wasm: Add DC8uv*, VE8uv, and HE8uv functions

BUG=webp:352

Change-Id: Ia0b2b0d5007c12fff201ac94673312420da42a53

src/dsp/dec_wasm.c

@@ -32,6 +32,12 @@ static WEBP_INLINE uint8x16 get_16_bytes(uint8_t* dst) {
   return a;
 }
 
+static WEBP_INLINE uint8x16 get_8_bytes(uint8_t* dst) {
+  uint8x16 a;
+  memcpy(&a, dst, 8);
+  return a;
+}
+
 static WEBP_INLINE uint8x16 splat_uint8(uint32_t val) {
   uint8x16 a;
   a[0] = val;
@@ -120,6 +126,83 @@ static void DC16NoTopLeft(uint8_t* dst) {  // DC with no top and left samples
   Put16(0x80, dst);
 }
 
+//------------------------------------------------------------------------------
+// Chroma
+
+static WEBP_INLINE uint32_t add_horizontal_8(uint8_t* dst) {
+  const uint8x16 zero = (uint8x16){0};
+  const uint8x16 a = get_8_bytes(dst);
+  const uint16x8 _a_lbw = (uint16x8)__builtin_shufflevector(
+      a, zero, 0, 16, 1, 16, 2, 16, 3, 16, 16, 16, 16, 16, 16, 16, 16, 16);
+  const uint16x8 _a_hbw = (uint16x8)__builtin_shufflevector(
+      a, zero, 4, 16, 5, 16, 6, 16, 7, 16, 16, 16, 16, 16, 16, 16, 16, 16);
+  const uint16x8 sum_a = _a_lbw + _a_hbw;
+  const uint16x8 sum_b = (uint16x8)__builtin_shufflevector(
+      sum_a, sum_a, 2, 3, 2, 3, 2, 3, 2, 3);
+  const uint16x8 sum_c = sum_a + sum_b;
+  const uint16x8 sum_d = (uint16x8)__builtin_shufflevector(
+      sum_c, sum_c, 1, 1, 1, 1, 1, 1, 1, 1);
+  const uint16x8 sum_e = sum_c + sum_d;
+  return sum_e[0] & 0xffff;
+}
+
+static void VE8uv(uint8_t* dst) {    // vertical
+  const uint8x16 top = get_8_bytes(dst - BPS);
+  int j;
+  for (j = 0; j < 8; ++j) {
+    memcpy(dst + j * BPS, &top, 8);
+  }
+}
+
+static void HE8uv(uint8_t* dst) {    // horizontal
+  int j;
+  for (j = 8; j > 0; --j) {
+    const uint8x16 values = splat_uint8(dst[-1]);
+    memcpy(dst, &values, 8);
+    dst += BPS;
+  }
+}
+
+// helper for chroma-DC predictions
+static WEBP_INLINE void Put8x8uv(uint8_t v, uint8_t* dst) {
+  int j;
+  const uint8x16 values = splat_uint8(v);
+  for (j = 0; j < 8; ++j) {
+    memcpy(dst + j * BPS, &values, 8);
+  }
+}
+
+static void DC8uv(uint8_t* dst) {     // DC
+  int left = 0;
+  int j;
+  const uint32_t sum = add_horizontal_8(dst - BPS);
+  for (j = 0; j < 8; ++j) {
+    left += dst[-1 + j * BPS];
+  }
+  {
+    const int DC = sum + left + 8;
+    Put8x8uv(DC >> 4, dst);
+  }
+}
+
+static void DC8uvNoLeft(uint8_t* dst) {   // DC with no left samples
+  const uint32_t DC = 4 + add_horizontal_8(dst - BPS);
+  Put8x8uv(DC >> 3, dst);
+}
+
+static void DC8uvNoTop(uint8_t* dst) {  // DC with no top samples
+  int dc0 = 4;
+  int i;
+  for (i = 0; i < 8; ++i) {
+    dc0 += dst[-1 + i * BPS];
+  }
+  Put8x8uv(dc0 >> 3, dst);
+}
+
+static void DC8uvNoTopLeft(uint8_t* dst) {    // DC with nothing
+  Put8x8uv(0x80, dst);
+}
+
 //------------------------------------------------------------------------------
 // Entry point
 
@@ -132,6 +215,13 @@ WEBP_TSAN_IGNORE_FUNCTION void VP8DspInitWASM(void) {
   VP8PredLuma16[4] = DC16NoTop;
   VP8PredLuma16[5] = DC16NoLeft;
   VP8PredLuma16[6] = DC16NoTopLeft;
+
+  VP8PredChroma8[0] = DC8uv;
+  VP8PredChroma8[2] = VE8uv;
+  VP8PredChroma8[3] = HE8uv;
+  VP8PredChroma8[4] = DC8uvNoTop;
+  VP8PredChroma8[5] = DC8uvNoLeft;
+  VP8PredChroma8[6] = DC8uvNoTopLeft;
 }
 
 #else  // !WEBP_USE_WASM