Missing "subgroups" extension declare in wgsl output if using subgroup

[mikialex]

Description

According to https://www.w3.org/TR/WGSL/#enable-extensions-sec, using the subgroup feature in WGSL requires the "subgroups" extension to be enabled(declaration), but we are missing it. This breaks the subgroup feature in Chrome.

Repro steps

Use any subgroup feature and open it in Chrome.

Expected vs observed behavior

No errors no warnings

[cwfitzgerald]

Is this an issue with our parsing of wgsl, or the generating of wgsl when targetting chrome? For context, when you hand us wgsl on wasm we pass it right through.

[mikialex]

I am directly using Naga module as shader source, so the issue is generating wgsl(https://github.com/gfx-rs/wgpu/blob/trunk/naga/src/back/wgsl/writer.rs#L242 write_enable_declarations). I'm not sure if parsing is ok(maybe missing this declaration's validation?)

[ErichDonGubler]

@mikialex: You should be able to easily create an MRE using cargo run -p naga-cli. Could you please do that?

[mikialex]

run this simple shader in chrome

@compute @workgroup_size(32)
fn main() {
    let mask = subgroupBallot(true);
}

will produce this error message in console

Error while parsing WGSL: :8:16 error: cannot call built-in function 'subgroupBallot' without extension 'subgroups'
    let mask = subgroupBallot(true);
               ^^^^^^^^^^^^^^^^^^^^


 - While calling [Device].CreateShaderModule([ShaderModuleDescriptor]).

I am currently using a shader edsl api for directly naga module building. The naga module generated wgsl output does not have the required extension declaration.