| /* |
| * ProGuard -- shrinking, optimization, obfuscation, and preverification |
| * of Java bytecode. |
| * |
| * Copyright (c) 2002-2014 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.CodeAttribute; |
| import proguard.classfile.editor.CodeAttributeEditor; |
| import proguard.classfile.instruction.*; |
| import proguard.classfile.instruction.visitor.InstructionVisitor; |
| import proguard.classfile.util.SimplifiedVisitor; |
| |
| /** |
| * This InstructionVisitor simplifies unconditional branches to other |
| * unconditional branches. |
| * |
| * @author Eric Lafortune |
| */ |
| public class GotoGotoReplacer |
| extends SimplifiedVisitor |
| implements InstructionVisitor |
| { |
| private final CodeAttributeEditor codeAttributeEditor; |
| private final InstructionVisitor extraInstructionVisitor; |
| |
| |
| /** |
| * Creates a new GotoGotoReplacer. |
| * @param codeAttributeEditor a code editor that can be used for |
| * accumulating changes to the code. |
| */ |
| public GotoGotoReplacer(CodeAttributeEditor codeAttributeEditor) |
| { |
| this(codeAttributeEditor, null); |
| } |
| |
| |
| /** |
| * Creates a new GotoGotoReplacer. |
| * @param codeAttributeEditor a code editor that can be used for |
| * accumulating changes to the code. |
| * @param extraInstructionVisitor an optional extra visitor for all replaced |
| * goto instructions. |
| */ |
| public GotoGotoReplacer(CodeAttributeEditor codeAttributeEditor, |
| InstructionVisitor extraInstructionVisitor) |
| { |
| this.codeAttributeEditor = codeAttributeEditor; |
| this.extraInstructionVisitor = extraInstructionVisitor; |
| } |
| |
| |
| // Implementations for InstructionVisitor. |
| |
| public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {} |
| |
| |
| public void visitBranchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, BranchInstruction branchInstruction) |
| { |
| // Check if the instruction is an unconditional goto instruction. |
| byte opcode = branchInstruction.opcode; |
| if (opcode == InstructionConstants.OP_GOTO || |
| opcode == InstructionConstants.OP_GOTO_W) |
| { |
| // Check if the goto instruction points to another simple goto |
| // instruction. |
| int branchOffset = branchInstruction.branchOffset; |
| int targetOffset = offset + branchOffset; |
| |
| if (branchOffset != 0 && |
| branchOffset != branchInstruction.length(offset) && |
| !codeAttributeEditor.isModified(offset) && |
| !codeAttributeEditor.isModified(targetOffset)) |
| { |
| Instruction targetInstruction = |
| InstructionFactory.create(codeAttribute.code, targetOffset); |
| |
| if (targetInstruction.opcode == InstructionConstants.OP_GOTO) |
| { |
| // Simplify the goto instruction. |
| int targetBranchOffset = ((BranchInstruction)targetInstruction).branchOffset; |
| |
| Instruction newBranchInstruction = |
| new BranchInstruction(opcode, |
| (branchOffset + targetBranchOffset)); |
| codeAttributeEditor.replaceInstruction(offset, |
| newBranchInstruction); |
| |
| // Visit the instruction, if required. |
| if (extraInstructionVisitor != null) |
| { |
| extraInstructionVisitor.visitBranchInstruction(clazz, method, codeAttribute, offset, branchInstruction); |
| } |
| } |
| } |
| } |
| } |
| } |