[runtime] Cache prototype chain enumerable keys in PrototypeInfo

This CL adds a prototype_chain_enum_cache to cache the enumeration of a
prototype and its entire chain on the PrototypeInfo. It can improve for-in
performance via simply merging the receiver enumeration with this cache.

It improves the score of JetStream2-tagcloud-SP case by ~9% on IA Chromebook.

Contributed by tao.pan@intel.com

Change-Id: Ib40bfe41e772672337155584672f06fa1ba1e70d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1870844
Commit-Queue: Shiyu Zhang <shiyu.zhang@intel.com>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65224}

src/objects/js-objects.cc

@@ -4398,6 +4398,11 @@ void InvalidateOnePrototypeValidityCellInternal(Map map) {
     Cell cell = Cell::cast(maybe_cell);
     cell.set_value(Smi::FromInt(Map::kPrototypeChainInvalid));
   }
+  Object maybe_prototype_info = map.prototype_info();
+  if (maybe_prototype_info.IsPrototypeInfo()) {
+    PrototypeInfo prototype_info = PrototypeInfo::cast(maybe_prototype_info);
+    prototype_info.set_prototype_chain_enum_cache(Object());
+  }
 }
 
 void InvalidatePrototypeChainsInternal(Map map) {

src/objects/keys.cc

@@ -44,6 +44,42 @@ static bool ContainsOnlyValidKeys(Handle<FixedArray> array) {
   return true;
 }
 
+static int AddKey(Object key, Handle<FixedArray> combined_keys,
+                  Handle<DescriptorArray> descs, int nof_descriptors,
+                  int target) {
+  for (InternalIndex i : InternalIndex::Range(nof_descriptors)) {
+    if (descs->GetKey(i) == key) return 0;
+  }
+  combined_keys->set(target, key);
+  return 1;
+}
+
+static Handle<FixedArray> CombineKeys(Isolate* isolate,
+                                      Handle<FixedArray> own_keys,
+                                      Handle<FixedArray> prototype_chain_keys,
+                                      Handle<JSReceiver> receiver) {
+  int prototype_chain_keys_length = prototype_chain_keys->length();
+  if (prototype_chain_keys_length == 0) return own_keys;
+
+  Map map = receiver->map();
+  int nof_descriptors = map.NumberOfOwnDescriptors();
+  if (nof_descriptors == 0) return prototype_chain_keys;
+
+  Handle<DescriptorArray> descs(map.instance_descriptors(), isolate);
+  int own_keys_length = own_keys.is_null() ? 0 : own_keys->length();
+  Handle<FixedArray> combined_keys = isolate->factory()->NewFixedArray(
+      own_keys_length + prototype_chain_keys_length);
+  if (own_keys_length != 0) {
+    own_keys->CopyTo(0, *combined_keys, 0, own_keys_length);
+  }
+  int target_keys_length = own_keys_length;
+  for (int i = 0; i < prototype_chain_keys_length; i++) {
+    target_keys_length += AddKey(prototype_chain_keys->get(i), combined_keys,
+                                 descs, nof_descriptors, target_keys_length);
+  }
+  return FixedArray::ShrinkOrEmpty(isolate, combined_keys, target_keys_length);
+}
+
 }  // namespace
 
 // static
@@ -68,6 +104,14 @@ Handle<FixedArray> KeyAccumulator::GetKeys(GetKeysConversion convert) {
   Handle<FixedArray> result =
       OrderedHashSet::ConvertToKeysArray(isolate(), keys(), convert);
   DCHECK(ContainsOnlyValidKeys(result));
+
+  if (try_prototype_info_cache_ && !first_prototype_map_.is_null()) {
+    PrototypeInfo::cast(first_prototype_map_->prototype_info())
+        .set_prototype_chain_enum_cache(*result);
+    Map::GetOrCreatePrototypeChainValidityCell(
+        Handle<Map>(receiver_->map(), isolate_), isolate_);
+    DCHECK(first_prototype_map_->IsPrototypeValidityCellValid());
+  }
   return result;
 }
 
@@ -275,6 +319,9 @@ void FastKeyAccumulator::Prepare() {
   DisallowHeapAllocation no_gc;
   // Directly go for the fast path for OWN_ONLY keys.
   if (mode_ == KeyCollectionMode::kOwnOnly) return;
+  // Check if we should try to create/use prototype info cache.
+  try_prototype_info_cache_ = TryPrototypeInfoCache(receiver_);
+  if (has_prototype_info_cache_) return;
   // Fully walk the prototype chain and find the last prototype with keys.
   is_receiver_simple_enum_ = false;
   has_empty_prototype_ = true;
@@ -432,6 +479,9 @@ MaybeHandle<FixedArray> FastKeyAccumulator::GetKeys(
     if (isolate_->has_pending_exception()) return MaybeHandle<FixedArray>();
   }
 
+  if (try_prototype_info_cache_) {
+    return GetKeysWithPrototypeInfoCache(keys_conversion);
+  }
   return GetKeysSlow(keys_conversion);
 }
 
@@ -503,12 +553,41 @@ MaybeHandle<FixedArray> FastKeyAccumulator::GetKeysSlow(
   accumulator.set_skip_indices(skip_indices_);
   accumulator.set_last_non_empty_prototype(last_non_empty_prototype_);
   accumulator.set_may_have_elements(may_have_elements_);
+  accumulator.set_first_prototype_map(first_prototype_map_);
+  accumulator.set_try_prototype_info_cache(try_prototype_info_cache_);
 
   MAYBE_RETURN(accumulator.CollectKeys(receiver_, receiver_),
                MaybeHandle<FixedArray>());
   return accumulator.GetKeys(keys_conversion);
 }
 
+MaybeHandle<FixedArray> FastKeyAccumulator::GetKeysWithPrototypeInfoCache(
+    GetKeysConversion keys_conversion) {
+  Handle<FixedArray> own_keys = KeyAccumulator::GetOwnEnumPropertyKeys(
+      isolate_, Handle<JSObject>::cast(receiver_));
+  Handle<FixedArray> prototype_chain_keys;
+  if (has_prototype_info_cache_) {
+    prototype_chain_keys =
+        handle(FixedArray::cast(
+                   PrototypeInfo::cast(first_prototype_map_->prototype_info())
+                       .prototype_chain_enum_cache()),
+               isolate_);
+  } else {
+    KeyAccumulator accumulator(isolate_, mode_, filter_);
+    accumulator.set_is_for_in(is_for_in_);
+    accumulator.set_skip_indices(skip_indices_);
+    accumulator.set_last_non_empty_prototype(last_non_empty_prototype_);
+    accumulator.set_may_have_elements(may_have_elements_);
+    accumulator.set_receiver(receiver_);
+    accumulator.set_first_prototype_map(first_prototype_map_);
+    accumulator.set_try_prototype_info_cache(try_prototype_info_cache_);
+    MAYBE_RETURN(accumulator.CollectKeys(first_prototype_, first_prototype_),
+                 MaybeHandle<FixedArray>());
+    prototype_chain_keys = accumulator.GetKeys(keys_conversion);
+  }
+  return CombineKeys(isolate_, own_keys, prototype_chain_keys, receiver_);
+}
+
 bool FastKeyAccumulator::MayHaveElements(JSReceiver receiver) {
   if (!receiver.IsJSObject()) return true;
   JSObject object = JSObject::cast(receiver);
@@ -517,6 +596,28 @@ bool FastKeyAccumulator::MayHaveElements(JSReceiver receiver) {
   return false;
 }
 
+bool FastKeyAccumulator::TryPrototypeInfoCache(Handle<JSReceiver> receiver) {
+  if (MayHaveElements(*receiver)) return false;
+  Handle<JSObject> object = Handle<JSObject>::cast(receiver);
+  if (!object->HasFastProperties()) return false;
+  if (object->HasNamedInterceptor()) return false;
+  if (object->IsAccessCheckNeeded() &&
+      !isolate_->MayAccess(handle(isolate_->context(), isolate_), object)) {
+    return false;
+  }
+  HeapObject prototype = receiver->map().prototype();
+  if (prototype.is_null()) return false;
+  if (!prototype.map().is_prototype_map()) return false;
+  first_prototype_ = handle(JSReceiver::cast(prototype), isolate_);
+  Handle<Map> map(prototype.map(), isolate_);
+  first_prototype_map_ = map;
+  has_prototype_info_cache_ = map->IsPrototypeValidityCellValid() &&
+                              PrototypeInfo::cast(map->prototype_info())
+                                  .prototype_chain_enum_cache()
+                                  .IsFixedArray();
+  return true;
+}
+
 namespace {
 
 enum IndexedOrNamed { kIndexed, kNamed };

src/objects/keys.h

@@ -87,6 +87,13 @@ class KeyAccumulator final {
   // indices.
   void set_is_for_in(bool value) { is_for_in_ = value; }
   void set_skip_indices(bool value) { skip_indices_ = value; }
+  void set_first_prototype_map(Handle<Map> value) {
+    first_prototype_map_ = value;
+  }
+  void set_try_prototype_info_cache(bool value) {
+    try_prototype_info_cache_ = value;
+  }
+  void set_receiver(Handle<JSReceiver> object) { receiver_ = object; }
   // The last_non_empty_prototype is used to limit the prototypes for which
   // we have to keep track of non-enumerable keys that can shadow keys
   // repeated on the prototype chain.
@@ -117,6 +124,8 @@ class KeyAccumulator final {
   // keys a Handle<FixedArray>. The OrderedHashSet is in-place converted to the
   // result list, a FixedArray containing all collected keys.
   Handle<FixedArray> keys_;
+  Handle<Map> first_prototype_map_;
+  Handle<JSReceiver> receiver_;
   Handle<JSReceiver> last_non_empty_prototype_;
   Handle<ObjectHashSet> shadowing_keys_;
   KeyCollectionMode mode_;
@@ -127,6 +136,7 @@ class KeyAccumulator final {
   // the shadow check.
   bool skip_shadow_check_ = true;
   bool may_have_elements_ = true;
+  bool try_prototype_info_cache_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(KeyAccumulator);
 };
@@ -160,13 +170,18 @@ class FastKeyAccumulator {
   void Prepare();
   MaybeHandle<FixedArray> GetKeysFast(GetKeysConversion convert);
   MaybeHandle<FixedArray> GetKeysSlow(GetKeysConversion convert);
+  MaybeHandle<FixedArray> GetKeysWithPrototypeInfoCache(
+      GetKeysConversion convert);
 
   MaybeHandle<FixedArray> GetOwnKeysWithUninitializedEnumCache();
 
   bool MayHaveElements(JSReceiver receiver);
+  bool TryPrototypeInfoCache(Handle<JSReceiver> receiver);
 
   Isolate* isolate_;
   Handle<JSReceiver> receiver_;
+  Handle<Map> first_prototype_map_;
+  Handle<JSReceiver> first_prototype_;
   Handle<JSReceiver> last_non_empty_prototype_;
   KeyCollectionMode mode_;
   PropertyFilter filter_;
@@ -175,6 +190,8 @@ class FastKeyAccumulator {
   bool is_receiver_simple_enum_ = false;
   bool has_empty_prototype_ = false;
   bool may_have_elements_ = true;
+  bool has_prototype_info_cache_ = false;
+  bool try_prototype_info_cache_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(FastKeyAccumulator);
 };

src/objects/prototype-info-inl.h

@@ -41,6 +41,8 @@ bool PrototypeInfo::HasObjectCreateMap() {
 
 ACCESSORS(PrototypeInfo, module_namespace, Object, kJsModuleNamespaceOffset)
 ACCESSORS(PrototypeInfo, prototype_users, Object, kPrototypeUsersOffset)
+ACCESSORS(PrototypeInfo, prototype_chain_enum_cache, Object,
+          kPrototypeChainEnumCacheOffset)
 WEAK_ACCESSORS(PrototypeInfo, object_create_map, kObjectCreateMapOffset)
 SMI_ACCESSORS(PrototypeInfo, registry_slot, kRegistrySlotOffset)
 SMI_ACCESSORS(PrototypeInfo, bit_field, kBitFieldOffset)

src/objects/prototype-info.h

@@ -30,6 +30,8 @@ class PrototypeInfo : public Struct {
   // this prototype, or Smi(0) if uninitialized.
   DECL_ACCESSORS(prototype_users, Object)
 
+  DECL_ACCESSORS(prototype_chain_enum_cache, Object)
+
   // [object_create_map]: A field caching the map for Object.create(prototype).
   static inline void SetObjectCreateMap(Handle<PrototypeInfo> info,
                                         Handle<Map> map);

src/objects/prototype-info.tq

@@ -5,6 +5,7 @@
 extern class PrototypeInfo extends Struct {
   js_module_namespace: JSModuleNamespace|Undefined;
   prototype_users: WeakArrayList|Zero;
+  prototype_chain_enum_cache: FixedArray|Object|Undefined;
   registry_slot: Smi;
   validity_cell: Object;
   object_create_map: Weak<Map>|Undefined;

test/mjsunit/for-in-special-cases.js

@@ -141,3 +141,129 @@ for_in_string_prototype();
     assertEquals(['prop2', 'prop1'], Accumulate(derived2));
   }
 })();
+
+(function for_in_prototype_itself_change() {
+  let prototype1 = {prop: 0, prop1: 1};
+  let derived1 = {prop2: 2, prop3: 3};
+
+  Object.setPrototypeOf(derived1, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop2', 'prop3', 'prop', 'prop1'], Accumulate(derived1));
+  }
+
+  prototype1.prop3 = 3;
+  let derived2 = {prop4: 4, prop5: 5};
+  Object.setPrototypeOf(derived2, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop4', 'prop5', 'prop', 'prop1', 'prop3'], Accumulate(derived2));
+  }
+})();
+
+(function for_in_prototype_change() {
+  let prototype1 = {prop: 0, prop1: 1};
+  let derived1 = {prop2: 2, prop3: 3};
+
+  Object.setPrototypeOf(derived1, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop2', 'prop3', 'prop', 'prop1'], Accumulate(derived1));
+  }
+
+  prototype1.__proto__ = {prop4: 4, prop5: 5};
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop2', 'prop3', 'prop', 'prop1', 'prop4', 'prop5'], Accumulate(derived1));
+  }
+
+  derived1.__proto__ = {prop6: 6, prop7: 7};
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop2', 'prop3', 'prop6', 'prop7'], Accumulate(derived1));
+  }
+})();
+
+(function for_in_non_enumerable1() {
+  let prototype1 = {prop: 0};
+  let derived1 = Object.create(prototype1, {
+    prop1: {enumerable: false, configurable: true, value: 1},
+  });
+  Object.setPrototypeOf(derived1, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop'], Accumulate(derived1));
+  }
+
+  let derived2 = {prop2: 2};
+  Object.setPrototypeOf(derived2, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop2', 'prop'], Accumulate(derived2));
+  }
+})();
+
+(function for_in_non_enumerable2() {
+  let prototype1 = {prop: 0};
+  let derived1 = {prop1: 1};
+  Object.setPrototypeOf(derived1, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop1', 'prop'], Accumulate(derived1));
+  }
+
+  let derived2 = Object.create(prototype1, {
+    prop: {enumerable: false, configurable: true, value: 0},
+    prop2: {enumerable: true, configurable: true, value: 2}
+  });
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop2'], Accumulate(derived2));
+  }
+})();
+
+(function for_in_same_key1() {
+  let prototype1 = {prop: 0, prop1: 1};
+  let derived1 = {prop: 0, prop2: 1};
+  Object.setPrototypeOf(derived1, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop', 'prop2', 'prop1'], Accumulate(derived1));
+  }
+
+  let derived2 = {prop3: 3, prop4: 4};
+  Object.setPrototypeOf(derived2, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop3', 'prop4', 'prop', 'prop1'], Accumulate(derived2));
+  }
+})();
+
+(function for_in_same_key2() {
+  let prototype1 = {prop: 0, prop1: 1};
+  let derived1 = {prop2: 2, prop3: 3};
+  Object.setPrototypeOf(derived1, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop2', 'prop3', 'prop', 'prop1'], Accumulate(derived1));
+  }
+
+  let derived2 = {prop: 0, prop4: 4};
+  Object.setPrototypeOf(derived2, prototype1);
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop', 'prop4', 'prop1'], Accumulate(derived2));
+  }
+})();
+
+(function for_in_redefine_property() {
+  Object.prototype.prop = 0;
+  let object1 = {prop1: 1, prop2: 2};
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop1', 'prop2', 'prop'], Accumulate(object1));
+  }
+
+  let object2 = {prop3: 3, prop4: 4};
+  Object.defineProperty(object2,
+    'prop', {enumerable: false, configurable: true, value: 0});
+  for (let i = 0; i < 3; i++) {
+    assertEquals(['prop3', 'prop4'], Accumulate(object2));
+  }
+})();
+
+(function for_in_empty_property() {
+  let prototype1 = {prop: 0};
+  let derived1 = Object.create(prototype1, {
+    prop: {enumerable: false, configurable: true, value: 0}
+  });
+  for (let i = 0; i < 3; i++) {
+    assertEquals([], Accumulate(derived1));
+  }
+})();