Function run_compilation

cranelift/codegen/build.rs:195–256

Build ISLE DSL source text into generated Rust code. NB: This must happen *after* the `cranelift-codegen-meta` functions, since it consumes files generated by them.

(compilation: &IsleCompilation)

/// NB: This must happen *after* the `cranelift-codegen-meta` functions, since
/// it consumes files generated by them.
fn run_compilation(compilation: &IsleCompilation) -> Result<(), Errors> {
    use cranelift_isle as isle;

    eprintln!("Rebuilding {}", compilation.output.display());

    let code = {
        let file_paths = compilation
            .inputs
            .iter()
            .chain(compilation.untracked_inputs.iter());

        let mut options = isle::codegen::CodegenOptions::default();
        // Because we include!() the generated ISLE source, we cannot
        // put the global pragmas (`#![allow(...)]`) in the ISLE
        // source itself; we have to put them in the source that
        // include!()s it. (See
        // https://github.com/rust-lang/rust/issues/47995.)
        options.exclude_global_allow_pragmas = true;

        // When `cranelift-codegen` is built with detailed tracing enabled, also
        // ask the ISLE compiler to emit `log::{debug,trace}!` invocations in
        // the generated code to help debug rule matching.
        options.emit_logging = std::env::var("CARGO_FEATURE_TRACE_LOG").is_ok();

        // Enable optional match-arm splitting in iterator terms for
        // faster compile times in release builds.
        //
        // In debug builds, *always* split with an aggressive
        // threshold, because we cannot rely on rustc doing regalloc
        // on all of the local bindings to shrink the stack frame to a
        // reasonable size.
        if cfg!(debug_assertions) {
            options.split_match_arms = true;
            options.match_arm_split_threshold = Some(4);
        } else {
            options.split_match_arms = std::env::var("CARGO_FEATURE_ISLE_SPLIT_MATCH").is_ok();
            if let Ok(value) = std::env::var("ISLE_SPLIT_MATCH_THRESHOLD") {
                options.match_arm_split_threshold = Some(value.parse().unwrap_or_else(|err| {
                    panic!("invalid ISLE_SPLIT_MATCH_THRESHOLD value '{value}': {err}");
                }));
            }
        }

        if let Ok(out_dir) = std::env::var("OUT_DIR") {
            options.prefixes.push(isle::codegen::Prefix {
                prefix: out_dir,
                name: "<OUT_DIR>".to_string(),
            })
        };

        isle::compile::from_files(file_paths, &options)?
    };

    eprintln!(
        "Writing ISLE-generated Rust code to {}",
        compilation.output.display()
    );
    std::fs::write(&compilation.output, code)