Initialize padding on buffer allocations

Buffer allocations in Dawn may be padded. This padding
could be visible, depending on how the backend
implements robust vertex buffer access. This commit
updates buffer creation to clear all padding bytes
immediately after creation.
It is not counted as a lazy clear.
And, add a test which reads off the end of a padded
vertex buffer to check that the padding bytes are also
initialized.

Also: Update Metal buffers to always allocate enough
space for Tint's vertex pulling, and pass the full
allocated size to Tint. While writing the test in this
commit, a bug was found where Tint assumes there is at
least 4 bytes in the vertex pulling buffer. The WebGPU
API currently allows zero-sized bindings, so Dawn needs
to always allocate enough space for one element.

Also: Update Vulkan vertex/index buffers to allocate
at least one more byte than requested because
vkCmdSetVertexBuffers and vkCmdSetIndexBuffer disallow
the offset to be equal to the buffer size. We need
at least one more byte to make zero-sized bindings
as the end of the buffer valid.

Lastly: Update helper so that a T2B copy of a single
row that touches all bytes in a buffer updates the
buffer state to be fully initialized. This is a small
optimization that is necessary to write the test.

Tested-In: https://chromium-review.googlesource.com/c/chromium/src/+/3107782
No-Try: true
Bug: dawn:837
Change-Id: I829f4764509c4ec784c5aeaaf40b6dcbd4be6866
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/62161
Commit-Queue: Austin Eng <enga@chromium.org>
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
(cherry picked from commit ddd0a0a856a2bd7013e82291974f1107f02fc1a9)
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/62382
13 files changed
tree: b0f6109841b6e48d14f4f37e0fae72f856f4bab1
  1. .vscode/
  2. build_overrides/
  3. docs/
  4. examples/
  5. generator/
  6. infra/
  7. scripts/
  8. src/
  9. third_party/
  10. tools/
  11. .clang-format
  12. .gitattributes
  13. .gitignore
  14. .gn
  15. AUTHORS
  16. BUILD.gn
  17. CMakeLists.txt
  18. codereview.settings
  19. dawn.json
  20. dawn_wire.json
  21. DEPS
  22. DIR_METADATA
  23. LICENSE
  24. OWNERS
  25. PRESUBMIT.py
  26. README.chromium
  27. README.md
README.md

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)

Status

(TODO)

License

Apache 2.0 Public License, please see LICENSE.

Disclaimer

This is not an officially supported Google product.