Index: lib/LTO/ThinLTOCodeGenerator.cpp
===================================================================
--- lib/LTO/ThinLTOCodeGenerator.cpp
+++ lib/LTO/ThinLTOCodeGenerator.cpp
@@ -950,11 +950,15 @@
   // Changes are made in the index, consumed in the ThinLTO backends.
   internalizeAndPromoteInIndex(ExportLists, GUIDPreservedSymbols, *Index);
 
-  // Make sure that every module has an entry in the ExportLists and
-  // ResolvedODR maps to enable threaded access to these maps below.
-  for (auto &DefinedGVSummaries : ModuleToDefinedGVSummaries) {
-    ExportLists[DefinedGVSummaries.first()];
-    ResolvedODR[DefinedGVSummaries.first()];
+  // Make sure that every module has an entry in the ExportLists, ImportList,
+  // GVSummary and ResolvedODR maps to enable threaded access to these maps
+  // below.
+  for (auto &Module : Modules) {
+    auto ModuleIdentifier = Module.getBufferIdentifier();
+    ExportLists[ModuleIdentifier];
+    ImportLists[ModuleIdentifier];
+    ResolvedODR[ModuleIdentifier];
+    ModuleToDefinedGVSummaries[ModuleIdentifier];
   }
 
   // Compute the ordering we will process the inputs: the rough heuristic here