Index: include/clang/Frontend/PrecompiledPreamble.h
===================================================================
--- include/clang/Frontend/PrecompiledPreamble.h
+++ include/clang/Frontend/PrecompiledPreamble.h
@@ -283,6 +283,8 @@
   /// Creates wrapper class for PPCallbacks so we can also process information
   /// about includes that are inside of a preamble
   virtual std::unique_ptr<PPCallbacks> createPPCallbacks();
+  /// Adds the returned CommentHandler to PreProcessor if not null.
+  virtual CommentHandler *getCommentHandler();
 };
 
 enum class BuildPreambleError {
Index: lib/Frontend/PrecompiledPreamble.cpp
===================================================================
--- lib/Frontend/PrecompiledPreamble.cpp
+++ lib/Frontend/PrecompiledPreamble.cpp
@@ -18,6 +18,7 @@
 #include "clang/Frontend/FrontendActions.h"
 #include "clang/Frontend/FrontendOptions.h"
 #include "clang/Lex/Lexer.h"
+#include "clang/Lex/Preprocessor.h"
 #include "clang/Lex/PreprocessorOptions.h"
 #include "clang/Serialization/ASTWriter.h"
 #include "llvm/ADT/StringExtras.h"
@@ -346,6 +347,8 @@
       Callbacks.createPPCallbacks();
   if (DelegatedPPCallbacks)
     Clang->getPreprocessor().addPPCallbacks(std::move(DelegatedPPCallbacks));
+  if (auto CommentHandler = Callbacks.getCommentHandler())
+    Clang->getPreprocessor().addCommentHandler(CommentHandler);
 
   Act->Execute();
 
@@ -742,6 +745,7 @@
 std::unique_ptr<PPCallbacks> PreambleCallbacks::createPPCallbacks() {
   return nullptr;
 }
+CommentHandler *PreambleCallbacks::getCommentHandler() { return nullptr; }
 
 static llvm::ManagedStatic<BuildPreambleErrorCategory> BuildPreambleErrCategory;