Check invalid debug info for enums. This may happen when underlyng enum is optimized away. Eventually DwarfChecker will clean this up during llvm verification stage.

llvm-svn: 83655
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 1ea148e..86532e8 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -950,8 +950,10 @@
     for (unsigned i = 0, N = Elements.getNumElements(); i < N; ++i) {
       DIE *ElemDie = NULL;
       DIEnumerator Enum(Elements.getElement(i).getNode());
-      ElemDie = ConstructEnumTypeDIE(DW_Unit, &Enum);
-      Buffer.AddChild(ElemDie);
+      if (!Enum.isNull()) {
+        ElemDie = ConstructEnumTypeDIE(DW_Unit, &Enum);
+        Buffer.AddChild(ElemDie);
+      }
     }
   }
     break;