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

runtime/vm/jit_optimizer.cc

Index: runtime/vm/jit_optimizer.cc
diff --git a/runtime/vm/jit_optimizer.cc b/runtime/vm/jit_optimizer.cc
index 00f1588f9eba4a371e5e32346d7717be82bb297c..63c79bc2a0f948c63075106fea7611d72b981b57 100644
--- a/runtime/vm/jit_optimizer.cc
+++ b/runtime/vm/jit_optimizer.cc
@@ -1707,13 +1707,20 @@ void JitOptimizer::VisitInstanceCall(InstanceCallInstr* instr) {
     // 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,