[heap] MarkCompactCollector::EmptyMarkingDeque never expects filler objects.

src/heap/mark-compact.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/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 1990 matching lines @@
   }
   ref_groups->Rewind(last);
 }
 
 
 // Mark all objects reachable from the objects on the marking stack.
 // Before: the marking stack contains zero or more heap object pointers.
 // After: the marking stack is empty, and all objects reachable from the
 // marking stack have been marked, or are overflowed in the heap.
 void MarkCompactCollector::EmptyMarkingDeque() {
-  Map* filler_map = heap_->one_pointer_filler_map();
   while (!marking_deque_.IsEmpty()) {
     HeapObject* object = marking_deque_.Pop();
-    // Explicitly skip one word fillers. Incremental markbit patterns are
-    // correct only for objects that occupy at least two words.
-    Map* map = object->map();
-    if (map == filler_map) continue;
 
+    DCHECK(!object->IsFiller());
     DCHECK(object->IsHeapObject());
     DCHECK(heap()->Contains(object));
     DCHECK(!Marking::IsWhite(ObjectMarking::MarkBitFrom(object)));
 
+    Map* map = object->map();
     MarkBit map_mark = ObjectMarking::MarkBitFrom(map);
     MarkObject(map, map_mark);
 
     MarkCompactMarkingVisitor::IterateBody(map, object);
   }
 }
 
 
 // Sweep the heap for overflowed objects, clear their overflow bits, and
 // push them on the marking stack.  Stop early if the marking stack fills
@@ skipping 2008 matching lines @@
       // The target is always in old space, we don't have to record the slot in
       // the old-to-new remembered set.
       DCHECK(!heap()->InNewSpace(target));
       RecordRelocSlot(host, &rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8