127 lines
4.2 KiB
Markdown
127 lines
4.2 KiB
Markdown
# GPU Documentation
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## The Xenos Chip
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The [Xenos](https://en.wikipedia.org/wiki/Xenos_\(graphics_chip\)) is a graphics
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chip designed by AMD based off of the R5xx architecture.
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### Command Processing
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The Xenos runs commands supplied to it directly by the DirectX bare-bones driver
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via a ringbuffer located in system memory.
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The bulk of the command processing code is located at
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[src/xenia/gpu/command_processor.cc](../src/xenia/gpu/command_processor.cc)
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### EDRAM
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The Xenos uses special high-speed memory located on the same die as the chip to
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store framebuffers/render targets.
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TODO: More documentation
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## Options
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### General
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See the top of [src/xenia/gpu/gpu_flags.cc](../src/xenia/gpu/gpu_flags.cc).
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`--vsync=false` will attempt to render the game as fast as possible instead of
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waiting for a fixed 60hz timer.
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### Vulkan
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See the top of [src/xenia/gpu/vulkan/vulkan_gpu_flags.cc](../src/xenia/vulkan/vulkan_gpu_flags.cc).
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`vulkan_dump_disasm=true` "Dump shader disassembly. NVIDIA only supported."
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## Tools
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### Shaders
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#### Shader Dumps
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Adding `--dump_shaders=path/` will write all translated shaders to the given
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path with names based on input hash (so they'll be stable across runs).
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Binaries containing the original microcode will be placed side-by-side with
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the dumped output to make it easy to pipe to `xe-gpu-shader-compiler`.
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#### xe-gpu-shader-compiler
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A standalone shader compiler exists to allow for quick shader translation
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testing. You can pass a binary ucode shader in and get either disassembled
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ucode or translated source out. This is best used through the Shader
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Playground tool.
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```
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xe-gpu-shader-compiler \
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--shader_input=input_file.bin.vs (or .fs)
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--shader_output=output_file.txt
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--shader_output_type=ucode (or spirvtext)
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```
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#### Shader Playground
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Built separately (for now) under [tools/shader-playground/](../tools/shader-playground/)
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is a GUI for interactive shader assembly, disassembly, validation, and
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translation.
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Entering shader microcode on the left will invoke the XNA Game Studio
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D3D compiler to translate the ucode to binary. The D3D compiler is then
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used to disassemble the binary and display the optimized form. If
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`xe-gpu-shader-compiler` has been built the ucode will be passed to that
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for disassembly and that will then be passed through D3D compiler. If
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the output of D3D compiler on the xenia disassembly doesn't match the
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original D3D compiler output the box will turn red, indicating that the
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disassembly is broken. Finally, the right most box will show the
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translated shader in the desired format.
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For more information and setup instructions see
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[tools/shader-playground/README.md](../tools/shader-playground/README.md).
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### xe-gpu-trace-viewer
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To quickly iterate on graphical issues, xenia can dump frames (or sequences of
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frames) while running that can be opened and inspected in a separate app.
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The basic workflow is:
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1. Capture the frame in game (using F4) or a stream of frames.
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2. Add the file path to the xe-gpu-trace-viewer Debugging command line in
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Visual Studio.
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3. Launch xe-gpu-trace-viewer.
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4. Poke around, find issues, etc.
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5. Modify code.
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6. Build and relaunch.
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7. Goto 4.
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#### Capturing Frames
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First, specify a path to capture traces to with
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`--trace_gpu_prefix=path/file_prefix_`. All files will have a randomish name
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based on that.
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When running xenia.exe you can hit F4 at any time to capture the next frame the
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game tries to draw (up until a VdSwap call). The file can be used immediately.
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#### Capturing Sequences
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Passing `--trace_gpu_stream` will write all frames rendered to a file, allowing
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you to seek through them in the trace viewer. These files will get large.
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## References
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### Command Buffer/Registers
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Registers documented at [src/xenia/gpu/register_table.inc](../src/xenia/gpu/register_table.inc).
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PM4 commands documented at [src/xenia/gpu/xenos.h](../src/xenia/gpu/xenos.h#L521).
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### Shaders
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* [LLVM R600 Tables](https://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AMDGPU/R600Instructions.td)
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** The opcode formats don't match, but the name->psuedo code is correct.
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* [xemit](https://github.com/gligli/libxemit/blob/master/xemitops.c)
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