a variable number of arguments.
target (options)On the x86, the following options are allowed:
sin, cos, and
sqrt instructions on the 387 floating-point unit.
target("fpmath=sse,387") option as
target("fpmath=sse+387") because the comma would separate
different options.
On the x86, the inliner does not inline a
function that has different target options than the caller, unless the
callee has a subset of the target options of the caller. For example
a function declared with target("sse3") can inline a function
with target("sse2"), since -msse3 implies -msse2.