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Unified Diff: src/opts/SkBlitRow_opts_arm_neon.cpp

Issue 1098913002: Convert Color32 code to perfect blend. (Closed) Base URL: https://skia.googlesource.com/skia@master
Patch Set: revert back to make more similar Created 5 years, 8 months ago
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Index: src/opts/SkBlitRow_opts_arm_neon.cpp
diff --git a/src/opts/SkBlitRow_opts_arm_neon.cpp b/src/opts/SkBlitRow_opts_arm_neon.cpp
index bd0c45f4c0b84c837877d99ef60779abd4ee39ef..b11dd41fbc2aa85e755f4a5db09cf310cfc9d2f8 100644
--- a/src/opts/SkBlitRow_opts_arm_neon.cpp
+++ b/src/opts/SkBlitRow_opts_arm_neon.cpp
@@ -1681,38 +1681,30 @@ void S32_D565_Opaque_Dither_neon(uint16_t* SK_RESTRICT dst,
#define SK_SUPPORT_LEGACY_COLOR32_MATHx
-// Color32 and its SIMD specializations use the blend_256_round_alt algorithm
-// from tests/BlendTest.cpp. It's not quite perfect, but it's never wrong in the
-// interesting edge cases, and it's quite a bit faster than blend_perfect.
-//
-// blend_256_round_alt is our currently blessed algorithm. Please use it or an analogous one.
+/* NEON version of Color32(), portable version is in core/SkBlitRow_D32.cpp */
+// Color32 and its SIMD specializations use the blend_perfect algorithm from tests/BlendTest.cpp.
+// An acceptable alternative is blend_256_round_alt, which is faster but not quite perfect.
void Color32_arm_neon(SkPMColor* dst, const SkPMColor* src, int count, SkPMColor color) {
switch (SkGetPackedA32(color)) {
case 0: memmove(dst, src, count * sizeof(SkPMColor)); return;
case 255: sk_memset32(dst, color, count); return;
}
- uint16x8_t colorHigh = vshll_n_u8((uint8x8_t)vdup_n_u32(color), 8);
-#ifdef SK_SUPPORT_LEGACY_COLOR32_MATH // blend_256_plus1_trunc, busted
- uint16x8_t colorAndRound = colorHigh;
-#else // blend_256_round_alt, good
- uint16x8_t colorAndRound = vaddq_u16(colorHigh, vdupq_n_u16(128));
-#endif
-
- unsigned invA = 255 - SkGetPackedA32(color);
-#ifdef SK_SUPPORT_LEGACY_COLOR32_MATH // blend_256_plus1_trunc, busted
- uint8x8_t invA8 = vdup_n_u8(invA);
-#else // blend_256_round_alt, good
- SkASSERT(invA + (invA >> 7) < 256); // This next part only works if alpha is not 0.
- uint8x8_t invA8 = vdup_n_u8(invA + (invA >> 7));
-#endif
+ uint16x8_t color_2x_high = vshll_n_u8((uint8x8_t)vdup_n_u32(color), 8);
+ uint8x8_t invA_8x = vdup_n_u8(255 - SkGetPackedA32(color));
// Does the core work of blending color onto 4 pixels, returning the resulting 4 pixels.
auto kernel = [&](const uint32x4_t& src4) -> uint32x4_t {
- uint16x8_t lo = vmull_u8(vget_low_u8( (uint8x16_t)src4), invA8),
- hi = vmull_u8(vget_high_u8((uint8x16_t)src4), invA8);
+ uint16x8_t lo = vmull_u8(vget_low_u8( (uint8x16_t)src4), invA_8x),
+ hi = vmull_u8(vget_high_u8((uint8x16_t)src4), invA_8x);
+ #ifndef SK_SUPPORT_LEGACY_COLOR32_MATH
+ lo = vaddq_u16(lo, vdupq_n_u16(128));
+ hi = vaddq_u16(hi, vdupq_n_u16(128));
+ lo = vaddq_u16(lo, vshrq_n_u16(lo, 8));
+ hi = vaddq_u16(hi, vshrq_n_u16(hi, 8));
+ #endif
return (uint32x4_t)
- vcombine_u8(vaddhn_u16(colorAndRound, lo), vaddhn_u16(colorAndRound, hi));
+ vcombine_u8(vaddhn_u16(color_2x_high, lo), vaddhn_u16(color_2x_high, hi));
};
while (count >= 8) {
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