1 /*
2 * Copyright (c) 2016, 2018, 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 package org.graalvm.compiler.core.common.spi;
26
27 import org.graalvm.compiler.debug.GraalError;
28 import org.graalvm.compiler.options.Option;
29 import org.graalvm.compiler.options.OptionKey;
30
31 import jdk.vm.ci.meta.JavaConstant;
32 import jdk.vm.ci.meta.JavaType;
33 import jdk.vm.ci.meta.MetaAccessProvider;
34 import jdk.vm.ci.meta.ResolvedJavaField;
35 import jdk.vm.ci.meta.ResolvedJavaType;
36
37 /**
38 * Utility for default constant folding semantics for Java fields.
39 */
40 public abstract class JavaConstantFieldProvider implements ConstantFieldProvider {
41
42 static class Options {
43 @Option(help = "Determines whether to treat final fields with default values as constant.")//
44 public static final OptionKey<Boolean> TrustFinalDefaultFields = new OptionKey<>(true);
45 }
46
47 protected JavaConstantFieldProvider(MetaAccessProvider metaAccess) {
48 try {
49 this.stringValueField = metaAccess.lookupJavaField(String.class.getDeclaredField("value"));
50 this.stringHashField = metaAccess.lookupJavaField(String.class.getDeclaredField("hash"));
51 } catch (NoSuchFieldException | SecurityException e) {
52 throw new GraalError(e);
53 }
54 }
55
56 @Override
57 public <T> T readConstantField(ResolvedJavaField field, ConstantFieldTool<T> tool) {
58 if (isStableField(field, tool)) {
59 JavaConstant value = tool.readValue();
60 if (value != null && isStableFieldValueConstant(field, value, tool)) {
61 return foldStableArray(value, field, tool);
62 }
63 }
64 if (isFinalField(field, tool)) {
65 JavaConstant value = tool.readValue();
66 if (value != null && isFinalFieldValueConstant(field, value, tool)) {
67 return tool.foldConstant(value);
68 }
69 }
70 return null;
71 }
72
73 protected <T> T foldStableArray(JavaConstant value, ResolvedJavaField field, ConstantFieldTool<T> tool) {
74 return tool.foldStableArray(value, getArrayDimension(field.getType()), isDefaultStableField(field, tool));
75 }
76
77 private static int getArrayDimension(JavaType type) {
78 int dimensions = 0;
79 JavaType componentType = type;
80 while ((componentType = componentType.getComponentType()) != null) {
81 dimensions++;
82 }
83 return dimensions;
84 }
85
86 private static boolean isArray(ResolvedJavaField field) {
87 JavaType fieldType = field.getType();
88 return fieldType instanceof ResolvedJavaType && ((ResolvedJavaType) fieldType).isArray();
89 }
90
91 @SuppressWarnings("unused")
92 protected boolean isStableFieldValueConstant(ResolvedJavaField field, JavaConstant value, ConstantFieldTool<?> tool) {
93 return !value.isDefaultForKind();
94 }
95
96 @SuppressWarnings("unused")
97 protected boolean isFinalFieldValueConstant(ResolvedJavaField field, JavaConstant value, ConstantFieldTool<?> tool) {
98 return !value.isDefaultForKind() || Options.TrustFinalDefaultFields.getValue(tool.getOptions());
99 }
100
101 @SuppressWarnings("unused")
102 protected boolean isStableField(ResolvedJavaField field, ConstantFieldTool<?> tool) {
103 if (isSyntheticEnumSwitchMap(field)) {
104 return true;
105 }
106 if (isWellKnownImplicitStableField(field)) {
107 return true;
108 }
109 if (field.equals(stringHashField)) {
110 return true;
111 }
112 return false;
113 }
114
115 protected boolean isDefaultStableField(ResolvedJavaField field, ConstantFieldTool<?> tool) {
116 assert isStableField(field, tool);
117 if (isSyntheticEnumSwitchMap(field)) {
118 return true;
119 }
120 return false;
121 }
122
123 @SuppressWarnings("unused")
124 protected boolean isFinalField(ResolvedJavaField field, ConstantFieldTool<?> tool) {
125 return field.isFinal();
126 }
127
128 protected boolean isSyntheticEnumSwitchMap(ResolvedJavaField field) {
129 if (field.isSynthetic() && field.isStatic() && isArray(field)) {
130 String name = field.getName();
131 if (field.isFinal() && name.equals("$VALUES") || name.equals("ENUM$VALUES")) {
132 // generated int[] field for EnumClass::values()
133 return true;
134 } else if (name.startsWith("$SwitchMap$") || name.startsWith("$SWITCH_TABLE$")) {
135 // javac and ecj generate a static field in an inner class for a switch on an enum
136 // named $SwitchMap$p$k$g$EnumClass and $SWITCH_TABLE$p$k$g$EnumClass, respectively
137 return true;
138 }
139 }
140 return false;
141 }
142
143 private final ResolvedJavaField stringValueField;
144 private final ResolvedJavaField stringHashField;
145
146 protected boolean isWellKnownImplicitStableField(ResolvedJavaField field) {
147 return field.equals(stringValueField);
148 }
149 }