[Webkit-unassigned] [Bug 72452] [Chromium] Avoid clear and color mask operations for root layers

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=72452





--- Comment #10 from Antoine Labour <piman at chromium.org>  2011-11-16 13:10:25 PST ---
(In reply to comment #8)
> (In reply to comment #5)
> > (In reply to comment #3)
> > > This seems like a lot of shaders.  Did you consider controlling the alpha behavior with a uniform instead of a new shader?
> > 
> > It's a tradeoff. Adding a uniform and dynamically controlling this behavior will slow down all shaders. It's not even clear that it'd be a win over the current version.
> > Same goes with the layer opacity.
> > I bet no more than a couple of shaders are used for 90% of the pixels we draw, and I think it's worth optimizing those as much as possible.
> > 
> 
> 
> Although if we only need this for the very simple shaders (and not AA), we are probably not limited by the pixel operations there, so I could probably just add a uniform to be added to the alpha channel (and set it to 0 or 1 respectively).

We most likely are limited by pixel operations. It depends on the architecture, but it's not clear that a single texture load could fully hide the ALUs for both the opacity multiply and the alpha squelching.

A benchmark would tell us...

> 
> Alternatively, I could simply reduce the current patch to only add the new shader variants for simlpe and swizzled.

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