GetUnsafeObjectG1PreBarrier.java revision 11707:ad7af1afda7a 
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8279424Srstone *
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21 * questions.
22 */
23
24/*
25 * @test
26 * @bug 8016474
27 * @summary The bug only happens with C1 and G1 using a different ObjectAlignmentInBytes than KlassAlignmentInBytes (which is 8)
28 *
29 * @modules java.base/jdk.internal.misc
30 * @run main/othervm -Xbatch -XX:+IgnoreUnrecognizedVMOptions -XX:ObjectAlignmentInBytes=32
31 *                   compiler.unsafe.GetUnsafeObjectG1PreBarrier
32 */
33
34package compiler.unsafe;
35
36import jdk.internal.misc.Unsafe;
37
38import java.lang.reflect.Field;
39
40public class GetUnsafeObjectG1PreBarrier {
41    private static final Unsafe unsafe;
42    private static final int N = 100_000;
43
44    static {
45        try {
46            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
47            theUnsafe.setAccessible(true);
48            unsafe = (Unsafe) theUnsafe.get(null);
49        } catch (NoSuchFieldException | IllegalAccessException e) {
50            throw new IllegalStateException(e);
51        }
52    }
53
54    public Object a;
55
56    public static void main(String[] args) throws Throwable {
57        new GetUnsafeObjectG1PreBarrier();
58    }
59
60    public GetUnsafeObjectG1PreBarrier() throws Throwable {
61        doit();
62    }
63
64    private void doit() throws Throwable {
65        Field field = GetUnsafeObjectG1PreBarrier.class.getField("a");
66        long fieldOffset = unsafe.objectFieldOffset(field);
67
68        for (int i = 0; i < N; i++) {
69            readField(this, fieldOffset);
70        }
71    }
72
73    private void readField(Object o, long fieldOffset) {
74        unsafe.getObject(o, fieldOffset);
75    }
76}
77