ladybird/Userland/Libraries/LibJS/Bytecode/CommonImplementations.cpp

/*
 * Copyright (c) 2021-2023, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibJS/Bytecode/CommonImplementations.h>
#include <LibJS/Bytecode/Interpreter.h>

namespace JS::Bytecode {

ThrowCompletionOr<NonnullGCPtr<Object>> base_object_for_get(Bytecode::Interpreter& interpreter, Value base_value)
{
    auto& vm = interpreter.vm();
    if (base_value.is_object())
        return base_value.as_object();

    // OPTIMIZATION: For various primitives we can avoid actually creating a new object for them.
    if (base_value.is_string())
        return vm.current_realm()->intrinsics().string_prototype();
    if (base_value.is_number())
        return vm.current_realm()->intrinsics().number_prototype();
    if (base_value.is_boolean())
        return vm.current_realm()->intrinsics().boolean_prototype();

    return base_value.to_object(vm);
}

ThrowCompletionOr<Value> get_by_id(Bytecode::Interpreter& interpreter, IdentifierTableIndex property, Value base_value, Value this_value, u32 cache_index)
{
    auto& vm = interpreter.vm();
    auto const& name = interpreter.current_executable().get_identifier(property);
    auto& cache = interpreter.current_executable().property_lookup_caches[cache_index];

    if (base_value.is_string()) {
        auto string_value = TRY(base_value.as_string().get(vm, name));
        if (string_value.has_value())
            return *string_value;
    }

    auto base_obj = TRY(base_object_for_get(interpreter, base_value));

    // OPTIMIZATION: If the shape of the object hasn't changed, we can use the cached property offset.
    // NOTE: Unique shapes don't change identity, so we compare their serial numbers instead.
    auto& shape = base_obj->shape();
    if (&shape == cache.shape
        && (!shape.is_unique() || shape.unique_shape_serial_number() == cache.unique_shape_serial_number)) {
        return base_obj->get_direct(cache.property_offset.value());
    }

    CacheablePropertyMetadata cacheable_metadata;
    auto value = TRY(base_obj->internal_get(name, this_value, &cacheable_metadata));

    if (cacheable_metadata.type == CacheablePropertyMetadata::Type::OwnProperty) {
        cache.shape = shape;
        cache.property_offset = cacheable_metadata.property_offset.value();
        cache.unique_shape_serial_number = shape.unique_shape_serial_number();
    }

    return value;
}

}