TestCAEAntiDep.java

/*
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 * Copyright (c) 2016, Red Hat, Inc. All rights reserved.
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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/**
 * @test
 * @bug 8167298
 * @summary Unsafe.compareAndExchangeReference 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.compareAndExchangeReference(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);
        }
    }
}