[cairo] Patches for speeding up _cairo_fixed_from_double

[Carl Worth]

On Mon, 6 Nov 2006 13:26:51 -0800, "Daniel Amelang" wrote:
> > ...I'm going to be putting together a development snapshot
> > with all the performance work that's been happening since the
> > 1.2 branch...
>
> You might want to hold off on that development snapshot for a just
> little longer. I have two more performance-related patches in the oven
> that could potentially make a number of people happy.

As a rule, we're going to try to break our bad habit of delaying
development snapshots to try to get the next great feature in. I think
we'll be a lot better off if we can release a new snapshot every week
and each one faster than the one from the week before.

> First, I'm fixing up this (orphaned?) patch:
>
> http://lists.freedesktop.org/archives/cairo/2006-September/007861.html

Fantastic! That's another one that I've been hoping would get some more
attention, as I obviously haven't been able to get around to do the
cleanups I recommended myself.

> to incorporate the feedback you gave. I addition, I have a little
> tweak for it that produces an even greater speedup. This patch is very
> important for the embedded guys, as it significantly reduces a common
> and clearly-identified bottleneck. They won't be nearly as excited
> about the upcoming development snapshot without it.

Yes, eliminating the floating-point multiplies for the identity matrix
will be very helpful. What's the additional tweak you have planned
here?

> Second, I have an optimization that's similar to this
> _cairo_fixed_from_double one that addresses some of the slowness in
> rendering glyphs, especially in the case that was profiled here:
>
> http://www.o-hand.com/~jorn/pango-benchmarks/210-softfloat/
>
> This optimization, plus a small patch for pango (also in the works),
> should improve text rendering on both ARM and x86.

Jorn will be very excited to hear about these, as will others at
opened hand and elsewhere in the embedded field. I'll look forward to
hearing more about your ideas here.

Over on performance-list at gnome.org some people have started to
maintain a set of patches to de-cairo-ify pango, (making it use Xft
instead). So if you can help make that kind of patch unnecessary that
will be exceedingly useful.

> Unfortunately, I've got midterms this week, but I should be able to
> finish the patches over the weekend.

Good luck with your studies. We'll see what you've got next week, (or
just drop some ideas here and see if anyone can beat you to the
implementation of any of them).

Exciting stuff,

-Carl
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