Add "fxc_optimizations" toggle set to false by default

FXC sometimes miscompiles code when optimizing (/O2), and there is no
discernable workaround. This change sets the optimization level to /O0
when compiling shaders with FXC.

Also, no longer default to enabling EmitHLSLDebugSymbols in Debug
builds, which disabled optimizations (/Od). This confused me a few
times, and is not necessary since we can set this toggle via command

Bug: dawn:1203
Bug: tint:1175
Bug: tint:1112
Change-Id: Ide9e6ecd45adeca951b8836dee91a8367eca3769
Reviewed-by: Corentin Wallez <>
Reviewed-by: Ben Clayton <>
Commit-Queue: Antonio Maiorano <>
5 files changed
tree: d1c673c0b866fcea3c79a81bf644ca479048bcd0
  1. .clang-format
  2. .gitattributes
  3. .gitignore
  4. .gn
  5. .vscode/
  8. CMakeLists.txt
  9. DEPS
  12. OWNERS
  14. README.chromium
  16. build_overrides/
  17. codereview.settings
  18. dawn.json
  19. dawn_wire.json
  20. docs/
  21. examples/
  22. generator/
  23. infra/
  24. scripts/
  25. src/
  26. third_party/
  27. tools/

Dawn's logo: a sun rising behind a stylized mountain inspired by the WebGPU logo. The text Dawn is written below it.

Dawn, a WebGPU implementation

Dawn is an open-source and cross-platform implementation of the work-in-progress WebGPU standard. More precisely it implements webgpu.h that is a one-to-one mapping with the WebGPU IDL. Dawn is meant to be integrated as part of a larger system and is the underlying implementation of WebGPU in Chromium.

Dawn provides several WebGPU building blocks:

  • WebGPU C/C++ headers that applications and other building blocks use.
    • The webgpu.h version that Dawn implements.
    • A C++ wrapper for the webgpu.h.
  • A “native” implementation of WebGPU using platforms' GPU APIs:
    • D3D12 on Windows 10
    • Metal on macOS and iOS
    • Vulkan on Windows, Linux, ChromeOS, Android and Fuchsia
    • OpenGL as best effort where available
  • A client-server implementation of WebGPU for applications that are in a sandbox without access to native drivers

Helpful links:

Documentation table of content

Developer documentation:

User documentation: (TODO, figure out what overlaps with the webgpu.h docs)




Apache 2.0 Public License, please see LICENSE.


This is not an officially supported Google product.