Reland: Add ETC1 powered SSE encoder for tile texture compression

cc/resources/texture_compressor_etc1.h

Index: cc/resources/texture_compressor_etc1.h
diff --git a/cc/resources/texture_compressor_etc1.h b/cc/resources/texture_compressor_etc1.h
index c4575627d8339df1ffadecc6d57b7de7d79c64f3..105f6e9ea3c93018904dece4131ae16373ec0bfa 100644
--- a/cc/resources/texture_compressor_etc1.h
+++ b/cc/resources/texture_compressor_etc1.h
@@ -7,8 +7,183 @@
 
 #include "cc/resources/texture_compressor.h"
 
+#include "base/compiler_specific.h"
+#include "base/logging.h"
+
 namespace cc {
 
+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
+ALIGNAS(16) 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]
+
+// [ 0][ 1][ 2][ 3]     [ 0][ 1][ 4][ 5]
+// [ 4][ 5][ 6][ 7] <-> [ 8][ 9][12][13]
+// [ 8][ 9][10][11]     [ 2][ 3][ 6][ 7]
+// [12][13][14][15]     [10][11][14][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) {
+  // Write output color for BGRA textures.
+  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_GE(delta_r, -4);
+  DCHECK_LE(delta_r, 3);
+  DCHECK_GE(delta_g, -4);
+  DCHECK_LE(delta_g, 3);
+  DCHECK_GE(delta_b, -4);
+  DCHECK_LE(delta_b, 3);
+
+  // Write output color for BGRA textures.
+  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;
+  // Added to distinguish between expanded 555 and 444 colors.
+  bgr444.channels.a = 0x44;
+  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);
+  // Added to distinguish between expanded 555 and 444 colors.
+  bgr555.channels.a = 0x55;
+  return bgr555;
+}
+
 class CC_EXPORT TextureCompressorETC1 : public TextureCompressor {
  public:
   TextureCompressorETC1() {}