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Java > Open Source Codes > soot > toolkits > scalar > UnusedLocalEliminator


1 /* Soot - a J*va Optimization Framework
2  * Copyright (C) 1997-1999 Raja Vallee-Rai
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
29 package soot.toolkits.scalar;
30 import soot.options.*;
31
32 import soot.*;
33 import java.util.*;
34
35
36
37
38
39 /**
40  * A BodyTransformer that removes all unused local variables from a given Body.
41  * Implemented as a singleton.
42  * @see BodyTransformer
43  * @see Body
44  */
45 public class UnusedLocalEliminator extends BodyTransformer
46 {
47     public UnusedLocalEliminator( Singletons.Global g ) {}
48     public static UnusedLocalEliminator v() { return G.v().soot_toolkits_scalar_UnusedLocalEliminator(); }
49
50     protected void internalTransform(Body body, String JavaDoc phaseName, Map options)
51     {
52         if(Options.v().verbose())
53             G.v().out.println("[" + body.getMethod().getName() + "] Eliminating unused locals...");
54
55         Set usedLocals = new HashSet();
56
57         // Traverse statements noting all the uses and defs
58 {
59             Iterator unitIt = body.getUnits().iterator();
60
61             while(unitIt.hasNext())
62             {
63                 Unit s = (Unit) unitIt.next();
64
65                 {
66                     Iterator boxIt;
67                     boxIt = s.getUseBoxes().iterator();
68                     while(boxIt.hasNext())
69                     {
70                         Value value = ((ValueBox) boxIt.next()).getValue();
71
72                         if(value instanceof Local && !usedLocals.contains(value))
73                             usedLocals.add(value);
74                     }
75                     boxIt = s.getDefBoxes().iterator();
76                     while(boxIt.hasNext())
77                     {
78                         Value value = ((ValueBox) boxIt.next()).getValue();
79
80                         if(value instanceof Local && !usedLocals.contains(value))
81                             usedLocals.add(value);
82                     }
83                 }
84             }
85
86         }
87
88         // Remove all locals that are unused.
89 {
90             Iterator it = body.getLocals().iterator();
91             
92             while(it.hasNext())
93             {
94                 Local local = (Local) it.next();
95
96                 if(!usedLocals.contains(local))
97                     it.remove();
98             }
99         }
100     }
101 }
102
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