Precompiled Shaders Tracking Issue

[inner-daemons]

Precompiled Shaders Tracking Issue

This is a tracking issue for all things precompiled shaders, as well as making naga an optional dependency.

Current open PRs

• Add GLSL passthrough #9064
• Split shader compilation logic into new wgpu-shaders crate #9080

Motivation

Precompiled shaders will greatly reduce the startup time for apps, something which linebender/vello for example has expressed interest in. Removing naga as a dependency will also reduce binary size significantly, which is useful for web or mobile applications.

Wgpu already has passthrough shaders, which technically allow using precompiled shaders already, but these have some downsides:

• Naga is still part of the binary, even though its unused
• Wgpu's compilation logic is hidden and must be reimplemented
• No validation can be dond. This means that users may compile shaders that require features not available on all hardware, and wgpu won't be able to catch this.

Prior work

The previous issue for this was #3103. There was lots of discussion there.

I've also been chipping away quietly at parts of this for a while now. Relevant PRs:

• DXIL & HLSL passthrough #7831
• Initial precompiled shaders implementation #7834
• Add more complete MSL passthrough #8140
• Changed wgpu to default to static dxc when the feature is enabled #8882
• Add metallib passthrough #8886
• Add a DX12 backend option to force a certain shader model #8984

Todo list

Below are some tasks, generally in order, that must happen for precompiled shaders to be considered "complete" in my opinion.

• GLSL passthrough #8524 - Add GLSL passthrough #9064
• Split shader compilation into wgpu-shaders crate #8842 - Split shader compilation logic into new wgpu-shaders crate #9080
• Naga backend supported capability detection #9006 - Add supported caps info to naga backends #9068
• Naga GLSL backend cross-platform output #9007 - probably will simply be part of wgpu-shaders
• Make said wgpu-shaders have a user-friendly public API
• Use passthrough shaders in wgpu-core internal shaders #9010
• Passthrough shader context & validation #9009
• Make the features spv, wgsl, glsl or naga-ir all enable naga, so that naga can be removed as dependency

Here are some other tasks that should also happen at some point

• Metal passthrough shaders have limitations #8330
• Allow use of and experiment with spirv-opt #8843 - at least in wgpu-shaders

[TimTheBig]

I would love to add support for this to wesl_build, my build system for WESL with extension support, without users having to make big changes by abstracting via the import macro