[GPU] Notes about tiled offset patterns

src/xenia/gpu/texture_util.h

@@ -83,6 +83,33 @@ void GetTextureTotalSize(Dimension dimension, uint32_t width, uint32_t height,
                          bool packed_mips, uint32_t mip_max_level,
                          uint32_t* base_size_out, uint32_t* mip_size_out);
 
+// Notes about tiled addresses that can be useful for simplifying and optimizing
+// tiling/untiling:
+// - Offset2D(X * 32 + x, Y * 32 + y) ==
+//       Offset2D(X * 32, Y * 32) + Offset2D(x, y)
+//   (true for negative offsets too).
+// - Offset3D(X * 32 + x, Y * 32 + y, Z * 8 + z) ==
+//       Offset3D(X * 32, Y * 32, Z * 8) + Offset3D(x, y, z)
+//   (true for negative offsets too).
+// - Addressing of blocks that are contiguous along X (for tiling/untiling of
+//   larger portions at once):
+//   - 1bpb - each 8 blocks are laid out sequentially, odd 8 blocks =
+//     even 8 blocks + 64 bytes (two R32G32_UINT tiled accesses for one
+//     R32G32B32A32_UINT linear access).
+//   - 2bpb, 4bpb, 8bpb, 16bpb - each 16 bytes contain blocks laid out
+//     sequentially (can tile/untile in R32G32B32A32_UINT portions).
+//   - 2bpb - odd 8 blocks = even 8 blocks + 64 bytes.
+//   - 4bpb - odd 4 blocks = even 4 blocks + 32 bytes.
+//   - 8bpb - odd 2 blocks = even 2 blocks + 32 bytes.
+//   - 16bpb - odd block = even block + 32 bytes.
+// - Resolve granularity for both offset and size is 8x8 pixels
+//   (GPU_RESOLVE_ALIGNMENT - for example, Halo 3 resolves a 24x16 region for a
+//   18x10 texture, 8x8 region for a 1x1 texture).
+//   https://github.com/jmfauvel/CSGO-SDK/blob/master/game/client/view.cpp#L944
+//   https://github.com/stanriders/hl2-asw-port/blob/master/src/game/client/vgui_int.cpp#L901
+//   So, multiple pixels can still be loaded/stored when resolving, taking
+//   contiguous storage patterns into account.
+
 int32_t GetTiledOffset2D(int32_t x, int32_t y, uint32_t width,
                          uint32_t bpb_log2);
 int32_t GetTiledOffset3D(int32_t x, int32_t y, int32_t z, uint32_t width,