1 /*
2 * Copyright (c) 2016, 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 package org.graalvm.compiler.core.common.spi;
24
25 import org.graalvm.compiler.debug.GraalError;
26 import org.graalvm.compiler.options.Option;
27 import org.graalvm.compiler.options.OptionValue;
28
29 import jdk.vm.ci.meta.JavaConstant;
30 import jdk.vm.ci.meta.JavaType;
31 import jdk.vm.ci.meta.MetaAccessProvider;
32 import jdk.vm.ci.meta.ResolvedJavaField;
33 import jdk.vm.ci.meta.ResolvedJavaType;
34
35 /**
36 * Utility for default constant folding semantics for Java fields.
37 */
38 public abstract class JavaConstantFieldProvider implements ConstantFieldProvider {
39
40 static class Options {
41 @Option(help = "Determines whether to treat final fields with default values as constant.")//
42 public static final OptionValue<Boolean> TrustFinalDefaultFields = new OptionValue<>(true);
43 }
44
45 protected JavaConstantFieldProvider(MetaAccessProvider metaAccess) {
46 try {
47 this.stringValueField = metaAccess.lookupJavaField(String.class.getDeclaredField("value"));
48 this.stringHashField = metaAccess.lookupJavaField(String.class.getDeclaredField("hash"));
49 } catch (NoSuchFieldException | SecurityException e) {
50 throw new GraalError(e);
51 }
52 }
53
54 @Override
55 public <T> T readConstantField(ResolvedJavaField field, ConstantFieldTool<T> tool) {
56 if (isStableField(field, tool)) {
57 JavaConstant value = tool.readValue();
58 if (value != null && isStableFieldValueConstant(field, value, tool)) {
59 return foldStableArray(value, field, tool);
60 }
61 }
62 if (isFinalField(field, tool)) {
63 JavaConstant value = tool.readValue();
64 if (value != null && isFinalFieldValueConstant(field, value, tool)) {
65 return tool.foldConstant(value);
66 }
67 }
68 return null;
69 }
70
71 protected <T> T foldStableArray(JavaConstant value, ResolvedJavaField field, ConstantFieldTool<T> tool) {
72 return tool.foldStableArray(value, getArrayDimension(field.getType()), isDefaultStableField(field, tool));
73 }
74
75 private static int getArrayDimension(JavaType type) {
76 int dimensions = 0;
77 JavaType componentType = type;
78 while ((componentType = componentType.getComponentType()) != null) {
79 dimensions++;
80 }
81 return dimensions;
82 }
83
84 private static boolean isArray(ResolvedJavaField field) {
85 JavaType fieldType = field.getType();
86 return fieldType instanceof ResolvedJavaType && ((ResolvedJavaType) fieldType).isArray();
87 }
88
89 @SuppressWarnings("unused")
90 protected boolean isStableFieldValueConstant(ResolvedJavaField field, JavaConstant value, ConstantFieldTool<?> tool) {
91 return !value.isDefaultForKind();
92 }
93
94 @SuppressWarnings("unused")
95 protected boolean isFinalFieldValueConstant(ResolvedJavaField field, JavaConstant value, ConstantFieldTool<?> tool) {
96 return !value.isDefaultForKind() || Options.TrustFinalDefaultFields.getValue();
97 }
98
99 @SuppressWarnings("unused")
100 protected boolean isStableField(ResolvedJavaField field, ConstantFieldTool<?> tool) {
101 if (isSyntheticEnumSwitchMap(field)) {
102 return true;
103 }
104 if (isWellKnownImplicitStableField(field)) {
105 return true;
106 }
107 if (field == stringHashField) {
108 return true;
109 }
110 return false;
111 }
112
113 protected boolean isDefaultStableField(ResolvedJavaField field, ConstantFieldTool<?> tool) {
114 assert isStableField(field, tool);
115 if (isSyntheticEnumSwitchMap(field)) {
116 return true;
117 }
118 return false;
119 }
120
121 @SuppressWarnings("unused")
122 protected boolean isFinalField(ResolvedJavaField field, ConstantFieldTool<?> tool) {
123 return field.isFinal();
124 }
125
126 protected boolean isSyntheticEnumSwitchMap(ResolvedJavaField field) {
127 if (field.isSynthetic() && field.isStatic() && isArray(field)) {
128 String name = field.getName();
129 if (field.isFinal() && name.equals("$VALUES") || name.equals("ENUM$VALUES")) {
130 // generated int[] field for EnumClass::values()
131 return true;
132 } else if (name.startsWith("$SwitchMap$") || name.startsWith("$SWITCH_TABLE$")) {
133 // javac and ecj generate a static field in an inner class for a switch on an enum
134 // named $SwitchMap$p$k$g$EnumClass and $SWITCH_TABLE$p$k$g$EnumClass, respectively
135 return true;
136 }
137 }
138 return false;
139 }
140
141 private final ResolvedJavaField stringValueField;
142 private final ResolvedJavaField stringHashField;
143
144 protected boolean isWellKnownImplicitStableField(ResolvedJavaField field) {
145 return field.equals(stringValueField);
146 }
147 }