a132c3869f
Change ARM implementation of alpha blending to work on 8 pixels at a time (using NEON). Also improve the accuracy of alpha blending by using a formula based on SkMulDiv255Round rather than SkPMSrcOver. Note that a number of variations of this code were considered. Here are some notes: - A 16 pixels at a time version was considered. This performs well for the case of extreme alpha (all-opaque or all-transparent pixels), but performs worst than the 8 pixels version when there are frequent transitions of alpha. Also gcc 6.2.1 seems to have troubles with register pressure when using this version. - If the branch to detect the fully-opaque or fully-transparent cases is removed, then the performance increases significantly for images which are all partially transparent (especially on ARM Cortex A72), but can significantly decrease for images that are almost fully opaque or fully transparent. This implementation is a compromise to the effects described above. This patch produces a ~10% improvement on the nanobench's sub-scores repeatTile_BGRA_8888_A, constXTile_MM_filter_trans, constXTile_CC_trans, constXTile_RR_filter_trans when running on ARM Cortex A72. Improvements of greater magnitude (20% to 30%) are observed when running on ARM Cortex A53. CQ_INCLUDE_TRYBOTS=skia.primary:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD Change-Id: I1f0c9f549057613bbffd26e6651f3beeb0019af9 Bug: skia: Reviewed-on: https://skia-review.googlesource.com/16520 Reviewed-by: Mike Klein <mtklein@chromium.org> Commit-Queue: Mike Klein <mtklein@chromium.org> |
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Skia is a complete 2D graphic library for drawing Text, Geometries, and Images. See full details, and build instructions, at https://skia.org.