Create a new paged heap space for global property cells. The new...

src/mark-compact.cc

 // Copyright 2006-2008 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 38 matching lines @@
 MarkCompactCollector::CollectorState MarkCompactCollector::state_ = IDLE;
 
 // Counters used for debugging the marking phase of mark-compact or mark-sweep
 // collection.
 int MarkCompactCollector::live_bytes_ = 0;
 int MarkCompactCollector::live_young_objects_ = 0;
 int MarkCompactCollector::live_old_data_objects_ = 0;
 int MarkCompactCollector::live_old_pointer_objects_ = 0;
 int MarkCompactCollector::live_code_objects_ = 0;
 int MarkCompactCollector::live_map_objects_ = 0;
+int MarkCompactCollector::live_cell_objects_ = 0;
 int MarkCompactCollector::live_lo_objects_ = 0;
 #endif
 
 void MarkCompactCollector::CollectGarbage() {
   // Make sure that Prepare() has been called. The individual steps below will
   // update the state as they proceed.
   ASSERT(state_ == PREPARE_GC);
 
   // Prepare has selected whether to compact the old generation or not.
   // Tell the tracer.
@@ skipping 79 matching lines @@
     space->PrepareForMarkCompact(compacting_collection_);
   }
 
 #ifdef DEBUG
   live_bytes_ = 0;
   live_young_objects_ = 0;
   live_old_pointer_objects_ = 0;
   live_old_data_objects_ = 0;
   live_code_objects_ = 0;
   live_map_objects_ = 0;
+  live_cell_objects_ = 0;
   live_lo_objects_ = 0;
 #endif
 }
 
 
 void MarkCompactCollector::Finish() {
 #ifdef DEBUG
   ASSERT(state_ == SWEEP_SPACES || state_ == REBUILD_RSETS);
   state_ = IDLE;
 #endif
@@ skipping 533 matching lines @@
   if (marking_stack.is_full()) return;
 
   HeapObjectIterator code_it(Heap::code_space(), &OverflowObjectSize);
   ScanOverflowedObjects(&code_it);
   if (marking_stack.is_full()) return;
 
   HeapObjectIterator map_it(Heap::map_space(), &OverflowObjectSize);
   ScanOverflowedObjects(&map_it);
   if (marking_stack.is_full()) return;
 
+  HeapObjectIterator cell_it(Heap::cell_space(), &OverflowObjectSize);
+  ScanOverflowedObjects(&cell_it);
+  if (marking_stack.is_full()) return;
+
   LargeObjectIterator lo_it(Heap::lo_space(), &OverflowObjectSize);
   ScanOverflowedObjects(&lo_it);
   if (marking_stack.is_full()) return;
 
   marking_stack.clear_overflowed();
 }
 
 
 // Mark all objects reachable (transitively) from objects on the marking
 // stack.  Before: the marking stack contains zero or more heap object
@@ skipping 80 matching lines @@
 
 
 #ifdef DEBUG
 void MarkCompactCollector::UpdateLiveObjectCount(HeapObject* obj) {
   live_bytes_ += obj->Size();
   if (Heap::new_space()->Contains(obj)) {
     live_young_objects_++;
   } else if (Heap::map_space()->Contains(obj)) {
     ASSERT(obj->IsMap());
     live_map_objects_++;
+  } else if (Heap::cell_space()->Contains(obj)) {
+    ASSERT(obj->IsJSGlobalPropertyCell());
+    live_cell_objects_++;
   } else if (Heap::old_pointer_space()->Contains(obj)) {
     live_old_pointer_objects_++;
   } else if (Heap::old_data_space()->Contains(obj)) {
     live_old_data_objects_++;
   } else if (Heap::code_space()->Contains(obj)) {
     live_code_objects_++;
   } else if (Heap::lo_space()->Contains(obj)) {
     live_lo_objects_++;
   } else {
     UNREACHABLE();
@@ skipping 139 matching lines @@
     forwarded = target_space->MCAllocateRaw(object_size);
   }
   if (forwarded->IsFailure()) {
     forwarded = Heap::new_space()->MCAllocateRaw(object_size);
   }
   return forwarded;
 }
 
 
 // Allocation functions for the paged spaces call the space's MCAllocateRaw.
-inline Object* MCAllocateFromOldPointerSpace(HeapObject* object,
+inline Object* MCAllocateFromOldPointerSpace(HeapObject* ignore,
                                              int object_size) {
   return Heap::old_pointer_space()->MCAllocateRaw(object_size);
 }
 
 
-inline Object* MCAllocateFromOldDataSpace(HeapObject* object, int object_size) {
+inline Object* MCAllocateFromOldDataSpace(HeapObject* ignore, int object_size) {
   return Heap::old_data_space()->MCAllocateRaw(object_size);
 }
 
 
-inline Object* MCAllocateFromCodeSpace(HeapObject* object, int object_size) {
+inline Object* MCAllocateFromCodeSpace(HeapObject* ignore, int object_size) {
   return Heap::code_space()->MCAllocateRaw(object_size);
 }
 
 
-inline Object* MCAllocateFromMapSpace(HeapObject* object, int object_size) {
+inline Object* MCAllocateFromMapSpace(HeapObject* ignore, int object_size) {
   return Heap::map_space()->MCAllocateRaw(object_size);
 }
 
 
+inline Object* MCAllocateFromCellSpace(HeapObject* ignore, int object_size) {
+  return Heap::cell_space()->MCAllocateRaw(object_size);
+}
+
+
 // The forwarding address is encoded at the same offset as the current
 // to-space object, but in from space.
 inline void EncodeForwardingAddressInNewSpace(HeapObject* old_object,
                                               int object_size,
                                               Object* new_object,
                                               int* ignored) {
   int offset =
       Heap::new_space()->ToSpaceOffsetForAddress(old_object->address());
   Memory::Address_at(Heap::new_space()->FromSpaceLow() + offset) =
       HeapObject::cast(new_object)->address();
@@ skipping 138 matching lines @@
       MarkCompactCollector::tracer()->decrement_marked_count();
     } else {
       // We give non-live objects a map that will correctly give their size,
       // since their existing map might not be live after the collection.
       int size = object->Size();
       if (size >= ByteArray::kHeaderSize) {
         object->set_map(Heap::byte_array_map());
         ByteArray::cast(object)->set_length(ByteArray::LengthFor(size));
       } else {
         ASSERT(size == kPointerSize);
-        object->set_map(Heap::one_word_filler_map());
+        object->set_map(Heap::one_pointer_filler_map());
       }
       ASSERT(object->Size() == size);
     }
     // The object is now unmarked for the call to Size() at the top of the
     // loop.
   }
 }
 
 
 static void SweepSpace(PagedSpace* space, DeallocateFunction dealloc) {
@@ skipping 29 matching lines @@
         }
         if (is_previous_alive) {  // Transition from live to free.
           free_start = current;
           is_previous_alive = false;
         }
       }
       // The object is now unmarked for the call to Size() at the top of the
       // loop.
     }
 
-    // If the last region was not live we need to from free_start to the
-    // allocation top in the page.
+    // If the last region was not live we need to deallocate from
+    // free_start to the allocation top in the page.
     if (!is_previous_alive) {
       int free_size = p->AllocationTop() - free_start;
       if (free_size > 0) {
         dealloc(free_start, free_size);
       }
     }
   }
 }
 
 
@@ skipping 23 matching lines @@
   // chunks and free them separately.
   ASSERT(size_in_bytes % Map::kSize == 0);
   Heap::ClearRSetRange(start, size_in_bytes);
   Address end = start + size_in_bytes;
   for (Address a = start; a < end; a += Map::kSize) {
     Heap::map_space()->Free(a);
   }
 }
 
 
+void MarkCompactCollector::DeallocateCellBlock(Address start,
+                                               int size_in_bytes) {
+  // Free-list elements in cell space are assumed to have a fixed size.
+  // We break the free block into chunks and add them to the free list
+  // individually.
+  int size = Heap::cell_space()->object_size_in_bytes();
+  ASSERT(size_in_bytes % size == 0);
+  Heap::ClearRSetRange(start, size_in_bytes);
+  Address end = start + size_in_bytes;
+  for (Address a = start; a < end; a += size) {
+    Heap::cell_space()->Free(a);
+  }
+}
+
+
 void MarkCompactCollector::EncodeForwardingAddresses() {
   ASSERT(state_ == ENCODE_FORWARDING_ADDRESSES);
   // Objects in the active semispace of the young generation may be
   // relocated to the inactive semispace (if not promoted).  Set the
   // relocation info to the beginning of the inactive semispace.
   Heap::new_space()->MCResetRelocationInfo();
 
   // Compute the forwarding pointers in each space.
   EncodeForwardingAddressesInPagedSpace<MCAllocateFromOldPointerSpace,
                                         IgnoreNonLiveObject>(
       Heap::old_pointer_space());
 
   EncodeForwardingAddressesInPagedSpace<MCAllocateFromOldDataSpace,
                                         IgnoreNonLiveObject>(
       Heap::old_data_space());
 
   EncodeForwardingAddressesInPagedSpace<MCAllocateFromCodeSpace,
                                         LogNonLiveCodeObject>(
       Heap::code_space());
 
+  EncodeForwardingAddressesInPagedSpace<MCAllocateFromCellSpace,
+                                        IgnoreNonLiveObject>(
+      Heap::cell_space());
+
+
   // Compute new space next to last after the old and code spaces have been
   // compacted.  Objects in new space can be promoted to old or code space.
   EncodeForwardingAddressesInNewSpace();
 
   // Compute map space last because computing forwarding addresses
   // overwrites non-live objects.  Objects in the other spaces rely on
   // non-live map pointers to get the sizes of non-live objects.
   EncodeForwardingAddressesInPagedSpace<MCAllocateFromMapSpace,
                                         IgnoreNonLiveObject>(
       Heap::map_space());
 
   // Write relocation info to the top page, so we can use it later.  This is
   // done after promoting objects from the new space so we get the correct
   // allocation top.
   Heap::old_pointer_space()->MCWriteRelocationInfoToPage();
   Heap::old_data_space()->MCWriteRelocationInfoToPage();
   Heap::code_space()->MCWriteRelocationInfoToPage();
   Heap::map_space()->MCWriteRelocationInfoToPage();
+  Heap::cell_space()->MCWriteRelocationInfoToPage();
 }
 
 
 void MarkCompactCollector::SweepSpaces() {
   ASSERT(state_ == SWEEP_SPACES);
   ASSERT(!IsCompacting());
   // Noncompacting collections simply sweep the spaces to clear the mark
   // bits and free the nonlive blocks (for old and map spaces).  We sweep
   // the map space last because freeing non-live maps overwrites them and
   // the other spaces rely on possibly non-live maps to get the sizes for
   // non-live objects.
   SweepSpace(Heap::old_pointer_space(), &DeallocateOldPointerBlock);
   SweepSpace(Heap::old_data_space(), &DeallocateOldDataBlock);
   SweepSpace(Heap::code_space(), &DeallocateCodeBlock);
+  SweepSpace(Heap::cell_space(), &DeallocateCellBlock);
   SweepSpace(Heap::new_space());
   SweepSpace(Heap::map_space(), &DeallocateMapBlock);
 }
 
 
 // Iterate the live objects in a range of addresses (eg, a page or a
 // semispace).  The live regions of the range have been linked into a list.
 // The first live region is [first_live_start, first_live_end), and the last
 // address in the range is top.  The callback function is used to get the
 // size of each live object.
@@ skipping 58 matching lines @@
  private:
   void UpdatePointer(Object** p) {
     if (!(*p)->IsHeapObject()) return;
 
     HeapObject* obj = HeapObject::cast(*p);
     Address old_addr = obj->address();
     Address new_addr;
     ASSERT(!Heap::InFromSpace(obj));
 
     if (Heap::new_space()->Contains(obj)) {
-      Address f_addr = Heap::new_space()->FromSpaceLow() +
-                       Heap::new_space()->ToSpaceOffsetForAddress(old_addr);
-      new_addr = Memory::Address_at(f_addr);
+      Address forwarding_pointer_addr =
+          Heap::new_space()->FromSpaceLow() +
+          Heap::new_space()->ToSpaceOffsetForAddress(old_addr);
+      new_addr = Memory::Address_at(forwarding_pointer_addr);
 
 #ifdef DEBUG
       ASSERT(Heap::old_pointer_space()->Contains(new_addr) ||
              Heap::old_data_space()->Contains(new_addr) ||
-             Heap::code_space()->Contains(new_addr) ||
-             Heap::new_space()->FromSpaceContains(new_addr));
+             Heap::new_space()->FromSpaceContains(new_addr) ||
+             Heap::lo_space()->Contains(HeapObject::FromAddress(new_addr)));
 
       if (Heap::new_space()->FromSpaceContains(new_addr)) {
         ASSERT(Heap::new_space()->FromSpaceOffsetForAddress(new_addr) <=
                Heap::new_space()->ToSpaceOffsetForAddress(old_addr));
       }
 #endif
 
     } else if (Heap::lo_space()->Contains(obj)) {
       // Don't move objects in the large object space.
       return;
 
     } else {
-      ASSERT(Heap::old_pointer_space()->Contains(obj) ||
-             Heap::old_data_space()->Contains(obj) ||
-             Heap::code_space()->Contains(obj) ||
-             Heap::map_space()->Contains(obj));
-
+#ifdef DEBUG
+      PagedSpaces spaces;
+      PagedSpace* original_space = spaces.next();
+      while (original_space != NULL) {
+        if (original_space->Contains(obj)) break;
+        original_space = spaces.next();
+      }
+      ASSERT(original_space != NULL);
+#endif
       new_addr = MarkCompactCollector::GetForwardingAddressInOldSpace(obj);
-      ASSERT(Heap::old_pointer_space()->Contains(new_addr) ||
-             Heap::old_data_space()->Contains(new_addr) ||
-             Heap::code_space()->Contains(new_addr) ||
-             Heap::map_space()->Contains(new_addr));
-
-#ifdef DEBUG
-      if (Heap::old_pointer_space()->Contains(obj)) {
-        ASSERT(Heap::old_pointer_space()->MCSpaceOffsetForAddress(new_addr) <=
-               Heap::old_pointer_space()->MCSpaceOffsetForAddress(old_addr));
-      } else if (Heap::old_data_space()->Contains(obj)) {
-        ASSERT(Heap::old_data_space()->MCSpaceOffsetForAddress(new_addr) <=
-               Heap::old_data_space()->MCSpaceOffsetForAddress(old_addr));
-      } else if (Heap::code_space()->Contains(obj)) {
-        ASSERT(Heap::code_space()->MCSpaceOffsetForAddress(new_addr) <=
-               Heap::code_space()->MCSpaceOffsetForAddress(old_addr));
-      } else {
-        ASSERT(Heap::map_space()->MCSpaceOffsetForAddress(new_addr) <=
-               Heap::map_space()->MCSpaceOffsetForAddress(old_addr));
-      }
-#endif
+      ASSERT(original_space->Contains(new_addr));
+      ASSERT(original_space->MCSpaceOffsetForAddress(new_addr) <=
+             original_space->MCSpaceOffsetForAddress(old_addr));
     }
 
     *p = HeapObject::FromAddress(new_addr);
 
 #ifdef DEBUG
     if (FLAG_gc_verbose) {
       PrintF("update %p : %p -> %p\n",
              reinterpret_cast<Address>(p), old_addr, new_addr);
     }
 #endif
@@ skipping 11 matching lines @@
   GlobalHandles::IterateWeakRoots(&updating_visitor);
 
   int live_maps = IterateLiveObjects(Heap::map_space(),
                                      &UpdatePointersInOldObject);
   int live_pointer_olds = IterateLiveObjects(Heap::old_pointer_space(),
                                              &UpdatePointersInOldObject);
   int live_data_olds = IterateLiveObjects(Heap::old_data_space(),
                                           &UpdatePointersInOldObject);
   int live_codes = IterateLiveObjects(Heap::code_space(),
                                       &UpdatePointersInOldObject);
+  int live_cells = IterateLiveObjects(Heap::cell_space(),
+                                      &UpdatePointersInOldObject);
   int live_news = IterateLiveObjects(Heap::new_space(),
                                      &UpdatePointersInNewObject);
 
   // Large objects do not move, the map word can be updated directly.
   LargeObjectIterator it(Heap::lo_space());
   while (it.has_next()) UpdatePointersInNewObject(it.next());
 
   USE(live_maps);
   USE(live_pointer_olds);
   USE(live_data_olds);
   USE(live_codes);
+  USE(live_cells);
   USE(live_news);
-
-#ifdef DEBUG
   ASSERT(live_maps == live_map_objects_);
   ASSERT(live_data_olds == live_old_data_objects_);
   ASSERT(live_pointer_olds == live_old_pointer_objects_);
   ASSERT(live_codes == live_code_objects_);
+  ASSERT(live_cells == live_cell_objects_);
   ASSERT(live_news == live_young_objects_);
-#endif
 }
 
 
 int MarkCompactCollector::UpdatePointersInNewObject(HeapObject* obj) {
   // Keep old map pointers
   Map* old_map = obj->map();
   ASSERT(old_map->IsHeapObject());
 
   Address forwarded = GetForwardingAddressInOldSpace(old_map);
 
@@ skipping 100 matching lines @@
   state_ = RELOCATE_OBJECTS;
 #endif
   // Relocates objects, always relocate map objects first. Relocating
   // objects in other space relies on map objects to get object size.
   int live_maps = IterateLiveObjects(Heap::map_space(), &RelocateMapObject);
   int live_pointer_olds = IterateLiveObjects(Heap::old_pointer_space(),
                                              &RelocateOldPointerObject);
   int live_data_olds = IterateLiveObjects(Heap::old_data_space(),
                                           &RelocateOldDataObject);
   int live_codes = IterateLiveObjects(Heap::code_space(), &RelocateCodeObject);
+  int live_cells = IterateLiveObjects(Heap::cell_space(), &RelocateCellObject);
   int live_news = IterateLiveObjects(Heap::new_space(), &RelocateNewObject);
 
   USE(live_maps);
   USE(live_data_olds);
   USE(live_pointer_olds);
   USE(live_codes);
+  USE(live_cells);
   USE(live_news);
-#ifdef DEBUG
   ASSERT(live_maps == live_map_objects_);
   ASSERT(live_data_olds == live_old_data_objects_);
   ASSERT(live_pointer_olds == live_old_pointer_objects_);
   ASSERT(live_codes == live_code_objects_);
+  ASSERT(live_cells == live_cell_objects_);
   ASSERT(live_news == live_young_objects_);
-#endif
 
   // Notify code object in LO to convert IC target to address
   // This must happen after lo_space_->Compact
   LargeObjectIterator it(Heap::lo_space());
   while (it.has_next()) { ConvertCodeICTargetToAddress(it.next()); }
 
-  // Flips from and to spaces
+  // Flip from and to spaces
   Heap::new_space()->Flip();
 
-  // Sets age_mark to bottom in to space
+  // Set age_mark to bottom in to space
   Address mark = Heap::new_space()->bottom();
   Heap::new_space()->set_age_mark(mark);
 
   Heap::new_space()->MCCommitRelocationInfo();
 #ifdef DEBUG
   // It is safe to write to the remembered sets as remembered sets on a
   // page-by-page basis after committing the m-c forwarding pointer.
   Page::set_rset_state(Page::IN_USE);
 #endif
   PagedSpaces spaces;
   while (PagedSpace* space = spaces.next()) space->MCCommitRelocationInfo();
 }
 
 
 int MarkCompactCollector::ConvertCodeICTargetToAddress(HeapObject* obj) {
   if (obj->IsCode()) {
     Code::cast(obj)->ConvertICTargetsFromObjectToAddress();
   }
   return obj->Size();
 }
 
 
 int MarkCompactCollector::RelocateMapObject(HeapObject* obj) {
-  // decode map pointer (forwarded address)
+  // Recover map pointer.
   MapWord encoding = obj->map_word();
   Address map_addr = encoding.DecodeMapAddress(Heap::map_space());
   ASSERT(Heap::map_space()->Contains(HeapObject::FromAddress(map_addr)));
 
   // Get forwarding address before resetting map pointer
   Address new_addr = GetForwardingAddressInOldSpace(obj);
 
-  // recover map pointer
+  // Reset map pointer.  The meta map object may not be copied yet so
+  // Map::cast does not yet work.
   obj->set_map(reinterpret_cast<Map*>(HeapObject::FromAddress(map_addr)));
 
-  // The meta map object may not be copied yet.
   Address old_addr = obj->address();
 
   if (new_addr != old_addr) {
     memmove(new_addr, old_addr, Map::kSize);  // copy contents
   }
 
 #ifdef DEBUG
   if (FLAG_gc_verbose) {
     PrintF("relocate %p -> %p\n", old_addr, new_addr);
   }
 #endif
 
   return Map::kSize;
 }
 
 
-static inline int RelocateOldObject(HeapObject* obj,
-                                    OldSpace* space,
-                                    Address new_addr,
-                                    Address map_addr) {
-  // recover map pointer
-  obj->set_map(reinterpret_cast<Map*>(HeapObject::FromAddress(map_addr)));
+static inline int RestoreMap(HeapObject* obj,
+                             PagedSpace* space,
+                             Address new_addr,
+                             Address map_addr) {
+  // This must be a non-map object, and the function relies on the
+  // assumption that the Map space is compacted before the other paged
+  // spaces (see RelocateObjects).
 
-  // This is a non-map object, it relies on the assumption that the Map space
-  // is compacted before the Old space (see RelocateObjects).
+  // Reset map pointer.
+  obj->set_map(Map::cast(HeapObject::FromAddress(map_addr)));
+
   int obj_size = obj->Size();
   ASSERT_OBJECT_SIZE(obj_size);
 
   ASSERT(space->MCSpaceOffsetForAddress(new_addr) <=
          space->MCSpaceOffsetForAddress(obj->address()));
 
-  space->MCAdjustRelocationEnd(new_addr, obj_size);
-
 #ifdef DEBUG
   if (FLAG_gc_verbose) {
     PrintF("relocate %p -> %p\n", obj->address(), new_addr);
   }
 #endif
 
   return obj_size;
 }
 
 
 int MarkCompactCollector::RelocateOldNonCodeObject(HeapObject* obj,
-                                                   OldSpace* space) {
-  // decode map pointer (forwarded address)
+                                                   PagedSpace* space) {
+  // Recover map pointer.
   MapWord encoding = obj->map_word();
   Address map_addr = encoding.DecodeMapAddress(Heap::map_space());
   ASSERT(Heap::map_space()->Contains(map_addr));
 
-  // Get forwarding address before resetting map pointer
+  // Get forwarding address before resetting map pointer.
   Address new_addr = GetForwardingAddressInOldSpace(obj);
 
-  int obj_size = RelocateOldObject(obj, space, new_addr, map_addr);
+  // Reset the map pointer.
+  int obj_size = RestoreMap(obj, space, new_addr, map_addr);
 
   Address old_addr = obj->address();
 
   if (new_addr != old_addr) {
-    memmove(new_addr, old_addr, obj_size);  // copy contents
+    memmove(new_addr, old_addr, obj_size);  // Copy contents
   }
 
   ASSERT(!HeapObject::FromAddress(new_addr)->IsCode());
 
   return obj_size;
 }
 
 
 int MarkCompactCollector::RelocateOldPointerObject(HeapObject* obj) {
   return RelocateOldNonCodeObject(obj, Heap::old_pointer_space());
 }
 
 
 int MarkCompactCollector::RelocateOldDataObject(HeapObject* obj) {
   return RelocateOldNonCodeObject(obj, Heap::old_data_space());
 }
 
 
+int MarkCompactCollector::RelocateCellObject(HeapObject* obj) {
+  return RelocateOldNonCodeObject(obj, Heap::cell_space());
+}
+
+
 int MarkCompactCollector::RelocateCodeObject(HeapObject* obj) {
-  // decode map pointer (forwarded address)
+  // Recover map pointer.
   MapWord encoding = obj->map_word();
   Address map_addr = encoding.DecodeMapAddress(Heap::map_space());
   ASSERT(Heap::map_space()->Contains(HeapObject::FromAddress(map_addr)));
 
   // Get forwarding address before resetting map pointer
   Address new_addr = GetForwardingAddressInOldSpace(obj);
 
-  int obj_size = RelocateOldObject(obj, Heap::code_space(), new_addr, map_addr);
+  // Reset the map pointer.
+  int obj_size = RestoreMap(obj, Heap::code_space(), new_addr, map_addr);
 
-  // convert inline cache target to address using old address
+  // Convert inline cache target to address using old address.
   if (obj->IsCode()) {
-    // convert target to address first related to old_address
     Code::cast(obj)->ConvertICTargetsFromObjectToAddress();
   }
 
   Address old_addr = obj->address();
 
   if (new_addr != old_addr) {
-    memmove(new_addr, old_addr, obj_size);  // copy contents
+    memmove(new_addr, old_addr, obj_size);  // Copy contents.
   }
 
   HeapObject* copied_to = HeapObject::FromAddress(new_addr);
   if (copied_to->IsCode()) {
-    // may also update inline cache target.
+    // May also update inline cache target.
     Code::cast(copied_to)->Relocate(new_addr - old_addr);
     // Notify the logger that compiled code has moved.
     LOG(CodeMoveEvent(old_addr, new_addr));
   }
 
   return obj_size;
 }
 
 
 int MarkCompactCollector::RelocateNewObject(HeapObject* obj) {
   int obj_size = obj->Size();
 
   // Get forwarding address
   Address old_addr = obj->address();
   int offset = Heap::new_space()->ToSpaceOffsetForAddress(old_addr);
 
   Address new_addr =
     Memory::Address_at(Heap::new_space()->FromSpaceLow() + offset);
 
+#ifdef DEBUG
   if (Heap::new_space()->FromSpaceContains(new_addr)) {
     ASSERT(Heap::new_space()->FromSpaceOffsetForAddress(new_addr) <=
            Heap::new_space()->ToSpaceOffsetForAddress(old_addr));
   } else {
-    OldSpace* target_space = Heap::TargetSpace(obj);
-    ASSERT(target_space == Heap::old_pointer_space() ||
-           target_space == Heap::old_data_space());
-    target_space->MCAdjustRelocationEnd(new_addr, obj_size);
+    ASSERT(Heap::TargetSpace(obj) == Heap::old_pointer_space() ||
+           Heap::TargetSpace(obj) == Heap::old_data_space());
   }
+#endif
 
   // New and old addresses cannot overlap.
   memcpy(reinterpret_cast<void*>(new_addr),
          reinterpret_cast<void*>(old_addr),
          obj_size);
 
 #ifdef DEBUG
   if (FLAG_gc_verbose) {
     PrintF("relocate %p -> %p\n", old_addr, new_addr);
   }
 #endif
 
   return obj_size;
 }
 
 
 // -------------------------------------------------------------------------
 // Phase 5: rebuild remembered sets
 
 void MarkCompactCollector::RebuildRSets() {
 #ifdef DEBUG
   ASSERT(state_ == RELOCATE_OBJECTS);
   state_ = REBUILD_RSETS;
 #endif
   Heap::RebuildRSets();
 }
 
 } }  // namespace v8::internal