--- a/src/hotspot/cpu/x86/x86.ad	Wed Oct 03 11:43:39 2018 +0530
+++ b/src/hotspot/cpu/x86/x86.ad	Wed Oct 03 03:41:57 2018 -0400
@@ -2804,11 +2804,7 @@
 
   format %{
     $$template
-    if (os::is_MP()) {
-      $$emit$$"pause\t! membar_onspinwait"
-    } else {
-      $$emit$$"MEMBAR-onspinwait ! (empty encoding)"
-    }
+    $$emit$$"pause\t! membar_onspinwait"
   %}
   ins_encode %{
     __ pause();