Reland "[heap] Refactor evacuation for young and old gen into visitors."

src/heap/mark-compact.h

 // 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.
 
 #ifndef V8_HEAP_MARK_COMPACT_H_
 #define V8_HEAP_MARK_COMPACT_H_
 
 #include "src/base/bits.h"
 #include "src/heap/spaces.h"
 
@@ skipping 296 matching lines @@
 
 
 // Defined in isolate.h.
 class ThreadLocalTop;
 
 
 // -------------------------------------------------------------------------
 // Mark-Compact collector
 class MarkCompactCollector {
  public:
+  enum IterationMode {
+    kKeepMarking,
+    kClearMarkbits,
+  };
+
+  class EvacuateNewSpaceVisitor;
+  class EvacuateOldSpaceVisitor;
+  class HeapObjectVisitor;
+
   static void Initialize();
 
   void SetUp();
 
   void TearDown();
 
   void CollectEvacuationCandidates(PagedSpace* space);
 
   void AddEvacuationCandidate(Page* p);
 
@@ skipping 361 matching lines @@
   //   After: Live objects are unmarked, non-live regions have been added to
   //          their space's free list. Active eden semispace is compacted by
   //          evacuation.
   //
 
   // If we are not compacting the heap, we simply sweep the spaces except
   // for the large object space, clearing mark bits and adding unmarked
   // regions to each space's free list.
   void SweepSpaces();
 
-  int DiscoverAndEvacuateBlackObjectsOnPage(NewSpace* new_space,
-                                            NewSpacePage* p);
+  // Iterates through all live objects on a page using marking information.
+  // Returns whether all objects have successfully been visited.
+  bool IterateLiveObjectsOnPage(MemoryChunk* page, HeapObjectVisitor* visitor,
+                                IterationMode mode);
 
   void EvacuateNewSpace();
 
-  bool EvacuateLiveObjectsFromPage(Page* p, PagedSpace* target_space,
-                                   SlotsBuffer** evacuation_slots_buffer);
-
   void AddEvacuationSlotsBufferSynchronized(
       SlotsBuffer* evacuation_slots_buffer);
 
   void EvacuatePages(CompactionSpaceCollection* compaction_spaces,
                      SlotsBuffer** evacuation_slots_buffer);
 
   void EvacuatePagesInParallel();
 
   // The number of parallel compaction tasks, including the main thread.
   int NumberOfParallelCompactionTasks();
@@ skipping 137 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_MARK_COMPACT_H_