[heap] Do not invoke GC to make heap iterable.

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index cbc6d72ad839a31822e64cbd93df6503ccca5133..4db0a8b8ba53cc4eaecc85b6f02ec7f0c8c6d7ea 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -893,7 +893,8 @@ void Heap::CollectAllAvailableGarbage(const char* gc_reason) {
     isolate()->optimizing_compile_dispatcher()->Flush();
   }
   isolate()->ClearSerializerData();
-  set_current_gc_flags(kMakeHeapIterableMask | kReduceMemoryFootprintMask);
+  set_current_gc_flags(kAbortIncrementalMarkingMask |
+                       kReduceMemoryFootprintMask);
   isolate_->compilation_cache()->Clear();
   const int kMaxNumberOfAttempts = 7;
   const int kMinNumberOfAttempts = 2;
@@ -4045,22 +4046,10 @@ AllocationResult Heap::AllocateStruct(InstanceType type) {
 }
 
 
-bool Heap::IsHeapIterable() {
-  // TODO(hpayer): This function is not correct. Allocation folding in old
-  // space breaks the iterability.
-  return new_space_top_after_last_gc_ == new_space()->top();
-}
-
-
 void Heap::MakeHeapIterable() {
-  DCHECK(AllowHeapAllocation::IsAllowed());
-  if (!IsHeapIterable()) {
-    CollectAllGarbage(kMakeHeapIterableMask, "Heap::MakeHeapIterable");
-  }
   if (mark_compact_collector()->sweeping_in_progress()) {
     mark_compact_collector()->EnsureSweepingCompleted();
   }
-  DCHECK(IsHeapIterable());
 }
 
 
@@ -4605,10 +4594,7 @@ void Heap::Verify() {
   CHECK(HasBeenSetUp());
   HandleScope scope(isolate());
 
-  if (mark_compact_collector()->sweeping_in_progress()) {
-    // We have to wait here for the sweeper threads to have an iterable heap.
-    mark_compact_collector()->EnsureSweepingCompleted();
-  }
+  MakeHeapIterable();
 
   VerifyPointersVisitor visitor;
   IterateRoots(&visitor, VISIT_ONLY_STRONG);
@@ -5802,118 +5788,35 @@ ObjectIterator* SpaceIterator::CreateIterator() {
   return iterator_;
 }
 
-
-class HeapObjectsFilter {
- public:
-  virtual ~HeapObjectsFilter() {}
-  virtual bool SkipObject(HeapObject* object) = 0;
-};
-
-
-class UnreachableObjectsFilter : public HeapObjectsFilter {
- public:
-  explicit UnreachableObjectsFilter(Heap* heap) : heap_(heap) {
-    MarkReachableObjects();
-  }
-
-  ~UnreachableObjectsFilter() {
-    heap_->mark_compact_collector()->ClearMarkbits();
-  }
-
-  bool SkipObject(HeapObject* object) {
-    if (object->IsFiller()) return true;
-    MarkBit mark_bit = Marking::MarkBitFrom(object);
-    return Marking::IsWhite(mark_bit);
-  }
-
- private:
-  class MarkingVisitor : public ObjectVisitor {
-   public:
-    MarkingVisitor() : marking_stack_(10) {}
-
-    void VisitPointers(Object** start, Object** end) override {
-      for (Object** p = start; p < end; p++) {
-        if (!(*p)->IsHeapObject()) continue;
-        HeapObject* obj = HeapObject::cast(*p);
-        MarkBit mark_bit = Marking::MarkBitFrom(obj);
-        if (Marking::IsWhite(mark_bit)) {
-          Marking::WhiteToBlack(mark_bit);
-          marking_stack_.Add(obj);
-        }
-      }
-    }
-
-    void TransitiveClosure() {
-      while (!marking_stack_.is_empty()) {
-        HeapObject* obj = marking_stack_.RemoveLast();
-        obj->Iterate(this);
-      }
-    }
-
-   private:
-    List<HeapObject*> marking_stack_;
-  };
-
-  void MarkReachableObjects() {
-    MarkingVisitor visitor;
-    heap_->IterateRoots(&visitor, VISIT_ALL);
-    visitor.TransitiveClosure();
-  }
-
-  Heap* heap_;
-  DisallowHeapAllocation no_allocation_;
-};
-
-
-HeapIterator::HeapIterator(Heap* heap,
-                           HeapIterator::HeapObjectsFiltering filtering)
-    : make_heap_iterable_helper_(heap),
-      no_heap_allocation_(),
-      heap_(heap),
-      filtering_(filtering),
-      filter_(nullptr),
-      space_iterator_(nullptr),
-      object_iterator_(nullptr) {
+HeapIterator::HeapIterator(Heap* heap, HeapObjectsFiltering filtering)
+    : heap_(heap), space_iterator_(nullptr), object_iterator_(nullptr) {
   heap_->heap_iterator_start();
   // Start the iteration.
   space_iterator_ = new SpaceIterator(heap_);
-  switch (filtering_) {
-    case kFilterUnreachable:
-      filter_ = new UnreachableObjectsFilter(heap_);
+  switch (filtering) {
+    case HeapObjectsFiltering::kFilterUnreachable:
+      heap_->CollectAllGarbage(Heap::kAbortIncrementalMarkingMask,
+                               "filter unreachable objects");
       break;
     default:
       break;
   }
+  heap_->MakeHeapIterable();
+  disallow_heap_allocation_ = new DisallowHeapAllocation();
   object_iterator_ = space_iterator_->next();
 }
 
 
 HeapIterator::~HeapIterator() {
   heap_->heap_iterator_end();
-#ifdef DEBUG
-  // Assert that in filtering mode we have iterated through all
-  // objects. Otherwise, heap will be left in an inconsistent state.
-  if (filtering_ != kNoFiltering) {
-    DCHECK(object_iterator_ == nullptr);
-  }
-#endif
   // Make sure the last iterator is deallocated.
   delete object_iterator_;
   delete space_iterator_;
-  delete filter_;
+  delete disallow_heap_allocation_;
 }
 
 
 HeapObject* HeapIterator::next() {
-  if (filter_ == nullptr) return NextObject();
-
-  HeapObject* obj = NextObject();
-  while ((obj != nullptr) && (filter_->SkipObject(obj))) obj = NextObject();
-  return obj;
-}
-
-
-HeapObject* HeapIterator::NextObject() {
   // No iterator means we are done.
   if (object_iterator_ == nullptr) return nullptr;