Fixed few warnings.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160493 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index d6e1834..8cbe818 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -942,7 +942,7 @@
   default: llvm_unreachable("Unknown instruction type encountered!");
     // Build the switch statement using the Instruction.def file.
 #define HANDLE_INST(NUM, OPCODE, CLASS) \
-    case Instruction::OPCODE: visit##OPCODE((CLASS&)I); break;
+    case Instruction::OPCODE: visit##OPCODE((const CLASS&)I); break;
 #include "llvm/Instruction.def"
   }