Store offset between fixed typed array base and data start in object

src/heap/heap.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/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 3989 matching lines @@
 
   HeapObject* object;
   AllocationResult allocation = AllocateRaw(
       size, space, OLD_SPACE,
       array_type == kExternalFloat64Array ? kDoubleAligned : kWordAligned);
   if (!allocation.To(&object)) return allocation;
 
   object->set_map(MapForFixedTypedArray(array_type));
   FixedTypedArrayBase* elements = FixedTypedArrayBase::cast(object);
   elements->set_base_pointer(elements, SKIP_WRITE_BARRIER);
+  elements->set_external_pointer(
+      reinterpret_cast<void*>(FixedTypedArrayBase::kDataOffset -
+                              kHeapObjectTag),

[Jarin, 2015/07/22 09:00:20]

Can't you say ExternalReference::fixed_typed_array_base_data_offset().address()
here?

[jochen (gone - plz use gerrit), 2015/07/22 09:08:13]

done

+      SKIP_WRITE_BARRIER);
   elements->set_length(length);
   if (initialize) memset(elements->DataPtr(), 0, elements->DataSize());
   return elements;
 }
 
 
 AllocationResult Heap::AllocateCode(int object_size, bool immovable) {
   DCHECK(IsAligned(static_cast<intptr_t>(object_size), kCodeAlignment));
   AllocationResult allocation =
       AllocateRaw(object_size, CODE_SPACE, CODE_SPACE);
@@ skipping 2867 matching lines @@
     *object_type = "CODE_TYPE";                                                \
     *object_sub_type = "CODE_AGE/" #name;                                      \
     return true;
     CODE_AGE_LIST_COMPLETE(COMPARE_AND_RETURN_NAME)
 #undef COMPARE_AND_RETURN_NAME
   }
   return false;
 }
 }  // namespace internal
 }  // namespace v8