1 /* 2 * Copyright (c) 2017, 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 8178047 27 * @run main/othervm -XX:CompileCommand=exclude,*.main -XX:-TieredCompilation -XX:-BackgroundCompilation compiler.unsafe.TestRawAliasing 28 */ 29 30 package compiler.unsafe; 31 32 import java.lang.reflect.Field; 33 34 public class TestRawAliasing { 35 static private final sun.misc.Unsafe UNSAFE; 36 static { 37 try { 38 Field f = sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); 39 f.setAccessible(true); 40 UNSAFE = (sun.misc.Unsafe) f.get(null); 41 } catch (Exception e) { 42 throw new RuntimeException("Unable to get Unsafe instance.", e); 43 } 44 } 45 46 static private final int OFFSET_X = 50; 47 static private final int OFFSET_Y = 100; 48 test(long base_plus_offset_x, long base_plus_offset_y, int magic_value)49 private static int test(long base_plus_offset_x, long base_plus_offset_y, int magic_value) { 50 // write 0 to a location 51 UNSAFE.putByte(base_plus_offset_x - OFFSET_X, (byte)0); 52 // write unfoldable value to really the same location with another base 53 UNSAFE.putByte(base_plus_offset_y - OFFSET_Y, (byte)magic_value); 54 // read the value back, should be equal to "unfoldable_value" 55 return UNSAFE.getByte(base_plus_offset_x - OFFSET_X); 56 } 57 58 private static final int OFF_HEAP_AREA_SIZE = 128; 59 private static final byte MAGIC = 123; 60 61 // main is excluded from compilation since we don't want the test method to inline and make base values fold main(String... args)62 public static void main(String... args) { 63 long base = UNSAFE.allocateMemory(OFF_HEAP_AREA_SIZE); 64 for (int i = 0; i < 100_000; i++) { 65 if (test(base + OFFSET_X, base + OFFSET_Y, MAGIC) != MAGIC) { 66 throw new RuntimeException("Unexpected magic value"); 67 } 68 } 69 } 70 } 71