Revert of Add ETC1 powered SSE encoder for tile texture compression

cc/resources/texture_compressor_etc1.cc

Index: cc/resources/texture_compressor_etc1.cc
diff --git a/cc/resources/texture_compressor_etc1.cc b/cc/resources/texture_compressor_etc1.cc
index 83c3f9fb034806a29bd86c669f405cae7256ddde..61c4438c21862342f8cf0ca10b19a375364a581c 100644
--- a/cc/resources/texture_compressor_etc1.cc
+++ b/cc/resources/texture_compressor_etc1.cc
@@ -18,11 +18,180 @@
 // performance hit.
 // #define USE_PERCEIVED_ERROR_METRIC
 
-namespace cc {
-
 namespace {
 
-// Constructs a color from a given base color and luminance value.
+template <typename T>
+inline T clamp(T val, T min, T max) {
+  return val < min ? min : (val > max ? max : val);
+}
+
+inline uint8_t round_to_5_bits(float val) {
+  return clamp<uint8_t>(val * 31.0f / 255.0f + 0.5f, 0, 31);
+}
+
+inline uint8_t round_to_4_bits(float val) {
+  return clamp<uint8_t>(val * 15.0f / 255.0f + 0.5f, 0, 15);
+}
+
+union Color {
+  struct BgraColorType {
+    uint8_t b;
+    uint8_t g;
+    uint8_t r;
+    uint8_t a;
+  } channels;
+  uint8_t components[4];
+  uint32_t bits;
+};
+
+/*
+ * Codeword tables.
+ * See: Table 3.17.2
+ */
+static const int16_t g_codeword_tables[8][4] = {{-8, -2, 2, 8},
+                                                {-17, -5, 5, 17},
+                                                {-29, -9, 9, 29},
+                                                {-42, -13, 13, 42},
+                                                {-60, -18, 18, 60},
+                                                {-80, -24, 24, 80},
+                                                {-106, -33, 33, 106},
+                                                {-183, -47, 47, 183}};
+
+/*
+ * Maps modifier indices to pixel index values.
+ * See: Table 3.17.3
+ */
+static const uint8_t g_mod_to_pix[4] = {3, 2, 0, 1};
+
+/*
+ * The ETC1 specification index texels as follows:
+ *
+ * [a][e][i][m]     [ 0][ 4][ 8][12]
+ * [b][f][j][n] <-> [ 1][ 5][ 9][13]
+ * [c][g][k][o]     [ 2][ 6][10][14]
+ * [d][h][l][p]     [ 3][ 7][11][15]
+ *
+ * However, when extracting sub blocks from BGRA data the natural array
+ * indexing order ends up different:
+ *
+ * vertical0: [a][e][b][f]  horizontal0: [a][e][i][m]
+ *            [c][g][d][h]               [b][f][j][n]
+ * vertical1: [i][m][j][n]  horizontal1: [c][g][k][o]
+ *            [k][o][l][p]               [d][h][l][p]
+ *
+ * In order to translate from the natural array indices in a sub block to the
+ * indices (number) used by specification and hardware we use this table.
+ */
+static const uint8_t g_idx_to_num[4][8] = {
+    {0, 4, 1, 5, 2, 6, 3, 7},        // Vertical block 0.
+    {8, 12, 9, 13, 10, 14, 11, 15},  // Vertical block 1.
+    {0, 4, 8, 12, 1, 5, 9, 13},      // Horizontal block 0.
+    {2, 6, 10, 14, 3, 7, 11, 15}     // Horizontal block 1.
+};
+
+inline void WriteColors444(uint8_t* block,
+                           const Color& color0,
+                           const Color& color1) {
+  block[0] = (color0.channels.r & 0xf0) | (color1.channels.r >> 4);
+  block[1] = (color0.channels.g & 0xf0) | (color1.channels.g >> 4);
+  block[2] = (color0.channels.b & 0xf0) | (color1.channels.b >> 4);
+}
+
+inline void WriteColors555(uint8_t* block,
+                           const Color& color0,
+                           const Color& color1) {
+  // Table for conversion to 3-bit two complement format.
+  static const uint8_t two_compl_trans_table[8] = {
+      4,  // -4 (100b)
+      5,  // -3 (101b)
+      6,  // -2 (110b)
+      7,  // -1 (111b)
+      0,  //  0 (000b)
+      1,  //  1 (001b)
+      2,  //  2 (010b)
+      3,  //  3 (011b)
+  };
+
+  int16_t delta_r =
+      static_cast<int16_t>(color1.channels.r >> 3) - (color0.channels.r >> 3);
+  int16_t delta_g =
+      static_cast<int16_t>(color1.channels.g >> 3) - (color0.channels.g >> 3);
+  int16_t delta_b =
+      static_cast<int16_t>(color1.channels.b >> 3) - (color0.channels.b >> 3);
+  DCHECK(delta_r >= -4 && delta_r <= 3);
+  DCHECK(delta_g >= -4 && delta_g <= 3);
+  DCHECK(delta_b >= -4 && delta_b <= 3);
+
+  block[0] = (color0.channels.r & 0xf8) | two_compl_trans_table[delta_r + 4];
+  block[1] = (color0.channels.g & 0xf8) | two_compl_trans_table[delta_g + 4];
+  block[2] = (color0.channels.b & 0xf8) | two_compl_trans_table[delta_b + 4];
+}
+
+inline void WriteCodewordTable(uint8_t* block,
+                               uint8_t sub_block_id,
+                               uint8_t table) {
+  DCHECK_LT(sub_block_id, 2);
+  DCHECK_LT(table, 8);
+
+  uint8_t shift = (2 + (3 - sub_block_id * 3));
+  block[3] &= ~(0x07 << shift);
+  block[3] |= table << shift;
+}
+
+inline void WritePixelData(uint8_t* block, uint32_t pixel_data) {
+  block[4] |= pixel_data >> 24;
+  block[5] |= (pixel_data >> 16) & 0xff;
+  block[6] |= (pixel_data >> 8) & 0xff;
+  block[7] |= pixel_data & 0xff;
+}
+
+inline void WriteFlip(uint8_t* block, bool flip) {
+  block[3] &= ~0x01;
+  block[3] |= static_cast<uint8_t>(flip);
+}
+
+inline void WriteDiff(uint8_t* block, bool diff) {
+  block[3] &= ~0x02;
+  block[3] |= static_cast<uint8_t>(diff) << 1;
+}
+
+/**
+ * Compress and rounds BGR888 into BGR444. The resulting BGR444 color is
+ * expanded to BGR888 as it would be in hardware after decompression. The
+ * actual 444-bit data is available in the four most significant bits of each
+ * channel.
+ */
+inline Color MakeColor444(const float* bgr) {
+  uint8_t b4 = round_to_4_bits(bgr[0]);
+  uint8_t g4 = round_to_4_bits(bgr[1]);
+  uint8_t r4 = round_to_4_bits(bgr[2]);
+  Color bgr444;
+  bgr444.channels.b = (b4 << 4) | b4;
+  bgr444.channels.g = (g4 << 4) | g4;
+  bgr444.channels.r = (r4 << 4) | r4;
+  return bgr444;
+}
+
+/**
+ * Compress and rounds BGR888 into BGR555. The resulting BGR555 color is
+ * expanded to BGR888 as it would be in hardware after decompression. The
+ * actual 555-bit data is available in the five most significant bits of each
+ * channel.
+ */
+inline Color MakeColor555(const float* bgr) {
+  uint8_t b5 = round_to_5_bits(bgr[0]);
+  uint8_t g5 = round_to_5_bits(bgr[1]);
+  uint8_t r5 = round_to_5_bits(bgr[2]);
+  Color bgr555;
+  bgr555.channels.b = (b5 << 3) | (b5 >> 2);
+  bgr555.channels.g = (g5 << 3) | (g5 >> 2);
+  bgr555.channels.r = (r5 << 3) | (r5 >> 2);
+  return bgr555;
+}
+
+/**
+ * Constructs a color from a given base color and luminance value.
+ */
 inline Color MakeColor(const Color& base, int16_t lum) {
   int b = static_cast<int>(base.channels.b) + lum;
   int g = static_cast<int>(base.channels.g) + lum;
@@ -34,8 +203,10 @@
   return color;
 }
 
-// Calculates the error metric for two colors. A small error signals that the
-// colors are similar to each other, a large error the signals the opposite.
+/**
+ * Calculates the error metric for two colors. A small error signals that the
+ * colors are similar to each other, a large error the signals the opposite.
+ */
 inline uint32_t GetColorError(const Color& u, const Color& v) {
 #ifdef USE_PERCEIVED_ERROR_METRIC
   float delta_b = static_cast<float>(u.channels.b) - v.channels.b;
@@ -290,15 +461,15 @@
 
 }  // namespace
 
+namespace cc {
+
 void TextureCompressorETC1::Compress(const uint8_t* src,
                                      uint8_t* dst,
                                      int width,
                                      int height,
                                      Quality quality) {
-  DCHECK_GE(width, 4);
-  DCHECK_EQ((width & 3), 0);
-  DCHECK_GE(height, 4);
-  DCHECK_EQ((height & 3), 0);
+  DCHECK(width >= 4 && (width & 3) == 0);
+  DCHECK(height >= 4 && (height & 3) == 0);
 
   Color ver_blocks[16];
   Color hor_blocks[16];