Ladybird/ladybird
1
0
Fork 0
mirror of https://github.com/LadybirdBrowser/ladybird.git synced 2025-06-08 05:27:14 +09:00
Code Activity

LibJS: Skip iterator result object allocation in for..of and for..in

Browse source 
Introduce special instruction for `for..of` and `for..in` loop that
skips `{ value, done }` result object allocation if iterator is builtin
(array, map, set, string). This reduces GC pressure significantly and
avoids extracting the `value` and `done` properties.

This change makes this micro benchmark 48% faster on my computer:
```js
const arr = new Array(10_000_000);
let counter = 0;
for (let _ of arr) {
    counter++;
}
```
This commit is contained in:
Aliaksandr Kalenik 2025-04-30 16:31:26 +03:00 • committed by Andreas Kling
parent ab52d86a69
commit 81b6a1100e
Notes: github-actions[bot] 2025-04-30 18:52:38 +00:00
4 changed files with 94 additions and 23 deletions
Download patch file Download diff file Expand all files Collapse all files

31
Libraries/LibJS/Bytecode/Interpreter.cpp
View file

@ -1,5 +1,6 @@
/*
* Copyright (c) 2021-2025, Andreas Kling <andreas@ladybird.org>
* Copyright (c) 2025, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -611,6 +612,7 @@ FLATTEN_ON_CLANG void Interpreter::run_bytecode(size_t entry_point)
HANDLE_INSTRUCTION_WITHOUT_EXCEPTION_CHECK(Dump);
HANDLE_INSTRUCTION(EnterObjectEnvironment);
HANDLE_INSTRUCTION(Exp);
HANDLE_INSTRUCTION(ForOfNext);
HANDLE_INSTRUCTION(GetById);
HANDLE_INSTRUCTION(GetByIdWithThis);
HANDLE_INSTRUCTION(GetByValue);
@ -2980,6 +2982,27 @@ ThrowCompletionOr<void> IteratorNext::execute_impl(Bytecode::Interpreter& interp
return {};
}
ThrowCompletionOr<void> ForOfNext::execute_impl(Bytecode::Interpreter& interpreter) const
{
auto& vm = interpreter.vm();
auto& iterator_record = static_cast<IteratorRecord&>(interpreter.get(m_iterator_record).as_cell());
Value value;
bool done = false;
if (auto* builtin_iterator = iterator_record.iterator->as_builtin_iterator()) {
TRY(builtin_iterator->next(vm, done, value));
} else {
auto result = TRY(iterator_next(vm, iterator_record));
value = TRY(result->internal_get(vm.names.value, {}));
done = TRY(result->internal_get(vm.names.done, {})).to_boolean();
}
interpreter.set(dst_done(), Value(done));
interpreter.set(dst_value(), value);
return {};
}
ThrowCompletionOr<void> NewClass::execute_impl(Bytecode::Interpreter& interpreter) const
{
Value super_class;
@ -3754,6 +3777,14 @@ ByteString IteratorNext::to_byte_string_impl(Executable const& executable) const
format_operand("iterator_record"sv, m_iterator_record, executable));
}
ByteString ForOfNext::to_byte_string_impl(Executable const& executable) const
{
return ByteString::formatted("ForOfNext {}, {}, {}",
format_operand("dst_value"sv, m_dst_value, executable),
format_operand("dst_done"sv, m_dst_done, executable),
format_operand("iterator_record"sv, m_iterator_record, executable));
}
ByteString ResolveThisBinding::to_byte_string_impl(Bytecode::Executable const&) const
{
return "ResolveThisBinding"sv;