- Add a size field to the header.

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 32 matching lines @@
     __ 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);

[siva, 2012/01/04 01:56:03]

ASSERT(instance_size <= RawObject::SizeTag::kMaxSizeTag);

[Ivan Posva, 2012/01/04 07:59:42]

ditto

+    __ movq(FieldAddress(instance_reg, Object::tags_offset()),
+            Immediate(RawObject::SizeTag::encode(instance_size)));
   } else {
     __ jmp(failure);
   }
 }
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64