Initial implementation of 'fence' instruction, the new C++0x-style replacement for llvm.memory.barrier.

This is just a LangRef entry and reading/writing/memory representation; optimizer+codegen support coming soon.

llvm-svn: 136009
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index ba18465..649a38a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3211,6 +3211,10 @@
   DAG.setRoot(StoreNode);
 }
 
+void SelectionDAGBuilder::visitFence(const FenceInst &I) {
+  llvm_unreachable("Not implemented yet");
+}
+
 /// visitTargetIntrinsic - Lower a call of a target intrinsic to an INTRINSIC
 /// node.
 void SelectionDAGBuilder::visitTargetIntrinsic(const CallInst &I,