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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 | +} | |