ladybird/Userland/Libraries/LibJS/Runtime/EnvironmentCoordinate.h

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

#pragma once

#include <LibJS/Forward.h>

namespace JS {

struct EnvironmentCoordinate {
    size_t hops { 0 };
    size_t index { 0 };
};

}
LibJS: Fast non-local variable access :^) This patch introduces the "environment coordinate" concept, which encodes the distance from a variable access to the binding it ends up resolving to. EnvironmentCoordinate has two fields: - hops: The number of hops up the lexical environment chain we have to make before getting to the resolved binding. - index: The index of the resolved binding within its declarative environment record. Whenever a variable lookup resolves somewhere inside a declarative environment, we now cache the coordinates and reuse them in subsequent lookups. This is achieved via a coordinate cache in JS::Identifier. Note that non-strict direct eval() breaks this optimization and so it will not be performed if the resolved environment has been permanently screwed by eval(). This makes variable access significantly faster. :^) 2021-10-07 01:06:21 +02:00			`/*`
			`* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>`
			`*`
			`* SPDX-License-Identifier: BSD-2-Clause`
			`*/`

			`#pragma once`

			`#include <LibJS/Forward.h>`

			`namespace JS {`

			`struct EnvironmentCoordinate {`
			`size_t hops { 0 };`
			`size_t index { 0 };`
			`};`

			`}`