From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Andrey Belenko Date: Tue, 18 May 2021 20:16:39 +0200 Subject: Merged: [const-tracking] Generalize constness when delete properties Revision: d570bbe0c74ec4ae40d1abc34bea617ff2d63f26 BUG=chromium:1201938 Change-Id: I2745bd574d9f971b3f1e41d5084ec9e9fbbeef07 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2880214 diff --git a/src/builtins/builtins-internal-gen.cc b/src/builtins/builtins-internal-gen.cc index 4e315e5ef584c6be12592d135c4ab92a37c19cff..2ac3deda3bea9e85802821eca239dcce0b3dbb03 100644 --- a/src/builtins/builtins-internal-gen.cc +++ b/src/builtins/builtins-internal-gen.cc @@ -513,8 +513,8 @@ TF_BUILTIN(DeleteProperty, DeletePropertyBaseAssembler) { Label dictionary(this), dont_delete(this); GotoIf(IsDictionaryMap(receiver_map), &dictionary); - // Fast properties need to clear recorded slots, which can only be done - // in C++. + // Fast properties need to clear recorded slots and mark the deleted + // property as mutable, which can only be done in C++. Goto(&slow); BIND(&dictionary); diff --git a/src/objects/map-inl.h b/src/objects/map-inl.h index df9c93a49753700e059519dad8aaf8cb5dca1aea..d1356a306f6174c047284ed3178dda3199c09791 100644 --- a/src/objects/map-inl.h +++ b/src/objects/map-inl.h @@ -186,6 +186,10 @@ bool Map::TooManyFastProperties(StoreOrigin store_origin) const { } } +Name Map::GetLastDescriptorName(Isolate* isolate) const { + return instance_descriptors(isolate, kRelaxedLoad).GetKey(LastAdded()); +} + PropertyDetails Map::GetLastDescriptorDetails(Isolate* isolate) const { return instance_descriptors(isolate, kRelaxedLoad).GetDetails(LastAdded()); } diff --git a/src/objects/map-updater.cc b/src/objects/map-updater.cc index 64f3c14a8940e05871a0b4e942b673e61983242a..0e0c3372cd8368c70c78a9f0fa76ac6a1e6ae689 100644 --- a/src/objects/map-updater.cc +++ b/src/objects/map-updater.cc @@ -121,41 +121,6 @@ Handle MapUpdater::ReconfigureToDataField(InternalIndex descriptor, PropertyDetails old_details = old_descriptors_->GetDetails(modified_descriptor_); - // If the {descriptor} was "const" data field so far, we need to update the - // {old_map_} here, otherwise we could get the constants wrong, i.e. - // - // o.x = 1; - // change o.x's attributes to something else - // delete o.x; - // o.x = 2; - // - // could trick V8 into thinking that `o.x` is still 1 even after the second - // assignment. - // This situation is similar to what might happen with property deletion. - if (old_details.constness() == PropertyConstness::kConst && - old_details.location() == kField && - old_details.attributes() != new_attributes_) { - Handle field_type( - old_descriptors_->GetFieldType(modified_descriptor_), isolate_); - Map::GeneralizeField(isolate_, old_map_, descriptor, - PropertyConstness::kMutable, - old_details.representation(), field_type); - // The old_map_'s property must become mutable. - // Note, that the {old_map_} and {old_descriptors_} are not expected to be - // updated by the generalization if the map is already deprecated. - DCHECK_IMPLIES( - !old_map_->is_deprecated(), - PropertyConstness::kMutable == - old_descriptors_->GetDetails(modified_descriptor_).constness()); - // Although the property in the old map is marked as mutable we still - // treat it as constant when merging with the new path in transition tree. - // This is fine because up until this reconfiguration the field was - // known to be constant, so it's fair to proceed treating it as such - // during this reconfiguration session. The issue is that after the - // reconfiguration the original field might become mutable (see the delete - // example above). - } - // If property kind is not reconfigured merge the result with // representation/field type from the old descriptor. if (old_details.kind() == new_kind_) { diff --git a/src/objects/map.h b/src/objects/map.h index 561dc8b6bfeccc7b3a9d737f1afe646a688a4d00..ab4466d418dbc1a172f04bc4b926b62b37302214 100644 --- a/src/objects/map.h +++ b/src/objects/map.h @@ -633,6 +633,7 @@ class Map : public HeapObject { // chain state. inline bool IsPrototypeValidityCellValid() const; + inline Name GetLastDescriptorName(Isolate* isolate) const; inline PropertyDetails GetLastDescriptorDetails(Isolate* isolate) const; inline InternalIndex LastAdded() const; diff --git a/src/objects/property-details.h b/src/objects/property-details.h index af6f0cdaeb5bd70c9e83c33fc494f7e33d7f23d5..c8e597d397efaaae03d0f3282495ed27e3ab40a7 100644 --- a/src/objects/property-details.h +++ b/src/objects/property-details.h @@ -31,6 +31,12 @@ enum PropertyAttributes { // a non-existent property. }; +// Number of distinct bits in PropertyAttributes. +static const int kPropertyAttributesBitsCount = 3; + +static const int kPropertyAttributesCombinationsCount = + 1 << kPropertyAttributesBitsCount; + enum PropertyFilter { ALL_PROPERTIES = 0, ONLY_WRITABLE = 1, @@ -62,6 +68,11 @@ STATIC_ASSERT(SKIP_STRINGS == STATIC_ASSERT(SKIP_SYMBOLS == static_cast(v8::PropertyFilter::SKIP_SYMBOLS)); +// Assert that kPropertyAttributesBitsCount value matches the definition of +// ALL_ATTRIBUTES_MASK. +STATIC_ASSERT((ALL_ATTRIBUTES_MASK == (READ_ONLY | DONT_ENUM | DONT_DELETE)) == + (kPropertyAttributesBitsCount == 3)); + class Smi; class TypeInfo; diff --git a/src/objects/transitions.cc b/src/objects/transitions.cc index 0b81ad372608bbfed6a1db20ca230648b82095db..29813977d37e85c3d7243fa83b8f3c6f51d784bc 100644 --- a/src/objects/transitions.cc +++ b/src/objects/transitions.cc @@ -270,6 +270,34 @@ MaybeHandle TransitionsAccessor::FindTransitionToDataProperty( return Handle(target, isolate_); } +void TransitionsAccessor::ForEachTransitionTo( + Name name, const ForEachTransitionCallback& callback, + DisallowGarbageCollection* no_gc) { + DCHECK(name.IsUniqueName()); + switch (encoding()) { + case kPrototypeInfo: + case kUninitialized: + case kMigrationTarget: + return; + case kWeakRef: { + Map target = Map::cast(raw_transitions_->GetHeapObjectAssumeWeak()); + InternalIndex descriptor = target.LastAdded(); + DescriptorArray descriptors = target.instance_descriptors(kRelaxedLoad); + Name key = descriptors.GetKey(descriptor); + if (key == name) { + callback(target); + } + return; + } + case kFullTransitionArray: { + base::SharedMutexGuardIf scope( + isolate_->transition_array_access(), concurrent_access_); + return transitions().ForEachTransitionTo(name, callback); + } + } + UNREACHABLE(); +} + bool TransitionsAccessor::CanHaveMoreTransitions() { if (map_.is_dictionary_map()) return false; if (encoding() == kFullTransitionArray) { @@ -612,6 +640,21 @@ Map TransitionArray::SearchAndGetTarget(PropertyKind kind, Name name, return SearchDetailsAndGetTarget(transition, kind, attributes); } +void TransitionArray::ForEachTransitionTo( + Name name, const ForEachTransitionCallback& callback) { + int transition = SearchName(name, nullptr); + if (transition == kNotFound) return; + + int nof_transitions = number_of_transitions(); + DCHECK(transition < nof_transitions); + Name key = GetKey(transition); + for (; transition < nof_transitions && GetKey(transition) == key; + transition++) { + Map target = GetTarget(transition); + callback(target); + } +} + void TransitionArray::Sort() { DisallowGarbageCollection no_gc; // In-place insertion sort. diff --git a/src/objects/transitions.h b/src/objects/transitions.h index 4f992bc6cfdf0d937eba8c2485bd3b5e86b2d686..237cfcd0efa7679c44a2e2a02db08e8942a4850e 100644 --- a/src/objects/transitions.h +++ b/src/objects/transitions.h @@ -19,6 +19,9 @@ namespace v8 { namespace internal { +// Find all transitions with given name and calls the callback. +using ForEachTransitionCallback = std::function; + // TransitionsAccessor is a helper class to encapsulate access to the various // ways a Map can store transitions to other maps in its respective field at // Map::kTransitionsOrPrototypeInfo. @@ -68,6 +71,14 @@ class V8_EXPORT_PRIVATE TransitionsAccessor { return FindTransitionToDataProperty(name, kFieldOnly); } + // Find all transitions with given name and calls the callback. + // Neither GCs nor operations requiring Isolate::full_transition_array_access + // lock are allowed inside the callback. + // If any of the GC- or lock-requiring processing is necessary, it has to be + // done outside of the callback. + void ForEachTransitionTo(Name name, const ForEachTransitionCallback& callback, + DisallowGarbageCollection* no_gc); + inline Handle ExpectedTransitionKey(); inline Handle ExpectedTransitionTarget(); @@ -320,6 +331,10 @@ class TransitionArray : public WeakFixedArray { Map SearchDetailsAndGetTarget(int transition, PropertyKind kind, PropertyAttributes attributes); + // Find all transitions with given name and calls the callback. + void ForEachTransitionTo(Name name, + const ForEachTransitionCallback& callback); + inline int number_of_transitions() const; static bool CompactPrototypeTransitionArray(Isolate* isolate, diff --git a/src/runtime/runtime-object.cc b/src/runtime/runtime-object.cc index 2bb98e674cd29ae60392a926c915ce04e1f06edc..adb05f8b8d096ca89b8c2594e0ef837a3f0dfc19 100644 --- a/src/runtime/runtime-object.cc +++ b/src/runtime/runtime-object.cc @@ -18,6 +18,7 @@ #include "src/objects/js-array-inl.h" #include "src/objects/property-descriptor-object.h" #include "src/objects/property-descriptor.h" +#include "src/objects/property-details.h" #include "src/runtime/runtime-utils.h" #include "src/runtime/runtime.h" @@ -94,6 +95,54 @@ MaybeHandle Runtime::HasProperty(Isolate* isolate, namespace { +void GeneralizeAllTransitionsToFieldAsMutable(Isolate* isolate, Handle map, + Handle name) { + InternalIndex descriptor(map->NumberOfOwnDescriptors()); + + Handle target_maps[kPropertyAttributesCombinationsCount]; + int target_maps_count = 0; + + // Collect all outgoing field transitions. + { + DisallowGarbageCollection no_gc; + TransitionsAccessor transitions(isolate, *map, &no_gc); + transitions.ForEachTransitionTo( + *name, + [&](Map target) { + DCHECK_EQ(descriptor, target.LastAdded()); + DCHECK_EQ(*name, target.GetLastDescriptorName(isolate)); + PropertyDetails details = target.GetLastDescriptorDetails(isolate); + // Currently, we track constness only for fields. + if (details.kind() == kData && + details.constness() == PropertyConstness::kConst) { + target_maps[target_maps_count++] = handle(target, isolate); + } + DCHECK_IMPLIES(details.kind() == kAccessor, + details.constness() == PropertyConstness::kConst); + }, + &no_gc); + CHECK_LE(target_maps_count, kPropertyAttributesCombinationsCount); + } + + for (int i = 0; i < target_maps_count; i++) { + Handle target = target_maps[i]; + PropertyDetails details = + target->instance_descriptors(isolate, kRelaxedLoad) + .GetDetails(descriptor); + Handle field_type( + target->instance_descriptors(isolate, kRelaxedLoad) + .GetFieldType(descriptor), + isolate); + Map::GeneralizeField(isolate, target, descriptor, + PropertyConstness::kMutable, details.representation(), + field_type); + DCHECK_EQ(PropertyConstness::kMutable, + target->instance_descriptors(isolate, kRelaxedLoad) + .GetDetails(descriptor) + .constness()); + } +} + bool DeleteObjectPropertyFast(Isolate* isolate, Handle receiver, Handle raw_key) { // This implements a special case for fast property deletion: when the @@ -103,6 +152,8 @@ bool DeleteObjectPropertyFast(Isolate* isolate, Handle receiver, // (1) The receiver must be a regular object and the key a unique name. Handle receiver_map(receiver->map(), isolate); if (receiver_map->IsSpecialReceiverMap()) return false; + DCHECK(receiver_map->IsJSObjectMap()); + if (!raw_key->IsUniqueName()) return false; Handle key = Handle::cast(raw_key); // (2) The property to be deleted must be the last property. @@ -125,26 +176,6 @@ bool DeleteObjectPropertyFast(Isolate* isolate, Handle receiver, // Preconditions successful. No more bailouts after this point. - // If the {descriptor} was "const" so far, we need to update the - // {receiver_map} here, otherwise we could get the constants wrong, i.e. - // - // o.x = 1; - // delete o.x; - // o.x = 2; - // - // could trick V8 into thinking that `o.x` is still 1 even after the second - // assignment. - if (details.constness() == PropertyConstness::kConst && - details.location() == kField) { - Handle field_type(descriptors->GetFieldType(descriptor), - isolate); - Map::GeneralizeField(isolate, receiver_map, descriptor, - PropertyConstness::kMutable, details.representation(), - field_type); - DCHECK_EQ(PropertyConstness::kMutable, - descriptors->GetDetails(descriptor).constness()); - } - // Zap the property to avoid keeping objects alive. Zapping is not necessary // for properties stored in the descriptor array. if (details.location() == kField) { @@ -191,6 +222,30 @@ bool DeleteObjectPropertyFast(Isolate* isolate, Handle receiver, receiver->HeapObjectVerify(isolate); receiver->property_array().PropertyArrayVerify(isolate); #endif + + // If the {descriptor} was "const" so far, we need to update the + // {receiver_map} here, otherwise we could get the constants wrong, i.e. + // + // o.x = 1; + // [change o.x's attributes or reconfigure property kind] + // delete o.x; + // o.x = 2; + // + // could trick V8 into thinking that `o.x` is still 1 even after the second + // assignment. + + // Step 1: Migrate object to an up-to-date shape. + if (parent_map->is_deprecated()) { + JSObject::MigrateInstance(isolate, Handle::cast(receiver)); + parent_map = handle(receiver->map(), isolate); + } + + // Step 2: Mark outgoing transitions from the up-to-date version of the + // parent_map to same property name of any kind or attributes as mutable. + // Also migrate object to the up-to-date map to make the object shapes + // converge sooner. + GeneralizeAllTransitionsToFieldAsMutable(isolate, parent_map, key); + return true; } diff --git a/src/runtime/runtime.h b/src/runtime/runtime.h index 311238c9d56fe344b977d5f5c67d0b60775c61c3..86bb613d1810032544b4cf76108b957bad5eb2bc 100644 --- a/src/runtime/runtime.h +++ b/src/runtime/runtime.h @@ -755,9 +755,9 @@ class Runtime : public AllStatic { // Get the runtime intrinsic function table. static const Function* RuntimeFunctionTable(Isolate* isolate); - V8_WARN_UNUSED_RESULT static Maybe DeleteObjectProperty( - Isolate* isolate, Handle receiver, Handle key, - LanguageMode language_mode); + V8_EXPORT_PRIVATE V8_WARN_UNUSED_RESULT static Maybe + DeleteObjectProperty(Isolate* isolate, Handle receiver, + Handle key, LanguageMode language_mode); V8_EXPORT_PRIVATE V8_WARN_UNUSED_RESULT static MaybeHandle SetObjectProperty(Isolate* isolate, Handle object, Handle key,