/*

 * Copyright (c) 2017, Oracle and/or its affiliates. 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 8178047

 * @run main/othervm -XX:CompileCommand=exclude,*.main -XX:-TieredCompilation -XX:-BackgroundCompilation compiler.unsafe.TestRawAliasing

 * @modules java.base/jdk.internal.misc:+open

 */

package compiler.unsafe;

import java.lang.reflect.Field;

public class TestRawAliasing {

    static private final jdk.internal.misc.Unsafe UNSAFE;

    static {

        try {

            Field f = jdk.internal.misc.Unsafe.class.getDeclaredField("theUnsafe");

            f.setAccessible(true);

            UNSAFE = (jdk.internal.misc.Unsafe) f.get(null);

        } catch (Exception e) {

            throw new RuntimeException("Unable to get Unsafe instance.", e);

        }

    }

    static private final int OFFSET_X = 50;

    static private final int OFFSET_Y = 100;

    private static int test(long base_plus_offset_x, long base_plus_offset_y, int magic_value) {

        // write 0 to a location

        UNSAFE.putByte(base_plus_offset_x - OFFSET_X, (byte)0);

        // write unfoldable value to really the same location with another base

        UNSAFE.putByte(base_plus_offset_y - OFFSET_Y, (byte)magic_value);

        // read the value back, should be equal to "unfoldable_value"

        return UNSAFE.getByte(base_plus_offset_x - OFFSET_X);

    }

    private static final int OFF_HEAP_AREA_SIZE = 128;

    private static final byte MAGIC = 123;

    // main is excluded from compilation since we don't want the test method to inline and make base values fold

    public static void main(String... args) {

        long base = UNSAFE.allocateMemory(OFF_HEAP_AREA_SIZE);

        for (int i = 0; i < 100_000; i++) {

            if (test(base + OFFSET_X, base + OFFSET_Y, MAGIC) != MAGIC) {

                throw new RuntimeException("Unexpected magic value");

            }

        }

    }

}