1 /*

     2  * Copyright (c) 2016, 2018, Red Hat, Inc. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

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    23 

    24 /**

    25  * @test TestExpandedWBLostNullCheckDep

    26  * @summary Logic that moves a null check in the expanded barrier may cause a memory access that doesn't depend on the barrier to bypass the null check

    27  * @key gc

    28  * @requires vm.gc.Shenandoah

    29  * @requires vm.flavor == "server"

    30  * @run main/othervm -XX:-BackgroundCompilation -XX:-UseOnStackReplacement -XX:-TieredCompilation

    31  *                   -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC

    32  *                   -XX:+StressGCM -XX:+StressLCM TestExpandedWBLostNullCheckDep

    33  */

    34 

    35 public class TestExpandedWBLostNullCheckDep {

    36 

    37     static void test(int i, int[] arr) {

    38         // arr.length depends on a null check for arr

    39         if (i < 0 || i >= arr.length) {

    40         }

    41         // The write barrier here also depends on the null check. The

    42         // null check is moved in the barrier to enable implicit null

    43         // checks. The null check must not be moved arr.length

    44         arr[i] = 0x42;

    45     }

    46 

    47     static public void main(String[] args) {

    48         int[] int_arr = new int[10];

    49         for (int i = 0; i < 20000; i++) {

    50             test(0, int_arr);

    51         }

    52         try {

    53             test(0, null);

    54         } catch (NullPointerException npe) {}

    55     }

    56 }