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https://github.com/LadybirdBrowser/ladybird.git
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d4deafe5fe
When an object becomes too big (currently 64 properties or more), we change its shape to a dictionary and don't do any further transitions. However, this means the Shape of the object no longer changes, so the cache invalidation check of `current_shape != cache.shape` is no longer a valid check. This fixes that by keeping track of a generation number for the Shape both on the Shape object and in the cache, allowing that to be checked instead of the Shape identity. The generation is incremented whenever the dictionary is mutated. Fixes stale cache lookups on Gmail preventing emails from being displayed. I was not able to produce a reproduction for this, plus the generation count was over the 20k mark on Gmail.
133 lines
3.9 KiB
C++
133 lines
3.9 KiB
C++
/*
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* Copyright (c) 2021-2024, Andreas Kling <andreas@ladybird.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/NonnullOwnPtr.h>
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#include <AK/OwnPtr.h>
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#include <AK/Utf16FlyString.h>
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#include <LibGC/CellAllocator.h>
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#include <LibGC/Weak.h>
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#include <LibGC/WeakInlines.h>
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#include <LibJS/Bytecode/IdentifierTable.h>
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#include <LibJS/Bytecode/Label.h>
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#include <LibJS/Bytecode/StringTable.h>
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#include <LibJS/Export.h>
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#include <LibJS/Forward.h>
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#include <LibJS/Heap/Cell.h>
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#include <LibJS/LocalVariable.h>
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#include <LibJS/Runtime/EnvironmentCoordinate.h>
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#include <LibJS/SourceRange.h>
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namespace JS::Bytecode {
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// Represents one polymorphic inline cache used for property lookups.
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struct PropertyLookupCache {
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static constexpr size_t max_number_of_shapes_to_remember = 4;
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struct Entry {
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enum class Type {
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Empty,
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AddOwnProperty,
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ChangeOwnProperty,
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GetOwnProperty,
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ChangePropertyInPrototypeChain,
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GetPropertyInPrototypeChain,
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};
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Type type { Type::Empty };
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GC::Weak<Shape> from_shape;
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GC::Weak<Shape> shape;
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Optional<u32> property_offset;
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GC::Weak<Object> prototype;
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GC::Weak<PrototypeChainValidity> prototype_chain_validity;
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Optional<u32> shape_dictionary_generation;
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};
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AK::Array<Entry, max_number_of_shapes_to_remember> entries;
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};
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struct GlobalVariableCache : public PropertyLookupCache {
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u64 environment_serial_number { 0 };
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u32 environment_binding_index { 0 };
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bool has_environment_binding_index { false };
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bool in_module_environment { false };
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};
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struct SourceRecord {
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u32 source_start_offset {};
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u32 source_end_offset {};
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};
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class JS_API Executable final : public Cell {
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GC_CELL(Executable, Cell);
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GC_DECLARE_ALLOCATOR(Executable);
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public:
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Executable(
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Vector<u8> bytecode,
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NonnullOwnPtr<IdentifierTable>,
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NonnullOwnPtr<StringTable>,
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NonnullOwnPtr<RegexTable>,
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Vector<Value> constants,
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NonnullRefPtr<SourceCode const>,
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size_t number_of_property_lookup_caches,
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size_t number_of_global_variable_caches,
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size_t number_of_registers,
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bool is_strict_mode);
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virtual ~Executable() override;
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Utf16FlyString name;
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Vector<u8> bytecode;
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Vector<PropertyLookupCache> property_lookup_caches;
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Vector<GlobalVariableCache> global_variable_caches;
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NonnullOwnPtr<StringTable> string_table;
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NonnullOwnPtr<IdentifierTable> identifier_table;
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NonnullOwnPtr<RegexTable> regex_table;
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Vector<Value> constants;
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NonnullRefPtr<SourceCode const> source_code;
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size_t number_of_registers { 0 };
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bool is_strict_mode { false };
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struct ExceptionHandlers {
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size_t start_offset;
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size_t end_offset;
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Optional<size_t> handler_offset;
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Optional<size_t> finalizer_offset;
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};
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Vector<ExceptionHandlers> exception_handlers;
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Vector<size_t> basic_block_start_offsets;
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HashMap<size_t, SourceRecord> source_map;
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Vector<LocalVariable> local_variable_names;
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size_t local_index_base { 0 };
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size_t argument_index_base { 0 };
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Optional<IdentifierTableIndex> length_identifier;
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Utf16String const& get_string(StringTableIndex index) const { return string_table->get(index); }
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Utf16FlyString const& get_identifier(IdentifierTableIndex index) const { return identifier_table->get(index); }
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Optional<Utf16FlyString const&> get_identifier(Optional<IdentifierTableIndex> const& index) const
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{
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if (!index.has_value())
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return {};
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return get_identifier(*index);
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}
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[[nodiscard]] Optional<ExceptionHandlers const&> exception_handlers_for_offset(size_t offset) const;
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[[nodiscard]] UnrealizedSourceRange source_range_at(size_t offset) const;
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void dump() const;
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private:
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virtual void visit_edges(Visitor&) override;
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};
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}
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