[x264-devel] Re: Compilation problem with x264 on Dual Opteron setup (SSE3)

[Loren Merritt]

On Mon, 1 May 2006, Guillaume POIRIER wrote:
> The main problem of that patch is that it unconditionally replaces all
> movdqu with lddqu, which isn't very smart. Intel optimization guide
> does state quite clearly that it's not how it should be done.
> What should be done is: instrument the code in a way that can tell you
> what are the loads that are always badly unaligned, and use lddqu only
> in these cases (loads that are sometimes aligned, sometimes not do not
> benefit from using lddqu).

All the variants of SAD are unaligned, SATD and SSD are usually aligned.

--Loren Merritt

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