1 /*
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3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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  *
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17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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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