s390x: Implement Ist_MBE
VEX IR provides the statement Ist_MBE which is used to implement memory
barriers (Imbe_Fence). We use this statement to implement serialization which
is similar.
Fixes #271385.  (Florian Krohm, britzel@acm.org)



git-svn-id: svn://svn.valgrind.org/vex/trunk@2134 8f6e269a-dfd6-0310-a8e1-e2731360e62c
diff --git a/priv/host_s390_isel.c b/priv/host_s390_isel.c
index 1e4ecdc..83da36e 100644
--- a/priv/host_s390_isel.c
+++ b/priv/host_s390_isel.c
@@ -2291,7 +2291,14 @@
    }
 
       /* --------- MEM FENCE --------- */
-   case Ist_MBE:  /* fixs390 later */
+   case Ist_MBE:
+      switch (stmt->Ist.MBE.event) {
+         case Imbe_Fence:
+            addInstr(env, s390_insn_mfence());
+            return;
+         default:
+            break;
+      }
       break;
 
       /* --------- Miscellaneous --------- */