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

runtime/vm/jit_optimizer.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/jit_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/branch_optimizer.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
@@ skipping 1689 matching lines @@
     return;
   }
 
   bool has_one_target = unary_checks.HasOneTarget();
 
   if (has_one_target) {
     // Check if the single target is a polymorphic target, if it is,
     // we don't have one target.
     const Function& target =
         Function::Handle(Z, unary_checks.GetTargetAt(0));
-    const bool polymorphic_target = MethodRecognizer::PolymorphicTarget(target);
-    has_one_target = !polymorphic_target;
+    if (target.recognized_kind() == MethodRecognizer::kObjectRuntimeType) {
+      has_one_target =
+          PolymorphicInstanceCallInstr::ComputeRuntimeType(unary_checks) !=
+              Type::null();
+    } else {
+      const bool polymorphic_target =
+          MethodRecognizer::PolymorphicTarget(target);
+      has_one_target = !polymorphic_target;
+    }
   }
 
   if (has_one_target) {
-    RawFunction::Kind function_kind =
-        Function::Handle(Z, unary_checks.GetTargetAt(0)).kind();
+    const Function& target = Function::Handle(Z, unary_checks.GetTargetAt(0));
+    const RawFunction::Kind function_kind = target.kind();
     if (!flow_graph()->InstanceCallNeedsClassCheck(instr, function_kind)) {
       PolymorphicInstanceCallInstr* call =
           new(Z) PolymorphicInstanceCallInstr(instr, unary_checks,
                                               /* call_with_checks = */ false,
                                               /* complete = */ false);
       instr->ReplaceWith(call, current_iterator());
       return;
     }
   }
 
@@ skipping 286 matching lines @@
 
   // Discard the environment from the original instruction because the store
   // can't deoptimize.
   instr->RemoveEnvironment();
   ReplaceCall(instr, store);
   return true;
 }
 
 
 }  // namespace dart