textures: Reintroduce CPU ASTC decoder

Users may want to fall back to the CPU ASTC texture decoder due to hangs
and crashes that may be caused by keeping the GPU under compute heavy
loads for extended periods of time. This is especially the case in games
such as Astral Chain which make extensive use of ASTC textures.

src/video_core/CMakeLists.txt

@@ -237,6 +237,7 @@ add_library(video_core STATIC
     texture_cache/util.cpp
     texture_cache/util.h
     textures/astc.h
+    textures/astc.cpp
     textures/decoders.cpp
     textures/decoders.h
     textures/texture.cpp

src/video_core/texture_cache/util.cpp

@@ -47,6 +47,7 @@
 #include "video_core/texture_cache/formatter.h"
 #include "video_core/texture_cache/samples_helper.h"
 #include "video_core/texture_cache/util.h"
+#include "video_core/textures/astc.h"
 #include "video_core/textures/decoders.h"
 
 namespace VideoCommon {
@@ -884,8 +885,16 @@ void ConvertImage(std::span<const u8> input, const ImageInfo& info, std::span<u8
         ASSERT(copy.image_extent == mip_size);
         ASSERT(copy.buffer_row_length == Common::AlignUp(mip_size.width, tile_size.width));
         ASSERT(copy.buffer_image_height == Common::AlignUp(mip_size.height, tile_size.height));
-        DecompressBC4(input.subspan(copy.buffer_offset), copy.image_extent,
-                      output.subspan(output_offset));
+        if (IsPixelFormatASTC(info.format)) {
+            ASSERT(copy.image_extent.depth == 1);
+            Tegra::Texture::ASTC::Decompress(input.subspan(copy.buffer_offset),
+                                             copy.image_extent.width, copy.image_extent.height,
+                                             copy.image_subresource.num_layers, tile_size.width,
+                                             tile_size.height, output.subspan(output_offset));
+        } else {
+            DecompressBC4(input.subspan(copy.buffer_offset), copy.image_extent,
+                          output.subspan(output_offset));
+        }
         copy.buffer_offset = output_offset;
         copy.buffer_row_length = mip_size.width;
         copy.buffer_image_height = mip_size.height;

src/video_core/textures/astc.h

@@ -129,4 +129,7 @@ struct AstcBufferData {
     decltype(REPLICATE_BYTE_TO_16_TABLE) replicate_byte_to_16 = REPLICATE_BYTE_TO_16_TABLE;
 } constexpr ASTC_BUFFER_DATA;
 
+void Decompress(std::span<const uint8_t> data, uint32_t width, uint32_t height, uint32_t depth,
+                uint32_t block_width, uint32_t block_height, std::span<uint8_t> output);
+
 } // namespace Tegra::Texture::ASTC