1 /*
2 * Copyright (c) 2024, 2025, 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.ArrayList;
29 import java.util.HashMap;
30 import java.util.HashSet;
31 import java.util.LinkedHashMap;
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.ClassSymbol;
37 import com.sun.tools.javac.code.Symbol.VarSymbol;
38 import com.sun.tools.javac.code.Symtab;
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.SYNTHETIC;
54 import static com.sun.tools.javac.code.TypeTag.BOT;
55 import static com.sun.tools.javac.tree.JCTree.Tag.VARDEF;
56
57 import com.sun.tools.javac.jvm.Target;
58 import com.sun.tools.javac.tree.JCTree;
59 import com.sun.tools.javac.tree.JCTree.JCClassDecl;
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 extends TreeTranslator {
78
79 protected static final Context.Key<LocalProxyVarsGen> valueInitializersKey = new Context.Key<>();
80
81 public static LocalProxyVarsGen instance(Context context) {
82 LocalProxyVarsGen instance = context.get(valueInitializersKey);
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 UnsetFieldsInfo unsetFieldsInfo;
94 private ClassSymbol currentClass = null;
95 private java.util.List<JCVariableDecl> instanceFields;
96 private Map<JCMethodDecl, Set<Symbol>> fieldsReadInPrologue = new HashMap<>();
97
98 private final boolean noLocalProxyVars;
99
100 @SuppressWarnings("this-escape")
101 protected LocalProxyVarsGen(Context context) {
102 context.put(valueInitializersKey, this);
103 make = TreeMaker.instance(context);
104 types = Types.instance(context);
105 names = Names.instance(context);
106 syms = Symtab.instance(context);
107 target = Target.instance(context);
108 unsetFieldsInfo = UnsetFieldsInfo.instance(context);
109 Options options = Options.instance(context);
110 noLocalProxyVars = options.isSet("noLocalProxyVars");
111 }
112
113 public void addFieldReadInPrologue(JCMethodDecl constructor, Symbol sym) {
114 Set<Symbol> fieldSet = fieldsReadInPrologue.getOrDefault(constructor, new HashSet<>());
115 fieldSet.add(sym);
116 fieldsReadInPrologue.put(constructor, fieldSet);
117 }
118
119 public JCTree translateTopLevelClass(JCTree cdef, TreeMaker make) {
120 if (!noLocalProxyVars) {
121 try {
122 this.make = make;
123 return translate(cdef);
124 } finally {
125 // note that recursive invocations of this method fail hard
126 this.make = null;
127 }
128 } else {
129 return cdef;
130 }
131 }
132
133 @Override
134 public void visitClassDef(JCClassDecl tree) {
135 ClassSymbol prevCurrentClass = currentClass;
136 java.util.List<JCVariableDecl> prevInstanceFields = instanceFields;
137 try {
138 currentClass = tree.sym;
139 instanceFields = tree.defs.stream()
140 .filter(t -> t.hasTag(VARDEF))
141 .map(t -> (JCVariableDecl)t)
142 .filter(vd -> !vd.sym.isStatic())
143 .collect(List.collector());
144 super.visitClassDef(tree);
145 } finally {
146 currentClass = prevCurrentClass;
147 instanceFields = prevInstanceFields;
148 }
149 }
150
151 public void visitMethodDef(JCMethodDecl tree) {
152 if (fieldsReadInPrologue.get(tree) != null) {
153 Set<Symbol> fieldSet = fieldsReadInPrologue.get(tree);
154 java.util.List<JCVariableDecl> fieldsRead = new ArrayList<>();
155 for (JCVariableDecl field : instanceFields) {
156 if (fieldSet.contains(field.sym)) {
157 fieldsRead.add(field);
158 }
159 }
160 addLocalProxiesFor(tree, fieldsRead);
161 fieldsReadInPrologue.remove(tree);
162 }
163 super.visitMethodDef(tree);
164 }
165
166 void addLocalProxiesFor(JCMethodDecl constructor, java.util.List<JCVariableDecl> fields) {
167 ListBuffer<JCStatement> localDeclarations = new ListBuffer<>();
168 Map<Symbol, Symbol> fieldToLocalMap = new LinkedHashMap<>();
169
170 for (JCVariableDecl fieldDecl : fields) {
171 long flags = SYNTHETIC;
172 VarSymbol proxy = new VarSymbol(flags, newLocalName(fieldDecl.name.toString()), fieldDecl.sym.erasure(types), constructor.sym);
173 fieldToLocalMap.put(fieldDecl.sym, proxy);
174 JCVariableDecl localDecl;
175 JCExpression initializer = fieldDecl.init;
176 if (initializer == null && !fieldDecl.sym.isFinal() && !fieldDecl.sym.isStrict()) {
177 initializer = fieldDecl.vartype.type.isPrimitive() ?
178 make.at(constructor.pos).Literal(0) :
179 make.at(constructor.pos).Literal(BOT, null).setType(syms.botType);
180 }
181 localDecl = make.at(constructor.pos).VarDef(proxy, initializer);
182 localDecl.vartype = fieldDecl.vartype;
183 localDeclarations = localDeclarations.append(localDecl);
184 }
185
186 FieldRewriter fieldRewriter = new FieldRewriter(constructor, fieldToLocalMap);
187 ListBuffer<JCStatement> newBody = new ListBuffer<>();
188 for (JCStatement st : constructor.body.stats) {
189 newBody = newBody.append(fieldRewriter.translate(st));
190 }
191 localDeclarations.addAll(newBody);
192 ListBuffer<JCStatement> assigmentsBeforeSuper = new ListBuffer<>();
193 for (Symbol vsym : fieldToLocalMap.keySet()) {
194 Symbol local = fieldToLocalMap.get(vsym);
195 assigmentsBeforeSuper.append(make.at(constructor.pos()).Assignment(vsym, make.at(constructor.pos()).Ident(local)));
196 }
197 constructor.body.stats = localDeclarations.toList();
198 JCTree.JCMethodInvocation constructorCall = TreeInfo.findConstructorCall(constructor);
199 if (constructorCall.args.isEmpty()) {
200 // this is just a super invocation with no arguments we can set the fields just before the invocation
201 // and let Gen do the rest
202 TreeInfo.mapSuperCalls(constructor.body, supercall -> make.Block(0, assigmentsBeforeSuper.toList().append(supercall)));
203 } else {
204 // we need to generate fresh local variables to catch the values of the arguments, then
205 // assign the proxy locals to the fields and finally invoke the super with the fresh local variables
206 int argPosition = 0;
207 ListBuffer<JCStatement> superArgsProxies = new ListBuffer<>();
208 for (JCExpression arg : constructorCall.args) {
209 long flags = SYNTHETIC | FINAL;
210 VarSymbol proxyForArgSym = new VarSymbol(flags, newLocalName("" + argPosition), types.erasure(arg.type), constructor.sym);
211 JCVariableDecl proxyForArgDecl = make.at(constructor.pos).VarDef(proxyForArgSym, arg);
212 superArgsProxies = superArgsProxies.append(proxyForArgDecl);
213 argPosition++;
214 }
215 List<JCStatement> superArgsProxiesList = superArgsProxies.toList();
216 ListBuffer<JCExpression> newArgs = new ListBuffer<>();
217 for (JCStatement argProxy : superArgsProxies) {
218 newArgs.add(make.at(argProxy.pos).Ident((JCVariableDecl) argProxy));
219 }
220 constructorCall.args = newArgs.toList();
221 TreeInfo.mapSuperCalls(constructor.body,
222 supercall -> make.Block(0, superArgsProxiesList.appendList(assigmentsBeforeSuper.toList()).append(supercall)));
223 }
224 }
225
226 private Name newLocalName(String name) {
227 return names.fromString("local" + target.syntheticNameChar() + name);
228 }
229
230 class FieldRewriter extends TreeTranslator {
231 JCMethodDecl md;
232 Map<Symbol, Symbol> fieldToLocalMap;
233 boolean ctorPrologue = true;
234
235 public FieldRewriter(JCMethodDecl md, Map<Symbol, Symbol> fieldToLocalMap) {
236 this.md = md;
237 this.fieldToLocalMap = fieldToLocalMap;
238 }
239
240 @Override
241 public void visitIdent(JCTree.JCIdent tree) {
242 if (ctorPrologue && fieldToLocalMap.get(tree.sym) != null) {
243 result = make.at(md).Ident(fieldToLocalMap.get(tree.sym));
244 } else {
245 result = tree;
246 }
247 }
248
249 @Override
250 public void visitSelect(JCTree.JCFieldAccess tree) {
251 super.visitSelect(tree);
252 if (ctorPrologue && fieldToLocalMap.get(tree.sym) != null) {
253 result = make.at(md).Ident(fieldToLocalMap.get(tree.sym));
254 } else {
255 result = tree;
256 }
257 }
258
259 @Override
260 public void visitAssign(JCAssign tree) {
261 JCExpression previousLHS = tree.lhs;
262 super.visitAssign(tree);
263 if (ctorPrologue && previousLHS != tree.lhs) {
264 unsetFieldsInfo.removeUnsetFieldInfo(currentClass, tree);
265 }
266 }
267
268 @Override
269 public void visitApply(JCTree.JCMethodInvocation tree) {
270 super.visitApply(tree);
271 if (TreeInfo.isConstructorCall(tree)) {
272 ctorPrologue = false;
273 }
274 }
275 }
276 }