Index: lib/Frontend/InitHeaderSearch.cpp
===================================================================
--- lib/Frontend/InitHeaderSearch.cpp	(revision 89764)
+++ lib/Frontend/InitHeaderSearch.cpp	(working copy)
@@ -111,6 +111,12 @@
 
   MappedPath.append(Path.begin(), Path.end());
 
+  // If there's a trailing path separator, remove it,
+  // as otherwise the existence check will fail.
+  if ((MappedPath.size() > 1) &&
+      ((MappedPath.back() == '/') || (MappedPath.back() == '\\')))
+    MappedPath.pop_back();
+
   // Compute the DirectoryLookup type.
   SrcMgr::CharacteristicKind Type;
   if (Group == Quoted || Group == Angled)