Fix a crash viewing dags that have target nodes in them

llvm-svn: 23300
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index ae0c2c8..c27523a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2263,7 +2263,8 @@
     else {
       if (G)
         if (const TargetInstrInfo *TII = G->getTarget().getInstrInfo())
-          return TII->getName(getOpcode()-ISD::BUILTIN_OP_END);
+          if (getOpcode()-ISD::BUILTIN_OP_END < TII->getNumOpcodes())
+            return TII->getName(getOpcode()-ISD::BUILTIN_OP_END);
       return "<<Unknown Target Node>>";
     }