[clang] Enable making the CompilerInstance module dependency collector thread-safe

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:

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;