For hardware that doesn't do actual jumps for conditionals (i915,
current vc4 driver), this reduces the number of texture fetches
performed (assuming the driver isn't really smart about noticing that
the same sampler is used on each side of an if just with different
coordinates).
No performance difference on i965 with x11perf -magpixwin100 (n=40).
Improves -magpixwin100 by 12.9174% +/- 0.405272% (n=5) on vc4.
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
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