1 /*
   2  * Copyright (c) 2017, 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
  26  * @summary cast before unsafe access moved in dominating null check null path causes crash
  27  * @modules java.base/jdk.internal.misc:+open
  28  *
  29  * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:-TieredCompilation TestMaybeNullUnsafeAccess
  30  *
  31  */
  32 
  33 import jdk.internal.misc.Unsafe;
  34 import java.lang.reflect.Field;
  35 
  36 public class TestMaybeNullUnsafeAccess {
  37 
  38     static final jdk.internal.misc.Unsafe UNSAFE = Unsafe.getUnsafe();
  39     static final long F_OFFSET;
  40 
  41     static class A {
  42         int f;
  43     }
  44 
  45     static {
  46         try {
  47             Field fField = A.class.getDeclaredField("f");
  48             F_OFFSET = UNSAFE.objectFieldOffset(fField);
  49         } catch (Exception e) {
  50             throw new RuntimeException(e);
  51         }
  52     }
  53 
  54     static A test_helper(Object o) {
  55         return (A)o;
  56     }
  57 
  58     static int test(Object o) {
  59         int f = 0;
  60         for (int i = 0; i < 100; i++) {
  61             A a = test_helper(o);
  62             f = UNSAFE.getInt(a, F_OFFSET);
  63         }
  64         return f;
  65     }
  66 
  67     static public void main(String[] args) {
  68         A a = new A();
  69         for (int i = 0; i < 20000; i++) {
  70             test_helper(null);
  71             test_helper(a);
  72             test(a);
  73         }
  74     }
  75 
  76 }