fastcall | 易学教程

MASM x86 fastcall function declaration… how?

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问题 I'm trying to make a VisualStudio 2010 C program call a fastcall convention assembly routine. This is the declaration in the C code: extern boolean _fastcall InNonSuspendableCriticalRegion(DWORD); This is the declaration in the assembly code: public @InNonSuspendableCriticalRegion@4 @InNonSuspendableCriticalRegion@4 proc near ; fastcall <code> @InNonSuspendableCriticalRegion@4 endp I get the following linker error: Assembling: C:\DMS\Domains\PARLANSE\Tools\RunTimeSystem\Source\PARLANSE0.asm 1

Is fastcall really faster?

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问题 Is the fastcall calling convention really faster than other calling conventions, such as cdecl? Are there any benchmarks out there that show how performance is affected by calling convention? 回答1: It depends on the platform. For a Xenon PowerPC, for example, it can be an order of magnitude difference due to a load-hit-store issue with passing data on the stack. I empirically timed the overhead of a cdecl function at about 45 cycles compared to ~4 for a fastcall . For an out-of-order x86

C manually call function with stack and register

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问题 i know this is the big deal to manipulate stack but i think it would be a great lesson for me. im searched the internet, and i found calling convention. I know how its working and why. I whant to simulate some of "Callee clean-up stack" maybe stdcall, fastcall its doesnt matter, important think is that who clean-up stack, then i will be have less work do to :) for example. i have function in C double __fastcall Add(int a, int b) { return a + b; } it will be Calee and i have pointer to this

Addressing variables (or, what is ML64 generating?)

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问题 I have an ASM file written for X64. It provides a leaf function. The file was assembled with MASM64/ML64. The C-pseduo code with a signature is: int GenerateBlock(byte* ptr, size_t size, unsigned int safety) { if (ptr == NUL) return 0; /*FAIL*/ ... } Here's the same portion of ASM code: ;; RCX (in): byte* buffer ;; RDX (in): size_t bsize ;; R8d (in): unsigned int safety ;; RAX (out): bool, success (1), failure (0) ASM_GenerateBlock PROC buffer:QWORD,bsize:QWORD,safety:DWORD LOCAL val:QWORD ;;

Is fastcall really faster?

阅读更多关于 Is fastcall really faster?

Is the fastcall calling convention really faster than other calling conventions, such as cdecl? Are there any benchmarks out there that show how performance is affected by calling convention? It depends on the platform. For a Xenon PowerPC, for example, it can be an order of magnitude difference due to a load-hit-store issue with passing data on the stack. I empirically timed the overhead of a cdecl function at about 45 cycles compared to ~4 for a fastcall . For an out-of-order x86 (Intel and AMD), the impact may be much less, because the registers are all shadowed and renamed anyway. The