IR: Allow multiple global metadata attachments with the same type.

This will be necessary to allow the global merge pass to attach
multiple debug info metadata nodes to global variables once we reverse
the edge from DIGlobalVariable to GlobalVariable.

Differential Revision: http://reviews.llvm.org/D20414

llvm-svn: 271358
diff --git a/llvm/lib/Transforms/Utils/CloneFunction.cpp b/llvm/lib/Transforms/Utils/CloneFunction.cpp
index 24f7d69..b64fdbd 100644
--- a/llvm/lib/Transforms/Utils/CloneFunction.cpp
+++ b/llvm/lib/Transforms/Utils/CloneFunction.cpp
@@ -122,11 +122,11 @@
   SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
   OldFunc->getAllMetadata(MDs);
   for (auto MD : MDs)
-    NewFunc->setMetadata(
+    NewFunc->addMetadata(
         MD.first,
-        MapMetadata(MD.second, VMap,
-                    ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
-                    TypeMapper, Materializer));
+        *MapMetadata(MD.second, VMap,
+                     ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
+                     TypeMapper, Materializer));
 
   // Loop over all of the basic blocks in the function, cloning them as
   // appropriate.  Note that we save BE this way in order to handle cloning of