[heap] Support clear and update operation in worklist.

BUG=chromium:694255

Change-Id: Ie4f14e62afa63339c586c3872d6acfa2bf4833d8
Reviewed-on: https://chromium-review.googlesource.com/545717Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46207}

src/heap/worklist.h

@@ -89,6 +89,46 @@ class Worklist {
     return global_pool_.empty();
   }
 
+  size_t LocalSize(int task_id) {
+    return private_pop_segment_[task_id]->Size() +
+           private_push_segment_[task_id]->Size();
+  }
+
+  // Clears all segments. Frees the global segment pool.
+  // This function assumes that other tasks are not running.
+  void Clear() {
+    for (int i = 0; i < kMaxNumTasks; i++) {
+      private_pop_segment_[i]->Clear();
+      private_push_segment_[i]->Clear();
+    }
+    for (Segment* segment : global_pool_) {
+      delete segment;
+    }
+    global_pool_.clear();
+  }
+
+  // Calls the specified callback on each element of the deques and replaces
+  // the element with the result of the callback. If the callback returns
+  // nullptr then the element is removed from the worklist.
+  // The callback must accept HeapObject* and return HeapObject*.
+  // This function assumes that other tasks are not running.
+  template <typename Callback>
+  void Update(Callback callback) {
+    for (int i = 0; i < kMaxNumTasks; i++) {
+      private_pop_segment_[i]->Update(callback);
+      private_push_segment_[i]->Update(callback);
+    }
+    for (size_t i = 0; i < global_pool_.size(); i++) {
+      Segment* segment = global_pool_[i];
+      segment->Update(callback);
+      if (segment->IsEmpty()) {
+        global_pool_[i] = global_pool_.back();
+        global_pool_.pop_back();
+        delete segment;
+      }
+    }
+  }
+
  private:
   FRIEND_TEST(Worklist, SegmentCreate);
   FRIEND_TEST(Worklist, SegmentPush);
@@ -98,6 +138,8 @@ class Worklist {
   FRIEND_TEST(Worklist, SegmentClear);
   FRIEND_TEST(Worklist, SegmentFullPushFails);
   FRIEND_TEST(Worklist, SegmentEmptyPopFails);
+  FRIEND_TEST(Worklist, SegmentUpdateNull);
+  FRIEND_TEST(Worklist, SegmentUpdate);
 
   class Segment {
    public:
@@ -124,6 +166,18 @@ class Worklist {
     bool IsFull() { return index_ == kCapacity; }
     void Clear() { index_ = 0; }
 
+    template <typename Callback>
+    void Update(Callback callback) {
+      size_t new_index = 0;
+      for (size_t i = 0; i < index_; i++) {
+        HeapObject* object = callback(objects_[i]);
+        if (object) {
+          objects_[new_index++] = object;
+        }
+      }
+      index_ = new_index;
+    }
+
    private:
     size_t index_;
     HeapObject* objects_[kCapacity];
@@ -135,8 +189,10 @@ class Worklist {
 
   V8_NOINLINE void PublishPushSegmentToGlobal(int task_id) {
     base::LockGuard<base::Mutex> guard(&lock_);
-    global_pool_.push_back(private_push_segment_[task_id]);
-    private_push_segment_[task_id] = new Segment();
+    if (!private_push_segment_[task_id]->IsEmpty()) {
+      global_pool_.push_back(private_push_segment_[task_id]);
+      private_push_segment_[task_id] = new Segment();
+    }
   }
 
   V8_NOINLINE bool StealPopSegmentFromGlobal(int task_id) {

test/unittests/heap/worklist-unittest.cc

@@ -80,6 +80,28 @@ TEST(Worklist, SegmentEmptyPopFails) {
   EXPECT_FALSE(segment.Pop(&object));
 }
 
+TEST(Worklist, SegmentUpdateNull) {
+  Worklist::Segment segment;
+  HeapObject* object;
+  object = reinterpret_cast<HeapObject*>(&object);
+  EXPECT_TRUE(segment.Push(object));
+  segment.Update([](HeapObject* object) { return nullptr; });
+  EXPECT_TRUE(segment.IsEmpty());
+}
+
+TEST(Worklist, SegmentUpdate) {
+  Worklist::Segment segment;
+  HeapObject* objectA;
+  objectA = reinterpret_cast<HeapObject*>(&objectA);
+  HeapObject* objectB;
+  objectB = reinterpret_cast<HeapObject*>(&objectB);
+  EXPECT_TRUE(segment.Push(objectA));
+  segment.Update([objectB](HeapObject* object) { return objectB; });
+  HeapObject* object;
+  EXPECT_TRUE(segment.Pop(&object));
+  EXPECT_EQ(object, objectB);
+}
+
 TEST(Worklist, CreateEmpty) {
   Worklist worklist;
   WorklistView worklist_view(&worklist, 0);
@@ -130,6 +152,51 @@ TEST(Worklist, LocalPushStaysPrivate) {
   EXPECT_TRUE(worklist.IsGlobalEmpty());
 }
 
+TEST(Worklist, GlobalUpdateNull) {
+  Worklist worklist;
+  WorklistView worklist_view(&worklist, 0);
+  HeapObject* object;
+  object = reinterpret_cast<HeapObject*>(&object);
+  for (size_t i = 0; i < Worklist::kSegmentCapacity; i++) {
+    EXPECT_TRUE(worklist_view.Push(object));
+  }
+  EXPECT_TRUE(worklist_view.Push(object));
+  worklist.Update([](HeapObject* object) { return nullptr; });
+  EXPECT_TRUE(worklist.IsGlobalEmpty());
+}
+
+TEST(Worklist, GlobalUpdate) {
+  Worklist worklist;
+  WorklistView worklist_view(&worklist, 0);
+  HeapObject* objectA;
+  objectA = reinterpret_cast<HeapObject*>(&objectA);
+  HeapObject* objectB;
+  objectB = reinterpret_cast<HeapObject*>(&objectB);
+  for (size_t i = 0; i < Worklist::kSegmentCapacity; i++) {
+    EXPECT_TRUE(worklist_view.Push(objectA));
+  }
+  EXPECT_TRUE(worklist_view.Push(objectA));
+  worklist.Update([objectB](HeapObject* object) { return objectB; });
+  for (size_t i = 0; i < Worklist::kSegmentCapacity + 1; i++) {
+    HeapObject* object;
+    EXPECT_TRUE(worklist_view.Pop(&object));
+    EXPECT_EQ(object, objectB);
+  }
+}
+
+TEST(Worklist, Clear) {
+  Worklist worklist;
+  WorklistView worklist_view(&worklist, 0);
+  HeapObject* object;
+  object = reinterpret_cast<HeapObject*>(&object);
+  for (size_t i = 0; i < Worklist::kSegmentCapacity; i++) {
+    EXPECT_TRUE(worklist_view.Push(object));
+  }
+  EXPECT_TRUE(worklist_view.Push(object));
+  worklist.Clear();
+  EXPECT_TRUE(worklist.IsGlobalEmpty());
+}
+
 TEST(Worklist, SingleSegmentSteal) {
   Worklist worklist;
   WorklistView worklist_view1(&worklist, 0);