1 /*
   2  * Copyright (c) 2017, 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 import java.lang.reflect.Field;
  25 
  26 /**
  27  * @test
  28  * @bug 8175887
  29  * @summary C1 value numbering handling of Unsafe.get*Volatile is incorrect
  30  * @modules java.base/jdk.internal.misc:+open
  31  * @run main/othervm -XX:TieredStopAtLevel=1 UnsafeVolatileGuardTest
  32  */
  33 public class UnsafeVolatileGuardTest {
  34     volatile static private int a;
  35     static private int b;
  36 
  37     static final jdk.internal.misc.Unsafe UNSAFE;
  38 
  39     static final Object BASE;
  40     static final long OFFSET;
  41 
  42     static {
  43         try {
  44             Field f = jdk.internal.misc.Unsafe.class.getDeclaredField("theUnsafe");
  45             f.setAccessible(true);
  46             UNSAFE = (jdk.internal.misc.Unsafe) f.get(null);
  47         } catch (Exception e) {
  48             throw new RuntimeException("Unable to get Unsafe instance.", e);
  49         }
  50 
  51         try {
  52             Field f = UnsafeVolatileGuardTest.class.getDeclaredField("a");
  53             BASE = UNSAFE.staticFieldBase(f);
  54             OFFSET = UNSAFE.staticFieldOffset(f);
  55         } catch (Exception e) {
  56             throw new RuntimeException(e);
  57         }
  58     }
  59 
  60     public static void main(String [] args) throws Exception {
  61         for (int i = 0; i < 100; i++) {
  62             new Thread() {
  63 
  64                 @Override
  65                 public void run() {
  66                     int tt = b; // makes the JVM CSE the value of b
  67 
  68                     while (UNSAFE.getIntVolatile(BASE, OFFSET) == 0) {} // burn
  69                     if (b == 0) {
  70                         System.out.println("error");
  71                         System.exit(1); // fail hard
  72                     }
  73                 }
  74 
  75             }.start();
  76         }
  77 
  78         b = 1;
  79         a = 1;
  80     }
  81 }