[FFmpeg-devel] [PATCH] Fix configure to disable MMX for Pentium Pro

[Michael Niedermayer]

On Thu, Aug 26, 2010 at 10:22:57PM +0200, Reimar D?ffinger wrote:
> On Thu, Aug 26, 2010 at 09:53:44PM +0200, Michael Niedermayer wrote:
> > On Thu, Aug 26, 2010 at 08:52:24PM +0200, Reimar D?ffinger wrote:
> > > On Thu, Aug 26, 2010 at 01:37:06PM -0400, Alex Converse wrote:
> > > > > We should revert r24946: ?Disable MMX for i686 and pentiumpro
> > > > 
> > > > If something should be reverted it is dropping runtime detection for MMX
> > > 
> > > At the very least I think it would be nice to be able to have SSE,
> > > does someone know out of their head why we have
> > > sse_deps="mmx"
> > > ? I always thought that at least in principle you could have and
> > > use SSE without MMX and that also would avoid the emms issue...
> > 
> > there is no cpu that supports SSE without MMX and if the features no
> > longer match the cpu then alot of assumtations of what is faster and
> > what cpus code will run on become wrong
> > its btw silly to disable mmx on a mmx cpu unless its for debuging or other
> > uncommon things
> 
> How about "emms causes all kinds of issues, I'd like a build without
> those issues but still ok speed?"

wrong assumtion thus following theorems are flawed

besides i object to allowing (distro) people to build slow versions of
ffmpeg like SSE without MMX this would only lead to a big disadvantage to
our users
also some SSE instructions access MMX registers, this whole idea of SSE
withouzt MMX is completly silly and sounds like trolling to me even if its
likely not intended to be
thats besides there are code paths that lack SSE* optimizations thus
it wont be ok speed at all for some common codecs


-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No great genius has ever existed without some touch of madness. -- Aristotle
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