/*

 * Copyright (c) 2009, 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.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * @test

 * @bug 6843752

 * @summary missing code for an anti-dependent Phi in GCM

 * @run main/othervm -Xbatch Test

 */

public class Test {

    Item list;

    static class Item {

        public Item    next;

        public Item    prev;

        public boolean remove;

        Item(boolean r) { remove = r; }

    }

    private void linkIn(Item item) {

        Item head = list;

        if (head == null) {

            item.next = item;

            item.prev = item;

            list = item;

        } else {

            item.next = head;

            item.prev = head.prev;

            head.prev.next = item;

            head.prev = item;

        }

    }

    private void linkOut(Item item) {

        Item head = list;

        if (item.next == item) {

            list = null;

        } else {

            item.prev.next = item.next;

            item.next.prev = item.prev;

            if (head == item) {

                list = item.next;

            }

        }

        item.next = null;

        item.prev = null; // this is the null pointer we are seeing

    }

    private void removeItems(int numItems) {

        Item item = list;

        if (item == null) {

            return;

        }

        Item last = item.prev;

        boolean done = false;

        while (!done && numItems > 1) {

            // the original code "done = (item == last);" triggered an infinite loop

            // and was changed slightly in order to produce an exception instead.

            done = (item.next == last.next);

            item = item.next;

            if (item.prev.remove) {

                linkOut(item.prev);

            }

        }

    }

    public void perform(int numItems) {

        for (int i = 0; i < numItems; i++) {

            linkIn(new Item(i == 0));

        }

        removeItems(numItems);

        list = null;

    }

    static public void main(String[] args) {

        int caseCnt = 0;

        Test bj = new Test();

        try {

            for (; caseCnt < 500000;) {

                int numItems = (++caseCnt % 2);

                if ((caseCnt % 64) == 0) {

                    numItems = 5;

                }

                bj.perform(numItems);

                if ((caseCnt % 100000) == 0) {

                    System.out.println("successfully performed " + caseCnt + " cases");

                }

            }

        } catch (Exception e) {

            System.out.println("ERROR: crashed during case " + caseCnt);

            e.printStackTrace(System.out);

            System.exit(97);

        }

    }

}