| /* |
| * Copyright (c) 1994, 2003, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package sun.tools.tree; |
| |
| import sun.tools.java.*; |
| import sun.tools.asm.Assembler; |
| import sun.tools.asm.Label; |
| import java.io.PrintStream; |
| import java.util.Hashtable; |
| |
| /** |
| * WARNING: The contents of this source file are not part of any |
| * supported API. Code that depends on them does so at its own risk: |
| * they are subject to change or removal without notice. |
| */ |
| public |
| class IfStatement extends Statement { |
| Expression cond; |
| Statement ifTrue; |
| Statement ifFalse; |
| |
| /** |
| * Constructor |
| */ |
| public IfStatement(long where, Expression cond, Statement ifTrue, Statement ifFalse) { |
| super(IF, where); |
| this.cond = cond; |
| this.ifTrue = ifTrue; |
| this.ifFalse = ifFalse; |
| } |
| |
| /** |
| * Check statement |
| */ |
| Vset check(Environment env, Context ctx, Vset vset, Hashtable exp) { |
| checkLabel(env, ctx); |
| CheckContext newctx = new CheckContext(ctx, this); |
| // Vset vsExtra = vset.copy(); // See comment below. |
| ConditionVars cvars = |
| cond.checkCondition(env, newctx, reach(env, vset), exp); |
| cond = convert(env, newctx, Type.tBoolean, cond); |
| // The following code, now deleted, was apparently an erroneous attempt |
| // at providing better error diagnostics. The comment read: 'If either |
| // the true clause or the false clause is unreachable, do a reasonable |
| // check on the child anyway.' |
| // Vset vsTrue = cvars.vsTrue.isDeadEnd() ? vsExtra : cvars.vsTrue; |
| // Vset vsFalse = cvars.vsFalse.isDeadEnd() ? vsExtra : cvars.vsFalse; |
| // Unfortunately, this violates the rules laid out in the JLS, and leads to |
| // blatantly incorrect results. For example, 'i' will not be recognized |
| // as definitely assigned following the statement 'if (true) i = 1;'. |
| // It is best to slavishly follow the JLS here. A cleverer approach could |
| // only correctly issue warnings, as JLS 16.2.6 is quite explicit, and it |
| // is OK for a dead branch of an if-statement to omit an assignment that |
| // would be required in the other branch. A complication: This code also |
| // had the effect of implementing the special-case rules for 'if-then' and |
| // 'if-then-else' in JLS 14.19, "Unreachable Statements". We now use |
| // 'Vset.clearDeadEnd' to remove the dead-end status of unreachable branches |
| // without affecting the definite-assignment status of the variables, thus |
| // maintaining a correct implementation of JLS 16.2.6. Fixes 4094353. |
| // Note that the code below will not consider the branches unreachable if |
| // the entire statement is unreachable. This is consistent with the error |
| // recovery policy that reports the only the first unreachable statement |
| // along an acyclic execution path. |
| Vset vsTrue = cvars.vsTrue.clearDeadEnd(); |
| Vset vsFalse = cvars.vsFalse.clearDeadEnd(); |
| vsTrue = ifTrue.check(env, newctx, vsTrue, exp); |
| if (ifFalse != null) |
| vsFalse = ifFalse.check(env, newctx, vsFalse, exp); |
| vset = vsTrue.join(vsFalse.join(newctx.vsBreak)); |
| return ctx.removeAdditionalVars(vset); |
| } |
| |
| /** |
| * Inline |
| */ |
| public Statement inline(Environment env, Context ctx) { |
| ctx = new Context(ctx, this); |
| cond = cond.inlineValue(env, ctx); |
| |
| // The compiler currently needs to perform inlining on both |
| // branches of the if statement -- even if `cond' is a constant |
| // true or false. Why? The compiler will later try to compile |
| // all classes that it has seen; this includes classes that |
| // appear in dead code. If we don't inline the dead branch here |
| // then the compiler will never perform inlining on any local |
| // classes appearing on the dead code. When the compiler tries |
| // to compile an un-inlined local class with uplevel references, |
| // it dies. (bug 4059492) |
| // |
| // A better solution to this would be to walk the dead branch and |
| // mark any local classes appearing therein as unneeded. Then the |
| // compilation phase could skip these classes. |
| if (ifTrue != null) { |
| ifTrue = ifTrue.inline(env, ctx); |
| } |
| if (ifFalse != null) { |
| ifFalse = ifFalse.inline(env, ctx); |
| } |
| if (cond.equals(true)) { |
| return eliminate(env, ifTrue); |
| } |
| if (cond.equals(false)) { |
| return eliminate(env, ifFalse); |
| } |
| if ((ifTrue == null) && (ifFalse == null)) { |
| return eliminate(env, new ExpressionStatement(where, cond).inline(env, ctx)); |
| } |
| if (ifTrue == null) { |
| cond = new NotExpression(cond.where, cond).inlineValue(env, ctx); |
| return eliminate(env, new IfStatement(where, cond, ifFalse, null)); |
| } |
| return this; |
| } |
| |
| /** |
| * Create a copy of the statement for method inlining |
| */ |
| public Statement copyInline(Context ctx, boolean valNeeded) { |
| IfStatement s = (IfStatement)clone(); |
| s.cond = cond.copyInline(ctx); |
| if (ifTrue != null) { |
| s.ifTrue = ifTrue.copyInline(ctx, valNeeded); |
| } |
| if (ifFalse != null) { |
| s.ifFalse = ifFalse.copyInline(ctx, valNeeded); |
| } |
| return s; |
| } |
| |
| /** |
| * The cost of inlining this statement |
| */ |
| public int costInline(int thresh, Environment env, Context ctx) { |
| int cost = 1 + cond.costInline(thresh, env, ctx); |
| if (ifTrue != null) { |
| cost += ifTrue.costInline(thresh, env, ctx); |
| } |
| if (ifFalse != null) { |
| cost += ifFalse.costInline(thresh, env, ctx); |
| } |
| return cost; |
| } |
| |
| /** |
| * Code |
| */ |
| public void code(Environment env, Context ctx, Assembler asm) { |
| CodeContext newctx = new CodeContext(ctx, this); |
| |
| Label l1 = new Label(); |
| cond.codeBranch(env, newctx, asm, l1, false); |
| ifTrue.code(env, newctx, asm); |
| if (ifFalse != null) { |
| Label l2 = new Label(); |
| asm.add(true, where, opc_goto, l2); |
| asm.add(l1); |
| ifFalse.code(env, newctx, asm); |
| asm.add(l2); |
| } else { |
| asm.add(l1); |
| } |
| |
| asm.add(newctx.breakLabel); |
| } |
| |
| /** |
| * Print |
| */ |
| public void print(PrintStream out, int indent) { |
| super.print(out, indent); |
| out.print("if "); |
| cond.print(out); |
| out.print(" "); |
| ifTrue.print(out, indent); |
| if (ifFalse != null) { |
| out.print(" else "); |
| ifFalse.print(out, indent); |
| } |
| } |
| } |