dawn-cmake/docs/dawn/debugging.md

Debugging Dawn

Toggles

There are various debug-related Toggles that can help diagnose issues. Useful debug toggles:

• dump_shaders: Log input WGSL shaders and translated backend shaders (MSL/ HLSL/DXBC/DXIL / SPIR-V).
• disable_symbol_renaming: As much as possible, disable renaming of symbols (variables, function names, etc.). This can make dumped shaders more readable.
• emit_hlsl_debug_symbols: Sets the D3DCOMPILE_SKIP_OPTIMIZATION and D3DCOMPILE_DEBUG compilation flags when compiling HLSL code.
• use_user_defined_labels_in_backend: Forward object labels to the backend so that they can be seen in native debugging tools like RenderDoc, PIX, or Mac Instruments.

Toggles may be enabled/disabled in different ways.

• In code:

  Use extension struct DawnTogglesDescriptor chained on DeviceDescriptor.

  For example:

  const char* const enabledToggles[] = {"dump_shaders", "disable_symbol_renaming"};
  
  wgpu::DawnTogglesDescriptor deviceTogglesDesc;
  deviceTogglesDesc.enabledToggles = enabledToggles;
  deviceTogglesDesc.enabledTogglesCount = 2;
  
  wgpu::DeviceDescriptor deviceDescriptor;
  deviceDescriptor.nextInChain = &deviceTogglesDesc;
  

• Command-line for Chrome

  Run Chrome with command line flags--enable-dawn-features and/or --disable-dawn-features to force enable/disable toggles. Toggles should be comma-delimited.

  For example: --enable-dawn-features=dump_shaders,disable_symbol_renaming

• Command-line for dawn_end2end_tests/dawn_unittests

  Run Dawn test binaries with command line flags--enable-toggles and/or --disable-toggles to force enable/disable toggles. Toggles should be comma-delimited.

  For example: dawn_end2end_tests --enable-toggles=dump_shaders,disable_symbol_renaming

Environment Variables

• DAWN_DEBUG_BREAK_ON_ERROR

  Errors in WebGPU are reported asynchronously which may make debugging difficult because at the time an error is reported, you can't easily create a breakpoint to inspect the callstack in your application.

  Setting DAWN_DEBUG_BREAK_ON_ERROR to a non-empty, non-zero value will execute a debug breakpoint instruction (dawn::Breakpoint()) as soon as any type of error is generated.