Bug 201246 – [WHLSL] Add discard; statement

• Component: WebGPU
• Status: RESOLVED WONTFIX

[Robin Morisset]

See https://github.com/gpuweb/WHLSL/issues/54.
HLSL documentation: https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-discard

This is kind of required to test the corresponding part of my uniformity analysis: https://bugs.webkit.org/show_bug.cgi?id=201240

[Robin Morisset]

The equivalent metal appears to be the function 
void discard_fragment(void)

[Robin Morisset]

Created attachment 378235 [details]
WIP

Missing tests + changelog.

[Robin Morisset]

Created attachment 378244 [details]
WIP

Fix a couple bugs:
- we tolerated discard that were called from non-fragment entry points as long as it was uniformly
- we erroneously marked every ternary expression as possibly discarding.

[Robin Morisset]

Created attachment 378406 [details]
WIP

Added trivial Changelog and a first test.

Still missing:
- more tests
- cleanup of the current test, some of it is cruft copy-pasted from texture-sample-bias which is probably needed.

[Myles C. Maxfield]

WHLSL is no longer relevant.