01: /*
02: * ProGuard -- shrinking, optimization, obfuscation, and preverification
03: * of Java bytecode.
04: *
05: * Copyright (c) 2002-2007 Eric Lafortune (eric@graphics.cornell.edu)
06: *
07: * This program is free software; you can redistribute it and/or modify it
08: * under the terms of the GNU General Public License as published by the Free
09: * 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.info;
22:
23: import proguard.classfile.*;
24: import proguard.classfile.attribute.CodeAttribute;
25: import proguard.classfile.instruction.*;
26: import proguard.classfile.instruction.visitor.InstructionVisitor;
27: import proguard.classfile.util.SimplifiedVisitor;
28:
29: /**
30: * This InstructionVisitor marks all methods that branch backward in any of the
31: * instructions that it visits.
32: *
33: * @author Eric Lafortune
34: */
35: public class BackwardBranchMarker extends SimplifiedVisitor implements
36: InstructionVisitor {
37: // Implementations for InstructionVisitor.
38:
39: public void visitAnyInstruction(Clazz clazz, Method method,
40: CodeAttribute codeAttribute, int offset,
41: Instruction instruction) {
42: }
43:
44: public void visitBranchInstruction(Clazz clazz, Method method,
45: CodeAttribute codeAttribute, int offset,
46: BranchInstruction branchInstruction) {
47: markBackwardBranch(method, branchInstruction.branchOffset);
48: }
49:
50: public void visitAnySwitchInstruction(Clazz clazz, Method method,
51: CodeAttribute codeAttribute, int offset,
52: SwitchInstruction switchInstruction) {
53: markBackwardBranch(method, switchInstruction.defaultOffset);
54:
55: for (int index = 0; index < switchInstruction.jumpOffsets.length; index++) {
56: markBackwardBranch(method,
57: switchInstruction.jumpOffsets[index]);
58: }
59: }
60:
61: // Small utility methods.
62:
63: /**
64: * Marks the given method if the given branch offset is negative.
65: */
66: private void markBackwardBranch(Method method, int branchOffset) {
67: if (branchOffset < 0) {
68: setBranchesBackward(method);
69: }
70: }
71:
72: private static void setBranchesBackward(Method method) {
73: MethodOptimizationInfo info = MethodOptimizationInfo
74: .getMethodOptimizationInfo(method);
75: if (info != null) {
76: info.setBranchesBackward();
77: }
78: }
79:
80: public static boolean branchesBackward(Method method) {
81: MethodOptimizationInfo info = MethodOptimizationInfo
82: .getMethodOptimizationInfo(method);
83: return info == null || info.branchesBackward();
84: }
85: }
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