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

llvm/lib/Bitcode/Writer/ValueEnumerator.cpp

@@ -345,6 +345,7 @@ ValueEnumerator::ValueEnumerator(const Module &M,
 
   SmallVector<std::pair<unsigned, MDNode *>, 8> MDs;
   for (const GlobalVariable &GV : M.globals()) {
+    MDs.clear();
     GV.getAllMetadata(MDs);
     for (const auto &I : MDs)
       EnumerateMetadata(&GV, I.second);
@@ -356,6 +357,7 @@ ValueEnumerator::ValueEnumerator(const Module &M,
       EnumerateType(A.getType());
 
     // Enumerate metadata attached to this function.
+    MDs.clear();
     F.getAllMetadata(MDs);
     for (const auto &I : MDs)
       EnumerateMetadata(&F, I.second);