1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
|
/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2013 Eric Lafortune (eric@graphics.cornell.edu)
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
* This program 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 for
* more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package proguard.optimize.peephole;
import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.editor.CodeAttributeEditor;
import proguard.classfile.instruction.Instruction;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;
/**
* This InstructionVisitor deletes blocks of code that can never be reached by
* regular calls or branches.
*
* @author Eric Lafortune
*/
public class UnreachableCodeRemover
extends SimplifiedVisitor
implements AttributeVisitor,
InstructionVisitor
{
//*
private static final boolean DEBUG = false;
/*/
private static boolean DEBUG = true;
//*/
private final InstructionVisitor extraInstructionVisitor;
private final ReachableCodeMarker reachableCodeMarker = new ReachableCodeMarker();
private final CodeAttributeEditor codeAttributeEditor = new CodeAttributeEditor();
/**
* Creates a new UnreachableCodeRemover.
*/
public UnreachableCodeRemover()
{
this(null);
}
/**
* Creates a new UnreachableCodeRemover.
* @param extraInstructionVisitor an optional extra visitor for all
* deleted instructions.
*/
public UnreachableCodeRemover(InstructionVisitor extraInstructionVisitor)
{
this.extraInstructionVisitor = extraInstructionVisitor;
}
// Implementations for AttributeVisitor.
public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}
public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
// DEBUG =
// clazz.getName().equals("abc/Def") &&
// method.getName(clazz).equals("abc");
// TODO: Remove this when the code has stabilized.
// Catch any unexpected exceptions from the actual visiting method.
try
{
// Process the code.
visitCodeAttribute0(clazz, method, codeAttribute);
}
catch (RuntimeException ex)
{
System.err.println("Unexpected error while removing unreachable code:");
System.err.println(" Class = ["+clazz.getName()+"]");
System.err.println(" Method = ["+method.getName(clazz)+method.getDescriptor(clazz)+"]");
System.err.println(" Exception = ["+ex.getClass().getName()+"] ("+ex.getMessage()+")");
throw ex;
}
}
public void visitCodeAttribute0(Clazz clazz, Method method, CodeAttribute codeAttribute)
{
if (DEBUG)
{
System.out.println("UnreachableCodeRemover: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz));
}
reachableCodeMarker.visitCodeAttribute(clazz, method, codeAttribute);
codeAttributeEditor.reset(codeAttribute.u4codeLength);
codeAttribute.instructionsAccept(clazz, method, this);
codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute);
}
// Implementations for InstructionVisitor.
public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction)
{
if (DEBUG)
{
System.out.println(" "+(reachableCodeMarker.isReachable(offset) ? "+" : "-")+" "+instruction.toString(offset));
}
// Is this instruction unreachable?
if (!reachableCodeMarker.isReachable(offset))
{
// Then delete it.
codeAttributeEditor.deleteInstruction(offset);
// Visit the instruction, if required.
if (extraInstructionVisitor != null)
{
instruction.accept(clazz, method, codeAttribute, offset, extraInstructionVisitor);
}
}
}
}
|
