Enable inobject double fields unboxing for 64-bit archs.

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 2746 matching lines @@
     InobjectPropertiesHelper helper(src->map());
     bool has_only_tagged_fields = helper.all_fields_tagged();
 #endif
     for (int remaining = size / kPointerSize; remaining > 0; remaining--) {
       Object* value = Memory::Object_at(src_slot);
 
       Memory::Object_at(dst_slot) = value;
 
 #if V8_DOUBLE_FIELDS_UNBOXING
       if (!may_contain_raw_values &&
-          (has_only_tagged_fields || helper.IsTagged(src_slot - src_addr)))
+          (has_only_tagged_fields ||
+           helper.IsTagged(static_cast<int>(src_slot - src_addr))))
 #else
       if (!may_contain_raw_values)
 #endif
       {
         RecordMigratedSlot(value, dst_slot);
       }
 
       src_slot += kPointerSize;
       dst_slot += kPointerSize;
     }
@@ skipping 1632 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }
 }  // namespace v8::internal