diff --git a/clang/include/clang/Serialization/ModuleManager.h b/clang/include/clang/Serialization/ModuleManager.h
--- a/clang/include/clang/Serialization/ModuleManager.h
+++ b/clang/include/clang/Serialization/ModuleManager.h
@@ -59,8 +59,8 @@
   // to implement short-circuiting logic when running DFS over the dependencies.
   SmallVector<ModuleFile *, 2> Roots;
 
-  /// All loaded modules, indexed by name.
-  llvm::DenseMap<const FileEntry *, ModuleFile *> Modules;
+  /// All loaded modules, indexed by file name.
+  llvm::StringMap<ModuleFile *> Modules;
 
   /// FileManager that handles translating between filenames and
   /// FileEntry *.
diff --git a/clang/lib/Serialization/ModuleManager.cpp b/clang/lib/Serialization/ModuleManager.cpp
--- a/clang/lib/Serialization/ModuleManager.cpp
+++ b/clang/lib/Serialization/ModuleManager.cpp
@@ -59,7 +59,7 @@
 }
 
 ModuleFile *ModuleManager::lookup(const FileEntry *File) const {
-  auto Known = Modules.find(File);
+  auto Known = Modules.find(File->tryGetRealPathName());
   if (Known == Modules.end())
     return nullptr;
 
@@ -133,7 +133,8 @@
   }
 
   // Check whether we already loaded this module, before
-  if (ModuleFile *ModuleEntry = Modules.lookup(Entry)) {
+  auto EntryKey = Entry ? Entry->tryGetRealPathName() : FileName;
+  if (ModuleFile *ModuleEntry = Modules.lookup(EntryKey)) {
     // Check the stored signature.
     if (checkSignature(ModuleEntry->Signature, ExpectedSignature, ErrorStr))
       return OutOfDate;
@@ -208,7 +209,7 @@
     return OutOfDate;
 
   // We're keeping this module.  Store it everywhere.
-  Module = Modules[Entry] = NewModule.get();
+  Module = Modules[EntryKey] = NewModule.get();
 
   updateModuleImports(*NewModule, ImportedBy, ImportLoc);
 
@@ -255,7 +256,7 @@
 
   // Delete the modules and erase them from the various structures.
   for (ModuleIterator victim = First; victim != Last; ++victim) {
-    Modules.erase(victim->File);
+    Modules.erase(victim->File->tryGetRealPathName());
 
     if (modMap) {
       StringRef ModuleName = victim->ModuleName;