1 /* 2 * Copyright (c) 2014, 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 TestIntegerComparison 26 * @bug 8043284 8042786 27 * @summary "Tests optimizations of signed and unsigned integer comparison." 28 * @run main/othervm -server -Xcomp -XX:+IgnoreUnrecognizedVMOptions -XX:-TieredCompilation -XX:CompileOnly=TestIntegerComparison::testSigned,TestIntegerComparison::testUnsigned TestIntegerComparison 29 */ 30 public class TestIntegerComparison { 31 /** 32 * Tests optimization of signed integer comparison (see BoolNode::Ideal). 33 * The body of the if statement is unreachable and should not be compiled. 34 * @param c Character (value in the integer range [0, 65535]) 35 */ 36 public static void testSigned(char c) { 37 // The following addition may overflow. The result is in one 38 // of the two ranges [IntMax] and [IntMin, IntMin + CharMax - 1]. 39 int result = c + Integer.MAX_VALUE; 40 // CmpINode has to consider both result ranges instead of only 41 // the general [IntMin, IntMax] range to be able to prove that 42 // result is always unequal to CharMax. 43 if (result == Character.MAX_VALUE) { 44 // Unreachable 45 throw new RuntimeException("Should not reach here!"); 46 } 47 } 48 49 /** 50 * Tests optimization of unsigned integer comparison (see CmpUNode::Value). 51 * The body of the if statement is unreachable and should not be compiled. 52 * @param c Character (value in the integer range [0, 65535]) 53 */ 54 public static void testUnsigned(char c) { 55 /* 56 * The following if statement consisting of two CmpIs is replaced 57 * by a CmpU during optimization (see 'IfNode::fold_compares'). 58 * 59 * The signed (lo < i) and (i < hi) are replaced by the unsigned 60 * (i - (lo+1) < hi - (lo+1)). In this case the unsigned comparison 61 * equals (result - 2) < 98 leading to the following CmpUNode: 62 * 63 * CmpU (AddI result, -2) 98 64 * 65 * With the value of result this is simplified to: 66 * 67 * CmpU (AddI c, -(CharMax - IntMin)) 98 68 * 69 * The subtraction may underflow. The result is in one of the two 70 * ranges [IntMin], [IntMax - CharMax + 1]. Both ranges have to be 71 * considered instead of only the general [IntMin, IntMax] to prove 72 * that due to the overflow the signed comparison result < 98 is 73 * always false. 74 */ 75 int result = c - (Character.MAX_VALUE - Integer.MIN_VALUE) + 2; 76 if (1 < result && result < 100) { 77 // Unreachable 78 throw new RuntimeException("Should not reach here!"); 79 } 80 } 81 82 /** 83 * Tests optimizations of signed and unsigned integer comparison. 84 */ 85 public static void main(String[] args) { 86 // We use characters to get a limited integer range for free 87 for (int i = Character.MIN_VALUE; i <= Character.MAX_VALUE; ++i) { 88 testSigned((char) i); 89 testUnsigned((char) i); 90 } 91 } 92 }