Reland [in-place weak refs] Use WeakArrayList in wasm

Now we can remove FixedArrayOfWeakCells (this was the last user).

Previous try: https://chromium-review.googlesource.com/1150170

BUG=v8:7308

Change-Id: Ie924e379ea8bbd797430e3ca591019fe001e78ad
Reviewed-on: https://chromium-review.googlesource.com/1154909Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54928}

src/heap/object-stats.cc

@@ -704,7 +704,7 @@ void ObjectStatsCollectorImpl::CollectGlobalStatistics() {
   RecordSimpleVirtualObjectStats(nullptr, heap_->retained_maps(),
                                  ObjectStats::RETAINED_MAPS_TYPE);
 
-  // FixedArrayOfWeakCells.
+  // WeakArrayList.
   RecordSimpleVirtualObjectStats(
       nullptr, WeakArrayList::cast(heap_->noscript_shared_function_infos()),
       ObjectStats::NOSCRIPT_SHARED_FUNCTION_INFOS_TYPE);

src/objects.cc

@@ -10366,78 +10366,6 @@ bool FixedArray::IsEqualTo(FixedArray* other) {
 }
 #endif
 
-// static
-void FixedArrayOfWeakCells::Set(Isolate* isolate,
-                                Handle<FixedArrayOfWeakCells> array, int index,
-                                Handle<HeapObject> value) {
-  DCHECK(array->IsEmptySlot(index));  // Don't overwrite anything.
-  DCHECK(!value->IsMap());
-  Handle<WeakCell> cell = isolate->factory()->NewWeakCell(value);
-  Handle<FixedArray>::cast(array)->set(index + kFirstIndex, *cell);
-  array->set_last_used_index(index);
-}
-
-
-// static
-Handle<FixedArrayOfWeakCells> FixedArrayOfWeakCells::Add(
-    Isolate* isolate, Handle<Object> maybe_array, Handle<HeapObject> value,
-    int* assigned_index) {
-  Handle<FixedArrayOfWeakCells> array =
-      (maybe_array.is_null() || !maybe_array->IsFixedArrayOfWeakCells())
-          ? Allocate(isolate, 1, Handle<FixedArrayOfWeakCells>::null())
-          : Handle<FixedArrayOfWeakCells>::cast(maybe_array);
-  // Try to store the new entry if there's room. Optimize for consecutive
-  // accesses.
-  int first_index = array->last_used_index();
-  int length = array->Length();
-  if (length > 0) {
-    for (int i = first_index;;) {
-      if (array->IsEmptySlot((i))) {
-        FixedArrayOfWeakCells::Set(isolate, array, i, value);
-        if (assigned_index != nullptr) *assigned_index = i;
-        return array;
-      }
-      i = (i + 1) % length;
-      if (i == first_index) break;
-    }
-  }
-
-  // No usable slot found, grow the array.
-  int new_length = length == 0 ? 1 : length + (length >> 1) + 4;
-  Handle<FixedArrayOfWeakCells> new_array =
-      Allocate(isolate, new_length, array);
-  FixedArrayOfWeakCells::Set(isolate, new_array, length, value);
-  if (assigned_index != nullptr) *assigned_index = length;
-  return new_array;
-}
-
-template <class CompactionCallback>
-void FixedArrayOfWeakCells::Compact(Isolate* isolate) {
-  FixedArray* array = FixedArray::cast(this);
-  int new_length = kFirstIndex;
-  for (int i = kFirstIndex; i < array->length(); i++) {
-    Object* element = array->get(i);
-    if (element->IsSmi()) continue;
-    if (WeakCell::cast(element)->cleared()) continue;
-    Object* value = WeakCell::cast(element)->value();
-    CompactionCallback::Callback(value, i - kFirstIndex,
-                                 new_length - kFirstIndex);
-    array->set(new_length++, element);
-  }
-  array->Shrink(isolate, new_length);
-  set_last_used_index(0);
-}
-
-void FixedArrayOfWeakCells::Iterator::Reset(Object* maybe_array) {
-  if (maybe_array->IsFixedArrayOfWeakCells()) {
-    list_ = FixedArrayOfWeakCells::cast(maybe_array);
-    index_ = 0;
-#ifdef DEBUG
-    last_used_index_ = list_->last_used_index();
-#endif  // DEBUG
-  }
-}
-
 void JSObject::PrototypeRegistryCompactionCallback(HeapObject* value,
                                                    int old_index,
                                                    int new_index) {
@@ -10449,51 +10377,6 @@ void JSObject::PrototypeRegistryCompactionCallback(HeapObject* value,
   proto_info->set_registry_slot(new_index);
 }
 
-template void FixedArrayOfWeakCells::Compact<
-    FixedArrayOfWeakCells::NullCallback>(Isolate* isolate);
-
-bool FixedArrayOfWeakCells::Remove(Handle<HeapObject> value) {
-  if (Length() == 0) return false;
-  // Optimize for the most recently added element to be removed again.
-  int first_index = last_used_index();
-  for (int i = first_index;;) {
-    if (Get(i) == *value) {
-      Clear(i);
-      // Users of FixedArrayOfWeakCells should make sure that there are no
-      // duplicates.
-      return true;
-    }
-    i = (i + 1) % Length();
-    if (i == first_index) return false;
-  }
-  UNREACHABLE();
-}
-
-
-// static
-Handle<FixedArrayOfWeakCells> FixedArrayOfWeakCells::Allocate(
-    Isolate* isolate, int size, Handle<FixedArrayOfWeakCells> initialize_from) {
-  DCHECK_LE(0, size);
-  Handle<FixedArray> result =
-      isolate->factory()->NewUninitializedFixedArray(size + kFirstIndex);
-  int index = 0;
-  if (!initialize_from.is_null()) {
-    DCHECK(initialize_from->Length() <= size);
-    Handle<FixedArray> raw_source = Handle<FixedArray>::cast(initialize_from);
-    // Copy the entries without compacting, since the PrototypeInfo relies on
-    // the index of the entries not to change.
-    while (index < raw_source->length()) {
-      result->set(index, raw_source->get(index));
-      index++;
-    }
-  }
-  while (index < result->length()) {
-    result->set(index, Smi::kZero);
-    index++;
-  }
-  return Handle<FixedArrayOfWeakCells>::cast(result);
-}
-
 // static
 Handle<ArrayList> ArrayList::Add(Isolate* isolate, Handle<ArrayList> array,
                                  Handle<Object> obj) {
@@ -10580,8 +10463,8 @@ Handle<WeakArrayList> WeakArrayList::AddToEnd(Isolate* isolate,
                                               MaybeObjectHandle value) {
   int length = array->length();
   array = EnsureSpace(isolate, array, length + 1);
-  // Check that GC didn't remove elements from the array.
-  DCHECK_EQ(array->length(), length);
+  // Reload length; GC might have removed elements from the array.
+  length = array->length();
   array->Set(length, *value);
   array->set_length(length + 1);
   return array;

src/objects.h

@@ -107,7 +107,6 @@
 //         - ScopeInfo
 //         - ModuleInfo
 //         - ScriptContextTable
-//         - FixedArrayOfWeakCells
 //       - FixedDoubleArray
 //     - Name
 //       - String
@@ -789,7 +788,6 @@ class ZoneForwardList;
   V(FixedArray)                                \
   V(FixedArrayBase)                            \
   V(FixedArrayExact)                           \
-  V(FixedArrayOfWeakCells)                     \
   V(FixedBigInt64Array)                        \
   V(FixedBigUint64Array)                       \
   V(FixedDoubleArray)                          \
@@ -961,7 +959,6 @@ class ZoneForwardList;
   V(FeedbackMetadata, FEEDBACK_METADATA_TYPE)                          \
   V(FeedbackVector, FEEDBACK_VECTOR_TYPE)                              \
   V(FixedArrayExact, FIXED_ARRAY_TYPE)                                 \
-  V(FixedArrayOfWeakCells, FIXED_ARRAY_TYPE)                           \
   V(FixedDoubleArray, FIXED_DOUBLE_ARRAY_TYPE)                         \
   V(Foreign, FOREIGN_TYPE)                                             \
   V(FreeSpace, FREE_SPACE_TYPE)                                        \

src/objects/fixed-array-inl.h

@@ -24,7 +24,6 @@ CAST_ACCESSOR(FixedArrayBase)
 CAST_ACCESSOR(FixedDoubleArray)
 CAST_ACCESSOR(FixedTypedArrayBase)
 CAST_ACCESSOR(TemplateList)
-CAST_ACCESSOR(FixedArrayOfWeakCells)
 CAST_ACCESSOR(WeakFixedArray)
 CAST_ACCESSOR(WeakArrayList)
 
@@ -297,48 +296,6 @@ HeapObject* WeakArrayList::Iterator::Next() {
   return nullptr;
 }
 
-Object* FixedArrayOfWeakCells::Get(int index) const {
-  Object* raw = FixedArray::cast(this)->get(index + kFirstIndex);
-  if (raw->IsSmi()) return raw;
-  DCHECK(raw->IsWeakCell());
-  return WeakCell::cast(raw)->value();
-}
-
-bool FixedArrayOfWeakCells::IsEmptySlot(int index) const {
-  DCHECK(index < Length());
-  return Get(index)->IsSmi();
-}
-
-void FixedArrayOfWeakCells::Clear(int index) {
-  FixedArray::cast(this)->set(index + kFirstIndex, Smi::kZero);
-}
-
-int FixedArrayOfWeakCells::Length() const {
-  return FixedArray::cast(this)->length() - kFirstIndex;
-}
-
-int FixedArrayOfWeakCells::last_used_index() const {
-  return Smi::ToInt(FixedArray::cast(this)->get(kLastUsedIndexIndex));
-}
-
-void FixedArrayOfWeakCells::set_last_used_index(int index) {
-  FixedArray::cast(this)->set(kLastUsedIndexIndex, Smi::FromInt(index));
-}
-
-template <class T>
-T* FixedArrayOfWeakCells::Iterator::Next() {
-  if (list_ != nullptr) {
-    // Assert that list did not change during iteration.
-    DCHECK_EQ(last_used_index_, list_->last_used_index());
-    while (index_ < list_->Length()) {
-      Object* item = list_->Get(index_++);
-      if (item != Empty()) return T::cast(item);
-    }
-    list_ = nullptr;
-  }
-  return nullptr;
-}
-
 int ArrayList::Length() const {
   if (FixedArray::cast(this)->length() == 0) return 0;
   return Smi::ToInt(FixedArray::cast(this)->get(kLengthIndex));

src/objects/fixed-array.h

@@ -406,79 +406,6 @@ class WeakArrayList : public HeapObject {
   DISALLOW_IMPLICIT_CONSTRUCTORS(WeakArrayList);
 };
 
-// Deprecated. Use WeakFixedArray instead.
-class FixedArrayOfWeakCells : public FixedArray {
- public:
-  // If |maybe_array| is not a FixedArrayOfWeakCells, a fresh one will be
-  // allocated. This function does not check if the value exists already,
-  // callers must ensure this themselves if necessary.
-  static Handle<FixedArrayOfWeakCells> Add(Isolate* isolate,
-                                           Handle<Object> maybe_array,
-                                           Handle<HeapObject> value,
-                                           int* assigned_index = nullptr);
-
-  // Returns true if an entry was found and removed.
-  bool Remove(Handle<HeapObject> value);
-
-  class NullCallback {
-   public:
-    static void Callback(Object* value, int old_index, int new_index) {}
-  };
-
-  template <class CompactionCallback>
-  void Compact(Isolate* isolate);
-
-  inline Object* Get(int index) const;
-  inline void Clear(int index);
-  inline int Length() const;
-
-  inline bool IsEmptySlot(int index) const;
-  static Object* Empty() { return Smi::kZero; }
-
-  class Iterator {
-   public:
-    explicit Iterator(Object* maybe_array) : list_(nullptr) {
-      Reset(maybe_array);
-    }
-    void Reset(Object* maybe_array);
-
-    template <class T>
-    inline T* Next();
-
-   private:
-    int index_;
-    FixedArrayOfWeakCells* list_;
-#ifdef DEBUG
-    int last_used_index_;
-    DisallowHeapAllocation no_gc_;
-#endif  // DEBUG
-    DISALLOW_COPY_AND_ASSIGN(Iterator);
-  };
-
-  DECL_CAST(FixedArrayOfWeakCells)
-
- private:
-  static const int kLastUsedIndexIndex = 0;
-  static const int kFirstIndex = 1;
-
-  static Handle<FixedArrayOfWeakCells> Allocate(
-      Isolate* isolate, int size,
-      Handle<FixedArrayOfWeakCells> initialize_from);
-
-  static void Set(Isolate* isolate, Handle<FixedArrayOfWeakCells> array,
-                  int index, Handle<HeapObject> value);
-  inline void clear(int index);
-
-  inline int last_used_index() const;
-  inline void set_last_used_index(int index);
-
-  // Disallow inherited setters.
-  void set(int index, Smi* value);
-  void set(int index, Object* value);
-  void set(int index, Object* value, WriteBarrierMode mode);
-  DISALLOW_IMPLICIT_CONSTRUCTORS(FixedArrayOfWeakCells);
-};
-
 // Generic array grows dynamically with O(1) amortized insertion.
 //
 // ArrayList is a FixedArray with static convenience methods for adding more

src/wasm/wasm-objects-inl.h

@@ -86,8 +86,7 @@ ACCESSORS(WasmTableObject, dispatch_tables, FixedArray, kDispatchTablesOffset)
 // WasmMemoryObject
 ACCESSORS(WasmMemoryObject, array_buffer, JSArrayBuffer, kArrayBufferOffset)
 SMI_ACCESSORS(WasmMemoryObject, maximum_pages, kMaximumPagesOffset)
-OPTIONAL_ACCESSORS(WasmMemoryObject, instances, FixedArrayOfWeakCells,
-                   kInstancesOffset)
+OPTIONAL_ACCESSORS(WasmMemoryObject, instances, WeakArrayList, kInstancesOffset)
 
 // WasmGlobalObject
 ACCESSORS(WasmGlobalObject, array_buffer, JSArrayBuffer, kArrayBufferOffset)

src/wasm/wasm-objects.cc

@@ -1019,12 +1019,13 @@ bool WasmMemoryObject::has_full_guard_region(Isolate* isolate) {
 void WasmMemoryObject::AddInstance(Isolate* isolate,
                                    Handle<WasmMemoryObject> memory,
                                    Handle<WasmInstanceObject> instance) {
-  Handle<FixedArrayOfWeakCells> old_instances =
+  Handle<WeakArrayList> old_instances =
       memory->has_instances()
-          ? Handle<FixedArrayOfWeakCells>(memory->instances(), isolate)
-          : Handle<FixedArrayOfWeakCells>::null();
-  Handle<FixedArrayOfWeakCells> new_instances =
-      FixedArrayOfWeakCells::Add(isolate, old_instances, instance);
+          ? Handle<WeakArrayList>(memory->instances(), isolate)
+          : handle(ReadOnlyRoots(isolate->heap()).empty_weak_array_list(),
+                   isolate);
+  Handle<WeakArrayList> new_instances = WeakArrayList::AddToEnd(
+      isolate, old_instances, MaybeObjectHandle::Weak(instance));
   memory->set_instances(*new_instances);
   Handle<JSArrayBuffer> buffer(memory->array_buffer(), isolate);
   SetInstanceMemory(instance, buffer);
@@ -1033,7 +1034,7 @@ void WasmMemoryObject::AddInstance(Isolate* isolate,
 void WasmMemoryObject::RemoveInstance(Handle<WasmMemoryObject> memory,
                                       Handle<WasmInstanceObject> instance) {
   if (memory->has_instances()) {
-    memory->instances()->Remove(instance);
+    memory->instances()->RemoveOne(MaybeObjectHandle::Weak(instance));
   }
 }
 
@@ -1059,14 +1060,17 @@ int32_t WasmMemoryObject::Grow(Isolate* isolate,
   }
 
   if (memory_object->has_instances()) {
-    Handle<FixedArrayOfWeakCells> instances(memory_object->instances(),
-                                            isolate);
-    for (int i = 0; i < instances->Length(); i++) {
-      Object* elem = instances->Get(i);
-      if (!elem->IsWasmInstanceObject()) continue;
-      Handle<WasmInstanceObject> instance(WasmInstanceObject::cast(elem),
-                                          isolate);
-      SetInstanceMemory(instance, new_buffer);
+    Handle<WeakArrayList> instances(memory_object->instances(), isolate);
+    for (int i = 0; i < instances->length(); i++) {
+      MaybeObject* elem = instances->Get(i);
+      HeapObject* heap_object;
+      if (elem->ToWeakHeapObject(&heap_object)) {
+        Handle<WasmInstanceObject> instance(
+            WasmInstanceObject::cast(heap_object), isolate);
+        SetInstanceMemory(instance, new_buffer);
+      } else {
+        DCHECK(elem->IsClearedWeakHeapObject());
+      }
     }
   }
   memory_object->set_array_buffer(*new_buffer);

src/wasm/wasm-objects.h

@@ -34,7 +34,6 @@ using FunctionSig = Signature<ValueType>;
 
 class BreakPoint;
 class JSArrayBuffer;
-class FixedArrayOfWeakCells;
 class SeqOneByteString;
 class WasmDebugInfo;
 class WasmInstanceObject;
@@ -284,7 +283,7 @@ class WasmMemoryObject : public JSObject {
 
   DECL_ACCESSORS(array_buffer, JSArrayBuffer)
   DECL_INT_ACCESSORS(maximum_pages)
-  DECL_OPTIONAL_ACCESSORS(instances, FixedArrayOfWeakCells)
+  DECL_OPTIONAL_ACCESSORS(instances, WeakArrayList)
 
 // Layout description.
 #define WASM_MEMORY_OBJECT_FIELDS(V)   \

test/cctest/heap/test-heap.cc

@@ -4773,20 +4773,6 @@ TEST(WritableVsImmortalRoots) {
   }
 }
 
-TEST(FixedArrayOfWeakCells) {
-  CcTest::InitializeVM();
-  v8::HandleScope scope(CcTest::isolate());
-  Isolate* isolate = CcTest::i_isolate();
-
-  Handle<HeapNumber> number = isolate->factory()->NewHeapNumber(1);
-  Handle<FixedArrayOfWeakCells> array =
-      FixedArrayOfWeakCells::Add(isolate, Handle<Object>(), number);
-  array->Remove(number);
-  array->Compact<FixedArrayOfWeakCells::NullCallback>(isolate);
-  FixedArrayOfWeakCells::Add(isolate, array, number);
-}
-
-
 TEST(PreprocessStackTrace) {
   // Do not automatically trigger early GC.
   FLAG_gc_interval = -1;