Revert "Revert "Recognize and optimize a.runtimeType == b.runtimeType pattern.""

runtime/vm/flow_graph.cc

Index: runtime/vm/flow_graph.cc
diff --git a/runtime/vm/flow_graph.cc b/runtime/vm/flow_graph.cc
index f513b304c012f92220fa118ad8641bb91b59e133..bdfd7082ad60fa7cb11cec3a0261b55e4fb4cd95 100644
--- a/runtime/vm/flow_graph.cc
+++ b/runtime/vm/flow_graph.cc
@@ -84,6 +84,14 @@ void FlowGraph::ReplaceCurrentInstruction(ForwardInstructionIterator* iterator,
       THR_Print("Removing v%" Pd ".\n", current_defn->ssa_temp_index());
     }
   }
+  if (current->ArgumentCount() != 0) {
+    // This is a call instruction. Must remove original push arguments.
+    for (intptr_t i = 0; i < current->ArgumentCount(); ++i) {
+      PushArgumentInstr* push = current->PushArgumentAt(i);
+      push->ReplaceUsesWith(push->value()->definition());
+      push->RemoveFromGraph();
+    }
+  }
   iterator->RemoveCurrentFromGraph();
 }