Add support for undef and unreachable

llvm-svn: 17041
diff --git a/llvm/lib/VMCore/Instruction.cpp b/llvm/lib/VMCore/Instruction.cpp
index 4ea5775..17970ac 100644
--- a/llvm/lib/VMCore/Instruction.cpp
+++ b/llvm/lib/VMCore/Instruction.cpp
@@ -88,6 +88,7 @@
   case Switch: return "switch";
   case Invoke: return "invoke";
   case Unwind: return "unwind";
+  case Unreachable: return "unreachable";
     
   // Standard binary operators...
   case Add: return "add";