[cairo] Performance work update

[Billy Biggs]

  Hi Carl,

  I'll add the cairo-benchmarks module in CVS, I think it is useful.

> One idea that I think would be helpful is a way to run the suite of
> tests and get some tabulated results. Maybe something with rows for
> each test and columns for each backend. And hopefully a table small
> enough to be easy to send back and forth in an email message, say.

  I agree this would be helpful, although it wasn't the goal of the
module.  It's currently a set of benchmarks to help profiling.
Benchmarks for statistical analysis I believe should be done
differently, especially if they are to be compared between systems.
Also, my benchmarks are x86-specific.

  However, this doesn't preclude them going into CVS, I just think I'd
feel really bad if people used their results to claim "my system is
faster than your system", "cairo is slower than X", or even just "cairo
is too slow", which sometimes happens when benchmark apps are posted.

> >   - I did an implementation of fbCompositeSrc_8888x8888mmx which
> >     makes my "over" test twice as fast.
> ...
> >   - I also found that mmxCombineMaskU and mmxCombineOverU missed
> >     special cases for 0 alpha and 0xff alpha.  Adding those checks
> >     gave a 2x speedup for my line test.
> 
> Keep up the good work! Are these new things all in cairo already?

  Not yet, I've been trying to ensure these sort of tweaks have the OK
from various people to ensure I'm not doing something which would hurt
xserver performance, and that I'm not breaking anything, although maybe
I'm beeing too cautious.

  -Billy