src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.nodes/src/org/graalvm/compiler/nodes/spi/ArrayLengthProvider.java

/*
 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
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package org.graalvm.compiler.nodes.spi;

import org.graalvm.compiler.nodes.ValueNode;
import org.graalvm.compiler.nodes.ValuePhiNode;
import org.graalvm.compiler.nodes.ValueProxyNode;
import org.graalvm.compiler.nodes.util.GraphUtil;

public interface ArrayLengthProvider {

    /**
     * The different modes that determine what the results of {@link GraphUtil#arrayLength} and
     * {@link ArrayLengthProvider#findLength} can be used for.
     */
    enum FindLengthMode {
        /**
         * Use the result of {@link GraphUtil#arrayLength} and
         * {@link ArrayLengthProvider#findLength} to replace the explicit load of the array length
         * with a node that does not involve a memory access of the array length.
         *
         * Values that are defined inside a loop and flow out the loop need to be proxied by
         * {@link ValueProxyNode}. When this mode is used, new necessary proxy nodes are created
         * base on the proxies that were found while traversing the path to the length node. In
         * addition, new {@link ValuePhiNode phi nodes} can be created. The caller is responsible
         * for adding these nodes to the graph, i.e., the return value can be a node that is not yet
         * added to the graph.
         */
        CANONICALIZE_READ,

        /**
         * Use the result of {@link GraphUtil#arrayLength} and
         * {@link ArrayLengthProvider#findLength} only for decisions whether a certain optimization
         * is possible. No new nodes are created during the search, i.e., the result is either a
         * node that is already in the graph, or null.
         */
        SEARCH_ONLY
    }

    /**
     * Returns the length of the array described by this node, or null if it is not available.
     * Details of the different modes are documented in {@link FindLengthMode}.
     *
     * This method should not be called directly. Use {@link GraphUtil#arrayLength} instead.
     */
    ValueNode findLength(FindLengthMode mode);
}