--- old/src/cpu/x86/vm/x86_32.ad	2011-12-14 16:45:44.131307323 +0100
+++ new/src/cpu/x86/vm/x86_32.ad	2011-12-14 16:45:43.660313787 +0100
@@ -7901,6 +7901,16 @@
   ins_pipe(empty);
 %}
 
+instruct unnecessary_membar_storestore() %{
+  match(MemBarStoreStore);
+  ins_cost(0);
+
+  size(0);
+  format %{ "!MEMBAR-storestore (unnecessary so empty encoding)" %}
+  ins_encode( );
+  ins_pipe(empty);
+%}
+
 //----------Move Instructions--------------------------------------------------
 instruct castX2P(eAXRegP dst, eAXRegI src) %{
   match(Set dst (CastX2P src));