| /* |
| * Copyright (c) 2017, Red Hat, Inc. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /** |
| * @test |
| * @bug 8176506 |
| * @summary cast before unsafe access moved in dominating null check null path causes crash |
| * @modules java.base/jdk.internal.misc:+open |
| * |
| * @run main/othervm -Xbatch -XX:-UseOnStackReplacement TestMaybeNullUnsafeAccess |
| * |
| */ |
| |
| import jdk.internal.misc.Unsafe; |
| import java.lang.reflect.Field; |
| |
| public class TestMaybeNullUnsafeAccess { |
| |
| static final jdk.internal.misc.Unsafe UNSAFE = Unsafe.getUnsafe(); |
| static final long F_OFFSET; |
| |
| static class A { |
| int f; |
| A(int f) { |
| this.f = f; |
| } |
| } |
| |
| static { |
| try { |
| Field fField = A.class.getDeclaredField("f"); |
| F_OFFSET = UNSAFE.objectFieldOffset(fField); |
| } catch (Exception e) { |
| throw new RuntimeException(e); |
| } |
| } |
| |
| static A test_helper(Object o) { |
| // this includes a check for null with both branches taken |
| return (A)o; |
| } |
| |
| |
| // Loop is unswitched because of the test for null from the |
| // checkcast above, unsafe access is copied in each branch, the |
| // compiler sees a memory access to a null object |
| static int test1(Object o, long offset) { |
| int f = 0; |
| for (int i = 0; i < 100; i++) { |
| A a = test_helper(o); |
| f = UNSAFE.getInt(a, offset); |
| } |
| return f; |
| } |
| |
| // Same as above except because we know the offset of the access |
| // is small, we can deduce object a cannot be null |
| static int test2(Object o) { |
| int f = 0; |
| for (int i = 0; i < 100; i++) { |
| A a = test_helper(o); |
| f = UNSAFE.getInt(a, F_OFFSET); |
| } |
| return f; |
| } |
| |
| static public void main(String[] args) { |
| A a = new A(0x42); |
| for (int i = 0; i < 20000; i++) { |
| test_helper(null); |
| test_helper(a); |
| test1(a, F_OFFSET); |
| test2(a); |
| } |
| } |
| |
| } |