[FFmpeg-cvslog] r21433 - trunk/libavcodec/get_bits.h

[Michael Niedermayer]

On Sun, Jan 24, 2010 at 08:22:54PM +0100, Reimar D?ffinger wrote:
> On Sun, Jan 24, 2010 at 08:19:09PM +0100, michael wrote:
> > Author: michael
> > Date: Sun Jan 24 20:19:09 2010
> > New Revision: 21433
> > 
> > Log:
> > Mark index as unsigend so gcc knows it doesnt need a sign extension on x86_64.
> > Any tips on how i can convince gcc that it doesnt need a
> > mov     %eax, %eax
> > in every get_bits() ?
> 
> That looks like a NOP, are there any branches around it might try to align?
> Of course considering elaborate NOPs is a favourite of gcc even when it does
> not try to do alignment...

heres a random piece of the mess: (dunno from what C code that came)
        movl    %esi, %eax
.LBE595:
.LBE593:
        .loc 90 161 0
        movl    %esi, %ecx
.LBB597:
.LBB594:
        .loc 72 42 0
        shrl    $3, %eax
.LBE594:
.LBE597:
        .loc 90 161 0
        andl    $7, %ecx
.LBB598:
.LBB596:
        .loc 72 42 0
        mov     %eax, %eax
        movl    (%rdx,%rax), %edx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The greatest way to live with honor in this world is to be what we pretend
to be. -- Socrates
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