Rollup merge of #137683 - Kobzol:tidy-gcc-submodule, r=GuillaumeGomez

Add a tidy check for GCC submodule version

To make sure that it stays in sync with the required GCC version of the GCC codegen backend.

The check should succeed on CI, although it will fail after https://github.com/rust-lang/rust/pull/137660, until the next GCC sync.

r? `@GuillaumeGomez`

4 files changed, 49 insertions, 0 deletions

diff --git a/src/gcc b/src/gcc
-Subproject 13cc8243226a9028bb08ab6c5e1c5fe6d533bcd
+Subproject 0ea98a1365b81f7488073512c850e8ee951a4af
diff --git a/src/tools/tidy/src/gcc_submodule.rs b/src/tools/tidy/src/gcc_submodule.rs
new file mode 100644
index 00000000000..952ebe9e0cf
--- /dev/null
+++ b/src/tools/tidy/src/gcc_submodule.rs
@@ -0,0 +1,47 @@
+//! Tidy check to ensure that the commit SHA of the `src/gcc` submodule is the same as the
+//! required GCC version of the GCC codegen backend.
+
+use std::path::Path;
+use std::process::Command;
+
+pub fn check(root_path: &Path, compiler_path: &Path, bad: &mut bool) {
+    let cg_gcc_version_path = compiler_path.join("rustc_codegen_gcc/libgccjit.version");
+    let cg_gcc_version = std::fs::read_to_string(&cg_gcc_version_path)
+        .expect(&format!("Cannot read GCC version from {}", cg_gcc_version_path.display()))
+        .trim()
+        .to_string();
+
+    let git_output = Command::new("git")
+        .current_dir(root_path)
+        .arg("submodule")
+        .arg("status")
+        // --cached asks for the version that is actually committed in the repository, not the one
+        // that is currently checked out.
+        .arg("--cached")
+        .arg("src/gcc")
+        .output()
+        .expect("Cannot determine git SHA of the src/gcc checkout");
+
+    // This can return e.g.
+    // -e607be166673a8de9fc07f6f02c60426e556c5f2 src/gcc
+    //  e607be166673a8de9fc07f6f02c60426e556c5f2 src/gcc (master-e607be166673a8de9fc07f6f02c60426e556c5f2.e607be)
+    // +e607be166673a8de9fc07f6f02c60426e556c5f2 src/gcc (master-e607be166673a8de9fc07f6f02c60426e556c5f2.e607be)
+    let git_output = String::from_utf8_lossy(&git_output.stdout)
+        .trim()
+        .split_whitespace()
+        .next()
+        .unwrap_or_default()
+        .to_string();
+
+    // The SHA can start with + if the submodule is modified or - if it is not checked out.
+    let gcc_submodule_sha = git_output.trim_start_matches(&['+', '-']);
+    if gcc_submodule_sha != cg_gcc_version {
+        *bad = true;
+        eprintln!(
+            r#"Commit SHA of the src/gcc submodule (`{gcc_submodule_sha}`) does not match the required GCC version of the GCC codegen backend (`{cg_gcc_version}`).
+Make sure to set the src/gcc submodule to commit {cg_gcc_version}.
+The GCC codegen backend commit is configured at {}."#,
+            cg_gcc_version_path.display(),
+        );
+    }
+}
diff --git a/src/tools/tidy/src/lib.rs b/src/tools/tidy/src/lib.rs
index 66856f5247b..ca45f8bb84b 100644
--- a/src/tools/tidy/src/lib.rs
+++ b/src/tools/tidy/src/lib.rs
@@ -75,6 +75,7 @@ pub mod features;
 pub mod fluent_alphabetical;
 pub mod fluent_period;
 mod fluent_used;
+pub mod gcc_submodule;
 pub(crate) mod iter_header;
 pub mod known_bug;
 pub mod mir_opt_tests;
diff --git a/src/tools/tidy/src/main.rs b/src/tools/tidy/src/main.rs
index 4078d462f55..48122129b01 100644
--- a/src/tools/tidy/src/main.rs
+++ b/src/tools/tidy/src/main.rs
@@ -116,6 +116,7 @@ fn main() {
         check!(fluent_alphabetical, &compiler_path, bless);
         check!(fluent_period, &compiler_path);
         check!(target_policy, &root_path);
+        check!(gcc_submodule, &root_path, &compiler_path);
 
         // Checks that only make sense for the std libs.
         check!(pal, &library_path);