Faster checks in polymorphic instance calls if Smi-s are involved

runtime/vm/intermediate_language_x64.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/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 5438 matching lines @@
     compiler->GenerateStaticCall(deopt_id(),
                                  instance_call()->token_pos(),
                                  target,
                                  instance_call()->ArgumentCount(),
                                  instance_call()->argument_names(),
                                  locs(),
                                  ICData::Handle());
     return;
   }
 
-  // Load receiver into RAX.
-  __ movq(RAX,
-      Address(RSP, (instance_call()->ArgumentCount() - 1) * kWordSize));
-
   Label* deopt = compiler->AddDeoptStub(
       deopt_id(), ICData::kDeoptPolymorphicInstanceCallTestFail);
-  LoadValueCid(compiler, RDI, RAX,
-               (ic_data().GetReceiverClassIdAt(0) == kSmiCid) ? NULL : deopt);
-
+  Label ok;
   compiler->EmitTestAndCall(ic_data(),
-                            RDI,  // Class id register.
                             instance_call()->ArgumentCount(),
                             instance_call()->argument_names(),
                             deopt,
+                            &ok,
                             deopt_id(),
                             instance_call()->token_pos(),
                             locs());
+  __ Bind(&ok);
 }
 
 
 LocationSummary* BranchInstr::MakeLocationSummary(Zone* zone,
                                                   bool opt) const {
   comparison()->InitializeLocationSummary(zone, opt);
   // Branches don't produce a result.
   comparison()->locs()->set_out(0, Location::NoLocation());
   return comparison()->locs();
 }
@@ skipping 975 matching lines @@
   __ Drop(1);
   __ popq(result);
 }
 
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64