WebGPU: Uniform buffer standard layout

Category: Graphics
Type: New or changed feature
Status: Proposed (Chrome Proposed)
Intent stage: None

Breaking change: No
Enterprise impact: None
Chromium flag: Enable Unsafe WebGPU
Spec maturity: Published standard
Web Platform Tests: Yes

WPT details: WebGPU/WGSL have a conformance test suite (https://github.com/gpuweb/cts) that is regularly pulled into Chromium and part of the testing of Dawn/Tint in Chromium. While the CTS can be embedded in WPT, the WebGPU team opted to keep it separate in Chromium testing to use a customized harness for robustness and performance. CTS coverage for this feature was added here: https://github.com/gpuweb/cts/pull/4484

Summary

Functionality added to the WebGPU spec after its first shipment in a browser. Uniform buffers declared in WGSL shaders are no longer required to have 16-byte alignment on array elements, or to pad nested structure offsets to a multiple of 16 bytes.

Motivation

This feature simplifies the use of uniform buffers in WGSL shaders by unifying their constraints with those of storage buffers. Without this, developers are required to align all array elements to 16 bytes and pad nested structures to achieve a 16-byte offset.

Standards & signals

Specification: https://www.w3.org/TR/WGSL/#language_extension-uniform_buffer_standard_layout
Firefox: No signal
Safari: Closed Without a Position
Web developers: No signals
Tracking bug: https://crbug.com/452662924

Ecosystem

Web Platform Tests: https://wpt.fyi/results/?q=webgpu%2FWGSL
Chrome Platform Showcase: https://chrome-platform-showcase.paulkinlan-ea.deno.net/features
GenDN reference: https://gendn.paulkinlan-ea.deno.net/features
chrome.dev demos search: https://www.google.com/search?q=site%3Achrome.dev+WebGPU%3A%20Uniform%20buffer%20standard%20layout
MDN Web Docs: https://developer.mozilla.org/en-US/search?q=WebGPU%3A%20Uniform%20buffer%20standard%20layout
Baseline status: https://webstatus.dev/?q=WebGPU%3A%20Uniform%20buffer%20standard%20layout

Explainers: https://github.com/gpuweb/gpuweb/issues/4973

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