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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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2
Userland/Libraries/LibJS/Bytecode/CommonImplementations.h
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@ -35,8 +35,6 @@ MarkedVector<Value> argument_list_evaluation(VM&, Value arguments);
ThrowCompletionOr<void> create_variable(VM&, DeprecatedFlyString const& name, Op::EnvironmentMode, bool is_global, bool is_immutable, bool is_strict);
ThrowCompletionOr<ECMAScriptFunctionObject*> new_class(VM&, Value super_class, ClassExpression const&, Optional<IdentifierTableIndex> const& lhs_name);
ThrowCompletionOr<NonnullGCPtr<Object>> super_call_with_argument_array(VM&, Value argument_array, bool is_synthetic);
Object* iterator_to_object(VM&, IteratorRecord);
IteratorRecord object_to_iterator(VM&, Object&);
ThrowCompletionOr<NonnullGCPtr<Array>> iterator_to_array(VM&, Value iterator);
ThrowCompletionOr<void> append(VM& vm, Value lhs, Value rhs, bool is_spread);
ThrowCompletionOr<Value> delete_by_id(Bytecode::Interpreter&, Value base, IdentifierTableIndex identifier);