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| 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 | */ | ||
| 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 | */ | ||
| 58 | Vset check(Environment env, Context ctx, Vset vset, Hashtable 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 | */ | ||
| 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 | */ | ||
| 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 | */ | ||
| 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 | */ | ||
| 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 | |||
| 191 | */ | ||
| 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 | } | ||