Rollup merge of #122632 - onur-ozkan:fix-llvm-caching-bug, r=albertlarsan68

fetch submodule before checking llvm stamp

Previously, we were checking the LLVM stamp before fetching the submodule which leads to not being able to compile llvm on submodule updates.

Fixes #122612
Fixes #122787

2 files changed, 18 insertions, 1 deletions

diff --git a/src/bootstrap/src/core/build_steps/llvm.rs b/src/bootstrap/src/core/build_steps/llvm.rs
index 420336fee14..7cb15fe5590 100644
--- a/src/bootstrap/src/core/build_steps/llvm.rs
+++ b/src/bootstrap/src/core/build_steps/llvm.rs
@@ -76,6 +76,9 @@ pub fn prebuilt_llvm_config(
     builder: &Builder<'_>,
     target: TargetSelection,
 ) -> Result<LlvmResult, Meta> {
+    // If we have llvm submodule initialized already, sync it.
+    builder.update_existing_submodule(&Path::new("src").join("llvm-project"));
+
     builder.config.maybe_download_ci_llvm();
 
     // If we're using a custom LLVM bail out here, but we can only use a
@@ -94,6 +97,9 @@ pub fn prebuilt_llvm_config(
         }
     }
 
+    // Initialize the llvm submodule if not initialized already.
+    builder.update_submodule(&Path::new("src").join("llvm-project"));
+
     let root = "src/llvm-project/llvm";
     let out_dir = builder.llvm_out(target);
 
@@ -280,7 +286,6 @@ impl Step for Llvm {
             Err(m) => m,
         };
 
-        builder.update_submodule(&Path::new("src").join("llvm-project"));
         if builder.llvm_link_shared() && target.is_windows() {
             panic!("shared linking to LLVM is not currently supported on {}", target.triple);
         }
diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index 1a8322c0dfd..a609bbbffb6 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -630,6 +630,18 @@ impl Build {
         }
     }
 
+    /// Updates the given submodule only if it's initialized already; nothing happens otherwise.
+    pub fn update_existing_submodule(&self, submodule: &Path) {
+        // Avoid running git when there isn't a git checkout.
+        if !self.config.submodules(self.rust_info()) {
+            return;
+        }
+
+        if GitInfo::new(false, submodule).is_managed_git_subrepository() {
+            self.update_submodule(submodule);
+        }
+    }
+
     /// Executes the entire build, as configured by the flags and configuration.
     pub fn build(&mut self) {
         unsafe {