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https://github.com/LadybirdBrowser/ladybird.git
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e123d48043
We specialize `Optional<T>` for value types that inherently support some kind of "empty" value or whose value range allow for a unlikely to be useful sentinel value that can mean "empty", instead of the boolean flag a regular Optional<T> needs to store. Because of padding, this often means saving 4 to 8 bytes per instance. By extending the new `SentinelOptional<T, Traits>`, these specializations are significantly simplified to just having to define what the sentinel value is, and how to identify a sentinel value.
76 lines
1.8 KiB
C++
76 lines
1.8 KiB
C++
/*
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* Copyright (c) 2024-2025, 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/Types.h>
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#include <LibJS/Forward.h>
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namespace JS::Bytecode {
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class Operand {
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public:
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enum class Type {
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Register,
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Local,
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Constant,
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Argument,
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};
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[[nodiscard]] bool operator==(Operand const&) const = default;
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explicit Operand(Type type, u32 index)
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: m_raw(to_underlying(type) << 29 | index)
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{
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}
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enum class ShouldMakeInvalid { Indeed };
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explicit Operand(ShouldMakeInvalid)
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: m_raw(0xffffffffu)
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{
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}
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explicit Operand(Register);
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[[nodiscard]] bool is_invalid() const { return m_raw == 0xffffffffu; }
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[[nodiscard]] bool is_register() const { return type() == Type::Register; }
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[[nodiscard]] bool is_local() const { return type() == Type::Local; }
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[[nodiscard]] bool is_constant() const { return type() == Type::Constant; }
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[[nodiscard]] Type type() const { return static_cast<Type>((m_raw & 0xe0000000u) >> 29); }
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[[nodiscard]] u32 index() const { return m_raw & 0x1fffffff; }
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[[nodiscard]] u32 raw() const { return m_raw; }
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[[nodiscard]] Register as_register() const;
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void offset_index_by(u32 offset)
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{
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m_raw &= 0x1fffffff;
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m_raw += offset;
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}
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private:
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u32 m_raw { 0 };
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};
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}
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namespace AK {
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template<>
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struct SentinelOptionalTraits<JS::Bytecode::Operand> {
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static JS::Bytecode::Operand sentinel_value() { return JS::Bytecode::Operand { JS::Bytecode::Operand::ShouldMakeInvalid::Indeed }; }
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static bool is_sentinel(JS::Bytecode::Operand const& value) { return value.is_invalid(); }
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};
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template<>
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class Optional<JS::Bytecode::Operand> : public SentinelOptional<JS::Bytecode::Operand> {
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public:
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using SentinelOptional::SentinelOptional;
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};
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}
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