--- old/src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp	2018-11-05 19:29:30.790164637 +0100
+++ new/src/hotspot/share/gc/shenandoah/c2/shenandoahBarrierSetC2.cpp	2018-11-05 19:29:30.546167638 +0100
@@ -1009,6 +1009,35 @@
       }
     }
   }
+  if (n->Opcode() == Op_CmpP) {
+    Node* in1 = n->in(1);
+    Node* in2 = n->in(2);
+    if (in1->bottom_type() == TypePtr::NULL_PTR) {
+      in2 = step_over_gc_barrier(in2);
+    }
+    if (in2->bottom_type() == TypePtr::NULL_PTR) {
+      in1 = step_over_gc_barrier(in1);
+    }
+    PhaseIterGVN* igvn = phase->is_IterGVN();
+    if (in1 != n->in(1)) {
+      if (igvn != NULL) {
+        n->set_req_X(1, in1, igvn);
+      } else {
+        n->set_req(1, in1);
+      }
+      assert(in2 == n->in(2), "only one change");
+      return n;
+    }
+    if (in2 != n->in(2)) {
+      if (igvn != NULL) {
+        n->set_req_X(2, in2, igvn);
+      } else {
+        n->set_req(2, in2);
+      }
+      return n;
+    }
+  }
+
   return NULL;
 }