skia /
skia /
5d3314c53ce5c966591f0b02349103f51f986e6e overhaul blit_row_s32a_opaque()
- Remove branching on source alpha, which
makes Skia susceptible to timing attacks.
- Remove SSE4.1 variant, which is nearly identical
to the SSE2 code once branching's removed.
- Reroll SIMD loops back to their native vector
size, leaving unrolling to the compiler.
- Allow wider SIMD sets to cascade down into the
narrower ones for the last few pixels instead of
always hitting the scalar fallback.
- Move code around, rewrite, refactor, etc. so it
all reads more consistently.
blit_row_color32() has not changed at all here,
just moved to the bottom of the file to prevent
it from interrupting blit_row_s32a_opaque().
This prevents me from seeing the timing reconstructions
on the Timing sample everywhere I've tested.
Charts to watch (ARMv7, ARMv8 AVX2, AVX512 geometric mean of SKP rendering):
https://perf.skia.org/e/?formulas=geo(filter(%22config%3D8888%26cpu_or_gpu_value%3DAVX2%26extra_config%3D!Fast%26extra_config%3D!SK_FORCE_RASTER_PIPELINE_BLITTER%26source_type%3Dskp%26sub_result%3Dmin_ms%22))&formulas=geo(filter(%22config%3D8888%26cpu_or_gpu_value%3DAVX512%26source_type%3Dskp%26sub_result%3Dmin_ms%22))&formulas=geo(filter(%22arch%3Darm64%26config%3D8888%26source_type%3Dskp%26sub_result%3Dmin_ms%22))&formulas=geo(filter(%22arch%3Darm%26config%3D8888%26source_type%3Dskp%26sub_result%3Dmin_ms%22))
Bug: chromium:1088224
Change-Id: I4baf2ccd58ac3129ef01c2cf79c3826c9c0d389e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/313716
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Herb Derby <herb@google.com>
1 file changed
