The Early-Z optimization is disabled when there is a discard
instruction in the shader used in the draw call.
But if discard is the only reason to disable Early-Z, and at
draw call time the updates in the draw call are disabled we
can enable Early-Z using a shader variant.
If there are occlussion queries active we also need to disable
Early-z optimization.
So this patch enables Early-Z in this scenario.
The performance improvement is significant when running gfxbench
benchmark showing an average improvement of 11.15%
fps_avg helped: gl_gfxbench_aztec_high.trace: 3.13 -> 3.73 (19.13%)
fps_avg helped: gl_gfxbench_aztec.trace: 4.82 -> 5.68 (17.88%)
fps_avg helped: gl_gfxbench_manhattan31.trace: 5.10 -> 6.00 (17.59%)
fps_avg helped: gl_gfxbench_manhattan.trace: 7.24 -> 8.36 (15.52%)
fps_avg helped: gl_gfxbench_trex.trace: 19.25 -> 20.17 ( 4.81%)
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Cc: mesa-stable
(cherry picked from commit 5b951bcdd7)
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32119>
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