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.Types;
39 import com.sun.tools.javac.tree.JCTree.JCAssign;
40 import com.sun.tools.javac.tree.JCTree.JCExpression;
41 import com.sun.tools.javac.tree.JCTree.JCMethodDecl;
42 import com.sun.tools.javac.tree.JCTree.JCVariableDecl;
43 import com.sun.tools.javac.tree.TreeMaker;
44 import com.sun.tools.javac.tree.TreeTranslator;
45 import com.sun.tools.javac.util.Context;
46 import com.sun.tools.javac.util.ListBuffer;
47 import com.sun.tools.javac.util.Name;
48 import com.sun.tools.javac.util.Names;
49
50 import static com.sun.tools.javac.code.Flags.FINAL;
51 import static com.sun.tools.javac.code.Flags.SYNTHETIC;
52 import static com.sun.tools.javac.tree.JCTree.Tag.VARDEF;
53
54 import com.sun.tools.javac.jvm.Target;
55 import com.sun.tools.javac.tree.JCTree;
56 import com.sun.tools.javac.tree.JCTree.JCClassDecl;
57 import com.sun.tools.javac.tree.JCTree.JCStatement;
58 import com.sun.tools.javac.tree.TreeInfo;
59 import com.sun.tools.javac.util.List;
60 import com.sun.tools.javac.util.Options;
61
62 /** This phase adds local variable proxies for strict fields that are read during the
63 * early construction phase (prologue)
64 *
65 * Assignments to the affected instance fields will be rewritten as assignments to a
66 * local proxy variable. Fields will be assigned to with its corresponding local variable
67 * proxy just before the super invocation and after its arguments, if any, have been evaluated.
68 *
69 * <p><b>This is NOT part of any supported API.
70 * If you write code that depends on this, you do so at your own risk.
71 * This code and its internal interfaces are subject to change or
72 * deletion without notice.</b>
73 */
74 public class LocalProxyVarsGen extends TreeTranslator {
75
76 protected static final Context.Key<LocalProxyVarsGen> valueInitializersKey = new Context.Key<>();
77
78 public static LocalProxyVarsGen instance(Context context) {
79 LocalProxyVarsGen instance = context.get(valueInitializersKey);
80 if (instance == null)
81 instance = new LocalProxyVarsGen(context);
82 return instance;
83 }
84
85 private final Types types;
86 private final Names names;
87 private final Target target;
88 private TreeMaker make;
89 private final UnsetFieldsInfo unsetFieldsInfo;
90 private ClassSymbol currentClass = null;
91 private java.util.List<JCVariableDecl> strictInstanceFields;
92 private Map<JCMethodDecl, Set<Symbol>> strictFieldsReadInPrologue = new HashMap<>();
93
94 private final boolean noLocalProxyVars;
95
96 @SuppressWarnings("this-escape")
97 protected LocalProxyVarsGen(Context context) {
98 context.put(valueInitializersKey, this);
99 make = TreeMaker.instance(context);
100 types = Types.instance(context);
101 names = Names.instance(context);
102 target = Target.instance(context);
103 unsetFieldsInfo = UnsetFieldsInfo.instance(context);
104 Options options = Options.instance(context);
105 noLocalProxyVars = options.isSet("noLocalProxyVars");
106 }
107
108 public void addStrictFieldReadInPrologue(JCMethodDecl constructor, Symbol sym) {
109 Set<Symbol> fieldSet = strictFieldsReadInPrologue.getOrDefault(constructor, new HashSet<>());
110 fieldSet.add(sym);
111 strictFieldsReadInPrologue.put(constructor, fieldSet);
112 }
113
114 public JCTree translateTopLevelClass(JCTree cdef, TreeMaker make) {
115 if (!noLocalProxyVars) {
116 try {
117 this.make = make;
118 return translate(cdef);
119 } finally {
120 // note that recursive invocations of this method fail hard
121 this.make = null;
122 }
123 } else {
124 return cdef;
125 }
126 }
127
128 @Override
129 public void visitClassDef(JCClassDecl tree) {
130 ClassSymbol prevCurrentClass = currentClass;
131 java.util.List<JCVariableDecl> prevStrictInstanceFields = strictInstanceFields;
132 try {
133 currentClass = tree.sym;
134 strictInstanceFields = tree.defs.stream()
135 .filter(t -> t.hasTag(VARDEF))
136 .map(t -> (JCVariableDecl)t)
137 .filter(vd -> vd.sym.isStrict() && !vd.sym.isStatic())
138 .collect(List.collector());
139 super.visitClassDef(tree);
140 } finally {
141 currentClass = prevCurrentClass;
142 strictInstanceFields = prevStrictInstanceFields;
143 }
144 }
145
146 public void visitMethodDef(JCMethodDecl tree) {
147 if (strictFieldsReadInPrologue.get(tree) != null) {
148 Set<Symbol> fieldSet = strictFieldsReadInPrologue.get(tree);
149 java.util.List<JCVariableDecl> strictFieldsRead = new ArrayList<>();
150 for (JCVariableDecl sfield : strictInstanceFields) {
151 if (fieldSet.contains(sfield.sym)) {
152 strictFieldsRead.add(sfield);
153 }
154 }
155 addLocalProxiesFor(tree, strictFieldsRead);
156 strictFieldsReadInPrologue.remove(tree);
157 }
158 super.visitMethodDef(tree);
159 }
160
161 void addLocalProxiesFor(JCMethodDecl constructor, java.util.List<JCVariableDecl> multiAssignedStrictFields) {
162 ListBuffer<JCStatement> localDeclarations = new ListBuffer<>();
163 Map<Symbol, Symbol> fieldToLocalMap = new LinkedHashMap<>();
164
165 for (JCVariableDecl fieldDecl : multiAssignedStrictFields) {
166 long flags = SYNTHETIC;
167 VarSymbol proxy = new VarSymbol(flags, newLocalName(fieldDecl.name.toString()), fieldDecl.sym.erasure(types), constructor.sym);
168 fieldToLocalMap.put(fieldDecl.sym, proxy);
169 JCVariableDecl localDecl = make.at(constructor.pos).VarDef(proxy, fieldDecl.init);
170 localDecl.vartype = fieldDecl.vartype;
171 localDeclarations = localDeclarations.append(localDecl);
172 }
173
174 FieldRewriter fieldRewriter = new FieldRewriter(constructor, fieldToLocalMap);
175 ListBuffer<JCStatement> newBody = new ListBuffer<>();
176 for (JCStatement st : constructor.body.stats) {
177 newBody = newBody.append(fieldRewriter.translate(st));
178 }
179 localDeclarations.addAll(newBody);
180 ListBuffer<JCStatement> assigmentsBeforeSuper = new ListBuffer<>();
181 for (Symbol vsym : fieldToLocalMap.keySet()) {
182 Symbol local = fieldToLocalMap.get(vsym);
183 assigmentsBeforeSuper.append(make.at(constructor.pos()).Assignment(vsym, make.at(constructor.pos()).Ident(local)));
184 }
185 constructor.body.stats = localDeclarations.toList();
186 JCTree.JCMethodInvocation constructorCall = TreeInfo.findConstructorCall(constructor);
187 if (constructorCall.args.isEmpty()) {
188 // this is just a super invocation with no arguments we can set the fields just before the invocation
189 // and let Gen do the rest
190 TreeInfo.mapSuperCalls(constructor.body, supercall -> make.Block(0, assigmentsBeforeSuper.toList().append(supercall)));
191 } else {
192 // we need to generate fresh local variables to catch the values of the arguments, then
193 // assign the proxy locals to the fields and finally invoke the super with the fresh local variables
194 int argPosition = 0;
195 ListBuffer<JCStatement> superArgsProxies = new ListBuffer<>();
196 for (JCExpression arg : constructorCall.args) {
197 long flags = SYNTHETIC | FINAL;
198 VarSymbol proxyForArgSym = new VarSymbol(flags, newLocalName("" + argPosition), types.erasure(arg.type), constructor.sym);
199 JCVariableDecl proxyForArgDecl = make.at(constructor.pos).VarDef(proxyForArgSym, arg);
200 superArgsProxies = superArgsProxies.append(proxyForArgDecl);
201 argPosition++;
202 }
203 List<JCStatement> superArgsProxiesList = superArgsProxies.toList();
204 ListBuffer<JCExpression> newArgs = new ListBuffer<>();
205 for (JCStatement argProxy : superArgsProxies) {
206 newArgs.add(make.at(argProxy.pos).Ident((JCVariableDecl) argProxy));
207 }
208 constructorCall.args = newArgs.toList();
209 TreeInfo.mapSuperCalls(constructor.body,
210 supercall -> make.Block(0, superArgsProxiesList.appendList(assigmentsBeforeSuper.toList()).append(supercall)));
211 }
212 }
213
214 Name newLocalName(String name) {
215 return names.fromString("local" + target.syntheticNameChar() + name);
216 }
217
218 class FieldRewriter extends TreeTranslator {
219 JCMethodDecl md;
220 Map<Symbol, Symbol> fieldToLocalMap;
221 boolean ctorPrologue = true;
222
223 public FieldRewriter(JCMethodDecl md, Map<Symbol, Symbol> fieldToLocalMap) {
224 this.md = md;
225 this.fieldToLocalMap = fieldToLocalMap;
226 }
227
228 @Override
229 public void visitIdent(JCTree.JCIdent tree) {
230 if (ctorPrologue && fieldToLocalMap.get(tree.sym) != null) {
231 result = make.at(md).Ident(fieldToLocalMap.get(tree.sym));
232 } else {
233 result = tree;
234 }
235 }
236
237 @Override
238 public void visitSelect(JCTree.JCFieldAccess tree) {
239 super.visitSelect(tree);
240 if (ctorPrologue && fieldToLocalMap.get(tree.sym) != null) {
241 result = make.at(md).Ident(fieldToLocalMap.get(tree.sym));
242 } else {
243 result = tree;
244 }
245 }
246
247 @Override
248 public void visitAssign(JCAssign tree) {
249 JCExpression previousLHS = tree.lhs;
250 super.visitAssign(tree);
251 if (ctorPrologue && previousLHS != tree.lhs) {
252 unsetFieldsInfo.removeUnsetFieldInfo(currentClass, tree);
253 }
254 }
255
256 @Override
257 public void visitApply(JCTree.JCMethodInvocation tree) {
258 Name methName = TreeInfo.name(tree.meth);
259 boolean isConstructorCall = methName == names._this || methName == names._super;
260 super.visitApply(tree);
261 if (isConstructorCall) {
262 ctorPrologue = false;
263 }
264 }
265 }
266 }