diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -328,10 +328,13 @@
 };
 
 /// Sema - This implements semantic analysis and AST building for C.
-class Sema {
+class Sema final {
   Sema(const Sema &) = delete;
   void operator=(const Sema &) = delete;
 
+  /// A key method to reduce duplicate debug info from Sema.
+  virtual void anchor();
+
   ///Source of additional semantic information.
   ExternalSemaSource *ExternalSource;
 
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -189,6 +189,9 @@
   SemaPPCallbackHandler->set(*this);
 }
 
+// Anchor Sema's type info to this TU.
+void Sema::anchor() {}
+
 void Sema::addImplicitTypedef(StringRef Name, QualType T) {
   DeclarationName DN = &Context.Idents.get(Name);
   if (IdResolver.begin(DN) == IdResolver.end())