4699c81fc1
This patch makes IteratorRecord an Object. Although it's not exposed to
author code, this does allow us to store it in a VM register.
Now that we can store it in a VM register, we don't need to convert it
back and forth between IteratorRecord and Object when accessing it from
bytecode.
The big win here is avoiding 3 [[Get]] accesses on every iteration step
of for..of loops. There are also a bunch of smaller efficiencies gained.
20% speed-up on this microbenchmark:
function go(a) {
for (const p of a) {
}
}
const a = [];
a.length = 1_000_000;
go(a);
89 lines
3.3 KiB
C++
89 lines
3.3 KiB
C++
/*
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* Copyright (c) 2023, Tim Flynn <trflynn89@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibJS/Runtime/AbstractOperations.h>
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#include <LibJS/Runtime/Intrinsics.h>
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#include <LibJS/Runtime/Iterator.h>
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#include <LibJS/Runtime/IteratorConstructor.h>
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#include <LibJS/Runtime/IteratorPrototype.h>
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#include <LibJS/Runtime/Realm.h>
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#include <LibJS/Runtime/VM.h>
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namespace JS {
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JS_DEFINE_ALLOCATOR(IteratorConstructor);
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// 3.1.1.1 The Iterator Constructor, https://tc39.es/proposal-iterator-helpers/#sec-iterator-constructor
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IteratorConstructor::IteratorConstructor(Realm& realm)
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: Base(realm.vm().names.Iterator.as_string(), realm.intrinsics().function_prototype())
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{
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}
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void IteratorConstructor::initialize(Realm& realm)
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{
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Base::initialize(realm);
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auto& vm = this->vm();
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// 3.1.1.2.1 Iterator.prototype, https://tc39.es/proposal-iterator-helpers/#sec-iterator.prototype
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define_direct_property(vm.names.prototype, realm.intrinsics().iterator_prototype(), 0);
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u8 attr = Attribute::Writable | Attribute::Configurable;
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define_native_function(realm, vm.names.from, from, 1, attr);
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define_direct_property(vm.names.length, Value(0), Attribute::Configurable);
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}
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// 3.1.1.1.1 Iterator ( ), https://tc39.es/proposal-iterator-helpers/#sec-iterator
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ThrowCompletionOr<Value> IteratorConstructor::call()
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{
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auto& vm = this->vm();
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// 1. If NewTarget is undefined or the active function object, throw a TypeError exception.
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return vm.throw_completion<TypeError>(ErrorType::ConstructorWithoutNew, "Iterator");
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}
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// 3.1.1.1.1 Iterator ( ), https://tc39.es/proposal-iterator-helpers/#sec-iterator
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ThrowCompletionOr<NonnullGCPtr<Object>> IteratorConstructor::construct(FunctionObject& new_target)
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{
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auto& vm = this->vm();
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// 1. If NewTarget is undefined or the active function object, throw a TypeError exception.
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if (&new_target == this)
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return vm.throw_completion<TypeError>(ErrorType::ClassIsAbstract, "Iterator");
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// 2. Return ? OrdinaryCreateFromConstructor(NewTarget, "%Iterator.prototype%").
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return TRY(ordinary_create_from_constructor<Iterator>(vm, new_target, &Intrinsics::iterator_prototype));
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}
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// 3.1.1.2.2 Iterator.from ( O ), https://tc39.es/proposal-iterator-helpers/#sec-iterator.from
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JS_DEFINE_NATIVE_FUNCTION(IteratorConstructor::from)
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{
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auto& realm = *vm.current_realm();
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auto object = vm.argument(0);
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// 1. Let iteratorRecord be ? GetIteratorFlattenable(O, iterate-strings).
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auto iterator_record = TRY(get_iterator_flattenable(vm, object, StringHandling::IterateStrings));
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// 2. Let hasInstance be ? OrdinaryHasInstance(%Iterator%, iteratorRecord.[[Iterator]]).
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auto has_instance = TRY(ordinary_has_instance(vm, iterator_record->iterator, realm.intrinsics().iterator_constructor()));
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// 3. If hasInstance is true, then
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if (has_instance.is_boolean() && has_instance.as_bool()) {
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// a. Return iteratorRecord.[[Iterator]].
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return iterator_record->iterator;
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}
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// 4. Let wrapper be OrdinaryObjectCreate(%WrapForValidIteratorPrototype%, « [[Iterated]] »).
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// 5. Set wrapper.[[Iterated]] to iteratorRecord.
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auto wrapper = Iterator::create(realm, realm.intrinsics().wrap_for_valid_iterator_prototype(), move(iterator_record));
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// 6. Return wrapper.
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return wrapper;
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}
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}
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