[cairo] Pixman refactoring, ARM and Altivec implementations needed

[Jonathan Morton]

> And having something like cairo's 'make perf' with utils to diff the 
> results would be nice as well, I have enough beagleboards with compilers 
> installed to do nightly builds and performance tests. If the suite can 
> run pretty much unattended I could dedicate one beagleboard to it and 
> put the results online.

We're using our own mx11mark tool to evaluate performance, but this
relies on running an X11 server that itself depends on pixman.  For
project-internal tests it would make more sense to call pixman handlers
directly.

Observation: blitters can perform very differently on framebuffer
devices (which are usually uncached or at best write-through cached) and
pixmaps (which are in cached main memory).  Any test suite that includes
performance evaluations should attempt to check both cases.

Note that Xorg uses a shadowed framebuffer by default, which attempts to
move the performance into cached memory, but has some nasty difficulties
when the damage region becomes complex (this is something that could be
fixed by preventing it from becoming complex at the expense of strict
blit efficiency), and also consumes too much RAM to be worthwhile for
most ARM devices (which would be harder to fix).

-- 
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From: Jonathan Morton
      jonathan.morton at movial.com