[clang] [clang] Enable making the `CompilerInstance` module dependency collector thread-safe (PR #137227)

[Jan Svoboda via cfe-commits]

https://github.com/jansvoboda11 created https://github.com/llvm/llvm-project/pull/137227

The same principle as #135473, #135737, #136178, #136601 & #137059.

>From 30fb74c3ff1197a6e1d7cdc8ff52fa2d2c0d9c33 Mon Sep 17 00:00:00 2001
From: Jan Svoboda <jan_svoboda at apple.com>
Date: Thu, 24 Apr 2025 11:26:17 -0700
Subject: [PATCH] [clang] Enable making the `CompilerInstance` module
 dependency collector thread-safe

The same principle as #135473, #135737, #136178, #136601 & #137059.
---
 clang/include/clang/Frontend/CompilerInstance.h | 13 ++++++++++---
 clang/lib/Frontend/CompilerInstance.cpp         | 12 ++++++++----
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/clang/include/clang/Frontend/CompilerInstance.h b/clang/include/clang/Frontend/CompilerInstance.h
index 8c91a2a86cfcd..b5b4de03e45f1 100644
--- a/clang/include/clang/Frontend/CompilerInstance.h
+++ b/clang/include/clang/Frontend/CompilerInstance.h
@@ -839,16 +839,23 @@ class CompilerInstance : public ModuleLoader {
   class ThreadSafeCloneConfig {
     IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS;
     DiagnosticConsumer &DiagConsumer;
+    std::shared_ptr<ModuleDependencyCollector> ModuleDepCollector;
 
   public:
-    ThreadSafeCloneConfig(IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
-                          DiagnosticConsumer &DiagConsumer)
-        : VFS(std::move(VFS)), DiagConsumer(DiagConsumer) {
+    ThreadSafeCloneConfig(
+        IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS,
+        DiagnosticConsumer &DiagConsumer,
+        std::shared_ptr<ModuleDependencyCollector> ModuleDepCollector = nullptr)
+        : VFS(std::move(VFS)), DiagConsumer(DiagConsumer),
+          ModuleDepCollector(std::move(ModuleDepCollector)) {
       assert(this->VFS && "Clone config requires non-null VFS");
     }
 
     IntrusiveRefCntPtr<llvm::vfs::FileSystem> getVFS() const { return VFS; }
     DiagnosticConsumer &getDiagConsumer() const { return DiagConsumer; }
+    std::shared_ptr<ModuleDependencyCollector> getModuleDepCollector() const {
+      return ModuleDepCollector;
+    }
   };
 
 private:
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 1526ea53add7d..58a01459f3c64 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -1257,10 +1257,14 @@ std::unique_ptr<CompilerInstance> CompilerInstance::cloneForModuleCompileImpl(
     Instance.GetDependencyDirectives =
         GetDependencyDirectives->cloneFor(Instance.getFileManager());
 
-  // If we're collecting module dependencies, we need to share a collector
-  // between all of the module CompilerInstances. Other than that, we don't
-  // want to produce any dependency output from the module build.
-  Instance.setModuleDepCollector(getModuleDepCollector());
+  if (ThreadSafeConfig) {
+    Instance.setModuleDepCollector(ThreadSafeConfig->getModuleDepCollector());
+  } else {
+    // If we're collecting module dependencies, we need to share a collector
+    // between all of the module CompilerInstances. Other than that, we don't
+    // want to produce any dependency output from the module build.
+    Instance.setModuleDepCollector(getModuleDepCollector());
+  }
   Inv.getDependencyOutputOpts() = DependencyOutputOptions();
 
   return InstancePtr;