[FFmpeg-cvslog] r10223 - in trunk/libavcodec/i386: dsputil_mmx.c snowdsp_mmx.c

[Michael Niedermayer]

Hi

On Mon, Aug 27, 2007 at 11:19:45AM +0200, Benoit Fouet wrote:
> michael wrote:
> > Author: michael
> > Date: Sat Aug 25 17:20:56 2007
> > New Revision: 10223
> >
> > Log:
> > update mmx code to latest snow changes
> > note, the code likely can overflow and thus needs some more changes
> > sse2 updated too but disabled as its untested
> >
> >   
> 
> i don't know if that can help you, but i enabled it and ran the
> regression test, i got a segmentation fault.
> here is the debugger info:

the SSE2 code is broken, in the case here it crashes due to alignment
to fix this properly (compared to just make it work at crap speed like before
the second half of the b array must be copied into an aligned buffer during
the second lifting step, it does so currently during he 4th requireing
unaligned accesses in the 3rd and 4th, now as i didnt expect this
i used aligned accesses which doesnt work ...)

whoever wrote this originally had no clue about asm or just plain didnt care
to implement it properly, iam puzzled how this passed review originally

if you want to fix it i dont mind helping, awnsering questions (even stupid
questions about asm)
i do mind fixing it myself because
1.i dont have a SSE2 system here, i only have ssh access to one which isnt
  that good for actually watching the result ...
2.if someone else fixes it that means someone else will afterwards be more
  familiar with the code and that means more potential developers who might
  improve it or other asm code in ffmpeg ...



[...]

-- 
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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