/*

 * 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

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 */

/**

 * @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);

        }

    }

}