Only double align in scavenger on non-64 bit platforms.

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 2087 matching lines @@
     }
   }
 
   template <int alignment>
   static inline bool SemiSpaceCopyObject(Map* map, HeapObject** slot,
                                          HeapObject* object, int object_size) {
     Heap* heap = map->GetHeap();
 
     DCHECK(heap->AllowedToBeMigrated(object, NEW_SPACE));
     AllocationResult allocation;
+#ifndef V8_HOST_ARCH_64_BIT
     if (alignment == kDoubleAlignment) {
       allocation = heap->new_space()->AllocateRawDoubleAligned(object_size);
     } else {
       allocation = heap->new_space()->AllocateRaw(object_size);
     }
+#else
+    allocation = heap->new_space()->AllocateRaw(object_size);
+#endif
 
     HeapObject* target = NULL;  // Initialization to please compiler.
     if (allocation.To(&target)) {
       // Order is important here: Set the promotion limit before storing a
       // filler for double alignment or migrating the object. Otherwise we
       // may end up overwriting promotion queue entries when we migrate the
       // object.
       heap->promotion_queue()->SetNewLimit(heap->new_space()->top());
 
       MigrateObject(heap, object, target, object_size);
 
       // Update slot to new target.
       *slot = target;
 
       heap->IncrementSemiSpaceCopiedObjectSize(object_size);
       return true;
     }
     return false;
   }
 
 
   template <ObjectContents object_contents, int alignment>
   static inline bool PromoteObject(Map* map, HeapObject** slot,
                                    HeapObject* object, int object_size) {
     Heap* heap = map->GetHeap();
 
     AllocationResult allocation;
+#ifndef V8_HOST_ARCH_64_BIT
     if (alignment == kDoubleAlignment) {
       allocation = heap->old_space()->AllocateRawDoubleAligned(object_size);
     } else {
       allocation = heap->old_space()->AllocateRaw(object_size);
     }
+#else
+    allocation = heap->old_space()->AllocateRaw(object_size);
+#endif
 
     HeapObject* target = NULL;  // Initialization to please compiler.
     if (allocation.To(&target)) {
       MigrateObject(heap, object, target, object_size);
 
       // Update slot to new target.
       *slot = target;
 
       if (object_contents == POINTER_OBJECT) {
         if (map->instance_type() == JS_FUNCTION_TYPE) {
@@ skipping 4314 matching lines @@
       }
       delete list;
     } else {
       prev = list;
     }
     list = next;
   }
 }
 }
 }  // namespace v8::internal