X64 inline asm

[jump]

Originally Posted by Fyyre

Hi all,

I discovered this for myself recently, and wanted to share. If this is already well known, disregard =)

The Intel C/C++ compiler add-on for Visual Studio will allow you to still use inline assembly language on the X64 platform. The syntax and such is close enough to MSVC that modifications needed to code to compile existing code with the Intel compiler are minimal at best, IMO.

-Fyyre

Very interesting news. I have read everywhere that inline assmbler isnt possible on x64 architecture.
Could you show us correct syntax for inline assembler which will Intel C++ Compiler accept ?

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Jump

[Fyyre]

Originally Posted by jump

Very interesting news. I have read everywhere that inline assmbler isnt possible on x64 architecture.
Could you show us correct syntax for inline assembler which will Intel C++ Compiler accept ?

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Jump

It is virtually the same as MSVC:

__asm mov rbx, rax;

or

__asm
{
...
}

emit format is:

__asm __emit 0xCC;

sample function:

__declspec(naked) int __fastcall strcmpW(const wchar_t *s1, const wchar_t *s2)
{
	__asm {
	push rdi
	push rsi
	mov rdi, rdx
	mov rsi, rcx
	or rcx, -1
	xor rax, rax
	repne scasw
	not rcx
	mov rdi, rdx
	repe cmpsw
	xor rdx, rdx
	mov ax, [rsi - 2]
	mov dx, [rdi - 2]
	sub rax, rdx
	pop rsi
	pop rdi
	ret
	}
}

[jump]

So if i understand correct, the inline assmbler have to be also x64 not x86,right?
So you cant tak source with inline x86 assembler and think it will be compileable for x64 architecture. You have to rewrite it, right?

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Jump

[Fyyre]

x86 or x64 depends upon your project (like Av0id said above).

Regarding re-writing of code, how big of task depends on the code itself...

i.e. the above strcmpW function, he only require change of registers from e*x to r*x....

AFAIK the calling covention always __fastcall on X64, more simple than x86 assembly, imo.

-Fyyre

Originally Posted by jump

So if i understand correct, the inline assmbler have to be also x64 not x86,right?
So you cant tak source with inline x86 assembler and think it will be compileable for x64 architecture. You have to rewrite it, right?
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