--- a/src/hotspot/share/opto/phaseX.cpp	Wed Nov 13 10:27:06 2019 +0900
+++ b/src/hotspot/share/opto/phaseX.cpp	Wed Nov 13 08:43:35 2019 +0100
@@ -891,7 +891,10 @@
 }
 
 bool PhaseGVN::is_dominator_helper(Node *d, Node *n, bool linear_only) {
-  if (d->is_top() || n->is_top()) {
+  if (d->is_top() || (d->is_Proj() && d->in(0)->is_top())) {
+    return false;
+  }
+  if (n->is_top() || (n->is_Proj() && n->in(0)->is_top())) {
     return false;
   }
   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");