[object-stats] Refactor to allow additional passes over objects

Move heap iteration to object stats to untangle the dependency from
MC.

Bug: v8:7266
Change-Id: I6f0f4f5f3bb0a911591a211ffd71580343765cdd
Reviewed-on: https://chromium-review.googlesource.com/860358Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50502}

src/heap/mark-compact.cc

@@ -1689,54 +1689,12 @@ void MarkCompactCollector::ProcessTopOptimizedFrame(ObjectVisitor* visitor) {
   }
 }
 
-class ObjectStatsVisitor : public HeapObjectVisitor {
- public:
-  ObjectStatsVisitor(Heap* heap, ObjectStats* live_stats,
-                     ObjectStats* dead_stats)
-      : live_collector_(heap, live_stats),
-        dead_collector_(heap, dead_stats),
-        marking_state_(
-            heap->mark_compact_collector()->non_atomic_marking_state()) {
-    DCHECK_NOT_NULL(live_stats);
-    DCHECK_NOT_NULL(dead_stats);
-    // Global objects are roots and thus recorded as live.
-    live_collector_.CollectGlobalStatistics();
-  }
-
-  bool Visit(HeapObject* obj, int size) override {
-    if (marking_state_->IsBlack(obj)) {
-      live_collector_.CollectStatistics(obj);
-    } else {
-      DCHECK(!marking_state_->IsGrey(obj));
-      dead_collector_.CollectStatistics(obj);
-    }
-    return true;
-  }
-
- private:
-  ObjectStatsCollector live_collector_;
-  ObjectStatsCollector dead_collector_;
-  MarkCompactCollector::NonAtomicMarkingState* marking_state_;
-};
-
-void MarkCompactCollector::VisitAllObjects(HeapObjectVisitor* visitor) {
-  SpaceIterator space_it(heap());
-  HeapObject* obj = nullptr;
-  while (space_it.has_next()) {
-    std::unique_ptr<ObjectIterator> it(space_it.next()->GetObjectIterator());
-    ObjectIterator* obj_it = it.get();
-    while ((obj = obj_it->Next()) != nullptr) {
-      visitor->Visit(obj, obj->Size());
-    }
-  }
-}
-
 void MarkCompactCollector::RecordObjectStats() {
   if (V8_UNLIKELY(FLAG_gc_stats)) {
     heap()->CreateObjectStats();
-    ObjectStatsVisitor visitor(heap(), heap()->live_object_stats_,
-                               heap()->dead_object_stats_);
-    VisitAllObjects(&visitor);
+    ObjectStatsCollector collector(heap(), heap()->live_object_stats_,
+                                   heap()->dead_object_stats_);
+    collector.Collect();
     if (V8_UNLIKELY(FLAG_gc_stats &
                     v8::tracing::TracingCategoryObserver::ENABLED_BY_TRACING)) {
       std::stringstream live, dead;

src/heap/mark-compact.h

@@ -723,8 +723,6 @@ class MarkCompactCollector final : public MarkCompactCollectorBase {
                                    int* target_fragmentation_percent,
                                    size_t* max_evacuated_bytes);
 
-  void VisitAllObjects(HeapObjectVisitor* visitor);
-
   void RecordObjectStats();
 
   // Finishes GC, performs heap verification if enabled.

src/heap/object-stats.h

@@ -88,37 +88,21 @@ class ObjectStats {
 
 class ObjectStatsCollector {
  public:
-  ObjectStatsCollector(Heap* heap, ObjectStats* stats);
+  ObjectStatsCollector(Heap* heap, ObjectStats* live, ObjectStats* dead)
+      : heap_(heap), live_(live), dead_(dead) {
+    DCHECK_NOT_NULL(heap_);
+    DCHECK_NOT_NULL(live_);
+    DCHECK_NOT_NULL(dead_);
+  }
 
-  void CollectGlobalStatistics();
-  void CollectStatistics(HeapObject* obj);
+  // Collects type information of live and dead objects. Requires mark bits to
+  // be present.
+  void Collect();
 
  private:
-  class CompilationCacheTableVisitor;
-
-  void RecordBytecodeArrayDetails(BytecodeArray* obj);
-  void RecordCodeDetails(Code* code);
-  void RecordFixedArrayDetails(FixedArray* array);
-  void RecordJSCollectionDetails(JSObject* obj);
-  void RecordJSObjectDetails(JSObject* object);
-  void RecordJSWeakCollectionDetails(JSWeakCollection* obj);
-  void RecordMapDetails(Map* map);
-  void RecordScriptDetails(Script* obj);
-  void RecordTemplateInfoDetails(TemplateInfo* obj);
-  void RecordSharedFunctionInfoDetails(SharedFunctionInfo* sfi);
-
-  bool RecordFixedArrayHelper(HeapObject* parent, FixedArray* array,
-                              int subtype, size_t overhead);
-  void RecursivelyRecordFixedArrayHelper(HeapObject* parent, FixedArray* array,
-                                         int subtype);
-  template <class HashTable>
-  void RecordHashTableHelper(HeapObject* parent, HashTable* array, int subtype);
-  bool SameLiveness(HeapObject* obj1, HeapObject* obj2);
-  Heap* heap_;
-  ObjectStats* stats_;
-  MarkCompactCollector::NonAtomicMarkingState* marking_state_;
-
-  friend class ObjectStatsCollector::CompilationCacheTableVisitor;
+  Heap* const heap_;
+  ObjectStats* const live_;
+  ObjectStats* const dead_;
 };
 
 }  // namespace internal