hotspot/test/compiler/intrinsics/unsafe/TestCAEAntiDep.java

/*
 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2016, 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.
 *
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 */

/**
 * @test
 * @bug 8167298
 * @summary Unsafe.compareAndExchangeObject should keep track of returned type after matching
 * @modules java.base/jdk.internal.misc
 * @run main/othervm -XX:+IgnoreUnrecognizedVMOptions -XX:-BackgroundCompilation -XX:-UseOnStackReplacement -XX:-UseCompressedOops TestCAEAntiDep
 *
 */

import java.lang.reflect.Field;
import jdk.internal.misc.Unsafe;

public class TestCAEAntiDep {
    static final jdk.internal.misc.Unsafe UNSAFE = Unsafe.getUnsafe();
    static final long O_OFFSET;

    static class C {
        int f1;
    }

    C o = new C();

    static {
        try {
            Field oField = TestCAEAntiDep.class.getDeclaredField("o");
            O_OFFSET = UNSAFE.objectFieldOffset(oField);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    static int m(TestCAEAntiDep test, Object expected, Object x) {
        C old = (C)UNSAFE.compareAndExchangeObject(test, O_OFFSET, expected, x);
        int res = old.f1;
        old.f1 = 0x42;
        return res;
    }

    static public void main(String[] args) {
        TestCAEAntiDep test = new TestCAEAntiDep();
        for (int i = 0; i < 20000; i++) {
            m(test, test.o, test.o);
        }
    }
}