1 /* 2 * Copyright (c) 1997, 2003, 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 sun.tools.tree; 27 28 import sun.tools.java.*; 29 import sun.tools.asm.Assembler; 30 import java.io.PrintStream; 31 32 /** 33 * This class encapsulates the information required to generate an update to a private 34 * field referenced from another class, e.g., an inner class. An expression denoting a 35 * reference to the object to which the field belongs is associated with getter and 36 * setter methods. 37 * <p> 38 * We use this class only for assignment, increment, and decrement operators, in which 39 * the old value is first retrieved and then a new value is computed and stored. 40 * Simple assignment expressions in which a value is copied without modification are 41 * handled by another mechanism. 42 * 43 * WARNING: The contents of this source file are not part of any 44 * supported API. Code that depends on them does so at its own risk: 45 * they are subject to change or removal without notice. 46 */ 47 48 class FieldUpdater implements Constants { 49 50 // Location for reporting errors. 51 // Errors will always indicate compiler failure, but these will be easier to diagnose 52 // if the bogus error is localized to the offending assignment. 53 private long where; 54 55 // The field to which this updater applies. 56 // It would be easy to eliminate the need to store the field here, but we retain it for 57 // diagnostic purposes. 58 private MemberDefinition field; 59 60 // Expression denoting the object to which the getter and setter are applied. 61 // If the field is static, 'base' may be null, but need not be, as a static field 62 // may be selected from an object reference. Even though the value of the object 63 // reference will be ignored, it may have side-effects. 64 private Expression base; 65 66 // The getter and setter methods, generated by 'getAccessMember' and 'getUpdateMember'. 67 private MemberDefinition getter; 68 private MemberDefinition setter; 69 70 // The number of words occupied on the stack by the object reference. 71 // For static fields, this is zero. 72 private int depth; 73 74 /** 75 * Constructor. 76 */ 77 FieldUpdater(long where, MemberDefinition field, Expression base, MemberDefinition getter, MemberDefinition setter)78 public FieldUpdater(long where, MemberDefinition field, 79 Expression base, MemberDefinition getter, MemberDefinition setter) { 80 this.where = where; 81 this.field = field; 82 this.base = base; 83 this.getter = getter; 84 this.setter = setter; 85 } 86 87 88 /** 89 * Since the object reference expression may be captured before it has been inlined, 90 * we must inline it later. A <code>FieldUpdater</code> is inlined essentially as if 91 * it were a child of the assignment node to which it belongs. 92 */ 93 inline(Environment env, Context ctx)94 public FieldUpdater inline(Environment env, Context ctx) { 95 if (base != null) { 96 if (field.isStatic()) { 97 base = base.inline(env, ctx); 98 } else { 99 base = base.inlineValue(env, ctx); 100 } 101 } 102 return this; 103 } 104 copyInline(Context ctx)105 public FieldUpdater copyInline(Context ctx) { 106 return new FieldUpdater(where, field, base.copyInline(ctx), getter, setter); 107 } 108 costInline(int thresh, Environment env, Context ctx, boolean needGet)109 public int costInline(int thresh, Environment env, Context ctx, boolean needGet) { 110 // Size of 'invokestatic' call for access method is 3 bytes. 111 int cost = needGet ? 7 : 3; // getter needs extra invokestatic + dup 112 // Size of expression to compute 'this' arg if needed. 113 if (!field.isStatic() && base != null) { 114 cost += base.costInline(thresh, env, ctx); 115 } 116 // We ignore the cost of duplicating value in value-needed context. 117 return cost; 118 } 119 120 /** 121 * Duplicate <code>items</code> words from the top of the stack, locating them 122 * below the topmost <code>depth</code> words on the stack. 123 */ 124 125 // This code was cribbed from 'Expression.java'. We cannot reuse that code here, 126 // because we do not inherit from class 'Expression'. 127 codeDup(Assembler asm, int items, int depth)128 private void codeDup(Assembler asm, int items, int depth) { 129 switch (items) { 130 case 0: 131 return; 132 case 1: 133 switch (depth) { 134 case 0: 135 asm.add(where, opc_dup); 136 return; 137 case 1: 138 asm.add(where, opc_dup_x1); 139 return; 140 case 2: 141 asm.add(where, opc_dup_x2); 142 return; 143 144 } 145 break; 146 case 2: 147 switch (depth) { 148 case 0: 149 asm.add(where, opc_dup2); 150 return; 151 case 1: 152 asm.add(where, opc_dup2_x1); 153 return; 154 case 2: 155 asm.add(where, opc_dup2_x2); 156 return; 157 158 } 159 break; 160 } 161 throw new CompilerError("can't dup: " + items + ", " + depth); 162 } 163 164 /** 165 * Begin a field update by an assignment, increment, or decrement operator. 166 * The current value of the field is left at the top of the stack. 167 * If <code>valNeeded</code> is true, we arrange for the initial value to remain 168 * on the stack after the update. 169 */ 170 startUpdate(Environment env, Context ctx, Assembler asm, boolean valNeeded)171 public void startUpdate(Environment env, Context ctx, Assembler asm, boolean valNeeded) { 172 if (!(getter.isStatic() && setter.isStatic())) { 173 throw new CompilerError("startUpdate isStatic"); 174 } 175 if (!field.isStatic()) { 176 // Provide explicit 'this' argument. 177 base.codeValue(env, ctx, asm); 178 depth = 1; 179 } else { 180 // May need to evaluate 'base' for effect. 181 // If 'base' was a type expression, it should have previously been inlined away. 182 if (base != null) { 183 base.code(env, ctx, asm); 184 } 185 depth = 0; 186 } 187 codeDup(asm, depth, 0); 188 asm.add(where, opc_invokestatic, getter); 189 if (valNeeded) { 190 codeDup(asm, field.getType().stackSize(), depth); 191 } 192 } 193 194 /** 195 * Complete a field update by an assignment, increment, or decrement operator. 196 * The original value of the field left on the stack by <code>startUpdate</code> 197 * must have been replaced with the updated value, with no other stack alterations. 198 * If <code>valNeeded</code> is true, we arrange for the updated value to remain 199 * on the stack after the update. The <code>valNeeded</code> argument must not be 200 * true in both <code>startUpdate</code> and <code>finishUpdate</code>. 201 */ 202 finishUpdate(Environment env, Context ctx, Assembler asm, boolean valNeeded)203 public void finishUpdate(Environment env, Context ctx, Assembler asm, boolean valNeeded) { 204 if (valNeeded) { 205 codeDup(asm, field.getType().stackSize(), depth); 206 } 207 asm.add(where, opc_invokestatic, setter); 208 } 209 210 /** 211 * Like above, but used when assigning a new value independent of the 212 * old, as in a simple assignment expression. After 'startAssign', 213 * code must be emitted to leave one additional value on the stack without 214 * altering any others, followed by 'finishAssign'. 215 */ 216 startAssign(Environment env, Context ctx, Assembler asm)217 public void startAssign(Environment env, Context ctx, Assembler asm) { 218 if (!setter.isStatic()) { 219 throw new CompilerError("startAssign isStatic"); 220 } 221 if (!field.isStatic()) { 222 // Provide explicit 'this' argument. 223 base.codeValue(env, ctx, asm); 224 depth = 1; 225 } else { 226 // May need to evaluate 'base' for effect. 227 // If 'base' was a type expression, it should have previously been inlined away. 228 if (base != null) { 229 base.code(env, ctx, asm); 230 } 231 depth = 0; 232 } 233 } 234 finishAssign(Environment env, Context ctx, Assembler asm, boolean valNeeded)235 public void finishAssign(Environment env, Context ctx, Assembler asm, boolean valNeeded) { 236 if (valNeeded) { 237 codeDup(asm, field.getType().stackSize(), depth); 238 } 239 asm.add(where, opc_invokestatic, setter); 240 } 241 242 } 243