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GPU: Bitwise texture swizzling
Replace the loop-based texture address swizzling code by a bit-twiddling implementation, providing a very small speed up. Also simplify addressing code.
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2012e1420f
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@ -304,7 +304,6 @@ std::unique_ptr<PicaTrace> FinishPicaTracing()
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}
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const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const TextureInfo& info, bool disable_alpha) {
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// Images are split into 8x8 tiles. Each tile is composed of four 4x4 subtiles each
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// of which is composed of four 2x2 subtiles each of which is composed of four texels.
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// Each structure is embedded into the next-bigger one in a diagonal pattern, e.g.
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@ -323,41 +322,39 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
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// 02 03 06 07 18 19 22 23
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// 00 01 04 05 16 17 20 21
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// TODO(neobrain): Not sure if this swizzling pattern is used for all textures.
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// To be flexible in case different but similar patterns are used, we keep this
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// somewhat inefficient code around for now.
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int texel_index_within_tile = 0;
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for (int block_size_index = 0; block_size_index < 3; ++block_size_index) {
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int sub_tile_width = 1 << block_size_index;
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int sub_tile_height = 1 << block_size_index;
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const unsigned int block_width = 8;
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const unsigned int block_height = 8;
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int sub_tile_index = (x & sub_tile_width) << block_size_index;
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sub_tile_index += 2 * ((y & sub_tile_height) << block_size_index);
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texel_index_within_tile += sub_tile_index;
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}
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const unsigned int coarse_x = x & ~7;
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const unsigned int coarse_y = y & ~7;
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const int block_width = 8;
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const int block_height = 8;
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// Interleave the lower 3 bits of each coordinate to get the intra-block offsets, which are
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// arranged in a Z-order curve. More details on the bit manipulation at:
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// https://fgiesen.wordpress.com/2009/12/13/decoding-morton-codes/
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unsigned int i = (x | (y << 8)) & 0x0707; // ---- -210
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i = (i ^ (i << 2)) & 0x1313; // ---2 --10
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i = (i ^ (i << 1)) & 0x1515; // ---2 -1-0
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i = (i | (i >> 7)) & 0x3F;
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int coarse_x = (x / block_width) * block_width;
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int coarse_y = (y / block_height) * block_height;
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source += coarse_y * info.stride;
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const unsigned int offset = coarse_x * block_height + i;
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switch (info.format) {
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case Regs::TextureFormat::RGBA8:
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{
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const u8* source_ptr = source + coarse_x * block_height * 4 + coarse_y * info.stride + texel_index_within_tile * 4;
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const u8* source_ptr = source + offset * 4;
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return { source_ptr[3], source_ptr[2], source_ptr[1], disable_alpha ? (u8)255 : source_ptr[0] };
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}
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case Regs::TextureFormat::RGB8:
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{
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const u8* source_ptr = source + coarse_x * block_height * 3 + coarse_y * info.stride + texel_index_within_tile * 3;
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const u8* source_ptr = source + offset * 3;
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return { source_ptr[2], source_ptr[1], source_ptr[0], 255 };
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}
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case Regs::TextureFormat::RGBA5551:
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{
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const u16 source_ptr = *(const u16*)(source + coarse_x * block_height * 2 + coarse_y * info.stride + texel_index_within_tile * 2);
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const u16 source_ptr = *(const u16*)(source + offset * 2);
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u8 r = (source_ptr >> 11) & 0x1F;
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u8 g = ((source_ptr) >> 6) & 0x1F;
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u8 b = (source_ptr >> 1) & 0x1F;
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@ -367,7 +364,7 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
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case Regs::TextureFormat::RGB565:
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{
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const u16 source_ptr = *(const u16*)(source + coarse_x * block_height * 2 + coarse_y * info.stride + texel_index_within_tile * 2);
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const u16 source_ptr = *(const u16*)(source + offset * 2);
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u8 r = (source_ptr >> 11) & 0x1F;
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u8 g = ((source_ptr) >> 5) & 0x3F;
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u8 b = (source_ptr) & 0x1F;
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@ -376,7 +373,7 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
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case Regs::TextureFormat::RGBA4:
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{
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const u8* source_ptr = source + coarse_x * block_height * 2 + coarse_y * info.stride + texel_index_within_tile * 2;
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const u8* source_ptr = source + offset * 2;
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u8 r = source_ptr[1] >> 4;
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u8 g = source_ptr[1] & 0xFF;
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u8 b = source_ptr[0] >> 4;
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@ -390,7 +387,7 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
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case Regs::TextureFormat::IA8:
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{
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const u8* source_ptr = source + coarse_x * block_height * 2 + coarse_y * info.stride + texel_index_within_tile * 2;
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const u8* source_ptr = source + offset * 2;
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// TODO: component order not verified
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@ -404,13 +401,13 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
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case Regs::TextureFormat::I8:
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{
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const u8* source_ptr = source + coarse_x * block_height + coarse_y * info.stride + texel_index_within_tile;
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const u8* source_ptr = source + offset;
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return { *source_ptr, *source_ptr, *source_ptr, 255 };
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}
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case Regs::TextureFormat::A8:
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{
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const u8* source_ptr = source + coarse_x * block_height + coarse_y * info.stride + texel_index_within_tile;
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const u8* source_ptr = source + offset;
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if (disable_alpha) {
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return { *source_ptr, *source_ptr, *source_ptr, 255 };
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@ -421,7 +418,7 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
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case Regs::TextureFormat::IA4:
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{
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const u8* source_ptr = source + coarse_x * block_height / 2 + coarse_y * info.stride + texel_index_within_tile / 2;
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const u8* source_ptr = source + offset / 2;
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// TODO: component order not verified
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@ -440,7 +437,7 @@ const Math::Vec4<u8> LookupTexture(const u8* source, int x, int y, const Texture
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case Regs::TextureFormat::A4:
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{
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const u8* source_ptr = source + coarse_x * block_height / 2 + coarse_y * info.stride + texel_index_within_tile / 2;
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const u8* source_ptr = source + offset / 2;
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// TODO: component order not verified
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