[FFmpeg-devel] Some IWMMXT functions for libavcodec

[Michael Niedermayer]

On Sat, May 17, 2008 at 03:13:34PM +0400, Dmitry Antipov wrote:
> Siarhei Siamashka wrote:
> 
> > Does Intel contradict itself? Or there is some variation between different
> > revisions of XScale cores and they have different optimization rules? Can you
> > provide a direct link to the document you are using?
> 
> There are two generations of WMMX hardware for now - WMMX inside PXA27x cores and WMMX2 inside
> PXA3xx cores (read the PXA genealogy at http://en.wikipedia.org/wiki/XScale if you're don't
> familiar with it).
> 
> The specification at http://www.intel.com/design/intelxscale/314510.htm describes WMMX2, but
> there is another (older) specification of WMMX. I can't find a direct link on Intel's sites,
> but you can grab my copy at http://78.153.153.8/tmp/Wireless_MMX.pdf.
> 
> I'm using the hardware based on PXA310 (http://www.marvell.com/products/cellular/application/pxa310.jsp).
> But the PXA27x cores are not out of the business - in fact, they forms today's end-user hardware mainstream,
> and PXA3x hardware goes to replace them in the near future.
> 
> As I understand, WMMX2 is a strict superset of WMMX in the sense of instructions semantic - it
> adds new instructions, but the rest is fully backward compatible. But WMMX and WMMX2 are (how many?)
> different on the hardware level, so the code which is perfectly tuned for WMMX2 may be not so
> perfect on WMMX.

So write code which is near perfect on both

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 
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