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  * @run main/othervm -XX:+UseCompressedOops -XX:-UseCompressedClassPointers FieldDensityTest
 42  */
 43 
 44 import java.lang.reflect.Field;
 45 import java.util.Arrays;
 46 import java.util.Comparator;
 47 import jdk.internal.misc.Unsafe;
 48 
 49 import jdk.test.lib.Asserts;
 50 
 51 public class FieldDensityTest {
 52 
 53     static int OOP_SIZE_IN_BYTES = 0;
 54 
 55     static {
 56         if (System.getProperty("sun.arch.data.model").equals("64")) {
 57             if (System.getProperty("java.vm.compressedOopsMode") == null) {
 58                 OOP_SIZE_IN_BYTES = 8;
 59             } else {
 60                 OOP_SIZE_IN_BYTES = 4;
 61             }
 62         } else {
 63             OOP_SIZE_IN_BYTES = 4;
 64         }
 65     }
 66 
 67     static class FieldInfo {
 68         public Field field;
 69         public long offset;
 70 
 71         FieldInfo(Field field, long offset) {
 72             this.field = field;
 73             this.offset = offset;
 74         }
 75 
 76         static void checkFieldsContiguity(FieldInfo[] fieldInfo) {
 77             Arrays.sort(fieldInfo, new SortByOffset());
 78             for (int i = 0 ; i <  fieldInfo.length - 2; i++) {
 79                 int size = sizeInBytesFromType(fieldInfo[i].field.getType());
 80                 Asserts.assertEquals((int)(fieldInfo[i].offset + size), (int)fieldInfo[i+1].offset,
 81                                      "Empty slot between fields, should not happen");
 82             }
 83         }
 84     }
 85 
 86     static int sizeInBytesFromType(Class type) {
 87         if (!type.isPrimitive()) {
 88             return OOP_SIZE_IN_BYTES;
 89         }
 90         switch(type.getTypeName()) {
 91         case "boolean":
 92         case "byte": return 1;
 93         case "char":
 94         case "short": return 2;
 95         case "int":
 96         case "float": return 4;
 97         case "long":
 98         case "double": return 8;
 99         default:
100             throw new RuntimeException("Unrecognized signature");
101         }
102     }
103 
104     static class SortByOffset implements Comparator<FieldInfo> {
105         public int compare(FieldInfo a, FieldInfo b)
106         {
107             return (int)(a.offset - b.offset);
108         }
109     }
110 
111     static class E {
112         public byte b0;
113     }
114 
115     static class F extends E {
116         public byte b1;
117     }
118 
119     static class G extends F {
120         public byte b2;
121     }
122 
123     static class H extends G {
124         public byte b3;
125     }
126 
127     public static class A {
128         public int i;
129         public byte b;
130         public long l;
131         public Object o;
132     }
133 
134     public static class B extends A {
135         public byte b0, b1, b2;
136     }
137 
138     static void testFieldsContiguity(Class c) {
139         Unsafe unsafe = Unsafe.getUnsafe();
140         Field[] fields = c.getFields();
141         FieldInfo[] fieldsInfo = new FieldInfo[fields.length];
142         int i = 0;
143         for (Field f : fields) {
144             long offset = unsafe.objectFieldOffset(f);
145             fieldsInfo[i] = new FieldInfo(f, offset);
146             i++;
147         }
148         FieldInfo.checkFieldsContiguity(fieldsInfo);
149     }
150 
151     public static void main(String[] args) {
152         H h = new H();
153         testFieldsContiguity(h.getClass());
154         B b = new B();
155         testFieldsContiguity(b.getClass());
156     }
157 }
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