Request for comments on overall approach.

runtime/vm/assembler_macros_x64.cc

 // Copyright (c) 2011, 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"
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler_macros.h"
 
 #include "vm/assembler.h"
@@ skipping 30 matching lines @@
     // instance_reg: potential next object start.
     __ movq(TMP, Immediate(heap->EndAddress()));
     __ cmpq(instance_reg, Address(TMP, 0));
     __ j(ABOVE_EQUAL, failure, Assembler::kNearJump);
     // Successfully allocated the object, now update top to point to
     // next object start and store the class in the class field of object.
     __ movq(TMP, Immediate(heap->TopAddress()));
     __ movq(Address(TMP, 0), instance_reg);
     ASSERT(instance_size >= kHeapObjectTag);
     __ subq(instance_reg, Immediate(instance_size - kHeapObjectTag));
-    __ StoreIntoObject(instance_reg,
-                       FieldAddress(instance_reg, Instance::class_offset()),
-                       class_reg);
     uword tags = 0;
     tags = RawObject::SizeTag::update(instance_size, tags);
     ASSERT(cls.index() != kIllegalObjectKind);
     tags = RawObject::ClassTag::update(cls.index(), tags);
     __ movq(FieldAddress(instance_reg, Object::tags_offset()), Immediate(tags));
   } else {
     __ jmp(failure);
   }
 }
 
@@ skipping 19 matching lines @@
 void AssemblerMacros::EnterStubFrame(Assembler* assembler) {
   __ EnterFrame(0);
   __ pushq(Immediate(0));  // Push 0 in the saved PC area for stub frames.
 }
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64