David Laight <david@l8s.co.uk> writes:
> Indeed, on a modern x86 you do not want (ever) to execute movs{b,w,l}
> unless it is repeated AND the repeat count is considerable
> (unless you are optimising for space).
> 
> ISTR that something like:
> 1:	mov	(%esi,%ecx,4),%eax
> 	mov	%eax,(%edi,%ecx,4)
> 	dec	%ecx
> 	jnc	1b
> is faster than 'rep movsw' for %ecx < (about) 16.

Are you including the overhead of calling the function?

In any case, it is possible to teach GCC to use different sequences
than the ones it uses right now.

Perry