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Java > Open Source Codes > soot > jimple > toolkits > scalar > ConditionalBranchFolder


1 /* Soot - a J*va Optimization Framework
2  * Copyright (C) 1999 Phong Co
3  *
4  * This library is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * This library is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with this library; if not, write to the
16  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17  * Boston, MA 02111-1307, USA.
18  */
19
20 /*
21  * Modified by the Sable Research Group and others 1997-1999.
22  * See the 'credits' file distributed with Soot for the complete list of
23  * contributors. (Soot is distributed at http://www.sable.mcgill.ca/soot)
24  */
25
26
27
28 package soot.jimple.toolkits.scalar;
29 import soot.options.*;
30
31 import soot.util.*;
32 import soot.*;
33 import soot.jimple.*;
34 import java.io.*;
35 import java.util.*;
36
37
38 public class ConditionalBranchFolder extends BodyTransformer
39 {
40     public ConditionalBranchFolder ( Singletons.Global g ) {}
41     public static ConditionalBranchFolder v() { return G.v().soot_jimple_toolkits_scalar_ConditionalBranchFolder (); }
42
43     protected void internalTransform(Body body, String JavaDoc phaseName, Map options)
44     {
45         StmtBody stmtBody = (StmtBody)body;
46
47         int numTrue = 0, numFalse = 0;
48
49         if (Options.v().verbose())
50             G.v().out.println("[" + stmtBody.getMethod().getName() +
51                                "] Folding conditional branches...");
52
53         Chain units = stmtBody.getUnits();
54         ArrayList unitList = new ArrayList(); unitList.addAll(units);
55
56         Iterator stmtIt = unitList.iterator();
57         while (stmtIt.hasNext()) {
58             Stmt stmt = (Stmt)stmtIt.next();
59             if (stmt instanceof IfStmt) {
60                 // check for constant-valued conditions
61 Value cond = ((IfStmt) stmt).getCondition();
62                 if (Evaluator.isValueConstantValued(cond)) {
63                     cond = Evaluator.getConstantValueOf(cond);
64
65                     if (((IntConstant) cond).value == 1) {
66                         // if condition always true, convert if to goto
67 Stmt newStmt =
68                             Jimple.v().newGotoStmt(((IfStmt)stmt).getTarget());
69                         
70                         units.insertAfter(newStmt, stmt);
71                         
72                         numTrue++;
73                     }
74                     else
75                         numFalse++;
76                         
77                     // remove if
78 units.remove(stmt);
79                 }
80             }
81         }
82
83        if (Options.v().verbose())
84             G.v().out.println("[" + stmtBody.getMethod().getName() +
85                 "] Folded " + numTrue + " true, " + numFalse +
86                                " conditional branches");
87
88     } // foldBranches
89
90 } // BranchFolder
91
92
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