1 /*
2 * Copyright (c) 2020, 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 8237767
27 * @summary Verify behaviour of field layout algorithm
28 * @library /test/lib
29 * @modules java.base/jdk.internal.misc
30 * java.management
31 * @run main/othervm FieldDensityTest
32 */
33
34 /*
35 * @test
36 * @requires vm.bits == "64"
37 * @library /test/lib
38 * @modules java.base/jdk.internal.misc
39 * java.management
40 * @run main/othervm -XX:+UseCompressedOops -XX:+UseCompressedClassPointers FieldDensityTest
41 */
42
43 import java.lang.reflect.Field;
44 import java.util.Arrays;
45 import java.util.Comparator;
46 import jdk.internal.misc.Unsafe;
47
48 import jdk.test.lib.Asserts;
49
50 public class FieldDensityTest {
51
52 static int OOP_SIZE_IN_BYTES = 0;
53
54 static {
55 if (System.getProperty("sun.arch.data.model").equals("64")) {
56 if (System.getProperty("java.vm.compressedOopsMode") == null) {
57 OOP_SIZE_IN_BYTES = 8;
58 } else {
59 OOP_SIZE_IN_BYTES = 4;
60 }
61 } else {
62 OOP_SIZE_IN_BYTES = 4;
63 }
64 }
65
66 static class FieldInfo {
67 public Field field;
68 public long offset;
69
70 FieldInfo(Field field, long offset) {
71 this.field = field;
72 this.offset = offset;
73 }
74
75 static void checkFieldsContiguity(FieldInfo[] fieldInfo) {
76 Arrays.sort(fieldInfo, new SortByOffset());
77 for (int i = 0 ; i < fieldInfo.length - 2; i++) {
78 int size = sizeInBytesFromType(fieldInfo[i].field.getType());
79 Asserts.assertEquals((int)(fieldInfo[i].offset + size), (int)fieldInfo[i+1].offset,
80 "Empty slot between fields, should not happen");
81 }
82 }
83 }
84
85 static int sizeInBytesFromType(Class type) {
86 if (!type.isPrimitive()) {
87 return OOP_SIZE_IN_BYTES;
88 }
89 switch(type.getTypeName()) {
90 case "boolean":
91 case "byte": return 1;
92 case "char":
93 case "short": return 2;
94 case "int":
95 case "float": return 4;
96 case "long":
97 case "double": return 8;
98 default:
99 throw new RuntimeException("Unrecognized signature");
100 }
101 }
102
103 static class SortByOffset implements Comparator<FieldInfo> {
104 public int compare(FieldInfo a, FieldInfo b)
105 {
106 return (int)(a.offset - b.offset);
107 }
108 }
109
110 static class E {
111 public byte b0;
112 }
113
114 static class F extends E {
115 public byte b1;
116 }
117
118 static class G extends F {
119 public byte b2;
120 }
121
122 static class H extends G {
123 public byte b3;
124 }
125
126 public static class A {
127 public int i;
128 public byte b;
129 public long l;
130 public Object o;
131 }
132
133 public static class B extends A {
134 public byte b0, b1, b2;
135 }
136
137 static void testFieldsContiguity(Class c) {
138 Unsafe unsafe = Unsafe.getUnsafe();
139 Field[] fields = c.getFields();
140 FieldInfo[] fieldsInfo = new FieldInfo[fields.length];
141 int i = 0;
142 for (Field f : fields) {
143 long offset = unsafe.objectFieldOffset(f);
144 fieldsInfo[i] = new FieldInfo(f, offset);
145 i++;
146 }
147 FieldInfo.checkFieldsContiguity(fieldsInfo);
148 }
149
150 public static void main(String[] args) {
151 H h = new H();
152 testFieldsContiguity(h.getClass());
153 B b = new B();
154 testFieldsContiguity(b.getClass());
155 }
156 }