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/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index b3d7fbf..7b01d63 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -3046,6 +3046,15 @@
     DAG.setRoot(DAG.getNode(ISD::TRAP, MVT::Other, getRoot()));
     return 0;
   }
+  case Intrinsic::memory_barrier: {
+    SDOperand Ops[6];
+    Ops[0] = getRoot();
+    for (int x = 1; x < 6; ++x)
+      Ops[x] = getValue(I.getOperand(x));
+
+    DAG.setRoot(DAG.getNode(ISD::MEMBARRIER, MVT::Other, &Ops[0], 6));
+    return 0;
+  }
   }
 }