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LibJS: Skip iteration result allocation in AsyncFunctionDriverWrapper

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- Create less GC pressure by making each `await` in async function skip
  iteration result object allocation.
- Skip uncached `Object::get()` calls to extract `value` and `done` from
  the iteration result object.

With this change, following function goes 30% faster on my computer:
```js
(async () => {
    const resolved = Promise.resolve();
    for (let i = 0; i < 5_000_000; i++) {
        await resolved;
    }
})();
```
This commit is contained in:
Aliaksandr Kalenik 2025-05-09 04:23:30 +03:00 • committed by Andreas Kling
commit 4c789ac689
Notes: github-actions[bot] 2025-05-09 10:31:18 +00:00
7 changed files with 47 additions and 28 deletions
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18
Libraries/LibJS/Runtime/GeneratorObject.h
View file

@ -21,8 +21,20 @@ public:
virtual ~GeneratorObject() override = default;
void visit_edges(Cell::Visitor&) override;
ThrowCompletionOr<Value> resume(VM&, Value value, Optional<StringView> const& generator_brand);
ThrowCompletionOr<Value> resume_abrupt(VM&, JS::Completion abrupt_completion, Optional<StringView> const& generator_brand);
struct IterationResult {
IterationResult() = delete;
explicit IterationResult(Value value, bool done)
: done(done)
, value(value)
{
}
bool done { false };
Value value;
};
ThrowCompletionOr<IterationResult> resume(VM&, Value value, Optional<StringView> const& generator_brand);
ThrowCompletionOr<IterationResult> resume_abrupt(VM&, JS::Completion abrupt_completion, Optional<StringView> const& generator_brand);
enum class GeneratorState {
SuspendedStart,
@ -37,7 +49,7 @@ protected:
GeneratorObject(Realm&, Object& prototype, NonnullOwnPtr<ExecutionContext>, Optional<StringView> generator_brand = {});
ThrowCompletionOr<GeneratorState> validate(VM&, Optional<StringView> const& generator_brand);
virtual ThrowCompletionOr<Value> execute(VM&, JS::Completion const& completion);
virtual ThrowCompletionOr<IterationResult> execute(VM&, JS::Completion const& completion);
private:
NonnullOwnPtr<ExecutionContext> m_execution_context;