[webkit-changes] [WebKit/WebKit] 12ca75: WebGPU shader emits NaN when it should discard

[mwyrzykowski]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 12ca75b0e5334bb7091ebc366c5ea65436a7f3a4
      
https://github.com/WebKit/WebKit/commit/12ca75b0e5334bb7091ebc366c5ea65436a7f3a4
  Author: Mike Wyrzykowski <mwyrzykow...@apple.com>
  Date:   2026-09-24 (Thu, 24 Sep 2026)

  Changed paths:
    A LayoutTests/fast/webgpu/discard-then-loops-nan-expected.txt
    A LayoutTests/fast/webgpu/discard-then-loops-nan.html
    M LayoutTests/platform/mac-wk2/TestExpectations
    M Source/WebGPU/WGSL/Metal/MetalFunctionWriter.cpp

  Log Message:
  -----------
  WebGPU shader emits NaN when it should discard
https://bugs.webkit.org/show_bug.cgi?id=324521
rdar://187997601

Reviewed by Dan Glastonbury and Tadeu Zagallo.

Using volatile uint in the forward progress workaround causes the frontend
to generate incorrect IR. Replace it with a non-volatile uint and __asm volatile
instead.

Test: fast/webgpu/discard-then-loops-nan.html

* LayoutTests/fast/webgpu/discard-then-loops-nan-expected.txt: Added.
* LayoutTests/fast/webgpu/discard-then-loops-nan.html: Added.
* Source/WebGPU/WGSL/Metal/MetalFunctionWriter.cpp:
(WGSL::Metal::FunctionDefinitionWriter::visit):

Canonical link: https://commits.webkit.org/321870@main



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