1 /*
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   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
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  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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  24 
  25 /**
  26  * @test
  27  * @bug 8139771
  28  * @summary Eliminating CastPP nodes at Phis when they all come from a unique input may cause crash
  29  * @requires vm.gc=="Serial" | vm.gc=="Parallel"
  30  *
  31  * @run main/othervm -XX:-BackgroundCompilation -XX:-UseOnStackReplacement
  32  *      -XX:+IgnoreUnrecognizedVMOptions -XX:+StressGCM
  33  *      compiler.controldependenc.TestEliminatedCastPPAtPhi
  34  *
  35  */
  36 
  37 package compiler.controldependency;
  38 
  39 public class TestEliminatedCastPPAtPhi {
  40 
  41     static TestEliminatedCastPPAtPhi saved;
  42     static TestEliminatedCastPPAtPhi saved_not_null;
  43 
  44     int f;
  45 
  46     static int test(TestEliminatedCastPPAtPhi obj, int[] array, boolean flag) {
  47         int ret = array[0] + array[20];
  48         saved = obj;
  49         if (obj == null) {
  50             return ret;
  51         }
  52         saved_not_null = obj;
  53 
  54         // empty loop to be optimized out. Delays range check smearing
  55         // for the array access below until the if diamond is
  56         // optimized out
  57         int i = 0;
  58         for (; i < 10; i++);
  59 
  60         ret += array[i];
  61 
  62         TestEliminatedCastPPAtPhi res;
  63         if (flag) {
  64             // load is optimized out and res is obj here
  65             res = saved;
  66         } else {
  67             // load is optimized out and res is non null CastPP of res here
  68             res = saved_not_null;
  69         }
  70         // null check + CastPP here for res field load below
  71 
  72         // 1) null check is pushed in the branches of the if above by
  73         // split through phi because res is non null in the second
  74         // branch and the null check can be optimized out in that
  75         // branch. The Castpp stays here.
  76 
  77         // 2) null check in the first branch is also optimized out
  78         // because a dominating null check is found (the explicit null
  79         // check at the beggining of the test)
  80 
  81         // 3) the Phi for the if above merges a CastPP'ed value and
  82         // the same value so it's optimized out and replaced by the
  83         // uncasted value: obj
  84 
  85         // 4) the if above has 2 empty branches so it's optimized
  86         // out. The control of the CastPP that is still here is now
  87         // the success branch of the range check for the array access
  88         // above
  89 
  90         // 5) the loop above is optimized out, i = 10, the range check
  91         // for the array access above is optimized out and all its
  92         // uses are replaced by the range check for the array accesses
  93         // at the beginning of the method. The castPP here is one of
  94         // the uses and so its control is now the range check at the
  95         // beginning of the method: the control of the CastPP bypasses
  96         // the explicit null check
  97 
  98         return ret + res.f;
  99     }
 100 
 101     static public void main(String[] args) {
 102         int[] array = new int[100];
 103         TestEliminatedCastPPAtPhi obj = new TestEliminatedCastPPAtPhi();
 104         for (int i = 0; i < 20000; i++) {
 105             test(obj, array, (i%2) == 0);
 106         }
 107         test(null, array, true);
 108     }
 109 
 110 }