llvm.memory.barrier, and impl for x86 and alpha

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47204 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index f8e1fea..c12c98b 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3792,6 +3792,7 @@
       return "<<Unknown Target Node>>";
     }
    
+  case ISD::MEMBARRIER:    return "MemBarrier";
   case ISD::PCMARKER:      return "PCMarker";
   case ISD::READCYCLECOUNTER: return "ReadCycleCounter";
   case ISD::SRCVALUE:      return "SrcValue";