Revert r12154

BUG=skia:1807



git-svn-id: http://skia.googlecode.com/svn/trunk@12156 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 286 insertions, 98 deletions

diff --git a/src/opts/SkBitmapProcState_opts_arm.cpp b/src/opts/SkBitmapProcState_opts_arm.cpp
index 96fbebd4e1..badb0f4d3b 100644
--- a/src/opts/SkBitmapProcState_opts_arm.cpp
+++ b/src/opts/SkBitmapProcState_opts_arm.cpp
@@ -50,54 +50,54 @@ void SI8_D16_nofilter_DX_arm(const SkBitmapProcState& s,
         const uint16_t* SK_RESTRICT xx = (const uint16_t*)(xy + 1);
 
         asm volatile (
-            "cmp        %[count8], #0                  \n\t"  // compare loop counter with 0
-            "beq        2f                             \n\t"  // if loop counter == 0, exit
-            "1:                                        \n\t"
-            "ldmia      %[xx]!, {r5, r7, r9, r11}      \n\t"  // load ptrs to pixels 0-7
-            "subs       %[count8], %[count8], #1       \n\t"  // decrement loop counter
-            "uxth       r4, r5                         \n\t"  // extract ptr 0
-            "mov        r5, r5, lsr #16                \n\t"  // extract ptr 1
-            "uxth       r6, r7                         \n\t"  // extract ptr 2
-            "mov        r7, r7, lsr #16                \n\t"  // extract ptr 3
-            "ldrb       r4, [%[srcAddr], r4]           \n\t"  // load pixel 0 from image
-            "uxth       r8, r9                         \n\t"  // extract ptr 4
-            "ldrb       r5, [%[srcAddr], r5]           \n\t"  // load pixel 1 from image
-            "mov        r9, r9, lsr #16                \n\t"  // extract ptr 5
-            "ldrb       r6, [%[srcAddr], r6]           \n\t"  // load pixel 2 from image
-            "uxth       r10, r11                       \n\t"  // extract ptr 6
-            "ldrb       r7, [%[srcAddr], r7]           \n\t"  // load pixel 3 from image
-            "mov        r11, r11, lsr #16              \n\t"  // extract ptr 7
-            "ldrb       r8, [%[srcAddr], r8]           \n\t"  // load pixel 4 from image
-            "add        r4, r4, r4                     \n\t"  // double pixel 0 for RGB565 lookup
-            "ldrb       r9, [%[srcAddr], r9]           \n\t"  // load pixel 5 from image
-            "add        r5, r5, r5                     \n\t"  // double pixel 1 for RGB565 lookup
-            "ldrb       r10, [%[srcAddr], r10]         \n\t"  // load pixel 6 from image
-            "add        r6, r6, r6                     \n\t"  // double pixel 2 for RGB565 lookup
-            "ldrb       r11, [%[srcAddr], r11]         \n\t"  // load pixel 7 from image
-            "add        r7, r7, r7                     \n\t"  // double pixel 3 for RGB565 lookup
-            "ldrh       r4, [%[table], r4]             \n\t"  // load pixel 0 RGB565 from colmap
-            "add        r8, r8, r8                     \n\t"  // double pixel 4 for RGB565 lookup
-            "ldrh       r5, [%[table], r5]             \n\t"  // load pixel 1 RGB565 from colmap
-            "add        r9, r9, r9                     \n\t"  // double pixel 5 for RGB565 lookup
-            "ldrh       r6, [%[table], r6]             \n\t"  // load pixel 2 RGB565 from colmap
-            "add        r10, r10, r10                  \n\t"  // double pixel 6 for RGB565 lookup
-            "ldrh       r7, [%[table], r7]             \n\t"  // load pixel 3 RGB565 from colmap
-            "add        r11, r11, r11                  \n\t"  // double pixel 7 for RGB565 lookup
-            "ldrh       r8, [%[table], r8]             \n\t"  // load pixel 4 RGB565 from colmap
-            "ldrh       r9, [%[table], r9]             \n\t"  // load pixel 5 RGB565 from colmap
-            "ldrh       r10, [%[table], r10]           \n\t"  // load pixel 6 RGB565 from colmap
-            "ldrh       r11, [%[table], r11]           \n\t"  // load pixel 7 RGB565 from colmap
-            "pkhbt      r5, r4, r5, lsl #16            \n\t"  // pack pixels 0 and 1
-            "pkhbt      r6, r6, r7, lsl #16            \n\t"  // pack pixels 2 and 3
-            "pkhbt      r8, r8, r9, lsl #16            \n\t"  // pack pixels 4 and 5
-            "pkhbt      r10, r10, r11, lsl #16         \n\t"  // pack pixels 6 and 7
-            "stmia      %[colors]!, {r5, r6, r8, r10}  \n\t"  // store last 8 pixels
-            "bgt        1b                             \n\t"  // loop if counter > 0
-            "2:                                        \n\t"
-            : [xx] "+r" (xx), [count8] "+r" (count8), [colors] "+r" (colors)
-            : [table] "r" (table), [srcAddr] "r" (srcAddr)
-            : "memory", "cc", "r4", "r5", "r6", "r7", "r8", "r9", "r10", "r11"
-        );
+                      "cmp        %[count8], #0                   \n\t"   // compare loop counter with 0
+                      "beq        2f                              \n\t"   // if loop counter == 0, exit
+                      "1:                                             \n\t"
+                      "ldmia      %[xx]!, {r5, r7, r9, r11}       \n\t"   // load ptrs to pixels 0-7
+                      "subs       %[count8], %[count8], #1        \n\t"   // decrement loop counter
+                      "uxth       r4, r5                          \n\t"   // extract ptr 0
+                      "mov        r5, r5, lsr #16                 \n\t"   // extract ptr 1
+                      "uxth       r6, r7                          \n\t"   // extract ptr 2
+                      "mov        r7, r7, lsr #16                 \n\t"   // extract ptr 3
+                      "ldrb       r4, [%[srcAddr], r4]            \n\t"   // load pixel 0 from image
+                      "uxth       r8, r9                          \n\t"   // extract ptr 4
+                      "ldrb       r5, [%[srcAddr], r5]            \n\t"   // load pixel 1 from image
+                      "mov        r9, r9, lsr #16                 \n\t"   // extract ptr 5
+                      "ldrb       r6, [%[srcAddr], r6]            \n\t"   // load pixel 2 from image
+                      "uxth       r10, r11                        \n\t"   // extract ptr 6
+                      "ldrb       r7, [%[srcAddr], r7]            \n\t"   // load pixel 3 from image
+                      "mov        r11, r11, lsr #16               \n\t"   // extract ptr 7
+                      "ldrb       r8, [%[srcAddr], r8]            \n\t"   // load pixel 4 from image
+                      "add        r4, r4, r4                      \n\t"   // double pixel 0 for RGB565 lookup
+                      "ldrb       r9, [%[srcAddr], r9]            \n\t"   // load pixel 5 from image
+                      "add        r5, r5, r5                      \n\t"   // double pixel 1 for RGB565 lookup
+                      "ldrb       r10, [%[srcAddr], r10]          \n\t"   // load pixel 6 from image
+                      "add        r6, r6, r6                      \n\t"   // double pixel 2 for RGB565 lookup
+                      "ldrb       r11, [%[srcAddr], r11]          \n\t"   // load pixel 7 from image
+                      "add        r7, r7, r7                      \n\t"   // double pixel 3 for RGB565 lookup
+                      "ldrh       r4, [%[table], r4]              \n\t"   // load pixel 0 RGB565 from colmap
+                      "add        r8, r8, r8                      \n\t"   // double pixel 4 for RGB565 lookup
+                      "ldrh       r5, [%[table], r5]              \n\t"   // load pixel 1 RGB565 from colmap
+                      "add        r9, r9, r9                      \n\t"   // double pixel 5 for RGB565 lookup
+                      "ldrh       r6, [%[table], r6]              \n\t"   // load pixel 2 RGB565 from colmap
+                      "add        r10, r10, r10                   \n\t"   // double pixel 6 for RGB565 lookup
+                      "ldrh       r7, [%[table], r7]              \n\t"   // load pixel 3 RGB565 from colmap
+                      "add        r11, r11, r11                   \n\t"   // double pixel 7 for RGB565 lookup
+                      "ldrh       r8, [%[table], r8]              \n\t"   // load pixel 4 RGB565 from colmap
+                      "ldrh       r9, [%[table], r9]              \n\t"   // load pixel 5 RGB565 from colmap
+                      "ldrh       r10, [%[table], r10]            \n\t"   // load pixel 6 RGB565 from colmap
+                      "ldrh       r11, [%[table], r11]            \n\t"   // load pixel 7 RGB565 from colmap
+                      "pkhbt      r5, r4, r5, lsl #16             \n\t"   // pack pixels 0 and 1
+                      "pkhbt      r6, r6, r7, lsl #16             \n\t"   // pack pixels 2 and 3
+                      "pkhbt      r8, r8, r9, lsl #16             \n\t"   // pack pixels 4 and 5
+                      "pkhbt      r10, r10, r11, lsl #16          \n\t"   // pack pixels 6 and 7
+                      "stmia      %[colors]!, {r5, r6, r8, r10}   \n\t"   // store last 8 pixels
+                      "bgt        1b                              \n\t"   // loop if counter > 0
+                      "2:                                             \n\t"
+                      : [xx] "+r" (xx), [count8] "+r" (count8), [colors] "+r" (colors)
+                      : [table] "r" (table), [srcAddr] "r" (srcAddr)
+                      : "memory", "cc", "r4", "r5", "r6", "r7", "r8", "r9", "r10", "r11"
+                      );
 
         for (i = (count & 7); i > 0; --i) {
             src = srcAddr[*xx++]; *colors++ = table[src];
@@ -136,52 +136,52 @@ void SI8_opaque_D32_nofilter_DX_arm(const SkBitmapProcState& s,
         const uint16_t* xx = (const uint16_t*)(xy + 1);
 
         asm volatile (
-            "subs       %[count], %[count], #8        \n\t"   // decrement count by 8, set flags
-            "blt        2f                            \n\t"   // if count < 0, branch to singles
-            "1:                                       \n\t"   // eights loop
-            "ldmia      %[xx]!, {r5, r7, r9, r11}     \n\t"   // load ptrs to pixels 0-7
-            "uxth       r4, r5                        \n\t"   // extract ptr 0
-            "mov        r5, r5, lsr #16               \n\t"   // extract ptr 1
-            "uxth       r6, r7                        \n\t"   // extract ptr 2
-            "mov        r7, r7, lsr #16               \n\t"   // extract ptr 3
-            "ldrb       r4, [%[srcAddr], r4]          \n\t"   // load pixel 0 from image
-            "uxth       r8, r9                        \n\t"   // extract ptr 4
-            "ldrb       r5, [%[srcAddr], r5]          \n\t"   // load pixel 1 from image
-            "mov        r9, r9, lsr #16               \n\t"   // extract ptr 5
-            "ldrb       r6, [%[srcAddr], r6]          \n\t"   // load pixel 2 from image
-            "uxth       r10, r11                      \n\t"   // extract ptr 6
-            "ldrb       r7, [%[srcAddr], r7]          \n\t"   // load pixel 3 from image
-            "mov        r11, r11, lsr #16             \n\t"   // extract ptr 7
-            "ldrb       r8, [%[srcAddr], r8]          \n\t"   // load pixel 4 from image
-            "ldrb       r9, [%[srcAddr], r9]          \n\t"   // load pixel 5 from image
-            "ldrb       r10, [%[srcAddr], r10]        \n\t"   // load pixel 6 from image
-            "ldrb       r11, [%[srcAddr], r11]        \n\t"   // load pixel 7 from image
-            "ldr        r4, [%[table], r4, lsl #2]    \n\t"   // load pixel 0 SkPMColor from colmap
-            "ldr        r5, [%[table], r5, lsl #2]    \n\t"   // load pixel 1 SkPMColor from colmap
-            "ldr        r6, [%[table], r6, lsl #2]    \n\t"   // load pixel 2 SkPMColor from colmap
-            "ldr        r7, [%[table], r7, lsl #2]    \n\t"   // load pixel 3 SkPMColor from colmap
-            "ldr        r8, [%[table], r8, lsl #2]    \n\t"   // load pixel 4 SkPMColor from colmap
-            "ldr        r9, [%[table], r9, lsl #2]    \n\t"   // load pixel 5 SkPMColor from colmap
-            "ldr        r10, [%[table], r10, lsl #2]  \n\t"   // load pixel 6 SkPMColor from colmap
-            "ldr        r11, [%[table], r11, lsl #2]  \n\t"   // load pixel 7 SkPMColor from colmap
-            "subs       %[count], %[count], #8        \n\t"   // decrement loop counter
-            "stmia      %[colors]!, {r4-r11}          \n\t"   // store 8 pixels
-            "bge        1b                            \n\t"   // loop if counter >= 0
-            "2:                                       \n\t"
-            "adds       %[count], %[count], #8        \n\t"   // fix up counter, set flags
-            "beq        4f                            \n\t"   // if count == 0, branch to exit
-            "3:                                       \n\t"   // singles loop
-            "ldrh       r4, [%[xx]], #2               \n\t"   // load pixel ptr
-            "subs       %[count], %[count], #1        \n\t"   // decrement loop counter
-            "ldrb       r5, [%[srcAddr], r4]          \n\t"   // load pixel from image
-            "ldr        r6, [%[table], r5, lsl #2]    \n\t"   // load SkPMColor from colmap
-            "str        r6, [%[colors]], #4           \n\t"   // store pixel, update ptr
-            "bne        3b                            \n\t"   // loop if counter != 0
-            "4:                                       \n\t"   // exit
-            : [xx] "+r" (xx), [count] "+r" (count), [colors] "+r" (colors)
-            : [table] "r" (table), [srcAddr] "r" (srcAddr)
-            : "memory", "cc", "r4", "r5", "r6", "r7", "r8", "r9", "r10", "r11"
-        );
+                      "subs       %[count], %[count], #8          \n\t"   // decrement count by 8, set flags
+                      "blt        2f                              \n\t"   // if count < 0, branch to singles
+                      "1:                                             \n\t"   // eights loop
+                      "ldmia      %[xx]!, {r5, r7, r9, r11}       \n\t"   // load ptrs to pixels 0-7
+                      "uxth       r4, r5                          \n\t"   // extract ptr 0
+                      "mov        r5, r5, lsr #16                 \n\t"   // extract ptr 1
+                      "uxth       r6, r7                          \n\t"   // extract ptr 2
+                      "mov        r7, r7, lsr #16                 \n\t"   // extract ptr 3
+                      "ldrb       r4, [%[srcAddr], r4]            \n\t"   // load pixel 0 from image
+                      "uxth       r8, r9                          \n\t"   // extract ptr 4
+                      "ldrb       r5, [%[srcAddr], r5]            \n\t"   // load pixel 1 from image
+                      "mov        r9, r9, lsr #16                 \n\t"   // extract ptr 5
+                      "ldrb       r6, [%[srcAddr], r6]            \n\t"   // load pixel 2 from image
+                      "uxth       r10, r11                        \n\t"   // extract ptr 6
+                      "ldrb       r7, [%[srcAddr], r7]            \n\t"   // load pixel 3 from image
+                      "mov        r11, r11, lsr #16               \n\t"   // extract ptr 7
+                      "ldrb       r8, [%[srcAddr], r8]            \n\t"   // load pixel 4 from image
+                      "ldrb       r9, [%[srcAddr], r9]            \n\t"   // load pixel 5 from image
+                      "ldrb       r10, [%[srcAddr], r10]          \n\t"   // load pixel 6 from image
+                      "ldrb       r11, [%[srcAddr], r11]          \n\t"   // load pixel 7 from image
+                      "ldr        r4, [%[table], r4, lsl #2]      \n\t"   // load pixel 0 SkPMColor from colmap
+                      "ldr        r5, [%[table], r5, lsl #2]      \n\t"   // load pixel 1 SkPMColor from colmap
+                      "ldr        r6, [%[table], r6, lsl #2]      \n\t"   // load pixel 2 SkPMColor from colmap
+                      "ldr        r7, [%[table], r7, lsl #2]      \n\t"   // load pixel 3 SkPMColor from colmap
+                      "ldr        r8, [%[table], r8, lsl #2]      \n\t"   // load pixel 4 SkPMColor from colmap
+                      "ldr        r9, [%[table], r9, lsl #2]      \n\t"   // load pixel 5 SkPMColor from colmap
+                      "ldr        r10, [%[table], r10, lsl #2]    \n\t"   // load pixel 6 SkPMColor from colmap
+                      "ldr        r11, [%[table], r11, lsl #2]    \n\t"   // load pixel 7 SkPMColor from colmap
+                      "subs       %[count], %[count], #8          \n\t"   // decrement loop counter
+                      "stmia      %[colors]!, {r4-r11}            \n\t"   // store 8 pixels
+                      "bge        1b                              \n\t"   // loop if counter >= 0
+                      "2:                                             \n\t"
+                      "adds       %[count], %[count], #8          \n\t"   // fix up counter, set flags
+                      "beq        4f                              \n\t"   // if count == 0, branch to exit
+                      "3:                                             \n\t"   // singles loop
+                      "ldrh       r4, [%[xx]], #2                 \n\t"   // load pixel ptr
+                      "subs       %[count], %[count], #1          \n\t"   // decrement loop counter
+                      "ldrb       r5, [%[srcAddr], r4]            \n\t"   // load pixel from image
+                      "ldr        r6, [%[table], r5, lsl #2]      \n\t"   // load SkPMColor from colmap
+                      "str        r6, [%[colors]], #4             \n\t"   // store pixel, update ptr
+                      "bne        3b                              \n\t"   // loop if counter != 0
+                      "4:                                             \n\t"   // exit
+                      : [xx] "+r" (xx), [count] "+r" (count), [colors] "+r" (colors)
+                      : [table] "r" (table), [srcAddr] "r" (srcAddr)
+                      : "memory", "cc", "r4", "r5", "r6", "r7", "r8", "r9", "r10", "r11"
+                      );
     }
 
     s.fBitmap->getColorTable()->unlockColors();
@@ -222,13 +222,201 @@ void SkBitmapProcState::platformProcs() {
     }
 }
 
-///////////////////////////////////////////////////////////////////////////////
+/////////////////////////////////////
+
+/* FUNCTIONS BELOW ARE SCALAR STUBS INTENDED FOR ARM DEVELOPERS TO REPLACE */
+
+/////////////////////////////////////
 
-extern void platformConvolutionProcs_arm_neon(SkConvolutionProcs* procs);
 
-void platformConvolutionProcs_arm(SkConvolutionProcs* procs) {
+static inline unsigned char ClampTo8(int a) {
+    if (static_cast<unsigned>(a) < 256) {
+        return a;  // Avoid the extra check in the common case.
+    }
+    if (a < 0) {
+        return 0;
+    }
+    return 255;
+}
+
+// Convolves horizontally along a single row. The row data is given in
+// |srcData| and continues for the numValues() of the filter.
+void convolveHorizontally_arm(const unsigned char* srcData,
+                              const SkConvolutionFilter1D& filter,
+                              unsigned char* outRow,
+                              bool hasAlpha) {
+    // Loop over each pixel on this row in the output image.
+    int numValues = filter.numValues();
+    for (int outX = 0; outX < numValues; outX++) {
+        // Get the filter that determines the current output pixel.
+        int filterOffset, filterLength;
+        const SkConvolutionFilter1D::ConvolutionFixed* filterValues =
+            filter.FilterForValue(outX, &filterOffset, &filterLength);
+
+        // Compute the first pixel in this row that the filter affects. It will
+        // touch |filterLength| pixels (4 bytes each) after this.
+        const unsigned char* rowToFilter = &srcData[filterOffset * 4];
+
+        // Apply the filter to the row to get the destination pixel in |accum|.
+        int accum[4] = {0};
+        for (int filterX = 0; filterX < filterLength; filterX++) {
+            SkConvolutionFilter1D::ConvolutionFixed curFilter = filterValues[filterX];
+            accum[0] += curFilter * rowToFilter[filterX * 4 + 0];
+            accum[1] += curFilter * rowToFilter[filterX * 4 + 1];
+            accum[2] += curFilter * rowToFilter[filterX * 4 + 2];
+            if (hasAlpha) {
+                accum[3] += curFilter * rowToFilter[filterX * 4 + 3];
+            }
+        }
+
+        // Bring this value back in range. All of the filter scaling factors
+        // are in fixed point with kShiftBits bits of fractional part.
+        accum[0] >>= SkConvolutionFilter1D::kShiftBits;
+        accum[1] >>= SkConvolutionFilter1D::kShiftBits;
+        accum[2] >>= SkConvolutionFilter1D::kShiftBits;
+        if (hasAlpha) {
+            accum[3] >>= SkConvolutionFilter1D::kShiftBits;
+        }
+
+        // Store the new pixel.
+        outRow[outX * 4 + 0] = ClampTo8(accum[0]);
+        outRow[outX * 4 + 1] = ClampTo8(accum[1]);
+        outRow[outX * 4 + 2] = ClampTo8(accum[2]);
+        if (hasAlpha) {
+            outRow[outX * 4 + 3] = ClampTo8(accum[3]);
+        }
+    }
+}
+
+// Does vertical convolution to produce one output row. The filter values and
+// length are given in the first two parameters. These are applied to each
+// of the rows pointed to in the |sourceDataRows| array, with each row
+// being |pixelWidth| wide.
+//
+// The output must have room for |pixelWidth * 4| bytes.
+template<bool hasAlpha>
+    void convolveVertically_arm(const SkConvolutionFilter1D::ConvolutionFixed* filterValues,
+                            int filterLength,
+                            unsigned char* const* sourceDataRows,
+                            int pixelWidth,
+                            unsigned char* outRow) {
+        // We go through each column in the output and do a vertical convolution,
+        // generating one output pixel each time.
+        for (int outX = 0; outX < pixelWidth; outX++) {
+            // Compute the number of bytes over in each row that the current column
+            // we're convolving starts at. The pixel will cover the next 4 bytes.
+            int byteOffset = outX * 4;
+
+            // Apply the filter to one column of pixels.
+            int accum[4] = {0};
+            for (int filterY = 0; filterY < filterLength; filterY++) {
+                SkConvolutionFilter1D::ConvolutionFixed curFilter = filterValues[filterY];
+                accum[0] += curFilter * sourceDataRows[filterY][byteOffset + 0];
+                accum[1] += curFilter * sourceDataRows[filterY][byteOffset + 1];
+                accum[2] += curFilter * sourceDataRows[filterY][byteOffset + 2];
+                if (hasAlpha) {
+                    accum[3] += curFilter * sourceDataRows[filterY][byteOffset + 3];
+                }
+            }
+
+            // Bring this value back in range. All of the filter scaling factors
+            // are in fixed point with kShiftBits bits of precision.
+            accum[0] >>= SkConvolutionFilter1D::kShiftBits;
+            accum[1] >>= SkConvolutionFilter1D::kShiftBits;
+            accum[2] >>= SkConvolutionFilter1D::kShiftBits;
+            if (hasAlpha) {
+                accum[3] >>= SkConvolutionFilter1D::kShiftBits;
+            }
+
+            // Store the new pixel.
+            outRow[byteOffset + 0] = ClampTo8(accum[0]);
+            outRow[byteOffset + 1] = ClampTo8(accum[1]);
+            outRow[byteOffset + 2] = ClampTo8(accum[2]);
+            if (hasAlpha) {
+                unsigned char alpha = ClampTo8(accum[3]);
+
+                // Make sure the alpha channel doesn't come out smaller than any of the
+                // color channels. We use premultipled alpha channels, so this should
+                // never happen, but rounding errors will cause this from time to time.
+                // These "impossible" colors will cause overflows (and hence random pixel
+                // values) when the resulting bitmap is drawn to the screen.
+                //
+                // We only need to do this when generating the final output row (here).
+                int maxColorChannel = SkTMax(outRow[byteOffset + 0],
+                                               SkTMax(outRow[byteOffset + 1],
+                                                      outRow[byteOffset + 2]));
+                if (alpha < maxColorChannel) {
+                    outRow[byteOffset + 3] = maxColorChannel;
+                } else {
+                    outRow[byteOffset + 3] = alpha;
+                }
+            } else {
+                // No alpha channel, the image is opaque.
+                outRow[byteOffset + 3] = 0xff;
+            }
+        }
+    }
+
+void convolveVertically_arm(const SkConvolutionFilter1D::ConvolutionFixed* filterValues,
+                            int filterLength,
+                            unsigned char* const* sourceDataRows,
+                            int pixelWidth,
+                            unsigned char* outRow,
+                            bool sourceHasAlpha) {
+    if (sourceHasAlpha) {
+        convolveVertically_arm<true>(filterValues, filterLength,
+                                     sourceDataRows, pixelWidth,
+                                     outRow);
+    } else {
+        convolveVertically_arm<false>(filterValues, filterLength,
+                                      sourceDataRows, pixelWidth,
+                                      outRow);
+    }
+}
+
+// Convolves horizontally along four rows. The row data is given in
+// |src_data| and continues for the num_values() of the filter.
+// The algorithm is almost same as |ConvolveHorizontally_SSE2|. Please
+// refer to that function for detailed comments.
+void convolve4RowsHorizontally_arm(const unsigned char* src_data[4],
+                                   const SkConvolutionFilter1D& filter,
+                                   unsigned char* out_row[4]) {
+}
+
+///////////////////////////
+
+/* STOP REWRITING FUNCTIONS HERE, BUT DON'T FORGET TO EDIT THE
+   PLATFORM CONVOLUTION PROCS BELOW */
+
+///////////////////////////
+
+void applySIMDPadding_arm(SkConvolutionFilter1D *filter) {
+    // Padding |paddingCount| of more dummy coefficients after the coefficients
+    // of last filter to prevent SIMD instructions which load 8 or 16 bytes
+    // together to access invalid memory areas. We are not trying to align the
+    // coefficients right now due to the opaqueness of <vector> implementation.
+    // This has to be done after all |AddFilter| calls.
+    for (int i = 0; i < 8; ++i) {
+        filter->addFilterValue(static_cast<SkConvolutionFilter1D::ConvolutionFixed>(0));
+    }
 }
 
 void SkBitmapProcState::platformConvolutionProcs(SkConvolutionProcs* procs) {
-    SK_ARM_NEON_WRAP(platformConvolutionProcs_arm)(procs);
+    if (sk_cpu_arm_has_neon()) {
+        procs->fExtraHorizontalReads = 3;
+        procs->fConvolveVertically = &convolveVertically_arm;
+
+        // next line is commented out because the four-row convolution function above is
+        // just a no-op.  Please see the comment above its definition, and the SSE implementation
+        // in SkBitmapProcState_opts_SSE2.cpp for guidance on its semantics.
+        // leaving it as NULL will just cause the convolution system to not attempt
+        // to operate on four rows at once, which is correct but not performance-optimal.
+
+        // procs->fConvolve4RowsHorizontally = &convolve4RowsHorizontally_arm;
+
+        procs->fConvolve4RowsHorizontally = NULL;
+
+        procs->fConvolveHorizontally = &convolveHorizontally_arm;
+        procs->fApplySIMDPadding = &applySIMDPadding_arm;
+    }
 }