[FFmpeg-devel] [PATCH] Altivec vector_fmul_scalar

Michael Niedermayer michaelni
Fri Jan 23 17:17:54 CET 2009

On Tue, Jan 06, 2009 at 04:49:00PM +0200, Siarhei Siamashka wrote:
> Sorry for barging it, but can you also try to benchmark an Altivec variant of
> the following patch (or even benchmark it as-is without Altivec)?
> http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2008-September/053256.html
> It should be much more useful for PPC platform than for the others because of 
> two reasons:
> 1. Vorbis uses "nonnative" bitstream byte order on PPC and UPDATE_CACHE
> operations are supposed to be more expensive there. As the patch optimizes
> bitstream reading to vastly reduce the number of such operations, benefit on
> PPC should be better.
> 2. As PPC uses intrinsics anyway, it avoids the controversy of mixing C and
> inline assembly :)
> I'm not expecting replies posted in *this* thread and hijacking it was not my
> intention.

> PS. This is also some kind of ping, asking for review/comments of that old
> patch, because it seems to be forgotten now. The performance improvement for
> vorbis is too good to be ignored.

about the old patch,
loren posted comments, you never posted an updated patch,
also the patch mixes the addition of x86 asm and new C code surely violating
the idea of self contained patches
also it has one asm() statement per instruction, litterally asking gcc to
mess up.
Thats what is immedeatly obvious, I dont mind doing a more complete review
once you dealt with these and any other issues that possibly where mentioned
in the thread (i dont remember).


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Many that live deserve death. And some that die deserve life. Can you give
it to them? Then do not be too eager to deal out death in judgement. For
even the very wise cannot see all ends. -- Gandalf
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