ARM Skia NEON patches - 34 - Blur Filter

src/opts/SkBlurImage_opts_neon.cpp

 /*
  * Copyright 2013 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkBitmap.h"
 #include "SkColorPriv.h"
 #include "SkBlurImage_opts.h"
 #include "SkRect.h"
 
 #include <arm_neon.h>
 
 namespace {
 
 enum BlurDirection {
     kX, kY
 };
 
 /**
  * Helper function to spread the components of a 32-bit integer into the
- * lower 8 bits of each 32-bit element of a NEON register.
+ * lower 8 bits of each 16-bit element of a NEON register.
  */
 
-inline uint32x4_t expand(uint32_t a) {
+static inline uint16x4_t expand(uint32_t a) {
     // ( ARGB ) -> ( ARGB ARGB ) -> ( A R G B A R G B )
     uint8x8_t v8 = vreinterpret_u8_u32(vdup_n_u32(a));
     // ( A R G B A R G B ) -> ( 0A 0R 0G 0B 0A 0R 0G 0B ) -> ( 0A 0R 0G 0B )
-    const uint16x4_t v16 = vget_low_u16(vmovl_u8(v8));
-    // ( 0A 0R 0G 0B ) -> ( 000A 000R 000G 000B )
-    return vmovl_u16(v16);
+    return vget_low_u16(vmovl_u8(v8));
 }
 
 template<BlurDirection srcDirection, BlurDirection dstDirection>
 void SkBoxBlur_NEON(const SkPMColor* src, int srcStride, SkPMColor* dst, int kernelSize,
                     int leftOffset, int rightOffset, int width, int height)
 {
     const int rightBorder = SkMin32(rightOffset + 1, width);
     const int srcStrideX = srcDirection == kX ? 1 : srcStride;
     const int dstStrideX = dstDirection == kX ? 1 : height;
     const int srcStrideY = srcDirection == kX ? srcStride : 1;
     const int dstStrideY = dstDirection == kX ? width : 1;
     const uint32x4_t scale = vdupq_n_u32((1 << 24) / kernelSize);
     const uint32x4_t half = vdupq_n_u32(1 << 23);
     for (int y = 0; y < height; ++y) {
         uint32x4_t sum = vdupq_n_u32(0);
         const SkPMColor* p = src;
         for (int i = 0; i < rightBorder; ++i) {
-            sum = vaddq_u32(sum, expand(*p));
+            sum = vaddw_u16(sum, expand(*p));
             p += srcStrideX;
         }
 
         const SkPMColor* sptr = src;
         SkPMColor* dptr = dst;
         for (int x = 0; x < width; ++x) {
             // ( half+sumA*scale half+sumR*scale half+sumG*scale half+sumB*scale )
             uint32x4_t result = vmlaq_u32(half, sum, scale);
 
-            // Shift down to lower 8 bits of each element.
-            // ( AAAA RRRR GGGG BBBB ) -> ( 000A 000R 000G 000B )
-            result = vshrq_n_u32(result, 24);
+            // Saturated conversion to 16-bit.
+            // ( AAAA RRRR GGGG BBBB ) -> ( 0A 0R 0G 0B )
+            uint16x4_t result16 = vqshrn_n_u32(result, 16);
 
-            // ( 000A 000R 000G 000B ) -> ( 0A 0R 0G 0B )
-            uint16x4_t result16 = vqmovn_u32(result);
-
+            // Saturated conversion to 8-bit.
             // ( 0A 0R 0G 0B ) -> ( 0A 0R 0G 0B 0A 0R 0G 0B ) -> ( A R G B A R G B )
-            uint8x8_t result8 = vqmovn_u16(vcombine_u16(result16, result16));
+            uint8x8_t result8 = vqshrn_n_u16(vcombine_u16(result16, result16), 8);
 
             // ( A R G B A R G B ) -> ( ARGB ARGB ) -> ( ARGB )
             // Store low 32 bits to destination.
             vst1_lane_u32(dptr, vreinterpret_u32_u8(result8), 0);
+
             if (x >= leftOffset) {
                 const SkPMColor* l = sptr - leftOffset * srcStrideX;
-                sum = vsubq_u32(sum, expand(*l));
+                sum = vsubw_u16(sum, expand(*l));
             }
             if (x + rightOffset + 1 < width) {
                 const SkPMColor* r = sptr + (rightOffset + 1) * srcStrideX;
-                sum = vaddq_u32(sum, expand(*r));
+                sum = vaddw_u16(sum, expand(*r));
             }
             sptr += srcStrideX;
             if (srcDirection == kY) {
                 SK_PREFETCH(sptr + (rightOffset + 1) * srcStrideX);
             }
             dptr += dstStrideX;
         }
         src += srcStrideY;
         dst += dstStrideY;
     }
 }
 
 } // namespace
 
 bool SkBoxBlurGetPlatformProcs_NEON(SkBoxBlurProc* boxBlurX,
                                     SkBoxBlurProc* boxBlurY,
                                     SkBoxBlurProc* boxBlurXY,
                                     SkBoxBlurProc* boxBlurYX) {
     *boxBlurX = SkBoxBlur_NEON<kX, kX>;
     *boxBlurY = SkBoxBlur_NEON<kY, kY>;
     *boxBlurXY = SkBoxBlur_NEON<kX, kY>;
     *boxBlurYX = SkBoxBlur_NEON<kY, kX>;
     return true;
 }