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
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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.flavor == "server"
  29  *
  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 }