[Ffmpeg-devel] [PATCH] Some MMX optimizations for Chinese AVS

Stefan Gehrer stefan.gehrer
Fri Jul 28 20:25:00 CEST 2006

Mike Melanson wrote:

> Search for uses of the existing START_TIMER() and STOP_TIMER() macros in
> the tree. They give you a good all-around picture of how tight pieces of
> code are performing. They will give you useful numbers for your purposes.

Thanks, I already used them. But that's rather what I meant with
benchmarking a whole block and trial and error. What I was looking for was
more like checking for rules. For example, the other code I looked at
before seems to adhere to the rule 
"If you use a MMX multiply, make sure you have two other instructions in
the code before you use the result of the multiply." 
But I don't know if this is a rule I should stick to or just coincidence.
So I would like either

- a good documentation "performant MMX code for dummies"

or (even better)

- the this-MMX-instruction-stalls-due-to-dependency-on-that-result checker

Stefan Gehrer

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