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LibJS: Make Optional<IdentifierTableIndex> use less space

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We can use the index's invalid state to signal an empty optional.
This makes Optional<IdentifierTableIndex> 4 bytes instead of 8,
shrinking every bytecode instruction that uses these.
This commit is contained in:
Andreas Kling 2025-03-27 14:59:34 +00:00 • committed by Andreas Kling
parent 904beef6d2
commit a29d820f87
Notes: github-actions[bot] 2025-03-27 19:51:23 +00:00
1 changed files with 101 additions and 1 deletions
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102
Libraries/LibJS/Bytecode/IdentifierTable.h
View file

@ -13,7 +13,8 @@
namespace JS::Bytecode {
struct IdentifierTableIndex {
bool is_valid() const { return value != NumericLimits<u32>::max(); }
static constexpr u32 invalid = 0xffffffffu;
bool is_valid() const { return value != invalid; }
u32 value { 0 };
};
@ -34,3 +35,102 @@ private:
};
}
namespace AK {
template<>
class Optional<JS::Bytecode::IdentifierTableIndex> : public OptionalBase<JS::Bytecode::IdentifierTableIndex> {
template<typename U>
friend class Optional;
public:
using ValueType = JS::Bytecode::IdentifierTableIndex;
Optional() = default;
template<SameAs<OptionalNone> V>
Optional(V) { }
Optional(Optional<JS::Bytecode::IdentifierTableIndex> const& other)
{
if (other.has_value())
m_value = other.m_value;
}
Optional(Optional&& other)
: m_value(other.m_value)
{
}
template<typename U = JS::Bytecode::IdentifierTableIndex>
requires(!IsSame<OptionalNone, RemoveCVReference<U>>)
explicit(!IsConvertible<U&&, JS::Bytecode::IdentifierTableIndex>) Optional(U&& value)
requires(!IsSame<RemoveCVReference<U>, Optional<JS::Bytecode::IdentifierTableIndex>> && IsConstructible<JS::Bytecode::IdentifierTableIndex, U &&>)
: m_value(forward<U>(value))
{
}
template<SameAs<OptionalNone> V>
Optional& operator=(V)
{
clear();
return *this;
}
Optional& operator=(Optional const& other)
{
if (this != &other) {
clear();
m_value = other.m_value;
}
return *this;
}
Optional& operator=(Optional&& other)
{
if (this != &other) {
clear();
m_value = other.m_value;
}
return *this;
}
void clear()
{
m_value.value = JS::Bytecode::IdentifierTableIndex::invalid;
}
[[nodiscard]] bool has_value() const
{
return m_value.is_valid();
}
[[nodiscard]] JS::Bytecode::IdentifierTableIndex& value() &
{
VERIFY(has_value());
return m_value;
}
[[nodiscard]] JS::Bytecode::IdentifierTableIndex const& value() const&
{
VERIFY(has_value());
return m_value;
}
[[nodiscard]] JS::Bytecode::IdentifierTableIndex value() &&
{
return release_value();
}
[[nodiscard]] JS::Bytecode::IdentifierTableIndex release_value()
{
VERIFY(has_value());
JS::Bytecode::IdentifierTableIndex released_value = m_value;
clear();
return released_value;
}
private:
JS::Bytecode::IdentifierTableIndex m_value { JS::Bytecode::IdentifierTableIndex::invalid };
};
}