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authorChia-I Wu <[email protected]>2013-09-12 13:00:52 +0800
committerChia-I Wu <[email protected]>2013-10-02 15:26:40 +0800
commit848c0e72f36d0e1e460193a2d30b2f631529156f (patch)
treea68300ffa0b3a4a30f584f5ea5733328a52a33a8 /configure.ac
parent72edba16592e6b1589f2db410b9ab2939e196a07 (diff)
i965: compute DDX in a subspan based only on top row
Consider only the top-left and top-right pixels to approximate DDX in a 2x2 subspan, unless the application requests a more accurate approximation via GL_FRAGMENT_SHADER_DERIVATIVE_HINT or this optimization is disabled from the new driconf option disable_derivative_optimization. This results in a less accurate approximation. However, it improves the performance of Xonotic with Ultra settings by 24.3879% +/- 0.832202% (at 95.0% confidence) on Haswell. No noticeable image quality difference observed. The improvement comes from faster sample_d. It seems, on Haswell, some optimizations are introduced to allow faster sample_d when all pixels in a subspan have the same derivative. I considered SAMPLE_STATE too, which allows one to control the quality of sample_d on Haswell. But it gave much worse image quality without giving better performance comparing to this change. No piglit quick.tests regression on Haswell (tested with v1). v2: better guess for precompile program key Signed-off-by: Chia-I Wu <[email protected]> Reviewed-by: Kenneth Graunke <[email protected]> Reviewed-by: Ian Romanick <[email protected]> Reviewed-by: Chris Forbes <[email protected]>
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