Google-Chrome's canvas opengl backend is very slow on i915

Submitted by Clemens Eisserer

Assigned to Ian Romanick

Using google-chrome's opengl html5-canvas backend, rendering is almost unuseable slow on my i945GM with mesa-7.11.1.

Sysprof hints software fallbacks executed: 61% in intel_ReadRGBASpan_ARGB888 15% in _mesa_pack_rgba_span_float

Steps to reproduce:

Download a version of google chrome that has canas GPU acceleration enabled by default (like 14 beta or higher)
Load a web-page which uses canvas for animation: http://themaninblue.com/experiment/AnimationBenchmark/canvas/

It would be great if somebody could analyze the root cause of the fallbacks, and try to implement the driver functionality missing.

Version: git

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