Rollup merge of #139322 - Kobzol:run-make-lld-refactor, r=jieyouxu

Add helper function for checking LLD usage to `run-make-support`

Extracted out of https://github.com/rust-lang/rust/pull/138645, should be a simple refactoring.

r? ``@jieyouxu``

2 files changed, 37 insertions, 0 deletions

diff --git a/src/tools/run-make-support/src/lib.rs b/src/tools/run-make-support/src/lib.rs
index fd22ff6c8bc..c75d500d2f0 100644
--- a/src/tools/run-make-support/src/lib.rs
+++ b/src/tools/run-make-support/src/lib.rs
@@ -17,6 +17,7 @@ pub mod assertion_helpers;
 pub mod diff;
 pub mod env;
 pub mod external_deps;
+pub mod linker;
 pub mod path_helpers;
 pub mod run;
 pub mod scoped_run;
diff --git a/src/tools/run-make-support/src/linker.rs b/src/tools/run-make-support/src/linker.rs
new file mode 100644
index 00000000000..89093cf0113
--- /dev/null
+++ b/src/tools/run-make-support/src/linker.rs
@@ -0,0 +1,36 @@
+use regex::Regex;
+
+use crate::{Rustc, is_msvc};
+
+/// Asserts that `rustc` uses LLD for linking when executed.
+pub fn assert_rustc_uses_lld(rustc: &mut Rustc) {
+    let stderr = get_stderr_with_linker_messages(rustc);
+    assert!(
+        has_lld_version_in_logs(&stderr),
+        "LLD version should be present in rustc stderr:\n{stderr}"
+    );
+}
+
+/// Asserts that `rustc` doesn't use LLD for linking when executed.
+pub fn assert_rustc_doesnt_use_lld(rustc: &mut Rustc) {
+    let stderr = get_stderr_with_linker_messages(rustc);
+    assert!(
+        !has_lld_version_in_logs(&stderr),
+        "LLD version should NOT be present in rustc stderr:\n{stderr}"
+    );
+}
+
+fn get_stderr_with_linker_messages(rustc: &mut Rustc) -> String {
+    // lld-link is used if msvc, otherwise a gnu-compatible lld is used.
+    let linker_version_flag = if is_msvc() { "--version" } else { "-Wl,-v" };
+
+    let output = rustc.arg("-Wlinker-messages").link_arg(linker_version_flag).run();
+    output.stderr_utf8()
+}
+
+fn has_lld_version_in_logs(stderr: &str) -> bool {
+    // Strip the `-Wlinker-messages` wrappers prefixing the linker output.
+    let stderr = Regex::new(r"warning: linker std(out|err):").unwrap().replace_all(&stderr, "");
+    let lld_version_re = Regex::new(r"^LLD [0-9]+\.[0-9]+\.[0-9]+").unwrap();
+    stderr.lines().any(|line| lld_version_re.is_match(line.trim()))
+}