[tint][msl] Replace volatile loop conditional with outer volatile conditional.

Instead of attempting to preserve UB loops with volatile loads in the conditional, instead wrap the loop in a conditional using a volatile load.
This means the UB loop might still get removed, but control flow that comes after will not be affected.

This has the following benefits:
• Doesn't (appear to) trigger control flow bugs on older hardware.
• Doesn't require a volatile load per iteration (O(n) -> O(1)).
• Looks like it might actually work for all of Skia's tests.

Bug: tint:2125
Change-Id: Ibb17f77d1291eff6a0d5b3244be711bd8ecaff62
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/170801
Kokoro: Kokoro <noreply+kokoro@google.com>
Auto-Submit: Ben Clayton <bclayton@google.com>
Commit-Queue: David Neto <dneto@google.com>
Reviewed-by: David Neto <dneto@google.com>
166 files changed
tree: 87153fb36b89a1193a9bc772e92ca1de33428e3f
  1. .github/
  2. .vscode/
  3. build_overrides/
  4. docs/
  5. generator/
  6. include/
  7. infra/
  8. scripts/
  9. src/
  10. test/
  11. third_party/
  12. tools/
  13. webgpu-cts/
  14. .bazelrc
  15. .clang-format
  16. .clang-tidy
  17. .gitattributes
  18. .gitignore
  19. .gitmodules
  20. .gn
  21. AUTHORS
  22. BUILD.bazel
  23. BUILD.gn
  24. CMakeLists.txt
  25. CMakeSettings.json
  26. CODE_OF_CONDUCT.md
  27. codereview.settings
  28. CONTRIBUTING.md
  29. CPPLINT.cfg
  30. DEPS
  31. DIR_METADATA
  32. Doxyfile
  33. go.mod
  34. go.sum
  35. go_presubmit_support.py
  36. LICENSE
  37. OWNERS
  38. PRESUBMIT.py
  39. README.chromium
  40. README.md
  41. WORKSPACE.bazel
README.md

Build Status Matrix Space

Dawn, a WebGPU implementation

Dawn is an open-source and cross-platform implementation of the 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, Metal, Vulkan and OpenGL. See per API support for more details.
  • A client-server implementation of WebGPU for applications that are in a sandbox without access to native drivers
  • Tint is a compiler for the WebGPU Shader Language (WGSL) that can be used in standalone to convert shaders from and to WGSL.

Helpful links:

Documentation table of content

Developer documentation:

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

License

BSD 3-Clause License, please see LICENSE.

Disclaimer

This is not an officially supported Google product.