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Java > Open Source Codes > proguard > optimize > peephole > PeepholeOptimizer


1 /*
2  * ProGuard -- shrinking, optimization, obfuscation, and preverification
3  * of Java bytecode.
4  *
5  * Copyright (c) 2002-2007 Eric Lafortune (eric@graphics.cornell.edu)
6  *
7  * This program is free software; you can redistribute it and/or modify it
8  * under the terms of the GNU General Public License as published by the Free
9  * Software Foundation; either version 2 of the License, or (at your option)
10  * any later version.
11  *
12  * This program is distributed in the hope that it will be useful, but WITHOUT
13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15  * more details.
16  *
17  * You should have received a copy of the GNU General Public License along
18  * with this program; if not, write to the Free Software Foundation, Inc.,
19  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20  */

21 package proguard.optimize.peephole;
22
23 import proguard.classfile.*;
24 import proguard.classfile.attribute.*;
25 import proguard.classfile.attribute.visitor.AttributeVisitor;
26 import proguard.classfile.editor.CodeAttributeEditor;
27 import proguard.classfile.instruction.visitor.InstructionVisitor;
28 import proguard.classfile.util.SimplifiedVisitor;
29
30 /**
31  * This AttributeVisitor sets up and applies the peephole optimizations of its
32  * instruction visitor. The instruction visitor should be using the same
33  * (optional) branch target finder and code attribute editor.
34  *
35  * @author Eric Lafortune
36  */

37 public class PeepholeOptimizer
38 extends SimplifiedVisitor
39 implements AttributeVisitor
40 {
41     private BranchTargetFinder branchTargetFinder;
42     private CodeAttributeEditor codeAttributeEditor;
43     private InstructionVisitor instructionVisitor;
44
45
46     /**
47      * Creates a new PeepholeOptimizer.
48      * @param codeAttributeEditor the code attribute editor that will be reset
49      * and then executed.
50      * @param instructionVisitor the instruction visitor that performs
51      * peephole optimizations using the above code
52      * attribute editor.
53      */

54     public PeepholeOptimizer(CodeAttributeEditor codeAttributeEditor,
55                              InstructionVisitor instructionVisitor)
56     {
57         this(null, codeAttributeEditor, instructionVisitor);
58     }
59
60
61     /**
62      * Creates a new PeepholeOptimizer.
63      * @param branchTargetFinder branch target finder that will be initialized
64      * to indicate branch targets in the visited code.
65      * @param codeAttributeEditor the code attribute editor that will be reset
66      * and then executed.
67      * @param instructionVisitor the instruction visitor that performs
68      * peephole optimizations using the above code
69      * attribute editor.
70      */

71     public PeepholeOptimizer(BranchTargetFinder branchTargetFinder,
72                              CodeAttributeEditor codeAttributeEditor,
73                              InstructionVisitor instructionVisitor)
74     {
75         this.branchTargetFinder = branchTargetFinder;
76         this.codeAttributeEditor = codeAttributeEditor;
77         this.instructionVisitor = instructionVisitor;
78     }
79
80
81     // Implementations for AttributeVisitor.
82

83     public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
84
85
86     public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
87     {
88         if (branchTargetFinder != null)
89         {
90             // Set up the branch target finder.
91
branchTargetFinder.visitCodeAttribute(clazz, method, codeAttribute);
92         }
93
94         // Set up the code attribute editor.
95
codeAttributeEditor.reset(codeAttribute.u4codeLength);
96
97         // Find the peephole optimizations.
98
codeAttribute.instructionsAccept(clazz, method, instructionVisitor);
99
100         // Apply the peephole optimizations.
101
codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute);
102     }
103 }
104
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