[naga] Allow dynamic indexing of array

[sagudev]

Connections
For arrays, at least, this fixes #4337, second commit is just gfx-rs/naga#723 ported to trunk.

Description
See commits and linked PR.

Testing
There are some new tests and I did CTS run in servo.

Checklist

• Run cargo fmt.
• Run cargo clippy. If applicable, add:
  • --target wasm32-unknown-unknown
  • --target wasm32-unknown-emscripten
• Run cargo xtask test to run tests.
• Add change to CHANGELOG.md. See simple instructions inside file.

[sagudev]

Servo's CTS run: https://github.com/sagudev/servo/actions/runs/10656885185/job/29537501039 (click view raw log, then find string Stable unexpected results, from there results start):
A lot of passes (do note that servo hit flakyl CRASH webgpu:shader,execution,expression,* due to servo/servo#31397) so I will only extract bad unexpected results:

TIMEOUT /_webgpu/webgpu/cts.https.html?q=webgpu:shader,execution,expression,call,builtin,textureSample:sampled_2d_coords:*
[2024-09-01T20:57:19Z ERROR wgpu_core::device::global] Device::create_shader_module error:
           Shader validation error:
              ┌─ :34:23
              │
         34 │           data[ndx] = textureLoad(tex, global_invocation_id.xy, mipLevel);
              │                                ^^^^^^^^^^^ naga::Expression [22]
       
 
    TIMEOUT [expected PASS] subtest: :format="bc1-rgba-unorm";sample_points="texel-centre"     
    NOTRUN [expected PASS] subtest: :format="bc1-rgba-unorm";sample_points="spiral"
    ...
TIMEOUT /_webgpu/webgpu/cts.https.html?q=webgpu:shader,execution,expression,call,builtin,textureSample:sampled_3d_coords:*
[2024-09-01T20:44:34Z ERROR wgpu_core::device::global] Device::create_shader_module error:
           Shader validation error:
              ┌─ :35:11
              │
         35 │           textureLoad(
              │           ^^^^^^^^^^^ naga::Expression [23]
    PASS [expected FAIL] subtest: :format="r8unorm";viewDimension="3d";sample_points="texel-centre"
    ...
    TIMEOUT [expected FAIL] subtest: :format="bc1-rgba-unorm";viewDimension="cube";sample_points="cube-edges" 
    NOTRUN [expected FAIL] subtest: :format="bc1-rgba-unorm";viewDimension="cube";sample_points="texel-centre"
    ...

[sagudev]

First CTS failures is from https://github.com/gpuweb/cts/blob/9b30f7a02d172ce36d138c02614d0a5a1edbfa72/src/webgpu/shader/execution/expression/call/builtin/texture_utils.ts#L3318, because servo does not support GPUExternalTexture, second is just timeout because tests would need to be spillted more (or servo should be faster).

TL;DR all ok

[ErichDonGubler]

Planning on reviewing this, and I heard @teoxoy also wanted to take a look. I'll consider this a learning experience for myself, since I'm still getting familiar with Naga, while @teoxoy would be the authoritative "LGTM". 🙂

[sagudev]

I'll consider this a learning experience for myself, since I'm still getting familiar with Naga, while @teoxoy would be the authoritative "LGTM". 🙂

I am relatively new to naga too (my first commit to naga is 34bb9e4, which landed 5 days ago).

[ErichDonGubler]

LGTM; let's see what @teoxoy has to say now. 😀

[jimblandy]

I think the sentence "Fixes #4337 for arrays" in the description of #6188 is confusing GitHub.

[jimblandy]

Note that this PR must be squashed when merged.

[jimblandy]

Overall, this looks really reasonable. Not approving yet because:

• I have some more tweaks I want to push
• I haven't actually looked over the test changes yet.
  I should be able to finish those tomorrow morning.

[sagudev]

What blocking this? Is there something I need to do?

[ErichDonGubler]

@sagudev: I don't see anything that's blocking; I see no objection to this PR merging, concrete or abstract, and there's an approving review (from me). We definitely dropped the ball on this one, sorry about that!

@gfx-rs/naga, unless you object in the next 24ish hours, I'm gonna merge this.

[jimblandy]

This looks good to me.