1 /*
2 * Copyright (c) 2024, 2026, 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. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package com.sun.tools.javac.comp;
27
28 import java.util.HashMap;
29 import java.util.HashSet;
30 import java.util.LinkedHashMap;
31 import java.util.LinkedHashSet;
32 import java.util.Map;
33 import java.util.Set;
34
35 import com.sun.tools.javac.code.Symbol;
36 import com.sun.tools.javac.code.Symbol.VarSymbol;
37 import com.sun.tools.javac.code.Symtab;
38 import com.sun.tools.javac.code.Type;
39 import com.sun.tools.javac.code.Types;
40 import com.sun.tools.javac.tree.JCTree.JCAssign;
41 import com.sun.tools.javac.tree.JCTree.JCExpression;
42 import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
43 import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
44 import com.sun.tools.javac.tree.TreeMaker;
45 import com.sun.tools.javac.tree.TreeTranslator;
46 import com.sun.tools.javac.util.Assert;
47 import com.sun.tools.javac.util.Context;
48 import com.sun.tools.javac.util.ListBuffer;
49 import com.sun.tools.javac.util.Name;
50 import com.sun.tools.javac.util.Names;
51
52 import static com.sun.tools.javac.code.Flags.FINAL;
53 import static com.sun.tools.javac.code.Flags.HASINIT;
54 import static com.sun.tools.javac.code.Flags.STRICT;
55 import static com.sun.tools.javac.code.Flags.SYNTHETIC;
56 import static com.sun.tools.javac.code.TypeTag.BOT;
57
58 import com.sun.tools.javac.jvm.Target;
59 import com.sun.tools.javac.tree.JCTree;
60 import com.sun.tools.javac.tree.JCTree.JCStatement;
61 import com.sun.tools.javac.tree.TreeInfo;
62 import com.sun.tools.javac.util.List;
63 import com.sun.tools.javac.util.Options;
64
65 /** This phase adds local variable proxies for fields that are read during the
66 * early construction phase (prologue)
67 *
68 * Assignments to the affected instance fields will be rewritten as assignments to a
69 * local proxy variable. Fields will be assigned to with its corresponding local variable
70 * proxy just before the super invocation and after its arguments, if any, have been evaluated.
71 *
72 * <p><b>This is NOT part of any supported API.
73 * If you write code that depends on this, you do so at your own risk.
74 * This code and its internal interfaces are subject to change or
75 * deletion without notice.</b>
76 */
77 public class LocalProxyVarsGen {
78
79 protected static final Context.Key<LocalProxyVarsGen> localProxyVarsGenKey = new Context.Key<>();
80
81 public static LocalProxyVarsGen instance(Context context) {
82 LocalProxyVarsGen instance = context.get(localProxyVarsGenKey);
83 if (instance == null)
84 instance = new LocalProxyVarsGen(context);
85 return instance;
86 }
87
88 private final Types types;
89 private final Names names;
90 private final Symtab syms;
91 private final Target target;
92 private TreeMaker make;
93 private final Map<Symbol, Set<Symbol>> fieldsReadInPrologue = new HashMap<>();
94
95 private final boolean noLocalProxyVars;
96
97 @SuppressWarnings("this-escape")
98 protected LocalProxyVarsGen(Context context) {
99 context.put(localProxyVarsGenKey, this);
100 make = TreeMaker.instance(context);
101 types = Types.instance(context);
102 names = Names.instance(context);
103 syms = Symtab.instance(context);
104 target = Target.instance(context);
105 Options options = Options.instance(context);
106 noLocalProxyVars = options.isSet("noLocalProxyVars");
107 }
108
109 public void addFieldReadInPrologue(Symbol owner, Symbol sym) {
110 Assert.checkNonNull(sym, "parameter 'sym' is null");
111 Set<Symbol> fieldSet = fieldsReadInPrologue.getOrDefault(owner, new LinkedHashSet<>());
112 fieldSet.add(sym);
113 fieldsReadInPrologue.put(owner, fieldSet);
114 }
115
116 public void patchConstructor(JCMethodDecl tree, TreeMaker make) {
117 /* if some fields have initializers those probably were added using the enclosing class as their map key
118 * we need to recover those now and add them to this constructor
119 */
120 Set<Symbol> earlyReads = null;
121 if (fieldsReadInPrologue.get(tree.sym.owner) != null) {
122 earlyReads = fieldsReadInPrologue.get(tree.sym.owner);
123 }
124 if (fieldsReadInPrologue.get(tree.sym) != null) {
125 Set<Symbol> constructorEarlyReads = fieldsReadInPrologue.remove(tree.sym);
126 if (constructorEarlyReads != null) {
127 if (earlyReads == null) {
128 earlyReads = constructorEarlyReads;
129 } else {
130 earlyReads.addAll(constructorEarlyReads);
131 }
132 }
133 }
134 if (earlyReads != null && !noLocalProxyVars) {
135 addLocalProxiesFor(tree, earlyReads, make);
136 }
137 }
138
139 public void allFieldNormalized(Symbol.ClassSymbol csym) {
140 fieldsReadInPrologue.remove(csym);
141 }
142
143 void addLocalProxiesFor(JCMethodDecl constructor, Set<Symbol> fields, TreeMaker make) {
144 ListBuffer<JCStatement> localDeclarations = new ListBuffer<>();
145 Map<Symbol, Symbol> fieldToLocalMap = new LinkedHashMap<>();
146
147 for (Symbol field : fields) {
148 long flags = SYNTHETIC;
149 VarSymbol proxy = new VarSymbol(flags, newLocalName(field.name.toString()), field.erasure(types), constructor.sym);
150 fieldToLocalMap.put(field, proxy);
151 JCVariableDecl localDecl;
152 JCExpression initializer = null;
153 if ((field.flags() & (HASINIT | FINAL | STRICT)) == 0) {
154 initializer = field.type.isPrimitive() ?
155 make.at(constructor.pos).Literal(0) :
156 make.at(constructor.pos).Literal(BOT, null).setType(syms.botType);
157 }
158 localDecl = make.at(constructor.pos).VarDef(proxy, initializer);
159 localDeclarations = localDeclarations.append(localDecl);
160 }
161
162 FieldRewriter fieldRewriter = new FieldRewriter(constructor, fieldToLocalMap);
163 ListBuffer<JCStatement> newBody = new ListBuffer<>();
164 for (JCStatement st : constructor.body.stats) {
165 newBody = newBody.append(fieldRewriter.translate(st));
166 }
167 localDeclarations.addAll(newBody);
168 ListBuffer<JCStatement> assigmentsBeforeSuper = new ListBuffer<>();
169 for (Symbol vsym : fieldToLocalMap.keySet()) {
170 Symbol local = fieldToLocalMap.get(vsym);
171 assigmentsBeforeSuper.append(make.at(constructor.pos()).Assignment(vsym, make.at(constructor.pos()).Ident(local)));
172 }
173 constructor.body.stats = localDeclarations.toList();
174 JCTree.JCMethodInvocation constructorCall = TreeInfo.findConstructorCall(constructor);
175 if (constructorCall.args.isEmpty()) {
176 // this is just a super invocation with no arguments we can set the fields just before the invocation
177 // and let Gen do the rest
178 TreeInfo.mapSuperCalls(constructor.body, supercall -> make.Block(0, assigmentsBeforeSuper.toList().append(supercall)));
179 } else {
180 // we need to generate fresh local variables to catch the values of the arguments, then
181 // assign the proxy locals to the fields and finally invoke the super with the fresh local variables
182 int argPosition = 0;
183 ListBuffer<JCStatement> superArgsProxies = new ListBuffer<>();
184 Symbol.MethodSymbol constructorCallSymbol = (Symbol.MethodSymbol) TreeInfo.symbolFor(constructorCall.meth);
185 List<Type> allDeclaredArgs = constructorCallSymbol.externalType(types).getParameterTypes();
186 for (JCExpression arg : constructorCall.args) {
187 Type declaredType = allDeclaredArgs.head;
188 long flags = SYNTHETIC | FINAL;
189 VarSymbol proxyForArgSym = new VarSymbol(flags, newLocalName("" + argPosition), types.erasure(declaredType), constructor.sym);
190 JCVariableDecl proxyForArgDecl = make.at(constructor.pos).VarDef(proxyForArgSym, arg);
191 superArgsProxies = superArgsProxies.append(proxyForArgDecl);
192 argPosition++;
193 allDeclaredArgs = allDeclaredArgs.tail;
194 }
195 List<JCStatement> superArgsProxiesList = superArgsProxies.toList();
196 ListBuffer<JCExpression> newArgs = new ListBuffer<>();
197 for (JCStatement argProxy : superArgsProxies) {
198 newArgs.add(make.at(argProxy.pos).Ident((JCVariableDecl) argProxy));
199 }
200 constructorCall.args = newArgs.toList();
201 TreeInfo.mapSuperCalls(constructor.body,
202 supercall -> make.Block(0, superArgsProxiesList.appendList(assigmentsBeforeSuper.toList()).append(supercall)));
203 }
204 }
205
206 private Name newLocalName(String name) {
207 return names.fromString("local" + target.syntheticNameChar() + name);
208 }
209
210 class FieldRewriter extends TreeTranslator {
211 JCMethodDecl md;
212 Map<Symbol, Symbol> fieldToLocalMap;
213 boolean ctorPrologue = true;
214
215 public FieldRewriter(JCMethodDecl md, Map<Symbol, Symbol> fieldToLocalMap) {
216 this.md = md;
217 this.fieldToLocalMap = fieldToLocalMap;
218 }
219
220 @Override
221 public void visitIdent(JCTree.JCIdent tree) {
222 if (ctorPrologue && fieldToLocalMap.get(tree.sym) != null) {
223 result = make.at(md).Ident(fieldToLocalMap.get(tree.sym));
224 } else {
225 result = tree;
226 }
227 }
228
229 @Override
230 public void visitSelect(JCTree.JCFieldAccess tree) {
231 super.visitSelect(tree);
232 if (ctorPrologue && fieldToLocalMap.get(tree.sym) != null) {
233 result = make.at(md).Ident(fieldToLocalMap.get(tree.sym));
234 } else {
235 result = tree;
236 }
237 }
238
239 @Override
240 public void visitApply(JCTree.JCMethodInvocation tree) {
241 super.visitApply(tree);
242 if (TreeInfo.isConstructorCall(tree)) {
243 ctorPrologue = false;
244 }
245 }
246 }
247 }