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Code Issues Projects Releases Packages Wiki Activity Actions 9

LibJS: Optimize array destructuring assignment for builtin iterators

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...by avoiding `{ value, done }` iterator result value allocation. This
change applies the same otimization 81b6a11 added for `for..in` and
`for..of`.

Makes following micro benchmark go 22% faster on my computer:
```js
function f() {
    const arr = [];
    for (let i = 0; i < 10_000_000; i++) {
        arr.push([i]);
    }
    let sum = 0;
    for (let [i] of arr) {
        sum += i;
    }
}

f();
```
This commit is contained in:
Aliaksandr Kalenik 2025-05-01 16:05:24 +03:00 • committed by Alexander Kalenik
parent 295b78f7d3
commit 60bd5012fe
Notes: github-actions[bot] 2025-05-01 13:58:54 +00:00
4 changed files with 11 additions and 15 deletions
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10
Libraries/LibJS/Bytecode/ASTCodegen.cpp
View file

@ -1504,8 +1504,8 @@ static Bytecode::CodeGenerationErrorOr<void> generate_array_binding_pattern_byte
generator.switch_to_basic_block(iterator_is_not_exhausted_block);
}
generator.emit<Bytecode::Op::IteratorNext>(temp_iterator_result, iterator);
generator.emit_iterator_complete(is_iterator_exhausted, temp_iterator_result);
auto value = generator.allocate_register();
generator.emit<Bytecode::Op::IteratorNextUnpack>(value, is_iterator_exhausted, iterator);
// We still have to check for exhaustion here. If the iterator is exhausted,
// we need to bail before trying to get the value
@ -1517,10 +1517,6 @@ static Bytecode::CodeGenerationErrorOr<void> generate_array_binding_pattern_byte
generator.switch_to_basic_block(no_bail_block);
// Get the next value in the iterator
auto value = generator.allocate_register();
generator.emit_iterator_value(value, temp_iterator_result);
auto& create_binding_block = generator.make_block();
generator.emit<Bytecode::Op::Jump>(Bytecode::Label { create_binding_block });
@ -3187,7 +3183,7 @@ static Bytecode::CodeGenerationErrorOr<Optional<ScopedOperand>> for_in_of_body_e
auto done = generator.allocate_register();
if (iterator_kind == IteratorHint::Sync) {
generator.emit<Bytecode::Op::ForOfNext>(next_value, done, *head_result.iterator);
generator.emit<Bytecode::Op::IteratorNextUnpack>(next_value, done, *head_result.iterator);
auto& loop_continue = generator.make_block();
generator.emit_jump_if(