Unify mechanism to find trailing AllocationMementos

src/objects.cc

 // Copyright 2013 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 12788 matching lines @@
 void JSObject::UpdateAllocationSite(Handle<JSObject> object,
                                     ElementsKind to_kind) {
   if (!object->IsJSArray()) return;
 
   Heap* heap = object->GetHeap();
   if (!heap->InNewSpace(*object)) return;
 
   Handle<AllocationSite> site;
   {
     DisallowHeapAllocation no_allocation;
-    // Check if there is potentially a memento behind the object. If
-    // the last word of the momento is on another page we return
-    // immediatelly.
-    Address object_address = object->address();
-    Address memento_address = object_address + JSArray::kSize;
-    Address last_memento_word_address = memento_address + kPointerSize;
-    if (!NewSpacePage::OnSamePage(object_address,
-                                  last_memento_word_address)) {
-      return;
-    }
 
-    // Either object is the last object in the new space, or there is another
-    // object of at least word size (the header map word) following it, so
-    // suffices to compare ptr and top here.
-    Address top = heap->NewSpaceTop();
-    ASSERT(memento_address == top ||
-           memento_address + HeapObject::kHeaderSize <= top);
-    if (memento_address == top) return;
-
-    HeapObject* candidate = HeapObject::FromAddress(memento_address);
-    if (candidate->map() != heap->allocation_memento_map()) return;
-
-    AllocationMemento* memento = AllocationMemento::cast(candidate);
-    if (!memento->IsValid()) return;
+    AllocationMemento* memento = heap->FindAllocationMemento(*object);
+    if (memento == NULL) return;
 
     // Walk through to the Allocation Site
     site = handle(memento->GetAllocationSite());
   }
   AllocationSite::DigestTransitionFeedback(site, to_kind);
 }
 
 
 void JSObject::TransitionElementsKind(Handle<JSObject> object,
                                       ElementsKind to_kind) {
@@ skipping 3786 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal