In generated code for x64 don't load object's class directly from class_ field.

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2012, 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 "lib/error.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/locations.h"
@@ skipping 694 matching lines @@
     __ j(EQUAL, &type_arguments_instantiated, Assembler::kNearJump);
   }
   // Instantiate non-null type arguments.
   if (type_arguments().IsUninstantiatedIdentity()) {
     Label type_arguments_uninstantiated;
     // Check if the instantiator type argument vector is a TypeArguments of a
     // matching length and, if so, use it as the instantiated type_arguments.
     // No need to check the instantiator ('instantiator_reg') for null here,
     // because a null instantiator will have the wrong class (Null instead of
     // TypeArguments).
-    __ LoadObject(temp_reg, Class::ZoneHandle(Object::type_arguments_class()));
-    __ cmpq(temp_reg, FieldAddress(instantiator_reg, Object::class_offset()));
+    __ CompareClassOfObject(instantiator_reg,
+                            Class::Handle(Object::type_arguments_class()),
+                            temp_reg);
     __ j(NOT_EQUAL, &type_arguments_uninstantiated, Assembler::kNearJump);
     Immediate arguments_length =
         Immediate(Smi::RawValue(type_arguments().Length()));
     __ cmpq(FieldAddress(instantiator_reg, TypeArguments::length_offset()),
         arguments_length);
     __ j(EQUAL, &type_arguments_instantiated, Assembler::kNearJump);
     __ Bind(&type_arguments_uninstantiated);
   }
   // A runtime call to instantiate the type arguments is required.
   __ PushObject(Object::ZoneHandle());  // Make room for the result.
@@ skipping 67 matching lines @@
     // TODO(regis): The following emitted code is duplicated in
     // VisitExtractConstructorTypeArguments above. The reason is that the code
     // is split between two computations, so that each one produces a
     // single value, rather than producing a pair of values.
     // If this becomes an issue, we should expose these tests at the IL level.
 
     // Check if the instantiator type argument vector is a TypeArguments of a
     // matching length and, if so, use it as the instantiated type_arguments.
     // No need to check the instantiator (RAX) for null here, because a null
     // instantiator will have the wrong class (Null instead of TypeArguments).
-    __ LoadObject(temp_reg, Class::ZoneHandle(Object::type_arguments_class()));
-    __ cmpq(temp_reg, FieldAddress(instantiator_reg, Object::class_offset()));
+    __ CompareClassOfObject(instantiator_reg,
+                            Class::Handle(Object::type_arguments_class()),
+                            temp_reg);
     __ j(NOT_EQUAL, &done, Assembler::kNearJump);
     Immediate arguments_length =
         Immediate(Smi::RawValue(type_arguments().Length()));
     __ cmpq(FieldAddress(instantiator_reg, TypeArguments::length_offset()),
         arguments_length);
     __ j(NOT_EQUAL, &done, Assembler::kNearJump);
     // The instantiator was used in VisitExtractConstructorTypeArguments as the
     // instantiated type arguments, no proper instantiator needed.
     __ movq(instantiator_reg,
             Immediate(Smi::RawValue(StubCode::kNoInstantiator)));
@@ skipping 149 matching lines @@
   if (locs()->out().reg() != RAX) {
     __ movq(locs()->out().reg(), RAX);
   }
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64