I cannot find a libgcc function for this builtin.  Therefor expanding it to a noop (which is how it use to be treated).  If someone who knows the x86 backend better than me could tell me how to get a lock prefix on an instruction, that would be nice to complete x86 support.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@47213 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/IA64/IA64ISelLowering.cpp b/lib/Target/IA64/IA64ISelLowering.cpp
index 6b9cf15..85db947 100644
--- a/lib/Target/IA64/IA64ISelLowering.cpp
+++ b/lib/Target/IA64/IA64ISelLowering.cpp
@@ -69,7 +69,8 @@
       setOperationAction(ISD::MEMMOVE          , MVT::Other, Expand);
       setOperationAction(ISD::MEMSET           , MVT::Other, Expand);
       setOperationAction(ISD::MEMCPY           , MVT::Other, Expand);
-      
+      setOperationAction(ISD::MEMBARRIER       , MVT::Other, Expand);
+
       setOperationAction(ISD::SINT_TO_FP       , MVT::i1   , Promote);
       setOperationAction(ISD::UINT_TO_FP       , MVT::i1   , Promote);