Align double array backing store during compaction and mark-sweep promotion.

src/heap-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 360 matching lines @@
 
 void Heap::RecordWrites(Address address, int start, int len) {
   if (!InNewSpace(address)) {
     for (int i = 0; i < len; i++) {
       store_buffer_.Mark(address + start + i * kPointerSize);
     }
   }
 }
 
 
+STATIC_ASSERT((FixedDoubleArray::kHeaderSize & kDoubleAlignmentMask) == 0);
+STATIC_ASSERT((ConstantPoolArray::kHeaderSize & kDoubleAlignmentMask) == 0);
+
+
+HeapObject* Heap::EnsureDoubleAligned(HeapObject* object, int size) {
+  if ((OffsetFrom(object->address()) & kDoubleAlignmentMask) != 0) {
+    CreateFillerObjectAt(object->address(), kPointerSize);
+    return HeapObject::FromAddress(object->address() + kPointerSize);
+  } else {
+    CreateFillerObjectAt(object->address() + size - kPointerSize,
+                         kPointerSize);
+    return object;
+  }
+}
+
+
+bool Heap::MustBeDoubleAligned(HeapObject* object) {
+  return  object->IsFixedDoubleArray() &&
+      (kObjectAlignment != kDoubleAlignment);
+}
+
+
 OldSpace* Heap::TargetSpace(HeapObject* object) {
   InstanceType type = object->map()->instance_type();
   AllocationSpace space = TargetSpaceId(type);
   return (space == OLD_POINTER_SPACE)
       ? old_pointer_space_
       : old_data_space_;
 }
 
 
 AllocationSpace Heap::TargetSpaceId(InstanceType type) {
@@ skipping 467 matching lines @@
 #ifdef DEBUG
   Isolate* isolate = Isolate::Current();
   isolate->heap()->disallow_allocation_failure_ = old_state_;
 #endif
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HEAP_INL_H_