Revert of [heap] Reland "Remove black pages and use black areas instead."

src/heap/spaces.h

 // Copyright 2011 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.
 
 #ifndef V8_HEAP_SPACES_H_
 #define V8_HEAP_SPACES_H_
 
 #include <list>
 #include <memory>
 
@@ skipping 232 matching lines @@
     HAS_PROGRESS_BAR,
 
     // |PAGE_NEW_OLD_PROMOTION|: A page tagged with this flag has been promoted
     // from new to old space during evacuation.
     PAGE_NEW_OLD_PROMOTION,
 
     // |PAGE_NEW_NEW_PROMOTION|: A page tagged with this flag has been moved
     // within the new space during evacuation.
     PAGE_NEW_NEW_PROMOTION,
 
+    // A black page has all mark bits set to 1 (black). A black page currently
+    // cannot be iterated because it is not swept. Moreover live bytes are also
+    // not updated.
+    BLACK_PAGE,
+
     // This flag is intended to be used for testing. Works only when both
     // FLAG_stress_compaction and FLAG_manual_evacuation_candidates_selection
     // are set. It forces the page to become an evacuation candidate at next
     // candidates selection cycle.
     FORCE_EVACUATION_CANDIDATE_FOR_TESTING,
 
     // This flag is intended to be used for testing.
     NEVER_ALLOCATE_ON_PAGE,
 
     // The memory chunk is already logically freed, however the actual freeing
@@ skipping 154 matching lines @@
   base::AtomicValue<ConcurrentSweepingState>& concurrent_sweeping_state() {
     return concurrent_sweeping_;
   }
 
   // Manage live byte count, i.e., count of bytes in black objects.
   inline void ResetLiveBytes();
   inline void IncrementLiveBytes(int by);
 
   int LiveBytes() {
     DCHECK_LE(static_cast<unsigned>(live_byte_count_), size_);
+    DCHECK(!IsFlagSet(BLACK_PAGE) || live_byte_count_ == 0);
     return live_byte_count_;
   }
 
   void SetLiveBytes(int live_bytes) {
+    if (IsFlagSet(BLACK_PAGE)) return;
     DCHECK_GE(live_bytes, 0);
     DCHECK_LE(static_cast<size_t>(live_bytes), size_);
     live_byte_count_ = live_bytes;
   }
 
   int write_barrier_counter() {
     return static_cast<int>(write_barrier_counter_);
   }
 
   void set_write_barrier_counter(int counter) {
@@ skipping 1620 matching lines @@
   void ResetFreeList() { free_list_.Reset(); }
 
   // Set space allocation info.
   void SetTopAndLimit(Address top, Address limit) {
     DCHECK(top == limit ||
            Page::FromAddress(top) == Page::FromAddress(limit - 1));
     MemoryChunk::UpdateHighWaterMark(allocation_info_.top());
     allocation_info_.Reset(top, limit);
   }
 
-  void SetAllocationInfo(Address top, Address limit);
-
   // Empty space allocation info, returning unused area to free list.
-  void EmptyAllocationInfo();
-
-  void MarkAllocationInfoBlack();
+  void EmptyAllocationInfo() {
+    // Mark the old linear allocation area with a free space map so it can be
+    // skipped when scanning the heap.
+    int old_linear_size = static_cast<int>(limit() - top());
+    Free(top(), old_linear_size);
+    SetTopAndLimit(NULL, NULL);
+  }
 
   void Allocate(int bytes) { accounting_stats_.AllocateBytes(bytes); }
 
   void IncreaseCapacity(int size);
 
   // Releases an unused page and shrinks the space.
   void ReleasePage(Page* page);
 
   // The dummy page that anchors the linked list of pages.
   Page* anchor() { return &anchor_; }
@@ skipping 898 matching lines @@
     count = 0;
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_SPACES_H_