1 /* 2 * Copyright (c) 2016, 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 /** 26 * @test 27 * @bug 8150804 28 * @summary Tests elimination of Phi nodes without losing type information. 29 * @run main/othervm -XX:-BackgroundCompilation -XX:-UseOnStackReplacement TestPhiElimination 30 */ 31 public class TestPhiElimination { 32 /* 33 A::get() is inlined into test(obj) producing the following graph: 34 35 Parm (obj) 36 TestPhiElimination 37 | 38 CastPP 39 TestPhiElimination:NotNull 40 | 41 CheckCastPP 42 A:NotNull 43 / \ 44 CheckCastPP | 45 A:NotNull | 46 \ / 47 Phi 48 A 49 | 50 Safepoint 51 52 PhiNode::ideal() then replaces the Phi by a CheckCastPP: 53 54 Parm (obj) 55 TestPhiElimination 56 | 57 CheckCastPP 58 A 59 | 60 Safepoint 61 62 losing the :NotNull information. Therefore, we cannot prove that obj != null 63 when accessing a field and add an uncommon trap. Since obj is used as monitor, we 64 set it to TOP in the uncommon trap branch and later fail in Process_OopMap_Node 65 because the monitor object is TOP. 66 */ 67 public Object test(TestPhiElimination obj) { 68 if (obj instanceof A) { 69 return ((A) obj).get(); 70 } 71 return null; 72 } 73 74 static public void main(String[] args) { 75 TestPhiElimination t = new TestPhiElimination(); 76 77 // Warmup 78 B b = new B(); 79 for (int i = 0; i < 1_000; ++i) { 80 t.test(b); 81 } 82 83 // Compile 84 A a = new A(); 85 for (int i = 0; i < 20_000; ++i) { 86 if (i % 2 == 0) { 87 a.f = null; 88 } 89 t.test(a); 90 } 91 } 92 93 } 94 95 class A extends TestPhiElimination { 96 public Object f; 97 98 public A create() { 99 return new A(); 100 } 101 102 public synchronized Object get() { 103 if (f == null) { 104 f = create(); 105 } 106 return f; 107 } 108 } 109 110 class B extends A { 111 112 }