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LibJS: Stop converting between Object <-> IteratorRecord all the time

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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);
This commit is contained in:
Andreas Kling 2023-12-07 10:44:41 +01:00
parent 4966c083df
commit 4699c81fc1
23 changed files with 226 additions and 144 deletions
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6
Userland/Libraries/LibJS/Runtime/IteratorHelper.cpp
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@ -13,12 +13,12 @@ namespace JS {
JS_DEFINE_ALLOCATOR(IteratorHelper);
ThrowCompletionOr<NonnullGCPtr<IteratorHelper>> IteratorHelper::create(Realm& realm, IteratorRecord underlying_iterator, Closure closure, Optional<AbruptClosure> abrupt_closure)
ThrowCompletionOr<NonnullGCPtr<IteratorHelper>> IteratorHelper::create(Realm& realm, NonnullGCPtr<IteratorRecord> underlying_iterator, Closure closure, Optional<AbruptClosure> abrupt_closure)
{
return realm.heap().allocate<IteratorHelper>(realm, realm, realm.intrinsics().iterator_helper_prototype(), move(underlying_iterator), move(closure), move(abrupt_closure));
}
IteratorHelper::IteratorHelper(Realm& realm, Object& prototype, IteratorRecord underlying_iterator, Closure closure, Optional<AbruptClosure> abrupt_closure)
IteratorHelper::IteratorHelper(Realm& realm, Object& prototype, NonnullGCPtr<IteratorRecord> underlying_iterator, Closure closure, Optional<AbruptClosure> abrupt_closure)
: GeneratorObject(realm, prototype, realm.vm().running_execution_context().copy(), "Iterator Helper"sv)
, m_underlying_iterator(move(underlying_iterator))
, m_closure(move(closure))
@ -29,7 +29,7 @@ IteratorHelper::IteratorHelper(Realm& realm, Object& prototype, IteratorRecord u
void IteratorHelper::visit_edges(Visitor& visitor)
{
Base::visit_edges(visitor);
visitor.visit(m_underlying_iterator.iterator);
visitor.visit(m_underlying_iterator);
}
Value IteratorHelper::result(Value value)