check for missing codegen backeng config

src/bootstrap/compile.rs

@@ -20,7 +20,7 @@ use serde_derive::Deserialize;
 
 use crate::builder::crate_description;
 use crate::builder::Cargo;
-use crate::builder::{Builder, Kind, RunConfig, ShouldRun, Step};
+use crate::builder::{Builder, Kind, PathSet, RunConfig, ShouldRun, Step, TaskPath};
 use crate::cache::{Interned, INTERNER};
 use crate::config::{LlvmLibunwind, RustcLto, TargetSelection};
 use crate::dist;
@@ -995,6 +995,44 @@ pub struct CodegenBackend {
  pub backend: Interned<String>,
 }
 
+fn needs_codegen_config(run: &RunConfig<'_>) -> bool {
+ let mut needs_codegen_cfg = false;
+ for path_set in &run.paths {
+ needs_codegen_cfg = match path_set {
+ PathSet::Set(set) => set.iter().any(|p| is_codegen_cfg_needed(p, run)),
+ PathSet::Suite(suite) => is_codegen_cfg_needed(&suite, run),
+ }
+ }
+ needs_codegen_cfg
+}
+
+const CODEGEN_BACKEND_PREFIX: &str = "rustc_codegen_";
+
+fn is_codegen_cfg_needed(path: &TaskPath, run: &RunConfig<'_>) -> bool {
+ if path.path.to_str().unwrap().contains(&CODEGEN_BACKEND_PREFIX) {
+ let mut needs_codegen_backend_config = true;
+ for &backend in &run.builder.config.rust_codegen_backends {
+ if path
+ .path
+ .to_str()
+ .unwrap()
+ .ends_with(&(CODEGEN_BACKEND_PREFIX.to_owned() + &backend))
+ {
+ needs_codegen_backend_config = false;
+ }
+ }
+ if needs_codegen_backend_config {
+ run.builder.info(
+ "Warning: no codegen-backends config matched the requested path to build a codegen backend. \
+ Help: add backend to codegen-backends in config.toml.",
+ );
+ return true;
+ }
+ }
+
+ return false;
+}
+
 impl Step for CodegenBackend {
  type Output = ();
  const ONLY_HOSTS: bool = true;
@@ -1006,6 +1044,10 @@ impl Step for CodegenBackend {
  }
 
  fn make_run(run: RunConfig<'_>) {
+ if needs_codegen_config(&run) {
+ return;
+ }
+
  for &backend in &run.builder.config.rust_codegen_backends {
  if backend == "llvm" {
  continue; // Already built as part of rustc