[FFmpeg-devel] [flamefest-start] A little something on MMX/SSE intrinsics
Wed Feb 27 23:04:14 CET 2008
On Wed, Feb 27, 2008 at 11:33 PM, M?ns Rullg?rd <mans at mansr.com> wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> > On Wed, Feb 27, 2008 at 03:29:56PM -0500, Alexander Strange wrote:
> >> 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()
> That depends on the CPU. Some CPUs are quite particular about
> instruction scheduling.
> >> 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.
> That's where you're wrong. Code using intrinsics can be well-written.
> The problem is not the code, but the compiler.
Intrinsics can also be analyzed easily by the compiler so they get
optimized easily where as its not possible for plain asm.
Never learn by your mistakes, if you do you may never dare to try again
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