[FFmpeg-devel] [FFmpeg-cvslog] r12171 - trunk/doc/optimization.txt

[Uoti Urpala]

On Thu, 2008-02-21 at 21:57 +0200, Uoti Urpala wrote:
> It'd need at least one other instruction instead though. Anyway I do not
> see that behavior with Debian's gcc-4.3, gcc always uses 3 instructions
> for the adds (same as the handwritten asm).

That was gcc-4.2 actually, gcc-4.3 seems to use either
        addq    %rcx, %rsi
        addq    %rcx, %rdx
        addq    $16, %rax

or

        leaq    (%rsi,%r8), %rdx
        leaq    (%r10,%r8), %rax
...
        addq    %rcx, %r8
        addq    $16, %r9

depending on whether the loop is unrolled.