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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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36
Userland/Libraries/LibJS/JIT/Compiler.cpp
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@ -3059,8 +3059,7 @@ void Compiler::compile_super_call_with_argument_array(Bytecode::Op::SuperCallWit
static Value cxx_get_iterator(VM& vm, Value value, IteratorHint hint)
{
auto iterator = TRY_OR_SET_EXCEPTION(get_iterator(vm, value, hint));
return Bytecode::iterator_to_object(vm, iterator);
return TRY_OR_SET_EXCEPTION(get_iterator(vm, value, hint));
}
void Compiler::compile_get_iterator(Bytecode::Op::GetIterator const& op)
@ -3074,10 +3073,33 @@ void Compiler::compile_get_iterator(Bytecode::Op::GetIterator const& op)
check_exception();
}
static Value cxx_get_object_from_iterator_record(VM&, Value value)
{
return verify_cast<IteratorRecord>(value.as_object()).iterator;
}
void Compiler::compile_get_object_from_iterator_record(Bytecode::Op::GetObjectFromIteratorRecord const& op)
{
load_vm_register(ARG1, op.iterator_record());
native_call((void*)cxx_get_object_from_iterator_record);
store_vm_register(op.object(), RET);
}
static Value cxx_next_method_from_iterator_record(VM&, Value value)
{
return verify_cast<IteratorRecord>(value.as_object()).next_method;
}
void Compiler::compile_get_next_method_from_iterator_record(Bytecode::Op::GetNextMethodFromIteratorRecord const& op)
{
load_vm_register(ARG1, op.iterator_record());
native_call((void*)cxx_next_method_from_iterator_record);
store_vm_register(op.next_method(), RET);
}
static Value cxx_iterator_next(VM& vm, Value iterator)
{
auto iterator_object = TRY_OR_SET_EXCEPTION(iterator.to_object(vm));
auto iterator_record = Bytecode::object_to_iterator(vm, iterator_object);
auto& iterator_record = verify_cast<IteratorRecord>(iterator.as_object());
return TRY_OR_SET_EXCEPTION(iterator_next(vm, iterator_record));
}
@ -3147,8 +3169,7 @@ void Compiler::compile_iterator_result_value(Bytecode::Op::IteratorResultValue c
static Value cxx_iterator_close(VM& vm, Value iterator, Completion::Type completion_type, Optional<Value> const& completion_value)
{
auto iterator_object = TRY_OR_SET_EXCEPTION(iterator.to_object(vm));
auto iterator_record = Bytecode::object_to_iterator(vm, iterator_object);
auto& iterator_record = verify_cast<IteratorRecord>(iterator.as_object());
// FIXME: Return the value of the resulting completion. (Note that m_completion_value can be empty!)
TRY_OR_SET_EXCEPTION(iterator_close(vm, iterator_record, Completion { completion_type, completion_value, {} }));
@ -3565,8 +3586,7 @@ void Compiler::compile_copy_object_excluding_properties(Bytecode::Op::CopyObject
static Value cxx_async_iterator_close(VM& vm, Value iterator, Completion::Type completion_type, Optional<Value> const& completion_value)
{
auto iterator_object = TRY_OR_SET_EXCEPTION(iterator.to_object(vm));
auto iterator_record = Bytecode::object_to_iterator(vm, iterator_object);
auto& iterator_record = verify_cast<IteratorRecord>(iterator.as_object());
// FIXME: Return the value of the resulting completion. (Note that completion_value can be empty!)
TRY_OR_SET_EXCEPTION(async_iterator_close(vm, iterator_record, Completion { completion_type, completion_value, {} }));