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/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 8ec8a5a..3e1f942 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -281,6 +281,10 @@
   setOperationAction(ISD::MEMSET          , MVT::Other, Custom);
   setOperationAction(ISD::MEMCPY          , MVT::Other, Custom);
 
+  if (!Subtarget->hasSSE2())
+    setOperationAction(ISD::MEMBARRIER    , MVT::Other, Expand);
+
+
   // Use the default ISD::LOCATION, ISD::DECLARE expansion.
   setOperationAction(ISD::LOCATION, MVT::Other, Expand);
   // FIXME - use subtarget debug flags