1 /*
   2  * Copyright (c) 2016, 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.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 /*
  27  * @test
  28  * @bug 8155781
  29  * @modules java.base/jdk.internal.misc
  30  *
  31  * @run main/bootclasspath/othervm -XX:+UnlockDiagnosticVMOptions -XX:-TieredCompilation -Xbatch
  32  *                                 -XX:+PrintCompilation -XX:+PrintInlining
  33  *                                 -XX:CompileCommand=dontinline,compiler.unsafe.OpaqueAccesses::test*
  34  *                                 compiler.unsafe.OpaqueAccesses
  35  */
  36 package compiler.unsafe;
  37 
  38 import jdk.internal.misc.Unsafe;
  39 
  40 import java.lang.reflect.Field;
  41 
  42 public class OpaqueAccesses {
  43     private static final Unsafe UNSAFE = Unsafe.getUnsafe();
  44 
  45     private static final Object INSTANCE = new OpaqueAccesses();
  46 
  47     private static final long F_OFFSET;
  48     static {
  49         try {
  50             Field field = OpaqueAccesses.class.getDeclaredField("f");
  51             F_OFFSET = UNSAFE.objectFieldOffset(field);
  52         } catch (NoSuchFieldException e) {
  53             throw new Error(e);
  54         }
  55     }
  56 
  57     private Object f = new Object();
  58 
  59     static Object testFixedOffsetField(Object o) {
  60         return UNSAFE.getObject(o, F_OFFSET);
  61     }
  62 
  63     static int testFixedOffsetHeader(Object o) {
  64         return UNSAFE.getInt(o, 4);
  65     }
  66 
  67     static Object testFixedBase(long off) {
  68         return UNSAFE.getObject(INSTANCE, off);
  69     }
  70 
  71     static Object testOpaque(Object o, long off) {
  72         return UNSAFE.getObject(o, off);
  73     }
  74 
  75     static final long ADDR = UNSAFE.allocateMemory(10);
  76     static boolean flag;
  77 
  78     static int testMixedAccess() {
  79         flag = !flag;
  80         Object o = (flag ? INSTANCE : null);
  81         long off = (flag ? F_OFFSET : ADDR);
  82         return UNSAFE.getInt(o, off);
  83     }
  84 
  85     public static void main(String[] args) {
  86         for (int i = 0; i < 20_000; i++) {
  87             testFixedOffsetField(INSTANCE);
  88             testFixedOffsetHeader(INSTANCE);
  89             testFixedBase(F_OFFSET);
  90             testOpaque(INSTANCE, F_OFFSET);
  91             testMixedAccess();
  92         }
  93         System.out.println("TEST PASSED");
  94     }
  95 }