Ensure double alignment when deserializing.

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 1811 matching lines @@
     heap->CreateFillerObjectAt(object->address(), kPointerSize);
     return HeapObject::FromAddress(object->address() + kPointerSize);
   } else {
     heap->CreateFillerObjectAt(object->address() + size - kPointerSize,
                                kPointerSize);
     return object;
   }
 }
 
 
+HeapObject* Heap::DoubleAlignForDeserialization(HeapObject* object, int size) {
+  return EnsureDoubleAligned(this, object, size);

[rmcilroy, 2014/11/26 17:44:40]

Could you add an ASSERT(object->NeedsToEnsureDoubleAlignment()) in
EnsureDoubleAligned to ensure that the list in NeedsToEnsureDoubleAlignment
keeps in sync with objects which call EnsureDoubleAligned during allocation.

[Yang, 2014/11/26 18:59:49]

Unfortunately, at this point, the object is no more than an allocation. It
doesn't have a map yet, so we can't check for its object type.

I could add a DCHECK(object->NeedsToEnsureDoubleAlignment) at the call sites 
(AllocateFixedDoubleArray etc.) after the map is set, though.

[rmcilroy, 2014/11/26 19:24:46]

Right enough.  Your suggestion stgt. It doesn't quite capture the check, but
would hopefully help someone realise they should add to this list if adding a
new double aligned object.

+}
+
+
 enum LoggingAndProfiling {
   LOGGING_AND_PROFILING_ENABLED,
   LOGGING_AND_PROFILING_DISABLED
 };
 
 
 enum MarksHandling { TRANSFER_MARKS, IGNORE_MARKS };
 
 
 template <MarksHandling marks_handling,
@@ skipping 4469 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal