[FFmpeg-devel] Mixed data type in SIMD code?

[Michael Niedermayer]

On Mon, Mar 03, 2008 at 05:25:52PM +0800, Zuxy Meng wrote:
> Hi,
> 
> I've always been unsure about the performance penalty (if there's any)
> brought in by using SIMD instructions that mismatch with the actual
> data type. For example to use pxor to clear a register that is later
> used as packet single, or to use movlhps to move part of a register
> that is later used as packet integer or packet double.
> 
> These instructions are bitwise equivalent, but instructions operating
> on packed integer and packed single are usually shorter than those on
> packed double, so Intel recommends only to differentiate integers and
> floatings, and to use *ps instructions even for packed doubles. Don't
> know what AMD suggests. So does that mean we should replace things
> like movapd, movlhpd, xorpd and andpd with their *ps equivalents?

benchmark ...
Also i doubt we use or ever will use packed double.

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

Many that live deserve death. And some that die deserve life. Can you give
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