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 TestMaybeNullUnsafeAccess
  26  * @summary cast before unsafe access moved in dominating null check null path causes crash
  27  * @requires vm.gc.Shenandoah
  28  * @modules java.base/jdk.internal.misc:+open
  29  *
  30  * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:-TieredCompilation
  31  *                   TestMaybeNullUnsafeAccess
  32  *
  33  * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:-TieredCompilation
  34  *                   -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC
  35  *                   TestMaybeNullUnsafeAccess
  36  *
  37  */
  38 
  39 import jdk.internal.misc.Unsafe;
  40 
  41 import java.lang.reflect.Field;
  42 
  43 public class TestMaybeNullUnsafeAccess {
  44 
  45     static final jdk.internal.misc.Unsafe UNSAFE = Unsafe.getUnsafe();
  46     static final long F_OFFSET;
  47 
  48     static class A {
  49         int f;
  50     }
  51 
  52     static {
  53         try {
  54             Field fField = A.class.getDeclaredField("f");
  55             F_OFFSET = UNSAFE.objectFieldOffset(fField);
  56         } catch (Exception e) {
  57             throw new RuntimeException(e);
  58         }
  59     }
  60 
  61     static A test_helper(Object o) {
  62         return (A) o;
  63     }
  64 
  65     static int test(Object o) {
  66         int f = 0;
  67         for (int i = 0; i < 100; i++) {
  68             A a = test_helper(o);
  69             f = UNSAFE.getInt(a, F_OFFSET);
  70         }
  71         return f;
  72     }
  73 
  74     static public void main(String[] args) {
  75         A a = new A();
  76         for (int i = 0; i < 20000; i++) {
  77             test_helper(null);
  78             test_helper(a);
  79             test(a);
  80         }
  81     }
  82 
  83 }