2 files changed, 24 insertions, 1 deletions
diff --git a/clang/lib/Frontend/ModuleDependencyCollector.cpp b/clang/lib/Frontend/ModuleDependencyCollector.cpp
index fc3958f601a..e0ec674a16c 100644
--- a/clang/lib/Frontend/ModuleDependencyCollector.cpp
+++ b/clang/lib/Frontend/ModuleDependencyCollector.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/Frontend/Utils.h"
+#include "clang/Lex/Preprocessor.h"
 #include "clang/Serialization/ASTReader.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/iterator_range.h"
@@ -22,7 +23,7 @@
 using namespace clang;
 
 namespace {
-/// Private implementation for ModuleDependencyCollector
+/// Private implementations for ModuleDependencyCollector
 class ModuleDependencyListener : public ASTReaderListener {
   ModuleDependencyCollector &Collector;
 public:
@@ -36,12 +37,30 @@ public:
     return true;
   }
 };
+
+struct ModuleDependencyMMCallbacks : public ModuleMapCallbacks {
+  ModuleDependencyCollector &Collector;
+  ModuleDependencyMMCallbacks(ModuleDependencyCollector &Collector)
+      : Collector(Collector) {}
+
+  void moduleMapAddHeader(const FileEntry &File) override {
+    StringRef HeaderPath = File.getName();
+    if (llvm::sys::path::is_absolute(HeaderPath))
+      Collector.addFile(HeaderPath);
+  }
+};
+
 }
 
 void ModuleDependencyCollector::attachToASTReader(ASTReader &R) {
   R.addListener(llvm::make_unique<ModuleDependencyListener>(*this));
 }
 
+void ModuleDependencyCollector::attachToPreprocessor(Preprocessor &PP) {
+  PP.getHeaderSearchInfo().getModuleMap().addModuleMapCallbacks(
+      llvm::make_unique<ModuleDependencyMMCallbacks>(*this));
+}
+
 void ModuleDependencyCollector::writeFileMap() {
   if (Seen.empty())
     return;
diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index 69cb574e2a0..4b782a3e8ec 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -811,6 +811,10 @@ void ModuleMap::addHeader(Module *Mod, Module::Header Header,
     HeaderInfo.MarkFileModuleHeader(Header.Entry, Role,
                                     isCompilingModuleHeader);
   }
+
+  // Notify callbacks that we just added a new header.
+  for (const auto &Cb : Callbacks)
+    Cb->moduleMapAddHeader(*Header.Entry);
 }
 
 void ModuleMap::excludeHeader(Module *Mod, Module::Header Header) {