Index: lib/Basic/FileManager.cpp
===================================================================
--- lib/Basic/FileManager.cpp
+++ lib/Basic/FileManager.cpp
@@ -214,6 +214,12 @@
 
 const FileEntry *FileManager::getFile(StringRef Filename, bool openFile,
                                       bool CacheFailure) {
+#ifdef LLVM_ON_WIN32
+  SmallString<128> NormalizedPath(Filename.str());
+  llvm::sys::path::native(NormalizedPath);
+  Filename = NormalizedPath;
+#endif // LLVM_ON_WIN32
+
   ++NumFileLookups;
 
   // See if there is already an entry in the map.