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