[FFmpeg-cvslog] r21432 - trunk/libavcodec/h264_cavlc.c

Michael Niedermayer michaelni
Mon Jan 25 10:23:17 CET 2010


On Mon, Jan 25, 2010 at 10:13:47AM +0100, Michael Niedermayer wrote:
> On Sun, Jan 24, 2010 at 11:59:25PM +0000, M?ns Rullg?rd wrote:
> > michael <subversion at mplayerhq.hu> writes:
> > 
> > > Author: michael
> > > Date: Sun Jan 24 19:42:22 2010
> > > New Revision: 21432
> > >
> > > Log:
> > > a[b-1] -> (a-1)[b].
> > > Helps gcc not to add seperate -1 instructions.
> > 
> > Do you have some asm to illustrate?
> 
> from h264_cavlc.c with this patch
> and thats with gcc-4.4 (Debian 4.4.3-1) 4.4.3
> 
> before:
> 
>         movl    %eax, %edx
>         movl    %eax, %ecx
>         leal    -1(%rbp), %r10d          <-----------
>         shrl    $3, %edx
>         andl    $7, %ecx
>         mov     %edx, %edx
>         movl    (%r11,%rdx), %edx
>         bswap   %edx
>         sall    %cl, %edx
>         movslq  %r10d,%rcx               <-----------
>         leaq    (%rcx,%rcx,2), %r12      <-----------
>         shrl $-9, %edx
>         mov     %edx, %edx
>         leaq    0(,%rdx,4), %rcx
>         addq    total_zeros_vlc+8(,%r12,8), %rcx
> 
> after:
>         movl    %eax, %edx
>         movl    %eax, %ecx
>         shrl    $3, %edx
>         andl    $7, %ecx
>         mov     %edx, %edx
>         movl    (%r11,%rdx), %edx
>         bswap   %edx
>         sall    %cl, %edx
>         movslq  %ebp,%rcx             <-------------
>         leaq    -3(%rcx,%rcx,2), %r10 <-------------
>         shrl $-9, %edx
>         mov     %edx, %edx
>         leaq    0(,%rdx,4), %rcx
>         addq    total_zeros_vlc+8(,%r10,8), %rcx
> 
> you can also see 2 of the 
> mov     %edx, %edx
> in there that i spoke off

And if someone would be reporting these 2 issues to gcc devs that would
be great! Iam a little too busy ATMwith h264, maintaining ffmpeg and
everything else to do find a minimal testcase and submit that

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

Frequently ignored awnser#1 FFmpeg bugs should be sent to our bugtracker. User
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.
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