[FFmpeg-devel] Some IWMMXT functions for libavcodec

[Michael Niedermayer]

On Sat, May 17, 2008 at 07:15:04PM +0400, Dmitry Antipov wrote:
> Michael Niedermayer wrote:
> 
> > So write code which is near perfect on both
> 
> How is it reasonable to implement different specialized version for
> each generation of the core like it does with MMX and MMX2?
> 
> As we're investigated,
> 
>      wldrd wr2, [%1, #8]
>      wldrd wr1, [%1], %2
> 
> is much better than
> 
>      wldrd wr1, [%1]
>      wldrd wr2, [%1, #8]
>      add %1, %1, %2
> 
> but the first version will work on PXA3xx cores only.
> 
> Moreover, WMMX2 adds some useful instructions - for example, WAVG4 may
> be used to implement very fast pix_abs16_xy2 and pix_abs8_xy2 (which
> will not work on PXA2xx cores).

You can write specialized WMMX1 & WMMX2 functions where a common function is
not optimal ...

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Old school: Use the lowest level language in which you can solve the problem
            conveniently.
New school: Use the highest level language in which the latest supercomputer
            can solve the problem without the user falling asleep waiting.
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