Index: lib/Transforms/IPO/FunctionImport.cpp
===================================================================
--- lib/Transforms/IPO/FunctionImport.cpp
+++ lib/Transforms/IPO/FunctionImport.cpp
@@ -332,16 +332,19 @@
     // Make exports in the source module.
     if (ExportLists) {
       auto &ExportList = (*ExportLists)[ExportModulePath];
-      ExportList.insert(GUID);
-      // Mark all functions and globals referenced by this function as exported
-      // to the outside if they are defined in the same source module.
-      for (auto &Edge : ResolvedCalleeSummary->calls()) {
-        auto CalleeGUID = Edge.first.getGUID();
-        exportGlobalInModule(Index, ExportModulePath, CalleeGUID, ExportList);
-      }
-      for (auto &Ref : ResolvedCalleeSummary->refs()) {
-        auto GUID = Ref.getGUID();
-        exportGlobalInModule(Index, ExportModulePath, GUID, ExportList);
+      auto InsertResult = ExportList.insert(GUID);
+      if (InsertResult.second) {
+        // This is the first time this function was exported from its source
+        // module, so mark all functions and globals it references as exported
+        // to the outside if they are defined in the same source module.
+        for (auto &Edge : ResolvedCalleeSummary->calls()) {
+          auto CalleeGUID = Edge.first.getGUID();
+          exportGlobalInModule(Index, ExportModulePath, CalleeGUID, ExportList);
+        }
+        for (auto &Ref : ResolvedCalleeSummary->refs()) {
+          auto GUID = Ref.getGUID();
+          exportGlobalInModule(Index, ExportModulePath, GUID, ExportList);
+        }
       }
     }