Add SIMD 128 alignment support to Heap.

src/heap/spaces-inl.h

 // Copyright 2011 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.
 
 #ifndef V8_HEAP_SPACES_INL_H_
 #define V8_HEAP_SPACES_INL_H_
 
 #include "src/heap/spaces.h"
 #include "src/heap-profiler.h"
 #include "src/isolate.h"
@@ skipping 293 matching lines @@
     // allocated, so assume the worst case.
     int filler_size = Heap::GetMaximumFillToAlign(alignment);
     allocation_size += filler_size;
     object = free_list_.Allocate(allocation_size);
     if (object == NULL) {
       object = SlowAllocateRaw(allocation_size);
     }
     if (object != NULL && filler_size != 0) {
       object = heap()->AlignWithFiller(object, size_in_bytes, allocation_size,
                                        alignment);
+      // Filler objects are initialized, so mark only the aligned object memory
+      // as uninitialized.
+      allocation_size = size_in_bytes;
     }
   }
 
   if (object != NULL) {
     MSAN_ALLOCATED_UNINITIALIZED_MEMORY(object->address(), allocation_size);
     return object;
   }
 
   return AllocationResult::Retry(identity());
 }
@@ skipping 77 matching lines @@
 
 
 intptr_t LargeObjectSpace::Available() {
   return ObjectSizeFor(heap()->isolate()->memory_allocator()->Available());
 }
 
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_SPACES_INL_H_