1 /* 2 * Copyright (c) 1994, 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 sun.tools.asm.Label; 31 import java.io.PrintStream; 32 import java.util.Hashtable; 33 34 /** 35 * WARNING: The contents of this source file are not part of any 36 * supported API. Code that depends on them does so at its own risk: 37 * they are subject to change or removal without notice. 38 */ 39 public 40 class IfStatement extends Statement { 41 Expression cond; 42 Statement ifTrue; 43 Statement ifFalse; 44 45 /** 46 * Constructor 47 */ IfStatement(long where, Expression cond, Statement ifTrue, Statement ifFalse)48 public IfStatement(long where, Expression cond, Statement ifTrue, Statement ifFalse) { 49 super(IF, where); 50 this.cond = cond; 51 this.ifTrue = ifTrue; 52 this.ifFalse = ifFalse; 53 } 54 55 /** 56 * Check statement 57 */ check(Environment env, Context ctx, Vset vset, Hashtable<Object, Object> exp)58 Vset check(Environment env, Context ctx, Vset vset, Hashtable<Object, Object> exp) { 59 checkLabel(env, ctx); 60 CheckContext newctx = new CheckContext(ctx, this); 61 // Vset vsExtra = vset.copy(); // See comment below. 62 ConditionVars cvars = 63 cond.checkCondition(env, newctx, reach(env, vset), exp); 64 cond = convert(env, newctx, Type.tBoolean, cond); 65 // The following code, now deleted, was apparently an erroneous attempt 66 // at providing better error diagnostics. The comment read: 'If either 67 // the true clause or the false clause is unreachable, do a reasonable 68 // check on the child anyway.' 69 // Vset vsTrue = cvars.vsTrue.isDeadEnd() ? vsExtra : cvars.vsTrue; 70 // Vset vsFalse = cvars.vsFalse.isDeadEnd() ? vsExtra : cvars.vsFalse; 71 // Unfortunately, this violates the rules laid out in the JLS, and leads to 72 // blatantly incorrect results. For example, 'i' will not be recognized 73 // as definitely assigned following the statement 'if (true) i = 1;'. 74 // It is best to slavishly follow the JLS here. A cleverer approach could 75 // only correctly issue warnings, as JLS 16.2.6 is quite explicit, and it 76 // is OK for a dead branch of an if-statement to omit an assignment that 77 // would be required in the other branch. A complication: This code also 78 // had the effect of implementing the special-case rules for 'if-then' and 79 // 'if-then-else' in JLS 14.19, "Unreachable Statements". We now use 80 // 'Vset.clearDeadEnd' to remove the dead-end status of unreachable branches 81 // without affecting the definite-assignment status of the variables, thus 82 // maintaining a correct implementation of JLS 16.2.6. Fixes 4094353. 83 // Note that the code below will not consider the branches unreachable if 84 // the entire statement is unreachable. This is consistent with the error 85 // recovery policy that reports the only the first unreachable statement 86 // along an acyclic execution path. 87 Vset vsTrue = cvars.vsTrue.clearDeadEnd(); 88 Vset vsFalse = cvars.vsFalse.clearDeadEnd(); 89 vsTrue = ifTrue.check(env, newctx, vsTrue, exp); 90 if (ifFalse != null) 91 vsFalse = ifFalse.check(env, newctx, vsFalse, exp); 92 vset = vsTrue.join(vsFalse.join(newctx.vsBreak)); 93 return ctx.removeAdditionalVars(vset); 94 } 95 96 /** 97 * Inline 98 */ inline(Environment env, Context ctx)99 public Statement inline(Environment env, Context ctx) { 100 ctx = new Context(ctx, this); 101 cond = cond.inlineValue(env, ctx); 102 103 // The compiler currently needs to perform inlining on both 104 // branches of the if statement -- even if `cond' is a constant 105 // true or false. Why? The compiler will later try to compile 106 // all classes that it has seen; this includes classes that 107 // appear in dead code. If we don't inline the dead branch here 108 // then the compiler will never perform inlining on any local 109 // classes appearing on the dead code. When the compiler tries 110 // to compile an un-inlined local class with uplevel references, 111 // it dies. (bug 4059492) 112 // 113 // A better solution to this would be to walk the dead branch and 114 // mark any local classes appearing therein as unneeded. Then the 115 // compilation phase could skip these classes. 116 if (ifTrue != null) { 117 ifTrue = ifTrue.inline(env, ctx); 118 } 119 if (ifFalse != null) { 120 ifFalse = ifFalse.inline(env, ctx); 121 } 122 if (cond.equals(true)) { 123 return eliminate(env, ifTrue); 124 } 125 if (cond.equals(false)) { 126 return eliminate(env, ifFalse); 127 } 128 if ((ifTrue == null) && (ifFalse == null)) { 129 return eliminate(env, new ExpressionStatement(where, cond).inline(env, ctx)); 130 } 131 if (ifTrue == null) { 132 cond = new NotExpression(cond.where, cond).inlineValue(env, ctx); 133 return eliminate(env, new IfStatement(where, cond, ifFalse, null)); 134 } 135 return this; 136 } 137 138 /** 139 * Create a copy of the statement for method inlining 140 */ copyInline(Context ctx, boolean valNeeded)141 public Statement copyInline(Context ctx, boolean valNeeded) { 142 IfStatement s = (IfStatement)clone(); 143 s.cond = cond.copyInline(ctx); 144 if (ifTrue != null) { 145 s.ifTrue = ifTrue.copyInline(ctx, valNeeded); 146 } 147 if (ifFalse != null) { 148 s.ifFalse = ifFalse.copyInline(ctx, valNeeded); 149 } 150 return s; 151 } 152 153 /** 154 * The cost of inlining this statement 155 */ costInline(int thresh, Environment env, Context ctx)156 public int costInline(int thresh, Environment env, Context ctx) { 157 int cost = 1 + cond.costInline(thresh, env, ctx); 158 if (ifTrue != null) { 159 cost += ifTrue.costInline(thresh, env, ctx); 160 } 161 if (ifFalse != null) { 162 cost += ifFalse.costInline(thresh, env, ctx); 163 } 164 return cost; 165 } 166 167 /** 168 * Code 169 */ code(Environment env, Context ctx, Assembler asm)170 public void code(Environment env, Context ctx, Assembler asm) { 171 CodeContext newctx = new CodeContext(ctx, this); 172 173 Label l1 = new Label(); 174 cond.codeBranch(env, newctx, asm, l1, false); 175 ifTrue.code(env, newctx, asm); 176 if (ifFalse != null) { 177 Label l2 = new Label(); 178 asm.add(true, where, opc_goto, l2); 179 asm.add(l1); 180 ifFalse.code(env, newctx, asm); 181 asm.add(l2); 182 } else { 183 asm.add(l1); 184 } 185 186 asm.add(newctx.breakLabel); 187 } 188 189 /** 190 * Print 191 */ print(PrintStream out, int indent)192 public void print(PrintStream out, int indent) { 193 super.print(out, indent); 194 out.print("if "); 195 cond.print(out); 196 out.print(" "); 197 ifTrue.print(out, indent); 198 if (ifFalse != null) { 199 out.print(" else "); 200 ifFalse.print(out, indent); 201 } 202 } 203 } 204