--- a/hotspot/src/cpu/x86/vm/x86_64.ad	Wed Dec 07 11:35:03 2011 +0100
+++ b/hotspot/src/cpu/x86/vm/x86_64.ad	Tue Dec 20 16:56:50 2011 +0100
@@ -6810,6 +6810,16 @@
   ins_pipe(empty);
 %}
 
+instruct membar_storestore() %{
+  match(MemBarStoreStore);
+  ins_cost(0);
+
+  size(0);
+  format %{ "MEMBAR-storestore (empty encoding)" %}
+  ins_encode( );
+  ins_pipe(empty);
+%}
+
 //----------Move Instructions--------------------------------------------------
 
 instruct castX2P(rRegP dst, rRegL src)