TestMaybeNullUnsafeAccess.java

/*
 * Copyright (c) 2017, 2018, 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 TestMaybeNullUnsafeAccess
 * @summary cast before unsafe access moved in dominating null check null path causes crash
 * @requires vm.gc.Shenandoah
 * @modules java.base/jdk.internal.misc:+open
 *
 * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:-TieredCompilation
 *                   TestMaybeNullUnsafeAccess
 *
 * @run main/othervm -XX:-UseOnStackReplacement -XX:-BackgroundCompilation -XX:-TieredCompilation
 *                   -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC
 *                   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;
    }

    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) {
        return (A) o;
    }

    static int test(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();
        for (int i = 0; i < 20000; i++) {
            test_helper(null);
            test_helper(a);
            test(a);
        }
    }

}