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3d92c26445
We previously had a concept of unique shapes, which meant that they couldn't be shared between multiple objects. Object shapes became unique in three situations: - They were the shape of the global object. - They had more than 100 properties added to them. - They had one or more properties deleted from them. Unfortunately, unique shapes presented an annoying problem for inline caches, and we added a "unique shape serial number" for being able to tell that a unique shape had been mutated. This patch gets rid of the concept of unique shapes, simplifying all the caching code, since inline caches can now simply perform a shape check and then we're good. To make this possible, we now have the concept of delete transitions, which occur when a property is deleted from a shape. Note that this patch by itself introduces a performance regression in some situtations, since we now create a lot more shapes, and marking their property keys can be very heavy. This will be addressed in a subsequent patch.
116 lines
3.6 KiB
C++
116 lines
3.6 KiB
C++
/*
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* Copyright (c) 2020-2021, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/HashMap.h>
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#include <AK/OwnPtr.h>
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#include <AK/StringView.h>
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#include <AK/WeakPtr.h>
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#include <AK/Weakable.h>
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#include <LibJS/Forward.h>
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#include <LibJS/Heap/Cell.h>
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#include <LibJS/Runtime/PropertyAttributes.h>
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#include <LibJS/Runtime/StringOrSymbol.h>
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#include <LibJS/Runtime/Value.h>
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namespace JS {
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struct PropertyMetadata {
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u32 offset { 0 };
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PropertyAttributes attributes { 0 };
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};
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struct TransitionKey {
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StringOrSymbol property_key;
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PropertyAttributes attributes { 0 };
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bool operator==(TransitionKey const& other) const
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{
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return property_key == other.property_key && attributes == other.attributes;
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}
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};
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class Shape final
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: public Cell
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, public Weakable<Shape> {
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JS_CELL(Shape, Cell);
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JS_DECLARE_ALLOCATOR(Shape);
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public:
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virtual ~Shape() override = default;
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enum class TransitionType {
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Invalid,
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Put,
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Configure,
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Prototype,
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Delete,
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};
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Shape* create_put_transition(StringOrSymbol const&, PropertyAttributes attributes);
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Shape* create_configure_transition(StringOrSymbol const&, PropertyAttributes attributes);
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Shape* create_prototype_transition(Object* new_prototype);
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[[nodiscard]] NonnullGCPtr<Shape> create_delete_transition(StringOrSymbol const&);
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void add_property_without_transition(StringOrSymbol const&, PropertyAttributes);
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void add_property_without_transition(PropertyKey const&, PropertyAttributes);
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Realm& realm() const { return m_realm; }
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Object* prototype() { return m_prototype; }
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Object const* prototype() const { return m_prototype; }
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Optional<PropertyMetadata> lookup(StringOrSymbol const&) const;
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OrderedHashMap<StringOrSymbol, PropertyMetadata> const& property_table() const;
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u32 property_count() const { return m_property_count; }
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struct Property {
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StringOrSymbol key;
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PropertyMetadata value;
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};
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void set_prototype_without_transition(Object* new_prototype) { m_prototype = new_prototype; }
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private:
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explicit Shape(Realm&);
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Shape(Shape& previous_shape, StringOrSymbol const& property_key, PropertyAttributes attributes, TransitionType);
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Shape(Shape& previous_shape, StringOrSymbol const& property_key, TransitionType);
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Shape(Shape& previous_shape, Object* new_prototype);
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virtual void visit_edges(Visitor&) override;
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Shape* get_or_prune_cached_forward_transition(TransitionKey const&);
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Shape* get_or_prune_cached_prototype_transition(Object* prototype);
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[[nodiscard]] GCPtr<Shape> get_or_prune_cached_delete_transition(StringOrSymbol const&);
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void ensure_property_table() const;
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NonnullGCPtr<Realm> m_realm;
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mutable OwnPtr<OrderedHashMap<StringOrSymbol, PropertyMetadata>> m_property_table;
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OwnPtr<HashMap<TransitionKey, WeakPtr<Shape>>> m_forward_transitions;
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OwnPtr<HashMap<GCPtr<Object>, WeakPtr<Shape>>> m_prototype_transitions;
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OwnPtr<HashMap<StringOrSymbol, WeakPtr<Shape>>> m_delete_transitions;
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GCPtr<Shape> m_previous;
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StringOrSymbol m_property_key;
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GCPtr<Object> m_prototype;
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u32 m_property_count { 0 };
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PropertyAttributes m_attributes { 0 };
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TransitionType m_transition_type { TransitionType::Invalid };
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};
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}
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template<>
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struct AK::Traits<JS::TransitionKey> : public DefaultTraits<JS::TransitionKey> {
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static unsigned hash(const JS::TransitionKey& key)
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{
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return pair_int_hash(key.attributes.bits(), Traits<JS::StringOrSymbol>::hash(key.property_key));
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}
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};
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