1 /*
   2  * Copyright (c) 2009, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 /*
  25  * @test
  26  * @bug 6843752
  27  * @summary missing code for an anti-dependent Phi in GCM
  28  * @run main/othervm -Xbatch Test
  29  */
  30 
  31 public class Test {
  32 
  33     Item list;
  34 
  35     static class Item {
  36         public Item    next;
  37         public Item    prev;
  38         public boolean remove;
  39 
  40         Item(boolean r) { remove = r; }
  41     }
  42 
  43     private void linkIn(Item item) {
  44         Item head = list;
  45         if (head == null) {
  46             item.next = item;
  47             item.prev = item;
  48             list = item;
  49         } else {
  50             item.next = head;
  51             item.prev = head.prev;
  52             head.prev.next = item;
  53             head.prev = item;
  54         }
  55     }
  56 
  57     private void linkOut(Item item) {
  58         Item head = list;
  59         if (item.next == item) {
  60             list = null;
  61         } else {
  62             item.prev.next = item.next;
  63             item.next.prev = item.prev;
  64             if (head == item) {
  65                 list = item.next;
  66             }
  67         }
  68         item.next = null;
  69         item.prev = null; // this is the null pointer we are seeing
  70     }
  71 
  72     private void removeItems(int numItems) {
  73         Item item = list;
  74         if (item == null) {
  75             return;
  76         }
  77         Item last = item.prev;
  78         boolean done = false;
  79         while (!done && numItems > 1) {
  80             // the original code "done = (item == last);" triggered an infinite loop
  81             // and was changed slightly in order to produce an exception instead.
  82             done = (item.next == last.next);
  83             item = item.next;
  84             if (item.prev.remove) {
  85                 linkOut(item.prev);
  86             }
  87         }
  88     }
  89 
  90     public void perform(int numItems) {
  91         for (int i = 0; i < numItems; i++) {
  92             linkIn(new Item(i == 0));
  93         }
  94         removeItems(numItems);
  95         list = null;
  96     }
  97 
  98     static public void main(String[] args) {
  99         int caseCnt = 0;
 100         Test bj = new Test();
 101         try {
 102             for (; caseCnt < 500000;) {
 103                 int numItems = (++caseCnt % 2);
 104                 if ((caseCnt % 64) == 0) {
 105                     numItems = 5;
 106                 }
 107                 bj.perform(numItems);
 108                 if ((caseCnt % 100000) == 0) {
 109                     System.out.println("successfully performed " + caseCnt + " cases");
 110                 }
 111             }
 112         } catch (Exception e) {
 113             System.out.println("ERROR: crashed during case " + caseCnt);
 114             e.printStackTrace(System.out);
 115             System.exit(97);
 116         }
 117     }
 118 }
 119