Index: gcc/config/rs6000/sync.md
===================================================================
--- gcc/config/rs6000/sync.md	(revision 181425)
+++ gcc/config/rs6000/sync.md	(working copy)
@@ -53,6 +53,15 @@ (define_expand "mem_thread_fence"
   DONE;
 })
 
+(define_expand "memory_barrier"
+  [(set (match_dup 0)
+	(unspec:BLK [(match_dup 0)] UNSPEC_SYNC))]
+  ""
+{
+  operands[0] = gen_rtx_MEM (BLKmode, gen_rtx_SCRATCH (Pmode));
+  MEM_VOLATILE_P (operands[0]) = 1;
+})
+
 (define_expand "hwsync"
   [(set (match_dup 0)
 	(unspec:BLK [(match_dup 0)] UNSPEC_SYNC))]