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test/compiler/unsafe/TestRawAliasing.java@6bc9abf210fd (annotated)

test/compiler/unsafe/TestRawAliasing.java

Tue, 25 Jul 2017 10:10:41 -0400

author

dbuck

date

Tue, 25 Jul 2017 10:10:41 -0400

changeset 8879

6bc9abf210fd

permissions

-rw-r--r--

8178047: Aliasing problem with raw memory accesses
Summary: Require equal bases when unaliasing offsets for raw accesses
Reviewed-by: thartmann, kvn

dbuck@8879	1	/*
dbuck@8879	2	* Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
dbuck@8879	3	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
dbuck@8879	4	*
dbuck@8879	5	* This code is free software; you can redistribute it and/or modify it
dbuck@8879	6	* under the terms of the GNU General Public License version 2 only, as
dbuck@8879	7	* published by the Free Software Foundation.
dbuck@8879	8	*
dbuck@8879	9	* This code is distributed in the hope that it will be useful, but WITHOUT
dbuck@8879	10	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
dbuck@8879	11	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
dbuck@8879	12	* version 2 for more details (a copy is included in the LICENSE file that
dbuck@8879	13	* accompanied this code).
dbuck@8879	14	*
dbuck@8879	15	* You should have received a copy of the GNU General Public License version
dbuck@8879	16	* 2 along with this work; if not, write to the Free Software Foundation,
dbuck@8879	17	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
dbuck@8879	18	*
dbuck@8879	19	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
dbuck@8879	20	* or visit www.oracle.com if you need additional information or have any
dbuck@8879	21	* questions.
dbuck@8879	22	*/
dbuck@8879	23
dbuck@8879	24	/*
dbuck@8879	25	* @test
dbuck@8879	26	* @bug 8178047
dbuck@8879	27	* @run main/othervm -XX:CompileCommand=exclude,*.main -XX:-TieredCompilation -XX:-BackgroundCompilation compiler.unsafe.TestRawAliasing
dbuck@8879	28	*/
dbuck@8879	29
dbuck@8879	30	package compiler.unsafe;
dbuck@8879	31
dbuck@8879	32	import java.lang.reflect.Field;
dbuck@8879	33
dbuck@8879	34	public class TestRawAliasing {
dbuck@8879	35	static private final sun.misc.Unsafe UNSAFE;
dbuck@8879	36	static {
dbuck@8879	37	try {
dbuck@8879	38	Field f = sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
dbuck@8879	39	f.setAccessible(true);
dbuck@8879	40	UNSAFE = (sun.misc.Unsafe) f.get(null);
dbuck@8879	41	} catch (Exception e) {
dbuck@8879	42	throw new RuntimeException("Unable to get Unsafe instance.", e);
dbuck@8879	43	}
dbuck@8879	44	}
dbuck@8879	45
dbuck@8879	46	static private final int OFFSET_X = 50;
dbuck@8879	47	static private final int OFFSET_Y = 100;
dbuck@8879	48
dbuck@8879	49	private static int test(long base_plus_offset_x, long base_plus_offset_y, int magic_value) {
dbuck@8879	50	// write 0 to a location
dbuck@8879	51	UNSAFE.putByte(base_plus_offset_x - OFFSET_X, (byte)0);
dbuck@8879	52	// write unfoldable value to really the same location with another base
dbuck@8879	53	UNSAFE.putByte(base_plus_offset_y - OFFSET_Y, (byte)magic_value);
dbuck@8879	54	// read the value back, should be equal to "unfoldable_value"
dbuck@8879	55	return UNSAFE.getByte(base_plus_offset_x - OFFSET_X);
dbuck@8879	56	}
dbuck@8879	57
dbuck@8879	58	private static final int OFF_HEAP_AREA_SIZE = 128;
dbuck@8879	59	private static final byte MAGIC = 123;
dbuck@8879	60
dbuck@8879	61	// main is excluded from compilation since we don't want the test method to inline and make base values fold
dbuck@8879	62	public static void main(String... args) {
dbuck@8879	63	long base = UNSAFE.allocateMemory(OFF_HEAP_AREA_SIZE);
dbuck@8879	64	for (int i = 0; i < 100_000; i++) {
dbuck@8879	65	if (test(base + OFFSET_X, base + OFFSET_Y, MAGIC) != MAGIC) {
dbuck@8879	66	throw new RuntimeException("Unexpected magic value");
dbuck@8879	67	}
dbuck@8879	68	}
dbuck@8879	69	}
dbuck@8879	70	}