Inobject slack tracking is done on a per-closure basis instead of per-shared info basis.

src/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 "v8.h"
 
 #include "code-stubs.h"
 #include "compilation-cache.h"
 #include "cpu-profiler.h"
 #include "deoptimizer.h"
@@ skipping 399 matching lines @@
   ClearWeakCollections();
 
 #ifdef VERIFY_HEAP
   if (FLAG_verify_heap) {
     VerifyMarking(heap_);
   }
 #endif
 
   SweepSpaces();
 
-  if (!FLAG_collect_maps) ReattachInitialMaps();
-
 #ifdef DEBUG
   if (FLAG_verify_native_context_separation) {
     VerifyNativeContextSeparation(heap_);
   }
 #endif
 
 #ifdef VERIFY_HEAP
   if (heap()->weak_embedded_objects_verification_enabled()) {
     VerifyWeakEmbeddedObjectsInCode();
   }
@@ skipping 2094 matching lines @@
         }
       }
     }
     // Move to next element in the list.
     raw_context = context->get(Context::NEXT_CONTEXT_LINK);
   }
   ProcessMarkingDeque();
 }
 
 
-void MarkCompactCollector::ReattachInitialMaps() {
-  HeapObjectIterator map_iterator(heap()->map_space());
-  for (HeapObject* obj = map_iterator.Next();
-       obj != NULL;
-       obj = map_iterator.Next()) {
-    Map* map = Map::cast(obj);
-
-    STATIC_ASSERT(LAST_TYPE == LAST_JS_RECEIVER_TYPE);
-    if (map->instance_type() < FIRST_JS_RECEIVER_TYPE) continue;
-
-    if (map->attached_to_shared_function_info()) {
-      JSFunction::cast(map->constructor())->shared()->AttachInitialMap(map);
-    }
-  }
-}
-
-
 void MarkCompactCollector::ClearNonLiveReferences() {
   // Iterate over the map space, setting map transitions that go from
   // a marked map to an unmarked map to null transitions.  This action
   // is carried out only on maps of JSObjects and related subtypes.
   HeapObjectIterator map_iterator(heap()->map_space());
   for (HeapObject* obj = map_iterator.Next();
        obj != NULL;
        obj = map_iterator.Next()) {
     Map* map = Map::cast(obj);
 
     if (!map->CanTransition()) continue;
 
     MarkBit map_mark = Marking::MarkBitFrom(map);
-    if (map_mark.Get() && map->attached_to_shared_function_info()) {
-      // This map is used for inobject slack tracking and has been detached
-      // from SharedFunctionInfo during the mark phase.
-      // Since it survived the GC, reattach it now.
-      JSFunction::cast(map->constructor())->shared()->AttachInitialMap(map);
-    }
-
     ClearNonLivePrototypeTransitions(map);
     ClearNonLiveMapTransitions(map, map_mark);
 
     if (map_mark.Get()) {
       ClearNonLiveDependentCode(map->dependent_code());
     } else {
       ClearDependentCode(map->dependent_code());
       map->set_dependent_code(DependentCode::cast(heap()->empty_fixed_array()));
     }
   }
@@ skipping 1948 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal