Debuggable Shader

[wicast]

SPV

The inital debuggable spv-out is already merged, which can be used with renderdoc. Works fine with WGSL as source code.

But some of the local variable names are missing when compiles a complex shader: debug-symbol-terrain.wgsl and debug-symbol-terrain.spvasm. This needs more investigations.

See spec for more information: https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#OpLine https://registry.khronos.org/SPIR-V/specs/unified1/SPIRV.html#OpString

TODOs:

• [ ] missing local variable names
• [ ] test glsl as source code
• [ ] test Linux + Renderdoc

Metal

.metallibsym

.metallibsym is the Metal Companion Symbol file according to Apple doc.

But with the help of https://github.com/YuAo/MetalLibraryArchive

I found that the .metallibsym is acturally a .metallib with debug info + source code archive. They have the same structure. MetalLibraryArchive can unpack .metallibsym directly.

debug symbol

the full metal shader symbol should generate by -gline-tables-only and -frecord-sources as the Xcode shows:

-gline-tables-only is a clang's parameter and the good news is metal is using llvm's debug info directly.

BTW: The metal shader compiler support lots of clang parameters like -g, -O0, etc.

source code

source code is compressed with Bzip2 and embedded in the .metallib

MetalLibraryArchive can unpack the source code data from .metallib.

Other metallib reverse engine resource I found: https://worthdoingbadly.com/metalbitcode/

What's missing for generating debuggable .metallib

• [ ] does .metallib accept source code other than .metal? We need to do some tests.
• [ ] metallib struct manipulation tool, this is a rather easy part. Wiki's information seems a bit outdated compares to MetalLibraryArchive.
• [ ] the llvm ir manipulation tool, there are some crates but relies on llvm-sys: Inkwell, llvm-ir. I haven't found any pure rust impl yet. Related issues: https://github.com/gfx-rs/wgpu/issues/4301
• [ ] bzip2 compression, crates candidates: bzip2 which relies on sys, banzai a pure rust encoder

DX/HLSL ecosystem

TODO Not investigated yet.

[teoxoy]

This is great stuff!

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YuAo/MetalLibraryArchive looks a lot more complete than our Wiki page and mtl-info (a cli tool in rust I found a while back).

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• [ ] the llvm ir manipulation tool, there are some crates but relies on llvm-sys: Inkwell, llvm-ir. I haven't found any pure rust impl yet. Related issues: https://github.com/gfx-rs/wgpu/issues/4301

I bumped into https://github.com/woodruffw/mollusc a few days ago while I was looking for pure rust LLVM-IR crates.

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But some of the local variable names are missing when compiles a complex shader: debug-symbol-terrain.wgsl and debug-symbol-terrain.spvasm. This needs more investigations.

The reason for this is that let declarations become 'named expressions' and right now, we only add debug info to statements.

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DXIL also makes use of LLVM's debug info (see SourceLevelDebuggingHLSL)