CALLING CONVENTIONS
Calling conventions specify the way a function is called. The standard calling conventions, cdecl, place an underscore ('_') before the function name in the function's label and pass all parameters on the stack. The caller of the function must remove those arguments from the stack. Structure return values are also stored on the stack. These calling conventions are slow because they require all arguments and structure return values to be passed through memory and only 4-byte alignment is maintained. VectorC provides some other calling conventions that can speed up function calling and return.CodePlay defined calling conventions cannot be called by code compiled in other compilers. You either need to compile all your code with VectorC or provide transfer functions compiled with VectorC, but with cdecl or fastcall calling conventions. Using codeplay_mmx, codeplay_3dnow or codeplay_sse when compiling for processors with the necessary support can speed up functions calls massively. Also, all CodePlay calling conventions maintain 16-byte alignment which can speed up MMX, SSE and floating-point code dramatically. Using codeplay_mmx, codeplay_3dnow and codeplay_sse will let VectorC use MMX and 3DNow! in more places than it would otherwise. This is because these calling conventions assume the processor is in MMX mode at the point of call and return. The compiler therefore doesn't have to include the cost of switching FPU/MMX mode when deciding whether to use MMX for a particular function.
You can specify a default calling convention on the command line. This makes it easier if you want to compile your entire program with VectorC.
For most calling conventions (apart from cdecl), function prototypes are required. Otherwise, cdecl will be assumed.
The "main" function will always be set to cdecl.
| Name | Format in C Source | Format on Command Line | Arguments | Return | Modifies |
Alignment
|
Label Name | Comments |
| cdecl | cdecl | /Gd /cdecl |
stack - caller cleanup |
byte: al |
eax, ecx, edx |
4
|
_name | Default |
| fastcall | __fastcall | /Gr /fastcall |
ecx, edx, stack |
byte: al word/dword: eax 8-byte: eax, edx other structure: address passed in eax |
eax, ecx, edx, st(0)..st(7), mm0..mm7, xmm0..xmm7 |
4
|
@name@size | Microsoft - defined register calling. Swaps to cdecl for non-prototyped functions or functions with variable number of arguments |
| watcom | __declspec (wcall) | /wcalls /vec:wcalls |
eax, ebx, ecx, edx |
byte: al |
4
|
name_ | Register calling conventions used by Watcom C/C++. Arguments passed on the stack for non-prototyped functions or functions with variable number of arguments | |
| pascal | __pascal | stack | byte: al word/dword: eax 8-byte: eax, edx other structure: address passed on stack |
eax, ecx, edx st(0)..st(7) mm0..mm7 xmm0..xmm7 |
4
|
_NAME | ||
| stdcall | __stdcall | /Gz | stack | byte: al word/dword: eax 8-byte: eax, edx other structure: address passed on stack |
eax, ecx, edx st(0)..st(7) mm0..mm7 xmm0..xmm7 |
4
|
_name@size | Used for DLLs. |
| syscall | __syscall | stack | byte: al word/dword: eax 8-byte: eax, edx other structure: address passed on stack |
eax, ecx, edx st(0)..st(7) mm0..mm7 xmm0..xmm7 |
4
|
name | Used in OS/2 | |
| codeplay | __declspec (codeplay) | /cpcalls /vec:cpcalls |
eax, ebx, ecx, edx stack |
byte: al word/dword: eax 8-byte: eax, edx other structure: address passed in esi |
eax, ecx, edx st(0)..st(7) mm0..mm7 xmm0..xmm7 |
16
|
@name@CP_size | CodePlay defined calling conventions. Swapped to |
| codeplay _mmx |
__declspec (codeplay_ mmx) |
/mmxcalls /vec:mmxcalls |
eax, ebx,,br.ecx, edx, mm0..mm4 stack |
byte: al word/dword: eax 8-byte: mm0 12/16-byte: mm0,mm1 other structure: address passed in esi |
eax, ecx, edx st(0)..st(7) mm0..mm7 xmm0..xmm7 |
16
|
@name@MMX_size | CodePlay defined calling conventions. Swaps to "codeplay" if any parameters or return value are floating-point values. Called in MMX mode. |
| codeplay _3dnow |
__declspec (codeplay_ 3dnow) |
/3dnowcalls /vec:3dnowcalls |
eax, ebx, |
byte: al word/dword: eax float: mm0 8-byte: mm0 12/16-byte: mm0,mm1 other structure: address passed in esi |
eax, ecx, edx st(0)..st(7) mm0..mm7 xmm0..xmm7 |
16
|
@name@3DN_size | CodePlay defined calling conventions. Swaps to "codeplay" if any parameters or return value are double or long double values. Called in MMX mode. Only works for processors with 3DNow! support |
| codeplay _sse |
__declspec (codeplay _sse) |
/ssecalls /vec:ssecalls |
eax, ebx, |
byte: al |
eax, ecx, edx st(0)..st(7) mm0..mm7 xmm0..xmm7 |
16
|
@name@SSE_size | CodePlay defined calling conventions. Swaps to "codeplay" if any parameters or return value are double or long double values. Called in MMX mode. Only works for processors with SSE support |
