[FFmpeg-devel] [flamefest-start] A little something on MMX/SSE intrinsics
Wed Feb 27 22:19:36 CET 2008
On Wed, Feb 27, 2008 at 03:29:56PM -0500, Alexander Strange wrote:
> On Wed, Feb 27, 2008 at 3:24 PM, Luca Barbato <lu_zero at gentoo.org> wrote:
> > Michael Niedermayer wrote:
> > > On Wed, Feb 27, 2008 at 05:42:58PM +0200, Ivan Kalvachev wrote:
> > >> On Wed, Feb 27, 2008 at 4:31 PM, Reimar D?ffinger
> > >> <Reimar.Doeffinger at stud.uni-karlsruhe.de> wrote:
> > >>> Hello,
> > >>> yet another case of someone relearning "intrinsics are still a mess and
> > >>> compilers still much too stupid" ;-) :
> > >>> http://www.virtualdub.org/blog/pivot/entry.php?id=188#body
> > >>>
> > >>> Let's see if we can make today the flame-heaviest day in FFmpeg history
> > >>> :-)
> > >> Nice read.
> > >>
> > >> I'd just like to add that there is already architecture in FFmpeg that
> > >> is entirely optimized on intrinsics - AltiVect. There were few
> > >> fundamental problems with it and I'm not sure if they have been
> > >> successfully solved. These include things like generating code that
> > >> picks up processor SIMD dialect at runtime.
> > >
> > > You just found us a new SOC qualification task
> > > rewrite intrinsics to proper asm()
> > >
> > And benchmark the result ^^;
> > lu
> I don't think anyone can get Altivec asm to work better than
> intrinsics on more than one CPU - PPC is really, really
> scheduling-sensitive, especially the G5 and Cell.
Until i see benchmarks id guess gcc+intrinsics will be slower than
unsheduled naively written asm()
> I guess you can always try, though, but don't do anything to
> discourage people who know altivec from adding more. There's still a
> lot missing from H.264.
Code is either well written or should be rejected.
Intrinsics != well written.
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Concerning the gods, I have no means of knowing whether they exist or not
or of what sort they may be, because of the obscurity of the subject, and
the brevity of human life -- Protagoras
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