Re: memmove.S for i386

Hi,

your function should be ok.

"ja" could be optimized to "jae" (same size and better speed in senseless case (dest==src)).

>>> void *memmove(void *dest, const void *src, size_t n);

movsb is only a good choice for small n.

You should use movsd instead, if there is enough codespace.

There are reference-implementations of memcpy and memmove at Intels- and AMDs-documentation.
momsq and MMX-Code can be an alternative for newer instruction sets.

Best regards,
Johannes

Nikola Vladov schrieb:
> Can some assembler guru verify next function?  For me it works fine.
> I'm not shure on cmpl and ja bellow.
> 
> -------------------------
> /*  public domain.  author: Nikola Vladov */
> ..text
> ..align 0
> ..global memmove
> ..type	memmove,@function
> memmove:
> 	pushl	%esi
> 	pushl	%edi
> 	movl	12(%esp),%edi
> 	movl	16(%esp),%esi
> 	movl	20(%esp),%ecx
> 	movl	%edi, %eax
> 	cld
> 	
> 	cmpl	%edi, %esi
> 	ja	.L1
> 
> 	std
>         decl	%edi
>         decl	%esi
>         addl	%ecx, %edi
>         addl    %ecx, %esi
> ..L1:	
> 	rep movsb
> 	cld
> 
> 	popl %edi
> 	popl %esi
> 	ret
>