Clean up aligned allocation code in preparation for SIMD alignments.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index f1cf40818787b3fa4703ff54f539e4f11c05d40a..ff4346ba9bca2e8e9c0772003763ef188747395d 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -716,13 +716,23 @@ class Heap {
   MUST_USE_RESULT AllocationResult
       CopyJSObject(JSObject* source, AllocationSite* site = NULL);
 
-  // This method assumes overallocation of one word. It will store a filler
-  // before the object if the given object is not double aligned, otherwise
-  // it will place the filler after the object.
-  MUST_USE_RESULT HeapObject* EnsureAligned(HeapObject* object, int size,
-                                            AllocationAlignment alignment);
-
-  MUST_USE_RESULT HeapObject* PrecedeWithFiller(HeapObject* object);
+  // Calculates the maximum amount of filler that could be required by the
+  // given alignment.
+  static int GetMaximumFillToAlign(AllocationAlignment alignment);
+  // Calculates the actual amount of filler required for a given address at the
+  // given alignment.
+  static int GetFillToAlign(Address address, AllocationAlignment alignment);
+
+  // Creates a filler object and returns a heap object immediately after it.
+  MUST_USE_RESULT HeapObject* PrecedeWithFiller(HeapObject* object,
+                                                int filler_size);
+  // Creates a filler object if needed for alignment and returns a heap object
+  // immediately after it. If any space is left after the returned object,
+  // another filler object is created so the over allocated memory is iterable.
+  MUST_USE_RESULT HeapObject* AlignWithFiller(HeapObject* object,
+                                              int object_size,
+                                              int allocation_size,
+                                              AllocationAlignment alignment);
 
   // Clear the Instanceof cache (used when a prototype changes).
   inline void ClearInstanceofCache();