Reland: Vulkan: Enforce fixed subgroup size for compute shaders.

Reland after a refactor of how the extension handling work in the Vulkan

The original author is David Turner <>.

This CL ensures that, on architectures with a varying subgroup size,
compute shaders are always compiled with a fixed subgroup size to
avoid consistency issues when one shader writes data in a subgroup-size
dependent layout to GPU memory, to be read by another shader in a
future dispatch.

At the moment, only Intel ICDs are known to implement this [1],
and the code uses a heuristics to chose the size of 16, which seems to
be the sweet spot according to Intel engineers.

+ Update the PNextChainBuilder class to deal with the fact that
  VkComputePipelineCreateInfo::pNext is defined as a const void*,
  which created compiler errors in the previous implementation.


Bug: dawn:464
Change-Id: I035ee06084fcc964742f0bff4c54cff257c742ae
Commit-Queue: Corentin Wallez <>
Reviewed-by: Austin Eng <>
Reviewed-by: Stephen White <>
3 files changed
tree: e1903714867712eddff2628b29e2530d38d1f2c7
  1. .clang-format
  2. .gitattributes
  3. .gitignore
  4. .gn
  7. CMakeLists.txt
  9. DEPS
  11. OWNERS
  13. README.chromium
  15. build_overrides/
  16. codereview.settings
  17. dawn.json
  18. dawn_wire.json
  19. docs/
  20. examples/
  21. generator/
  22. infra/
  23. scripts/
  24. src/
  25. third_party/
  26. tools/

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 webgpu.h docs)




Apache 2.0 Public License, please see LICENSE.


This is not an officially supported Google product.