Thread --jobs from bootstrap -> compiletest -> run-make-support

src/bootstrap/src/core/build_steps/test.rs

@@ -2265,6 +2265,8 @@ Please disable assertions with `rust.debug-assertions = false`.
             cmd.arg("--with-std-remap-debuginfo");
         }
 
+        cmd.arg("--jobs").arg(builder.jobs().to_string());
+
         let mut llvm_components_passed = false;
         let mut copts_passed = false;
         if builder.config.llvm_enabled(test_compiler.host) {

src/tools/compiletest/src/common.rs

@@ -715,6 +715,11 @@ pub struct Config {
     pub override_codegen_backend: Option<String>,
     /// Whether to ignore `//@ ignore-backends`.
     pub bypass_ignore_backends: bool,
+
+    /// Number of parallel jobs configured for the build.
+    ///
+    /// This is forwarded from bootstrap's `jobs` configuration.
+    pub jobs: u32,
 }
 
 impl Config {

src/tools/compiletest/src/directives/tests.rs

@@ -225,6 +225,7 @@ impl ConfigBuilder {
             "--nightly-branch=",
             "--git-merge-commit-email=",
             "--minicore-path=",
+            "--jobs=0",
         ];
         let mut args: Vec<String> = args.iter().map(ToString::to_string).collect();
 

src/tools/compiletest/src/lib.rs

@@ -218,7 +218,8 @@ fn parse_config(args: Vec<String>) -> Config {
             "the codegen backend to use instead of the default one",
             "CODEGEN BACKEND [NAME | PATH]",
         )
-        .optflag("", "bypass-ignore-backends", "ignore `//@ ignore-backends` directives");
+        .optflag("", "bypass-ignore-backends", "ignore `//@ ignore-backends` directives")
+        .reqopt("", "jobs", "number of parallel jobs bootstrap was configured with", "JOBS");
 
     let (argv0, args_) = args.split_first().unwrap();
     if args.len() == 1 || args[1] == "-h" || args[1] == "--help" {
@@ -363,6 +364,11 @@ fn parse_config(args: Vec<String>) -> Config {
     let build_test_suite_root = opt_path(matches, "build-test-suite-root");
     assert!(build_test_suite_root.starts_with(&build_root));
 
+    let jobs = match matches.opt_str("jobs") {
+        Some(jobs) => jobs.parse::<u32>().expect("expected `--jobs` to be an `u32`"),
+        None => panic!("`--jobs` is required"),
+    };
+
     Config {
         bless: matches.opt_present("bless"),
         fail_fast: matches.opt_present("fail-fast")
@@ -481,6 +487,8 @@ fn parse_config(args: Vec<String>) -> Config {
         default_codegen_backend,
         override_codegen_backend,
         bypass_ignore_backends: matches.opt_present("bypass-ignore-backends"),
+
+        jobs,
     }
 }
 

src/tools/compiletest/src/runtest/run_make.rs

@@ -249,6 +249,9 @@ impl TestCx<'_> {
             cmd.env("__STD_REMAP_DEBUGINFO_ENABLED", "1");
         }
 
+        // Used for `run_make_support::env::jobs`.
+        cmd.env("__BOOTSTRAP_JOBS", self.config.jobs.to_string());
+
         // We don't want RUSTFLAGS set from the outside to interfere with
         // compiler flags set in the test cases:
         cmd.env_remove("RUSTFLAGS");

src/tools/compiletest/src/rustdoc_gui_test.rs

@@ -139,5 +139,6 @@ fn incomplete_config_for_rustdoc_gui_test() -> Config {
         default_codegen_backend: CodegenBackend::Llvm,
         override_codegen_backend: None,
         bypass_ignore_backends: Default::default(),
+        jobs: Default::default(),
     }
 }

src/tools/run-make-support/src/env.rs

@@ -49,3 +49,17 @@ pub fn set_current_dir<P: AsRef<std::path::Path>>(dir: P) {
     std::env::set_current_dir(dir.as_ref())
         .expect(&format!("could not set current directory to \"{}\"", dir.as_ref().display()));
 }
+
+/// Number of parallel jobs bootstrap was configured with.
+///
+/// This may fallback to [`std::thread::available_parallelism`] when no explicit jobs count has been
+/// configured. Refer to bootstrap's jobs fallback logic.
+#[track_caller]
+pub fn jobs() -> u32 {
+    std::env::var_os("__BOOTSTRAP_JOBS")
+        .expect("`__BOOTSTRAP_JOBS` must be set by `compiletest`")
+        .to_str()
+        .expect("`__BOOTSTRAP_JOBS` must be a valid string")
+        .parse::<u32>()
+        .expect("`__BOOTSTRAP_JOBS` must be a valid `u32`")
+}

tests/run-make/compiletest-self-test/jobs/rmake.rs

@@ -0,0 +1,5 @@
+//! Very basic smoke test to make sure `run_make_support::env::jobs` at least does not panic.
+
+fn main() {
+    println!("{}", run_make_support::env::jobs());
+}