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https://github.com/LadybirdBrowser/ladybird.git
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5e6e1fd482
This patch adds JS::Shape, which implements a transition tree for our Object class. Object property keys, prototypes and attributes are now stored in a Shape, and each Object has a Shape. When adding a property to an Object, we make a transition from the old Shape to a new Shape. If we've made the same exact transition in the past (with another Object), we reuse the same transition and both objects may now share a Shape. This will become the foundation of inline caching and other engine optimizations in the future. :^)
78 lines
2.8 KiB
C++
78 lines
2.8 KiB
C++
/*
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* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <AK/FlyString.h>
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#include <AK/HashMap.h>
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#include <AK/OwnPtr.h>
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#include <LibJS/Forward.h>
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#include <LibJS/Runtime/Cell.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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size_t offset { 0 };
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u8 attributes { 0 };
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};
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class Shape final : public Cell {
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public:
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virtual ~Shape() override;
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Shape();
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Shape(Shape* previous_shape, const FlyString& property_name, u8 property_attributes);
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Shape(Shape* previous_shape, Object* new_prototype);
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Shape* create_put_transition(const FlyString& name, u8 attributes);
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Shape* create_prototype_transition(Object* new_prototype);
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Object* prototype() { return m_prototype; }
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const Object* prototype() const { return m_prototype; }
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Optional<PropertyMetadata> lookup(const FlyString&) const;
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const HashMap<FlyString, PropertyMetadata>& property_table() const;
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size_t property_count() const;
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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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virtual const char* class_name() const override { return "Shape"; }
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virtual void visit_children(Visitor&) override;
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void ensure_property_table() const;
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mutable OwnPtr<HashMap<FlyString, PropertyMetadata>> m_property_table;
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HashMap<FlyString, Shape*> m_forward_transitions;
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Shape* m_previous { nullptr };
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FlyString m_property_name;
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u8 m_property_attributes { 0 };
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Object* m_prototype { nullptr };
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};
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}
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