[heap] Track transition arrays using worklists.

This allows handling transitions arrays in concurrent marking

Bug: chromium:694255
Change-Id: I28196fccbf03bfba7d7dada1884813be372ddb54
Reviewed-on: https://chromium-review.googlesource.com/610961
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47303}

src/heap/concurrent-marking.cc

@@ -74,13 +74,13 @@ class ConcurrentMarkingVisitor final
  public:
   using BaseClass = HeapVisitor<int, ConcurrentMarkingVisitor>;
 
-  explicit ConcurrentMarkingVisitor(
-      ConcurrentMarking::MarkingWorklist* shared,
-      ConcurrentMarking::MarkingWorklist* bailout,
-      ConcurrentMarking::WeakCellWorklist* weak_cells, int task_id)
+  explicit ConcurrentMarkingVisitor(ConcurrentMarking::MarkingWorklist* shared,
+                                    ConcurrentMarking::MarkingWorklist* bailout,
+                                    WeakObjects* weak_objects, int task_id)
       : shared_(shared, task_id),
         bailout_(bailout, task_id),
-        weak_cells_(weak_cells, task_id) {}
+        weak_objects_(weak_objects),
+        task_id_(task_id) {}
 
   bool ShouldVisit(HeapObject* object) {
     return marking_state_.GreyToBlack(object);
@@ -217,10 +217,30 @@ class ConcurrentMarkingVisitor final
     return 0;
   }
 
-  int VisitTransitionArray(Map* map, TransitionArray* object) {
-    // TODO(ulan): implement iteration of strong fields.
-    bailout_.Push(object);
-    return 0;
+  int VisitTransitionArray(Map* map, TransitionArray* array) {
+    if (!ShouldVisit(array)) return 0;
+    VisitMapPointer(array, array->map_slot());
+    // Visit strong references.
+    if (array->HasPrototypeTransitions()) {
+      VisitPointer(array, array->GetPrototypeTransitionsSlot());
+    }
+    int num_transitions = array->number_of_entries();
+    for (int i = 0; i < num_transitions; ++i) {
+      VisitPointer(array, array->GetKeySlot(i));
+      // A TransitionArray can hold maps or (transitioning StoreIC) handlers.
+      // Maps have custom weak handling; handlers (which in turn weakly point
+      // to maps) are marked strongly for now, and will be cleared during
+      // compaction when the maps they refer to are dead.
+      Object* target = array->GetRawTarget(i);
+      if (target->IsHeapObject()) {
+        Map* map = HeapObject::cast(target)->synchronized_map();
+        if (map->instance_type() != MAP_TYPE) {
+          VisitPointer(array, array->GetTargetSlot(i));
+        }
+      }
+    }
+    weak_objects_->transition_arrays.Push(task_id_, array);
+    return TransitionArray::BodyDescriptor::SizeOf(map, array);
   }
 
   int VisitWeakCell(Map* map, WeakCell* object) {
@@ -237,7 +257,7 @@ class ConcurrentMarkingVisitor final
         // If we do not know about liveness of values of weak cells, we have to
         // process them when we know the liveness of the whole transitive
         // closure.
-        weak_cells_.Push(object);
+        weak_objects_->weak_cells.Push(task_id_, object);
       }
     }
     return WeakCell::BodyDescriptor::SizeOf(map, object);
@@ -295,8 +315,9 @@ class ConcurrentMarkingVisitor final
   }
   ConcurrentMarking::MarkingWorklist::View shared_;
   ConcurrentMarking::MarkingWorklist::View bailout_;
-  ConcurrentMarking::WeakCellWorklist::View weak_cells_;
+  WeakObjects* weak_objects_;
   ConcurrentMarkingState marking_state_;
+  int task_id_;
   SlotSnapshot slot_snapshot_;
 };
 
@@ -325,11 +346,11 @@ class ConcurrentMarking::Task : public CancelableTask {
 
 ConcurrentMarking::ConcurrentMarking(Heap* heap, MarkingWorklist* shared,
                                      MarkingWorklist* bailout,
-                                     WeakCellWorklist* weak_cells)
+                                     WeakObjects* weak_objects)
     : heap_(heap),
       shared_(shared),
       bailout_(bailout),
-      weak_cells_(weak_cells),
+      weak_objects_(weak_objects),
       pending_task_count_(0) {
 // The runtime flag should be set only if the compile time flag was set.
 #ifndef V8_CONCURRENT_MARKING
@@ -343,7 +364,7 @@ ConcurrentMarking::ConcurrentMarking(Heap* heap, MarkingWorklist* shared,
 void ConcurrentMarking::Run(int task_id, TaskInterrupt* interrupt) {
   size_t kBytesUntilInterruptCheck = 64 * KB;
   int kObjectsUntilInterrupCheck = 1000;
-  ConcurrentMarkingVisitor visitor(shared_, bailout_, weak_cells_, task_id);
+  ConcurrentMarkingVisitor visitor(shared_, bailout_, weak_objects_, task_id);
   double time_ms;
   size_t total_bytes_marked = 0;
   if (FLAG_trace_concurrent_marking) {
@@ -386,7 +407,8 @@ void ConcurrentMarking::Run(int task_id, TaskInterrupt* interrupt) {
       base::LockGuard<base::Mutex> guard(&interrupt->lock);
       bailout_->FlushToGlobal(task_id);
     }
-    weak_cells_->FlushToGlobal(task_id);
+    weak_objects_->weak_cells.FlushToGlobal(task_id);
+    weak_objects_->transition_arrays.FlushToGlobal(task_id);
     {
       base::LockGuard<base::Mutex> guard(&pending_lock_);
       is_pending_[task_id] = false;

src/heap/concurrent-marking.h

@@ -16,7 +16,7 @@ namespace internal {
 
 class Heap;
 class Isolate;
-class WeakCell;
+struct WeakObjects;
 
 class ConcurrentMarking {
  public:
@@ -33,10 +33,9 @@ class ConcurrentMarking {
 
   static const int kTasks = 4;
   using MarkingWorklist = Worklist<HeapObject*, 64 /* segment size */>;
-  using WeakCellWorklist = Worklist<WeakCell*, 64 /* segment size */>;
 
   ConcurrentMarking(Heap* heap, MarkingWorklist* shared,
-                    MarkingWorklist* bailout, WeakCellWorklist* weak_cells);
+                    MarkingWorklist* bailout, WeakObjects* weak_objects);
 
   void ScheduleTasks();
   void EnsureCompleted();
@@ -60,7 +59,7 @@ class ConcurrentMarking {
   Heap* heap_;
   MarkingWorklist* shared_;
   MarkingWorklist* bailout_;
-  WeakCellWorklist* weak_cells_;
+  WeakObjects* weak_objects_;
   TaskInterrupt task_interrupt_[kTasks + 1];
   base::Mutex pending_lock_;
   base::ConditionVariable pending_condition_;

src/heap/heap.cc

@@ -177,7 +177,6 @@ Heap::Heap()
   set_native_contexts_list(NULL);
   set_allocation_sites_list(Smi::kZero);
   set_encountered_weak_collections(Smi::kZero);
-  set_encountered_transition_arrays(Smi::kZero);
   // Put a dummy entry in the remembered pages so we can find the list the
   // minidump even if there are no real unmapped pages.
   RememberUnmappedPage(NULL, false);
@@ -2738,11 +2737,7 @@ AllocationResult Heap::AllocateTransitionArray(int capacity) {
   // Transition arrays are tenured. When black allocation is on we have to
   // add the transition array to the list of encountered_transition_arrays.
   if (incremental_marking()->black_allocation()) {
-    array->set_next_link(encountered_transition_arrays(),
-                         UPDATE_WEAK_WRITE_BARRIER);
-    set_encountered_transition_arrays(array);
-  } else {
-    array->set_next_link(undefined_value(), SKIP_WRITE_BARRIER);
+    mark_compact_collector()->AddTransitionArray(array);
   }
   return array;
 }
@@ -5965,7 +5960,7 @@ bool Heap::SetUp() {
         mark_compact_collector_->marking_worklist();
     concurrent_marking_ = new ConcurrentMarking(
         this, marking_worklist->shared(), marking_worklist->bailout(),
-        mark_compact_collector_->weak_cells());
+        mark_compact_collector_->weak_objects());
   } else {
     concurrent_marking_ =
         new ConcurrentMarking(this, nullptr, nullptr, nullptr);

src/heap/heap.h

@@ -748,13 +748,6 @@ class Heap {
   }
   void IterateEncounteredWeakCollections(RootVisitor* visitor);
 
-  void set_encountered_transition_arrays(Object* transition_array) {
-    encountered_transition_arrays_ = transition_array;
-  }
-  Object* encountered_transition_arrays() const {
-    return encountered_transition_arrays_;
-  }
-
   // Number of mark-sweeps.
   int ms_count() const { return ms_count_; }
 
@@ -2291,8 +2284,6 @@ class Heap {
   // contains Smi(0) while marking is not active.
   Object* encountered_weak_collections_;
 
-  Object* encountered_transition_arrays_;
-
   List<GCCallbackPair> gc_epilogue_callbacks_;
   List<GCCallbackPair> gc_prologue_callbacks_;
 

src/heap/mark-compact.cc

@@ -481,7 +481,7 @@ void MinorMarkCompactCollector::SetUp() {}
 
 void MarkCompactCollector::TearDown() {
   AbortCompaction();
-  weak_cells_.Clear();
+  AbortWeakObjects();
   marking_worklist()->TearDown();
 }
 
@@ -1008,8 +1008,7 @@ void MarkCompactCollector::Prepare() {
     heap()->incremental_marking()->AbortBlackAllocation();
     ClearMarkbits();
     AbortWeakCollections();
-    AbortWeakCells();
-    AbortTransitionArrays();
+    AbortWeakObjects();
     AbortCompaction();
     heap_->local_embedder_heap_tracer()->AbortTracing();
     marking_worklist()->Clear();
@@ -2798,6 +2797,9 @@ void MarkCompactCollector::ClearNonLiveReferences() {
   MarkDependentCodeForDeoptimization(dependent_code_list);
 
   ClearWeakCollections();
+
+  DCHECK(weak_objects_.weak_cells.IsGlobalEmpty());
+  DCHECK(weak_objects_.transition_arrays.IsGlobalEmpty());
 }
 
 
@@ -2894,10 +2896,8 @@ void MarkCompactCollector::ClearSimpleMapTransition(Map* map,
 }
 
 void MarkCompactCollector::ClearFullMapTransitions() {
-  HeapObject* undefined = heap()->undefined_value();
-  Object* obj = heap()->encountered_transition_arrays();
-  while (obj != Smi::kZero) {
-    TransitionArray* array = TransitionArray::cast(obj);
+  TransitionArray* array;
+  while (weak_objects_.transition_arrays.Pop(kMainThread, &array)) {
     int num_transitions = array->number_of_entries();
     if (num_transitions > 0) {
       Map* map = array->GetTarget(0);
@@ -2912,10 +2912,7 @@ void MarkCompactCollector::ClearFullMapTransitions() {
         TrimDescriptorArray(parent, descriptors);
       }
     }
-    obj = array->next_link();
-    array->set_next_link(undefined, SKIP_WRITE_BARRIER);
   }
-  heap()->set_encountered_transition_arrays(Smi::kZero);
 }
 
 bool MarkCompactCollector::CompactTransitionArray(
@@ -3088,7 +3085,7 @@ void MarkCompactCollector::ClearWeakCellsAndSimpleMapTransitions(
   DependentCode* dependent_code_head =
       DependentCode::cast(heap->empty_fixed_array());
   WeakCell* weak_cell;
-  while (weak_cells_.Pop(kMainThread, &weak_cell)) {
+  while (weak_objects_.weak_cells.Pop(kMainThread, &weak_cell)) {
     // We do not insert cleared weak cells into the list, so the value
     // cannot be a Smi here.
     HeapObject* value = HeapObject::cast(weak_cell->value());
@@ -3139,17 +3136,9 @@ void MarkCompactCollector::ClearWeakCellsAndSimpleMapTransitions(
   *dependent_code_list = dependent_code_head;
 }
 
-void MarkCompactCollector::AbortWeakCells() { weak_cells_.Clear(); }
-
-void MarkCompactCollector::AbortTransitionArrays() {
-  HeapObject* undefined = heap()->undefined_value();
-  Object* obj = heap()->encountered_transition_arrays();
-  while (obj != Smi::kZero) {
-    TransitionArray* array = TransitionArray::cast(obj);
-    obj = array->next_link();
-    array->set_next_link(undefined, SKIP_WRITE_BARRIER);
-  }
-  heap()->set_encountered_transition_arrays(Smi::kZero);
+void MarkCompactCollector::AbortWeakObjects() {
+  weak_objects_.weak_cells.Clear();
+  weak_objects_.transition_arrays.Clear();
 }
 
 void MarkCompactCollector::RecordRelocSlot(Code* host, RelocInfo* rinfo,

src/heap/mark-compact.h

@@ -477,6 +477,12 @@ class MajorNonAtomicMarkingState final
   }
 };
 
+// Weak objects encountered during marking.
+struct WeakObjects {
+  Worklist<WeakCell*, 64> weak_cells;
+  Worklist<TransitionArray*, 64> transition_arrays;
+};
+
 // Collector for young and old generation.
 class MarkCompactCollector final : public MarkCompactCollectorBase {
  public:
@@ -587,8 +593,6 @@ class MarkCompactCollector final : public MarkCompactCollectorBase {
     ConcurrentMarkingWorklist bailout_;
   };
 
-  using WeakCellWorklist = Worklist<WeakCell*, 64 /* segment size */>;
-
   class RootMarkingVisitor;
   class CustomRootBodyMarkingVisitor;
 
@@ -738,10 +742,14 @@ class MarkCompactCollector final : public MarkCompactCollectorBase {
 
   MarkingWorklist* marking_worklist() { return &marking_worklist_; }
 
-  WeakCellWorklist* weak_cells() { return &weak_cells_; }
+  WeakObjects* weak_objects() { return &weak_objects_; }
 
   void AddWeakCell(WeakCell* weak_cell) {
-    weak_cells_.Push(kMainThread, weak_cell);
+    weak_objects_.weak_cells.Push(kMainThread, weak_cell);
+  }
+
+  void AddTransitionArray(TransitionArray* array) {
+    weak_objects_.transition_arrays.Push(kMainThread, array);
   }
 
   Sweeper& sweeper() { return sweeper_; }
@@ -878,9 +886,7 @@ class MarkCompactCollector final : public MarkCompactCollectorBase {
   // transition.
   void ClearWeakCellsAndSimpleMapTransitions(
       DependentCode** dependent_code_list);
-  void AbortWeakCells();
-
-  void AbortTransitionArrays();
+  void AbortWeakObjects();
 
   // Starts sweeping of spaces by contributing on the main thread and setting
   // up other pages for sweeping. Does not start sweeper tasks.
@@ -939,7 +945,7 @@ class MarkCompactCollector final : public MarkCompactCollectorBase {
   bool have_code_to_deoptimize_;
 
   MarkingWorklist marking_worklist_;
-  WeakCellWorklist weak_cells_;
+  WeakObjects weak_objects_;
 
   // Candidates for pages that should be evacuated.
   std::vector<Page*> evacuation_candidates_;

src/heap/objects-visiting-inl.h

@@ -210,13 +210,7 @@ int MarkingVisitor<ConcreteVisitor>::VisitTransitionArray(
       visitor->VisitPointer(array, array->GetTargetSlot(i));
     }
   }
-  // Enqueue the array in linked list of encountered transition arrays if it is
-  // not already in the list.
-  if (array->next_link()->IsUndefined(heap_->isolate())) {
-    array->set_next_link(heap_->encountered_transition_arrays(),
-                         UPDATE_WEAK_WRITE_BARRIER);
-    heap_->set_encountered_transition_arrays(array);
-  }
+  collector_->AddTransitionArray(array);
   return TransitionArray::BodyDescriptor::SizeOf(map, array);
 }
 

src/objects-debug.cc

@@ -513,8 +513,6 @@ void TransitionArray::TransitionArrayVerify() {
     VerifyPointer(e);
   }
   CHECK_LE(LengthFor(number_of_transitions()), length());
-  CHECK(next_link()->IsUndefined(GetIsolate()) || next_link()->IsSmi() ||
-        next_link()->IsTransitionArray());
 }
 
 void JSArgumentsObject::JSArgumentsObjectVerify() {

src/objects-printer.cc

@@ -687,7 +687,6 @@ void TransitionArray::TransitionArrayPrint(std::ostream& os) {  // NOLINT
   os << "\n - capacity: " << length();
   for (int i = 0; i < length(); i++) {
     os << "\n  [" << i << "]: " << Brief(get(i));
-    if (i == kNextLinkIndex) os << " (next link)";
     if (i == kPrototypeTransitionsIndex) os << " (prototype transitions)";
     if (i == kTransitionLengthIndex) os << " (number of transitions)";
   }

src/transitions-inl.h

@@ -40,14 +40,6 @@ TransitionArray* TransitionArray::cast(Object* object) {
 }
 
 
-Object* TransitionArray::next_link() { return get(kNextLinkIndex); }
-
-
-void TransitionArray::set_next_link(Object* next, WriteBarrierMode mode) {
-  return set(kNextLinkIndex, next, mode);
-}
-
-
 bool TransitionArray::HasPrototypeTransitions() {
   return get(kPrototypeTransitionsIndex) != Smi::kZero;
 }

src/transitions.cc

@@ -519,8 +519,6 @@ Handle<TransitionArray> TransitionArray::Allocate(Isolate* isolate,
 }
 
 void TransitionArray::Zap() {
-  // Do not zap the next link that is used by GC.
-  STATIC_ASSERT(kNextLinkIndex + 1 == kPrototypeTransitionsIndex);
   MemsetPointer(data_start() + kPrototypeTransitionsIndex,
                 GetHeap()->the_hole_value(),
                 length() - kPrototypeTransitionsIndex);

src/transitions.h

@@ -235,10 +235,6 @@ class TransitionArray : public FixedArray {
 
   void Sort();
 
-  // This field should be used only by the GC.
-  inline void set_next_link(Object* next, WriteBarrierMode mode);
-  inline Object* next_link();
-
 #if defined(DEBUG) || defined(OBJECT_PRINT)
   // For our gdb macros.
   void Print();
@@ -281,10 +277,9 @@ class TransitionArray : public FixedArray {
                                               int value);
 
   // Layout for full transition arrays.
-  static const int kNextLinkIndex = 0;
-  static const int kPrototypeTransitionsIndex = 1;
-  static const int kTransitionLengthIndex = 2;
-  static const int kFirstIndex = 3;
+  static const int kPrototypeTransitionsIndex = 0;
+  static const int kTransitionLengthIndex = 1;
+  static const int kFirstIndex = 2;
 
   // Layout of map transition entries in full transition arrays.
   static const int kTransitionKey = 0;

test/cctest/heap/test-concurrent-marking.cc

@@ -9,6 +9,7 @@
 #include "src/heap/concurrent-marking.h"
 #include "src/heap/heap-inl.h"
 #include "src/heap/heap.h"
+#include "src/heap/mark-compact.h"
 #include "src/heap/worklist.h"
 #include "test/cctest/cctest.h"
 #include "test/cctest/heap/heap-utils.h"
@@ -30,9 +31,9 @@ TEST(ConcurrentMarking) {
   CcTest::InitializeVM();
   Heap* heap = CcTest::heap();
   ConcurrentMarking::MarkingWorklist shared, bailout;
-  ConcurrentMarking::WeakCellWorklist weak_cells;
+  WeakObjects weak_objects;
   ConcurrentMarking* concurrent_marking =
-      new ConcurrentMarking(heap, &shared, &bailout, &weak_cells);
+      new ConcurrentMarking(heap, &shared, &bailout, &weak_objects);
   PublishSegment(&shared, heap->undefined_value());
   concurrent_marking->ScheduleTasks();
   concurrent_marking->EnsureCompleted();
@@ -44,9 +45,9 @@ TEST(ConcurrentMarkingReschedule) {
   CcTest::InitializeVM();
   Heap* heap = CcTest::heap();
   ConcurrentMarking::MarkingWorklist shared, bailout;
-  ConcurrentMarking::WeakCellWorklist weak_cells;
+  WeakObjects weak_objects;
   ConcurrentMarking* concurrent_marking =
-      new ConcurrentMarking(heap, &shared, &bailout, &weak_cells);
+      new ConcurrentMarking(heap, &shared, &bailout, &weak_objects);
   PublishSegment(&shared, heap->undefined_value());
   concurrent_marking->ScheduleTasks();
   concurrent_marking->EnsureCompleted();