[FFmpeg-devel] [flamefest-start] A little something on MMX/SSE intrinsics

[İsmail Dönmez]

Hi,

On Thu, Feb 28, 2008 at 12:30 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
>
> On Thu, Feb 28, 2008 at 12:04:14AM +0200, ?smail D?nmez wrote:
>  > 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.
>
>  Thats like giving a painting from Leonardo da Vinci to a wild boar so it can
>  correct the fine details.

That assumes every assembly coder is talented like Leonardo da Vinci,
good luck with that assumption :-)

-- 
Never learn by your mistakes, if you do you may never dare to try again