1 /*
   2  * Copyright (c) 2013, 2015, 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 8016474
  27  * @summary The bug only happens with C1 and G1 using a different ObjectAlignmentInBytes than KlassAlignmentInBytes (which is 8)
  28  * @modules java.base/jdk.internal.misc
  29  * @run main/othervm -Xbatch -XX:+IgnoreUnrecognizedVMOptions -XX:ObjectAlignmentInBytes=32 GetUnsafeObjectG1PreBarrier
  30  */
  31 
  32 import java.lang.reflect.Field;
  33 
  34 import jdk.internal.misc.Unsafe;
  35 
  36 public class GetUnsafeObjectG1PreBarrier {
  37     private static final Unsafe unsafe;
  38     private static final int N = 100_000;
  39 
  40     static {
  41         try {
  42             Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
  43             theUnsafe.setAccessible(true);
  44             unsafe = (Unsafe) theUnsafe.get(null);
  45         } catch (NoSuchFieldException | IllegalAccessException e) {
  46             throw new IllegalStateException(e);
  47         }
  48     }
  49 
  50     public Object a;
  51 
  52     public static void main(String[] args) throws Throwable {
  53         new GetUnsafeObjectG1PreBarrier();
  54     }
  55 
  56     public GetUnsafeObjectG1PreBarrier() throws Throwable {
  57         doit();
  58     }
  59 
  60     private void doit() throws Throwable {
  61         Field field = GetUnsafeObjectG1PreBarrier.class.getField("a");
  62         long fieldOffset = unsafe.objectFieldOffset(field);
  63 
  64         for (int i = 0; i < N; i++) {
  65             readField(this, fieldOffset);
  66         }
  67     }
  68 
  69     private void readField(Object o, long fieldOffset) {
  70         unsafe.getObject(o, fieldOffset);
  71     }
  72 }