[WIP] [WebGPU] allow WGSL template generation

[fs-eire]

Description

This PR introduces the WGSL-Template into WebGPU EP to enable the capability of template based WGSL source generation.

The purpose of this change is to improve the readability of the WGSL source code and reduce the future maintenance cost due to the difficulty of understanding the current WGSL code generation logic.

Currently, this is still WIP and a lot of things are subject to change.

Explanation

• build
  append flag --use_wgsl_template

• the template files use extension .wgsl.template and are located in core/providers/webgpu/ folder.

• the corresponding C++ file should use shader_helper.ApplyTemplate<...>() to apply the template. (check pad.cc for example)

• for documentation - https://github.com/fs-eire/wgsl-template

[github-actions]

You can commit the suggested changes from lintrunner.

[prathikr]

Can we add a file under /docs with details/examples on how to use this feature for debugging?

[sushraja-msft]

instead of $MAIN, what is the downside of supporting actual wgsl main

@compute @workgroup_size(workgroup_size_x, workgroup_size_y, workgroup_size_z)
fn main(@Builtin(global_invocation_id) global_id : vec3,
@Builtin(workgroup_id) workgroup_id : vec3,
@Builtin(local_invocation_index) local_idx : u32,
@Builtin(local_invocation_id) local_id : vec3,
@Builtin(subgroup_invocation_id) sg_id : u32,
@Builtin(subgroup_size) sg_size : u32,
@Builtin(num_workgroups) num_workgroups : vec3) {

In your preprocessing, you can replace this with $MAIN by regex matching
/@compute.*\n+.fn main((.|\n){/gm

This approach makes it clear where variables like sg_id come from in the code, it makes it easy to copy paste standalone shaders into .template files without having to modify them too much. Avoids creation of a new concept $MAIN

Regex testing
https://regex101.com/

Later iterations can parse out the built-in name and type and validate with auto generated code.

[fs-eire]

see fs-eire/wgsl-template#9

[sushraja-msft]

will #include be supported ?

[fs-eire]

it's already supported

[fs-eire]

please see https://github.com/fs-eire/wgsl-template?tab=readme-ov-file#template-syntax for explanation of supported syntax

[sushraja-msft]

missing at this point. Would be good to add template-syntax section

[github-actions]

You can commit the suggested changes from lintrunner.

[snnn]

So, you will add an embeded javascript engine to ORT?