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646457099c
With this change, `GetIterator` no longer GC-allocates an
`IteratorRecord`. Instead, it stores the iterator record fields in
bytecode registers. This avoids per-iteration allocations in patterns
like: `for (let [x] of array) {}`.
`IteratorRecord` now inherits from `IteratorRecordImpl`, which holds the
iteration state. This allows the existing iteration helpers
(`iterator_next()`, `iterator_step()`, etc.) operate on both the
GC-allocated and the register-backed forms.
Microbenchmarks:
1.1x array-destructuring-assignment-rest.js
1.226x array-destructuring-assignment.js
63 lines
1.6 KiB
C++
63 lines
1.6 KiB
C++
/*
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* Copyright (c) 2020, Matthew Olsson <mattco@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 <AK/Utf8View.h>
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#include <LibJS/Runtime/GlobalObject.h>
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#include <LibJS/Runtime/NativeFunction.h>
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#include <LibJS/Runtime/StringIterator.h>
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namespace JS {
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GC_DEFINE_ALLOCATOR(StringIterator);
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GC::Ref<StringIterator> StringIterator::create(Realm& realm, String string)
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{
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return realm.create<StringIterator>(move(string), realm.intrinsics().string_iterator_prototype());
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}
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StringIterator::StringIterator(String string, Object& prototype)
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: Object(ConstructWithPrototypeTag::Tag, prototype)
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, m_string(move(string))
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, m_iterator(Utf8View(m_string).begin())
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{
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}
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BuiltinIterator* StringIterator::as_builtin_iterator_if_next_is_not_redefined(Value next_method)
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{
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if (next_method.is_object()) {
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auto const& next_function = next_method.as_object();
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if (next_function.is_native_function()) {
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auto const& native_function = static_cast<NativeFunction const&>(next_function);
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if (native_function.is_string_prototype_next_builtin())
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return this;
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}
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}
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return nullptr;
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}
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ThrowCompletionOr<void> StringIterator::next(VM& vm, bool& done, Value& value)
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{
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if (m_done) {
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done = true;
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value = js_undefined();
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return {};
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}
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if (m_iterator.done()) {
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m_done = true;
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done = true;
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value = js_undefined();
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return {};
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}
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auto code_point = String::from_code_point(*m_iterator);
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++m_iterator;
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value = PrimitiveString::create(vm, move(code_point));
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return {};
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}
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}
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