ddb039b9c9
spirv-builder only looks for the exact
librustc_codegen_spirv.{so,dylib,dll} filename in the dylib search path.
That works in the rust-gpu workspace, but it misses external build.rs
consumers where Cargo only exposes hashed deps artifacts such as
librustc_codegen_spirv-<hash>.so. This showed up in a downstream
workspace update to current rust-gpu main where the consumer path only
had hashed backend artifacts available to default SpirvBuilder
discovery.
Keep preferring the exact filename when present, then fall back to the
newest hashed rustc_codegen_spirv dylib in the same search paths. Add
tests for exact matches, hashed fallback, and exact-over-hashed
precedence.
spirv-builder
This crate gives you SpirvBuilder, a tool to build shaders using rust-gpu.
It takes care of pulling in the SPIR-V backend for Rust, rustc_codegen_spirv, and invoking a nested build using appropriate compiler options, some of which may be set using the SpirvBuilder API.
Example
# use spirv_builder::SpirvBuilder;
#
fn main() -> Result<(), Box<dyn std::error::Error>> {
let mut builder = SpirvBuilder::new("my_shaders", "spirv-unknown-vulkan1.3");
builder.build_script.defaults = true;
builder.build_script.env_shader_spv_path = Some(true);
builder.build()?;
Ok(())
}
This example will build a shader crate called my_shaders. You typically insert this code in your crate's build.rs that requires the shader binary. The path to the shader module's binary will be set in the my_shaders.spv environment variable, which you can include in your project using something along the lines of:
const SHADER: &[u8] = include_bytes!(env!("my_shaders.spv"));
Building with spirv-builder
As spirv-builder relies on rustc_codegen_spirv being built for it (by Cargo, as a direct dependency), and due to the special nature of the latter (as a rustc codegen backend "plugin"), both end up sharing the requirement for a very specific nightly toolchain version of Rust.
The current Rust toolchain version is: nightly-2024-04-24.
Rust toolchain version history across rust-gpu releases (since 0.4):
spirv-builderversion |
Rust toolchain version |
|---|---|
0.10 |
nightly-2024-04-24 |
0.9 |
nightly-2023-05-27 |
0.8 |
nightly-2023-04-15 |
0.7 |
nightly-2023-03-04 |
0.6 |
nightly-2023-01-21 |
0.5 |
nightly-2022-12-18 |
0.4 |
nightly-2022-10-29 |
As patch versions must be semver-compatible, they will always require the
same toolchain (for example, 0.6.0 and 0.6.1 both use nightly-2023-01-21).
Only that exact Rust nightly toolchain version is supported. Since 0.4, the commit hash of your current Rust toolchain is checked and you'll get a build error when building rustc_codegen_spirv with the wrong toolchain.
Notably, the error will also show what the rust-toolchain.toml file should contain (to get the expected toolchain), which you can rely on when updating to a new release.
If you want to experiment with different, unsupported, Rust toolchain versions, this check can be omitted by defining the environment variable RUSTGPU_SKIP_TOOLCHAIN_CHECK. Keep in mind that, as rustc_codegen_spirv is heavily dependent on rustc's internal APIs, diverging too much from the supported toolchain version will quickly result in compile errors (or worse, e.g. spurious errors and/or incorrect behavior, when compiling shaders with it).