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LibJS: Make IteratorRecord inherit from Cell, not Object

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This shaves its size down from 104 bytes to 48 bytes, cutting GC
pressure caused by this type in more than half.
This commit is contained in:
Andreas Kling 2025-03-22 11:46:54 -05:00
parent 842eb7c2e8
commit 86cc9395d0
5 changed files with 18 additions and 25 deletions
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19
Libraries/LibJS/Bytecode/Interpreter.cpp
View file

@ -1613,7 +1613,7 @@ inline ThrowCompletionOr<GC::Ref<Object>> super_call_with_argument_array(VM& vm,
inline ThrowCompletionOr<GC::Ref<Array>> iterator_to_array(VM& vm, Value iterator)
{
auto& iterator_record = as<IteratorRecord>(iterator.as_object());
auto& iterator_record = static_cast<IteratorRecord&>(iterator.as_cell());
auto array = MUST(Array::create(*vm.current_realm(), 0));
size_t index = 0;
@ -1719,7 +1719,7 @@ inline ThrowCompletionOr<Value> delete_by_value_with_this(Bytecode::Interpreter&
}
// 14.7.5.9 EnumerateObjectProperties ( O ), https://tc39.es/ecma262/#sec-enumerate-object-properties
inline ThrowCompletionOr<Object*> get_object_property_iterator(VM& vm, Value value)
inline ThrowCompletionOr<Value> get_object_property_iterator(VM& vm, Value value)
{
// While the spec does provide an algorithm, it allows us to implement it ourselves so long as we meet the following invariants:
// 1- Returned property keys do not include keys that are Symbols
@ -1804,7 +1804,7 @@ inline ThrowCompletionOr<Object*> get_object_property_iterator(VM& vm, Value val
}
},
1, vm.names.next);
return realm.create<IteratorRecord>(realm, object, callback, false).ptr();
return vm.heap().allocate<IteratorRecord>(object, callback, false);
}
ByteString Instruction::to_byte_string(Bytecode::Executable const& executable) const
@ -2915,14 +2915,14 @@ ThrowCompletionOr<void> GetIterator::execute_impl(Bytecode::Interpreter& interpr
ThrowCompletionOr<void> GetObjectFromIteratorRecord::execute_impl(Bytecode::Interpreter& interpreter) const
{
auto& iterator_record = as<IteratorRecord>(interpreter.get(m_iterator_record).as_object());
auto& iterator_record = static_cast<IteratorRecord&>(interpreter.get(m_iterator_record).as_cell());
interpreter.set(m_object, iterator_record.iterator);
return {};
}
ThrowCompletionOr<void> GetNextMethodFromIteratorRecord::execute_impl(Bytecode::Interpreter& interpreter) const
{
auto& iterator_record = as<IteratorRecord>(interpreter.get(m_iterator_record).as_object());
auto& iterator_record = static_cast<IteratorRecord&>(interpreter.get(m_iterator_record).as_cell());
interpreter.set(m_next_method, iterator_record.next_method);
return {};
}
@ -2938,14 +2938,15 @@ ThrowCompletionOr<void> GetMethod::execute_impl(Bytecode::Interpreter& interpret
ThrowCompletionOr<void> GetObjectPropertyIterator::execute_impl(Bytecode::Interpreter& interpreter) const
{
interpreter.set(dst(), TRY(get_object_property_iterator(interpreter.vm(), interpreter.get(object()))));
auto iterator_record = TRY(get_object_property_iterator(interpreter.vm(), interpreter.get(object())));
interpreter.set(dst(), iterator_record);
return {};
}
ThrowCompletionOr<void> IteratorClose::execute_impl(Bytecode::Interpreter& interpreter) const
{
auto& vm = interpreter.vm();
auto& iterator = as<IteratorRecord>(interpreter.get(m_iterator_record).as_object());
auto& iterator = static_cast<IteratorRecord&>(interpreter.get(m_iterator_record).as_cell());
// FIXME: Return the value of the resulting completion. (Note that m_completion_value can be empty!)
TRY(iterator_close(vm, iterator, Completion { m_completion_type, m_completion_value }));
@ -2955,7 +2956,7 @@ ThrowCompletionOr<void> IteratorClose::execute_impl(Bytecode::Interpreter& inter
ThrowCompletionOr<void> AsyncIteratorClose::execute_impl(Bytecode::Interpreter& interpreter) const
{
auto& vm = interpreter.vm();
auto& iterator = as<IteratorRecord>(interpreter.get(m_iterator_record).as_object());
auto& iterator = static_cast<IteratorRecord&>(interpreter.get(m_iterator_record).as_cell());
// FIXME: Return the value of the resulting completion. (Note that m_completion_value can be empty!)
TRY(async_iterator_close(vm, iterator, Completion { m_completion_type, m_completion_value }));
@ -2965,7 +2966,7 @@ ThrowCompletionOr<void> AsyncIteratorClose::execute_impl(Bytecode::Interpreter&
ThrowCompletionOr<void> IteratorNext::execute_impl(Bytecode::Interpreter& interpreter) const
{
auto& vm = interpreter.vm();
auto& iterator_record = as<IteratorRecord>(interpreter.get(m_iterator_record).as_object());
auto& iterator_record = static_cast<IteratorRecord&>(interpreter.get(m_iterator_record).as_cell());
interpreter.set(dst(), TRY(iterator_next(vm, iterator_record)));
return {};
}

2
Libraries/LibJS/Runtime/AsyncFromSyncIteratorPrototype.cpp
View file

@ -211,7 +211,7 @@ GC::Ref<IteratorRecord> create_async_from_sync_iterator(VM& vm, GC::Ref<Iterator
auto next_method = MUST(async_iterator->get(vm.names.next));
// 4. Let iteratorRecord be the Iterator Record { [[Iterator]]: asyncIterator, [[NextMethod]]: nextMethod, [[Done]]: false }.
auto iterator_record = realm.create<IteratorRecord>(realm, async_iterator, next_method, false);
auto iterator_record = vm.heap().allocate<IteratorRecord>(async_iterator, next_method, false);
// 5. Return iteratorRecord.
return iterator_record;

8
Libraries/LibJS/Runtime/Iterator.cpp
View file

@ -31,7 +31,7 @@ Iterator::Iterator(Object& prototype, GC::Ref<IteratorRecord> iterated)
}
Iterator::Iterator(Object& prototype)
: Iterator(prototype, prototype.shape().realm().create<IteratorRecord>(prototype.shape().realm(), nullptr, js_undefined(), false))
: Iterator(prototype, prototype.heap().allocate<IteratorRecord>(nullptr, js_undefined(), false))
{
}
@ -43,8 +43,7 @@ ThrowCompletionOr<GC::Ref<IteratorRecord>> get_iterator_direct(VM& vm, Object& o
// 2. Let iteratorRecord be Record { [[Iterator]]: obj, [[NextMethod]]: nextMethod, [[Done]]: false }.
// 3. Return iteratorRecord.
auto& realm = *vm.current_realm();
return realm.create<IteratorRecord>(realm, object, next_method, false);
return vm.heap().allocate<IteratorRecord>(object, next_method, false);
}
// 7.4.3 GetIteratorFromMethod ( obj, method ), https://tc39.es/ecma262/#sec-getiteratorfrommethod
@ -61,8 +60,7 @@ ThrowCompletionOr<GC::Ref<IteratorRecord>> get_iterator_from_method(VM& vm, Valu
auto next_method = TRY(iterator.get(vm, vm.names.next));
// 4. Let iteratorRecord be the Iterator Record { [[Iterator]]: iterator, [[NextMethod]]: nextMethod, [[Done]]: false }.
auto& realm = *vm.current_realm();
auto iterator_record = realm.create<IteratorRecord>(realm, iterator.as_object(), next_method, false);
auto iterator_record = vm.heap().allocate<IteratorRecord>(iterator.as_object(), next_method, false);
// 5. Return iteratorRecord.
return iterator_record;

13
Libraries/LibJS/Runtime/Iterator.h
View file

@ -17,14 +17,13 @@
namespace JS {
// 7.4.1 Iterator Records, https://tc39.es/ecma262/#sec-iterator-records
class IteratorRecord final : public Object {
JS_OBJECT(IteratorRecord, Object);
class IteratorRecord final : public Cell {
GC_CELL(IteratorRecord, Cell);
GC_DECLARE_ALLOCATOR(IteratorRecord);
public:
IteratorRecord(Realm& realm, GC::Ptr<Object> iterator, Value next_method, bool done)
: Object(ConstructWithoutPrototypeTag::Tag, realm)
, iterator(iterator)
IteratorRecord(GC::Ptr<Object> iterator, Value next_method, bool done)
: iterator(iterator)
, next_method(next_method)
, done(done)
{
@ -36,12 +35,8 @@ public:
private:
virtual void visit_edges(Cell::Visitor&) override;
virtual bool is_iterator_record() const override { return true; }
};
template<>
inline bool Object::fast_is<IteratorRecord>() const { return is_iterator_record(); }
class Iterator : public Object {
JS_OBJECT(Iterator, Object);
GC_DECLARE_ALLOCATOR(Iterator);

1
Libraries/LibJS/Runtime/Object.h
View file

@ -195,7 +195,6 @@ public:
virtual bool is_proxy_object() const { return false; }
virtual bool is_native_function() const { return false; }
virtual bool is_ecmascript_function_object() const { return false; }
virtual bool is_iterator_record() const { return false; }
virtual bool is_array_iterator() const { return false; }
// B.3.7 The [[IsHTMLDDA]] Internal Slot, https://tc39.es/ecma262/#sec-IsHTMLDDA-internal-slot