If a PolymorphicInstanceCall has a single target, ..

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
===================================================================
--- runtime/vm/intermediate_language_x64.cc	(revision 11256)
+++ runtime/vm/intermediate_language_x64.cc	(working copy)
@@ -1967,6 +1967,17 @@
   }
   ASSERT(HasICData());
   ASSERT(ic_data()->num_args_tested() == 1);
+  if (!with_checks()) {
+    const Function& target = Function::ZoneHandle(ic_data()->GetTargetAt(0));
+    compiler->GenerateStaticCall(instance_call()->deopt_id(),
+                                 instance_call()->token_pos(),
+                                 instance_call()->try_index(),
+                                 target,
+                                 instance_call()->ArgumentCount(),
+                                 instance_call()->argument_names(),
+                                 locs());
+    return;
+  }
   Label handle_smi;
   Label* is_smi_label =
       ic_data()->GetReceiverClassIdAt(0) == kSmiCid ?  &handle_smi : deopt;