[Mesa-dev] [PATCH 7/7] i965: Enable ARB_transform_feedback2 on Sandybridge.

[Matt Turner]

On Fri, Feb 17, 2017 at 1:56 AM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> The only feature over and above ES 3.0 is DrawTransformFeedback().
>
> We already have to do the whole SOL_NUM_PRIMS_WRITTEN counter dance in
> order to compute the SVBI value for ResumeTransformFeedback(), at which
> point our existing GetTransformFeedbackVertexCount() implementation will
> do the trick (though with a stall to CPU map the buffer).
>
> Someday, we could probably implement DrawTransformFeedback() more
> efficiently, using the "Load Internal Vertex Count" feature of
> 3DSTATE_SVB_INDEX and the 3DPRIMITIVE indirect vertex count bit.
>
> Rumor has it this allows people to use WebGL 2.0 on Sandybridge.
>
> Note that we don't need pipelined register writes like Gen7+ because
> we use the 3DSTATE_SVB_INDEX command rather than MI_LOAD_REGISTER_MEM.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99842
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>

Should update the release notes and features.txt as well.