Refactor SkBlurImageFilter_opts.h for readability.

This is mostly reindentation to make each platform's code clear, and
rewriting comments to match the usual way we orient vector comments
these days (in memory order).

Change-Id: I7ceb98c5af88980e74b6a124507e0ef1900fc731
Reviewed-on: https://skia-review.googlesource.com/19663
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>

1 files changed, 184 insertions, 186 deletions

diff --git a/src/opts/SkBlurImageFilter_opts.h b/src/opts/SkBlurImageFilter_opts.h
index f953a2e7e8..246aba5e12 100644
--- a/src/opts/SkBlurImageFilter_opts.h
+++ b/src/opts/SkBlurImageFilter_opts.h
@@ -20,209 +20,201 @@ namespace SK_OPTS_NS {
 enum class BlurDirection { kX, kY };
 
 #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
-#if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE41
-// ARGB -> 000A 000R 000G 000B
-static inline __m128i expand(SkPMColor p) {
-    return _mm_cvtepu8_epi32(_mm_cvtsi32_si128(p));
-};
-// Axxx Rxxx Gxxx Bxxx -> ARGB
-static inline SkPMColor repack(__m128i p) {
-    const char _ = ~0;  // Don't care what ends up in these bytes.  This zeros them.
-    p = _mm_shuffle_epi8(p, _mm_set_epi8(_,_,_,_, _,_,_,_, _,_,_,_, 15,11,7,3));
-    return _mm_cvtsi128_si32(p);
-};
-#define mullo_epi32 _mm_mullo_epi32
+    #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE41
+        // RGBA -> R000 G000 B000 A000
+        static inline __m128i expand(SkPMColor p) {
+            return _mm_cvtepu8_epi32(_mm_cvtsi32_si128(p));
+        };
+        // 000R 000G 000B 000A -> RGBA
+        static inline SkPMColor repack(__m128i p) {
+            const char _ = ~0;  // Don't care what ends up in these bytes.  This zeros them.
+            p = _mm_shuffle_epi8(p, _mm_setr_epi8(3,7,11,15, _,_,_,_, _,_,_,_, _,_,_,_));
+            return _mm_cvtsi128_si32(p);
+        };
+        #define mullo_epi32 _mm_mullo_epi32
 
-#else
-// ARGB -> 000A 000R 000G 000B
-static inline __m128i expand(int p) {
-    auto result = _mm_cvtsi32_si128(p);
-    result = _mm_unpacklo_epi8(result, _mm_setzero_si128());
-    result = _mm_unpacklo_epi16(result, _mm_setzero_si128());
-    return result;
-};
-// Axxx Rxxx Gxxx Bxxx -> ARGB
-static inline SkPMColor repack(__m128i p) {
-    p = _mm_srli_epi32(p, 24);  // 000A 000R 000G 000B
-    p = _mm_packs_epi32(p, p);  // xxxx xxxx 0A0R 0G0B
-    p = _mm_packus_epi16(p, p); // xxxx xxxx xxxx ARGB
-    return _mm_cvtsi128_si32(p);
-};
+    #else
+        static inline __m128i expand(int p) {
+            auto result = _mm_cvtsi32_si128(p);
+            result = _mm_unpacklo_epi8 (result, _mm_setzero_si128());
+            result = _mm_unpacklo_epi16(result, _mm_setzero_si128());
+            return result;
+        };
+        static inline SkPMColor repack(__m128i p) {
+            p = _mm_srli_epi32(p, 24);  // R000 G000 B000 A000
+            p = _mm_packs_epi32(p, p);  // R0G0 B0A0 xxxx xxxx
+            p = _mm_packus_epi16(p, p); // RGBA xxxx xxxx xxxx
+            return _mm_cvtsi128_si32(p);
+        };
 
-// _mm_mullo_epi32 is not available, so use the standard trick to emulate it.
-static inline __m128i mullo_epi32(__m128i a, __m128i b) {
-    __m128i p02 = _mm_mul_epu32(a, b),
-            p13 = _mm_mul_epu32(_mm_srli_si128(a, 4),
-                                _mm_srli_si128(b, 4));
-    return _mm_unpacklo_epi32(_mm_shuffle_epi32(p02, _MM_SHUFFLE(0,0,2,0)),
-                              _mm_shuffle_epi32(p13, _MM_SHUFFLE(0,0,2,0)));
-};
-#endif
-#define INIT_SCALE const __m128i scale = _mm_set1_epi32((1 << 24) / kernelSize);
-#define INIT_HALF const __m128i half = _mm_set1_epi32(1 << 23);
-#define INIT_SUMS __m128i sum = _mm_setzero_si128();
-#define INCREMENT_SUMS(c) sum = _mm_add_epi32(sum, expand(c))
-#define DECREMENT_SUMS(c) sum = _mm_sub_epi32(sum, expand(c))
-#define STORE_SUMS \
-    auto result = mullo_epi32(sum, scale); \
-    result = _mm_add_epi32(result, half); \
-    *dptr = repack(result);
-#define DOUBLE_ROW_OPTIMIZATION
+        // _mm_mullo_epi32 is not available, so use the standard trick to emulate it.
+        static inline __m128i mullo_epi32(__m128i a, __m128i b) {
+            __m128i p02 = _mm_mul_epu32(a, b),
+                    p13 = _mm_mul_epu32(_mm_srli_si128(a, 4),
+                                        _mm_srli_si128(b, 4));
+            return _mm_unpacklo_epi32(_mm_shuffle_epi32(p02, _MM_SHUFFLE(0,0,2,0)),
+                                      _mm_shuffle_epi32(p13, _MM_SHUFFLE(0,0,2,0)));
+        };
+    #endif
+
+    #define INIT_SCALE const __m128i scale = _mm_set1_epi32((1 << 24) / kernelSize);
+    #define INIT_HALF const __m128i half = _mm_set1_epi32(1 << 23);
+    #define INIT_SUMS __m128i sum = _mm_setzero_si128();
+    #define INCREMENT_SUMS(c) sum = _mm_add_epi32(sum, expand(c))
+    #define DECREMENT_SUMS(c) sum = _mm_sub_epi32(sum, expand(c))
+    #define STORE_SUMS *dptr = repack(_mm_add_epi32(mullo_epi32(sum, scale), half));
+    #define DOUBLE_ROW_OPTIMIZATION /*none*/
 
 #elif defined(SK_ARM_HAS_NEON)
 
-// val = (sum * scale * 2 + 0x8000) >> 16
-#define STORE_SUMS_DOUBLE \
-    uint16x8_t resultPixels = vreinterpretq_u16_s16(vqrdmulhq_s16( \
-        vreinterpretq_s16_u16(sum), vreinterpretq_s16_u16(scale))); \
-    if (dstDirection == BlurDirection::kX) { \
-        uint32x2_t px2 = vreinterpret_u32_u8(vmovn_u16(resultPixels)); \
-        vst1_lane_u32(dptr +     0, px2, 0); \
-        vst1_lane_u32(dptr + width, px2, 1); \
-    } else { \
-        vst1_u8((uint8_t*)dptr, vmovn_u16(resultPixels)); \
-    }
+    // val = (sum * scale * 2 + 0x8000) >> 16
+    #define STORE_SUMS_DOUBLE \
+        uint16x8_t resultPixels = vreinterpretq_u16_s16(vqrdmulhq_s16( \
+            vreinterpretq_s16_u16(sum), vreinterpretq_s16_u16(scale))); \
+        if (dstDirection == BlurDirection::kX) { \
+            uint32x2_t px2 = vreinterpret_u32_u8(vmovn_u16(resultPixels)); \
+            vst1_lane_u32(dptr +     0, px2, 0); \
+            vst1_lane_u32(dptr + width, px2, 1); \
+        } else { \
+            vst1_u8((uint8_t*)dptr, vmovn_u16(resultPixels)); \
+        }
 
-#define INCREMENT_SUMS_DOUBLE(p) sum = vaddw_u8(sum, load_2_pixels(p))
-#define DECREMENT_SUMS_DOUBLE(p) sum = vsubw_u8(sum, load_2_pixels(p))
+    #define INCREMENT_SUMS_DOUBLE(p) sum = vaddw_u8(sum, load_2_pixels(p))
+    #define DECREMENT_SUMS_DOUBLE(p) sum = vsubw_u8(sum, load_2_pixels(p))
 
-// Fast path for kernel sizes between 2 and 127, working on two rows at a time.
-template<BlurDirection srcDirection, BlurDirection dstDirection>
-static int box_blur_double(const SkPMColor** src, int srcStride, const SkIRect& srcBounds,
-                           SkPMColor** dst, int kernelSize,
-                           int leftOffset, int rightOffset, int width, int height) {
-    // Load 2 pixels from adjacent rows.
-    auto load_2_pixels = [&](const SkPMColor* s) {
-        if (srcDirection == BlurDirection::kX) {
-            // 10% faster by adding these 2 prefetches
-            SK_PREFETCH(s + 16);
-            SK_PREFETCH(s + 16 + srcStride);
-            auto one = vld1_lane_u32(s +         0, vdup_n_u32(0), 0),
-                 two = vld1_lane_u32(s + srcStride,           one, 1);
-            return vreinterpret_u8_u32(two);
-        } else {
-            return vld1_u8((uint8_t*)s);
-        }
-    };
-    int left = srcBounds.left();
-    int right = srcBounds.right();
-    int top = srcBounds.top();
-    int bottom = srcBounds.bottom();
-    int incrementStart = SkMax32(left - rightOffset - 1, left - right);
-    int incrementEnd = SkMax32(right - rightOffset - 1, 0);
-    int decrementStart = SkMin32(left + leftOffset, width);
-    int decrementEnd = SkMin32(right + leftOffset, width);
-    const int srcStrideX = srcDirection == BlurDirection::kX ? 1 : srcStride;
-    const int dstStrideX = dstDirection == BlurDirection::kX ? 1 : height;
-    const int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
-    const int dstStrideY = dstDirection == BlurDirection::kX ? width : 1;
-    const uint16x8_t scale = vdupq_n_u16((1 << 15) / kernelSize);
+    // Fast path for kernel sizes between 2 and 127, working on two rows at a time.
+    template<BlurDirection srcDirection, BlurDirection dstDirection>
+    static int box_blur_double(const SkPMColor** src, int srcStride, const SkIRect& srcBounds,
+                               SkPMColor** dst, int kernelSize,
+                               int leftOffset, int rightOffset, int width, int height) {
+        // Load 2 pixels from adjacent rows.
+        auto load_2_pixels = [&](const SkPMColor* s) {
+            if (srcDirection == BlurDirection::kX) {
+                // 10% faster by adding these 2 prefetches
+                SK_PREFETCH(s + 16);
+                SK_PREFETCH(s + 16 + srcStride);
+                auto one = vld1_lane_u32(s +         0, vdup_n_u32(0), 0),
+                     two = vld1_lane_u32(s + srcStride,           one, 1);
+                return vreinterpret_u8_u32(two);
+            } else {
+                return vld1_u8((uint8_t*)s);
+            }
+        };
+        int left = srcBounds.left();
+        int right = srcBounds.right();
+        int top = srcBounds.top();
+        int bottom = srcBounds.bottom();
+        int incrementStart = SkMax32(left - rightOffset - 1, left - right);
+        int incrementEnd = SkMax32(right - rightOffset - 1, 0);
+        int decrementStart = SkMin32(left + leftOffset, width);
+        int decrementEnd = SkMin32(right + leftOffset, width);
+        const int srcStrideX = srcDirection == BlurDirection::kX ? 1 : srcStride;
+        const int dstStrideX = dstDirection == BlurDirection::kX ? 1 : height;
+        const int srcStrideY = srcDirection == BlurDirection::kX ? srcStride : 1;
+        const int dstStrideY = dstDirection == BlurDirection::kX ? width : 1;
+        const uint16x8_t scale = vdupq_n_u16((1 << 15) / kernelSize);
 
-    for (; bottom - top >= 2; top += 2) {
-        uint16x8_t sum = vdupq_n_u16(0);
-        const SkPMColor* lptr = *src;
-        const SkPMColor* rptr = *src;
-        SkPMColor* dptr = *dst;
-        int x;
-        for (x = incrementStart; x < 0; ++x) {
-            INCREMENT_SUMS_DOUBLE(rptr);
-            rptr += srcStrideX;
-        }
-        // Clear to zero when sampling to the left our domain. "sum" is zero here because we
-        // initialized it above, and the preceeding loop has no effect in this case.
-        for (x = 0; x < incrementStart; ++x) {
-            STORE_SUMS_DOUBLE
-            dptr += dstStrideX;
-        }
-        for (; x < decrementStart && x < incrementEnd; ++x) {
-            STORE_SUMS_DOUBLE
-            dptr += dstStrideX;
-            INCREMENT_SUMS_DOUBLE(rptr);
-            rptr += srcStrideX;
-        }
-        for (x = decrementStart; x < incrementEnd; ++x) {
-            STORE_SUMS_DOUBLE
-            dptr += dstStrideX;
-            INCREMENT_SUMS_DOUBLE(rptr);
-            rptr += srcStrideX;
-            DECREMENT_SUMS_DOUBLE(lptr);
-            lptr += srcStrideX;
-        }
-        for (x = incrementEnd; x < decrementStart; ++x) {
-            STORE_SUMS_DOUBLE
-            dptr += dstStrideX;
+        for (; bottom - top >= 2; top += 2) {
+            uint16x8_t sum = vdupq_n_u16(0);
+            const SkPMColor* lptr = *src;
+            const SkPMColor* rptr = *src;
+            SkPMColor* dptr = *dst;
+            int x;
+            for (x = incrementStart; x < 0; ++x) {
+                INCREMENT_SUMS_DOUBLE(rptr);
+                rptr += srcStrideX;
+            }
+            // Clear to zero when sampling to the left our domain. "sum" is zero here because we
+            // initialized it above, and the preceeding loop has no effect in this case.
+            for (x = 0; x < incrementStart; ++x) {
+                STORE_SUMS_DOUBLE
+                dptr += dstStrideX;
+            }
+            for (; x < decrementStart && x < incrementEnd; ++x) {
+                STORE_SUMS_DOUBLE
+                dptr += dstStrideX;
+                INCREMENT_SUMS_DOUBLE(rptr);
+                rptr += srcStrideX;
+            }
+            for (x = decrementStart; x < incrementEnd; ++x) {
+                STORE_SUMS_DOUBLE
+                dptr += dstStrideX;
+                INCREMENT_SUMS_DOUBLE(rptr);
+                rptr += srcStrideX;
+                DECREMENT_SUMS_DOUBLE(lptr);
+                lptr += srcStrideX;
+            }
+            for (x = incrementEnd; x < decrementStart; ++x) {
+                STORE_SUMS_DOUBLE
+                dptr += dstStrideX;
+            }
+            for (; x < decrementEnd; ++x) {
+                STORE_SUMS_DOUBLE
+                dptr += dstStrideX;
+                DECREMENT_SUMS_DOUBLE(lptr);
+                lptr += srcStrideX;
+            }
+            // Clear to zero when sampling to the right of our domain. "sum" is
+            // zero here because we added on then subtracted off all of the pixels, leaving zero.
+            for (; x < width; ++x) {
+                STORE_SUMS_DOUBLE
+                dptr += dstStrideX;
+            }
+            *src += srcStrideY * 2;
+            *dst += dstStrideY * 2;
         }
-        for (; x < decrementEnd; ++x) {
-            STORE_SUMS_DOUBLE
-            dptr += dstStrideX;
-            DECREMENT_SUMS_DOUBLE(lptr);
-            lptr += srcStrideX;
-        }
-        // Clear to zero when sampling to the right of our domain. "sum" is zero here because we
-        // added on then subtracted off all of the pixels, leaving zero.
-        for (; x < width; ++x) {
-            STORE_SUMS_DOUBLE
-            dptr += dstStrideX;
-        }
-        *src += srcStrideY * 2;
-        *dst += dstStrideY * 2;
+        return top;
     }
-    return top;
-}
 
-// ARGB -> 0A0R 0G0B
-static inline uint16x4_t expand(SkPMColor p) {
-    return vget_low_u16(vmovl_u8(vreinterpret_u8_u32(vdup_n_u32(p))));
-};
+    // RGBA -> R0G0 B0A0
+    static inline uint16x4_t expand(SkPMColor p) {
+        return vget_low_u16(vmovl_u8(vreinterpret_u8_u32(vdup_n_u32(p))));
+    };
 
-#define INIT_SCALE const uint32x4_t scale = vdupq_n_u32((1 << 24) / kernelSize);
-#define INIT_HALF const uint32x4_t half = vdupq_n_u32(1 << 23);
-#define INIT_SUMS uint32x4_t sum = vdupq_n_u32(0);
-#define INCREMENT_SUMS(c) sum = vaddw_u16(sum, expand(c));
-#define DECREMENT_SUMS(c) sum = vsubw_u16(sum, expand(c));
+    #define INIT_SCALE const uint32x4_t scale = vdupq_n_u32((1 << 24) / kernelSize);
+    #define INIT_HALF const uint32x4_t half = vdupq_n_u32(1 << 23);
+    #define INIT_SUMS uint32x4_t sum = vdupq_n_u32(0);
+    #define INCREMENT_SUMS(c) sum = vaddw_u16(sum, expand(c));
+    #define DECREMENT_SUMS(c) sum = vsubw_u16(sum, expand(c));
 
-#define STORE_SUMS \
-    uint32x4_t result = vmlaq_u32(half, sum, scale); \
-    uint16x4_t result16 = vqshrn_n_u32(result, 16); \
-    uint8x8_t result8 = vqshrn_n_u16(vcombine_u16(result16, result16), 8); \
-    vst1_lane_u32(dptr, vreinterpret_u32_u8(result8), 0);
+    #define STORE_SUMS \
+        uint32x4_t result = vmlaq_u32(half, sum, scale); \
+        uint16x4_t result16 = vqshrn_n_u32(result, 16); \
+        uint8x8_t result8 = vqshrn_n_u16(vcombine_u16(result16, result16), 8); \
+        vst1_lane_u32(dptr, vreinterpret_u32_u8(result8), 0);
 
-#define DOUBLE_ROW_OPTIMIZATION \
-    if (1 < kernelSize && kernelSize < 128) { \
-        top = box_blur_double<srcDirection, dstDirection>(&src, srcStride, srcBounds, &dst, \
-                                                          kernelSize, leftOffset, rightOffset, \
-                                                          width, height); \
-    }
+    #define DOUBLE_ROW_OPTIMIZATION \
+        if (1 < kernelSize && kernelSize < 128) { \
+            top = box_blur_double<srcDirection, dstDirection>(&src, srcStride, srcBounds, &dst, \
+                                                              kernelSize, \
+                                                              leftOffset, rightOffset, \
+                                                              width, height); \
+        }
 
 #else  // Neither NEON nor >=SSE2.
 
-#define INIT_SCALE uint32_t scale = (1 << 24) / kernelSize;
-#define INIT_HALF  uint32_t half = 1 << 23;
-#define INIT_SUMS int sumA = 0, sumR = 0, sumG = 0, sumB = 0;
-#define INCREMENT_SUMS(c) \
-    sumA += SkGetPackedA32(c); \
-    sumR += SkGetPackedR32(c); \
-    sumG += SkGetPackedG32(c); \
-    sumB += SkGetPackedB32(c)
-#define DECREMENT_SUMS(c) \
-    sumA -= SkGetPackedA32(c); \
-    sumR -= SkGetPackedR32(c); \
-    sumG -= SkGetPackedG32(c); \
-    sumB -= SkGetPackedB32(c)
-#define STORE_SUMS \
-    *dptr = SkPackARGB32((sumA * scale + half) >> 24, \
-                         (sumR * scale + half) >> 24, \
-                         (sumG * scale + half) >> 24, \
-                         (sumB * scale + half) >> 24);
-#define DOUBLE_ROW_OPTIMIZATION
+    #define INIT_SCALE uint32_t scale = (1 << 24) / kernelSize;
+    #define INIT_HALF  uint32_t half = 1 << 23;
+    #define INIT_SUMS int sumA = 0, sumR = 0, sumG = 0, sumB = 0;
+    #define INCREMENT_SUMS(c) \
+        sumA += SkGetPackedA32(c); \
+        sumR += SkGetPackedR32(c); \
+        sumG += SkGetPackedG32(c); \
+        sumB += SkGetPackedB32(c)
+    #define DECREMENT_SUMS(c) \
+        sumA -= SkGetPackedA32(c); \
+        sumR -= SkGetPackedR32(c); \
+        sumG -= SkGetPackedG32(c); \
+        sumB -= SkGetPackedB32(c)
+    #define STORE_SUMS \
+        *dptr = SkPackARGB32((sumA * scale + half) >> 24, \
+                             (sumR * scale + half) >> 24, \
+                             (sumG * scale + half) >> 24, \
+                             (sumB * scale + half) >> 24);
+    #define DOUBLE_ROW_OPTIMIZATION
 
 #endif
 
-#define PREFETCH_RPTR \
-    if (srcDirection == BlurDirection::kY) { \
-        SK_PREFETCH(rptr); \
-    }
-
 template<BlurDirection srcDirection, BlurDirection dstDirection>
 static void box_blur(const SkPMColor* src, int srcStride, const SkIRect& srcBounds, SkPMColor* dst,
                      int kernelSize, int leftOffset, int rightOffset, int width, int height) {
@@ -262,7 +254,9 @@ static void box_blur(const SkPMColor* src, int srcStride, const SkIRect& srcBoun
         for (x = incrementStart; x < 0; ++x) {
             INCREMENT_SUMS(*rptr);
             rptr += srcStrideX;
-            PREFETCH_RPTR
+            if (srcDirection == BlurDirection::kY) {
+                SK_PREFETCH(rptr);
+            }
         }
         // Clear to zero when sampling to the left of our domain.
         for (x = 0; x < incrementStart; ++x) {
@@ -274,14 +268,18 @@ static void box_blur(const SkPMColor* src, int srcStride, const SkIRect& srcBoun
             dptr += dstStrideX;
             INCREMENT_SUMS(*rptr);
             rptr += srcStrideX;
-            PREFETCH_RPTR
+            if (srcDirection == BlurDirection::kY) {
+                SK_PREFETCH(rptr);
+            }
         }
         for (x = decrementStart; x < incrementEnd; ++x) {
             STORE_SUMS
             dptr += dstStrideX;
             INCREMENT_SUMS(*rptr);
             rptr += srcStrideX;
-            PREFETCH_RPTR
+            if (srcDirection == BlurDirection::kY) {
+                SK_PREFETCH(rptr);
+            }
             DECREMENT_SUMS(*lptr);
             lptr += srcStrideX;
         }