1 /*
   2  * Copyright (c) 2020, 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.
  22  */
  23 
  24 /**
  25  * @test
  26  * @bug 8237007
  27  * @summary Shenandoah: assert(_base == Tuple) failure during C2 compilation
  28  * @key gc
  29  *
  30  * @run main/othervm -XX:+UnlockExperimentalVMOptions -XX:-BackgroundCompilation -XX:+UseShenandoahGC LRBRightAfterMemBar
  31  *
  32  */
  33 
  34 public class LRBRightAfterMemBar {
  35     private static Object field1;
  36     private static Object field2;
  37     static volatile int barrier;
  38 
  39     public static void main(String[] args) {
  40         for (int i = 0; i < 20_000; i++) {
  41             test(true, true, new Object());
  42             test(false, false, new Object());
  43         }
  44     }
  45 
  46     private static Object test(boolean flag, boolean flag2, Object o2) {
  47         for (int i = 0; i < 10; i++) {
  48             barrier = 0x42; // Membar
  49             if (o2 == null) { // hoisted out of loop
  50             }
  51             // The following line is converted to a CMove with an out
  52             // of loop control once the null check above is
  53             // hoisted. The CMove is pinned right after the membar and
  54             // assigned the membar as control.
  55             Object o = flag ? field1 : field2;
  56             if (flag2) {
  57                 return o;
  58             }
  59         }
  60 
  61         return null;
  62     }
  63 }