1 /*
   2  * Copyright (c) 2016, 2018, Red Hat, Inc. 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 TestWriteBarrierClearControl
  26  * @summary Clearing control during final graph reshape causes memory barrier to loose dependency on null check
  27  * @key gc
  28  * @requires vm.gc.Shenandoah
  29  * @run main/othervm -XX:-BackgroundCompilation -XX:-UseOnStackReplacement -XX:-TieredCompilation
  30  *                   -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC
  31  *                   -XX:+UnlockDiagnosticVMOptions -XX:+StressLCM -XX:+StressGCM
  32  *                   TestWriteBarrierClearControl
  33  *
  34  */
  35 public class TestWriteBarrierClearControl {
  36 
  37     int f;
  38 
  39     static void test1(TestWriteBarrierClearControl o) {
  40         o.f = 0x42;
  41     }
  42 
  43     static TestWriteBarrierClearControl fo = new TestWriteBarrierClearControl();
  44 
  45     static void test2() {
  46         TestWriteBarrierClearControl o = fo;
  47         o.f = 0x42;
  48     }
  49 
  50     static public void main(String[] args) {
  51         TestWriteBarrierClearControl o = new TestWriteBarrierClearControl();
  52         for (int i = 0; i < 20000; i++) {
  53             test1(o);
  54             test2();
  55         }
  56         try {
  57             test1(null);
  58         } catch (NullPointerException npe) {}
  59         fo = null;
  60         try {
  61             test2();
  62         } catch (NullPointerException npe) {}
  63     }
  64 }