1 /*
   2  * Copyright (c) 2019, Oracle and/or its affiliates. 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 8235452
  27  * @library /test/lib /
  28  * @summary Test loop strip mining verification with dying outer loop.
  29  * @run main/othervm -Xbatch -XX:-TieredCompilation
  30  *                   compiler.loopstripmining.TestDeadOuterStripMinedLoop
  31  */
  32 
  33 package compiler.loopstripmining;
  34 
  35 import jdk.test.lib.Asserts;
  36 
  37 public class TestDeadOuterStripMinedLoop {
  38 
  39     public static int test(boolean b) {
  40         int res = 5000;
  41         for (int i = 0; i < 42; i++) {
  42             if (!b) {
  43                 break;
  44             }
  45             // Strip mined loop
  46             while (--res > 0) {
  47                 if (res < 1) {
  48                     throw new RuntimeException("Should not reach here!");
  49                 }
  50             }
  51 
  52             /*
  53             After parsing:
  54                 Loop:
  55                     res--;
  56                     if (res <= 0) {
  57                         goto End;
  58                     }
  59                     if (res < 1) {  <- Treated as loop exit check (res <= 0)
  60                         UncommonTrap();
  61                     }
  62                 goto Loop;
  63                 End:
  64 
  65             Loop opts convert this into:
  66                 // Outer strip mined loop
  67                 do {
  68                     // Strip mined loop
  69                     do {
  70                         res--;
  71                         if (res <= 0) {
  72                             goto End;
  73                         }
  74                     } while (res > 0);  <- Always false due to above res <= 0 check
  75                     Safepoint()
  76                 } while (false);
  77                 UncommonTrap();
  78                 End:
  79 
  80             The safepoint path dies, because the exit condition of the strip mined loop is always false:
  81                 // Strip mined loop
  82                 do {
  83                     res--;
  84                     if (res <= 0) {
  85                         goto End;
  86                     }
  87                 } while (true);
  88                 End:
  89             */
  90         }
  91         return res;
  92     }
  93 
  94     public static void main(String[] args) {
  95         for (int i = 0; i < 100; i++) {
  96             Asserts.assertEQ(test(true), -41);
  97         }
  98         Asserts.assertEQ(test(false), 5000);
  99     }
 100 }