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| author |  Mike Klein <mtklein@chromium.org> | 2018-03-10 11:34:53 -0500 |
|---|---|---|
| committer |  Skia Commit-Bot <skia-commit-bot@chromium.org> | 2018-03-14 02:38:52 +0000 |
| commit | d8853ec0fd01ecd45c225aee1f22b3d342dcacd7 (patch) | |
| tree | 671a3ec019016f1f42565b7f99ab3ecf9e140a60 /src/opts/SkRasterPipeline_opts.h | |
| parent | ba321b601782b4dd7cd060506dcc222ccdaac408 (diff) | |
exact divide by 255 with NEON
Change-Id: Ib121eb0d5af1f22f48f517fe909112a77d92032e
Reviewed-on: https://skia-review.googlesource.com/113666
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Herb Derby <herb@google.com>
Diffstat (limited to 'src/opts/SkRasterPipeline_opts.h')
| -rw-r--r-- | src/opts/SkRasterPipeline_opts.h | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/src/opts/SkRasterPipeline_opts.h b/src/opts/SkRasterPipeline_opts.h index 212a5d16aa..73624d1b02 100644 --- a/src/opts/SkRasterPipeline_opts.h +++ b/src/opts/SkRasterPipeline_opts.h @@ -2487,6 +2487,11 @@ static void start_pipeline(const size_t x0, const size_t y0, SI U16 div255(U16 v) { #if 0 return (v+127)/255; // The ideal rounding divide by 255. +#elif 1 && defined(__ARM_NEON) + // With NEON we can compute (v+127)/255 as (v + ((v+128)>>8) + 128)>>8 + // just as fast as we can do the approximation below, so might as well be correct! + // First we compute v + ((v+128)>>8), then one more round of (...+128)>>8 to finish up. + return vrshrq_n_u16(vrsraq_n_u16(v, v, 8), 8); #else return (v+255)/256; // A good approximation of (v+127)/255. #endif |