1822096 - Support WGSL const-expressions and override-expressions in Naga

Status: RESOLVED FIXED

(Core :: Graphics: WebGPU, task, P2)

Description

[Jim Blandy :jimb]

To implement v1 of the WebGPU spec, Naga needs to support WGSL const-expressions and override-expressions.

The WGSL spec permits expressions in many places that require a value known at shader module creation time or pipeline creation time. These are limited to "const-expressions", which don't depend on variables, buffer contents, etc, or "override-expressions", which are like const-expressions but can also refer to override constants, whose values are supplied at pipeline creation time.

Comment 1

[Teodor Tanasoaia [:teoxoy]]

Upstream meta issue: https://github.com/gfx-rs/naga/issues/2274

Comment 2

[Erich Gubler [:ErichDonGubler] (he/him)]

This is currently known to block the following demos from webgpu-v1-samples particularly with local const variables (upstream Naga issue: https://github.com/gfx-rs/naga/issues/2316):

• deferredRendering
• imageBlur
• reversedZ
• shadowMapping
• videoUploadingWebCodecs

Comment 3

[Jim Blandy :jimb]

Upstream for const declarations: https://github.com/gfx-rs/naga/issues/2316
Upsteram for override declarations: https://github.com/gfx-rs/naga/issues/1426

Comment 4

[Erich Gubler [:ErichDonGubler] (he/him)]

I noticed that some shaders at https://compute.toys are failing because of this issue, i.e., https://compute.toys/view/153.

Comment 6

[Teodor Tanasoaia [:teoxoy]]

const-expressions landed upstream in https://github.com/gfx-rs/naga/pull/2266 & https://github.com/gfx-rs/naga/pull/2309.

This work will be brought in by https://bugzilla.mozilla.org/show_bug.cgi?id=1859999.

Comment 7

[Erich Gubler [:ErichDonGubler] (he/him)]

Oh, derp, sorry, wrong bug link! This is the most recent re-vendoring that should unblock overrides. 🙂

Comment 8

[Teodor Tanasoaia [:teoxoy]]

Attachment: Bug 1822096 - [webgpu] add plumbing for pipeline-overridable constants. r=#webgpu-reviewers

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/49aba74b154f
[webgpu] add plumbing for pipeline-overridable constants. r=webgpu-reviewers,webidl,smaug,nical,ErichDonGubler

Comment 10

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/49aba74b154f