| /* |
| * ProGuard -- shrinking, optimization, obfuscation, and preverification |
| * of Java bytecode. |
| * |
| * Copyright (c) 2002-2017 Eric Lafortune @ GuardSquare |
| * |
| * 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.*; |
| import proguard.classfile.instruction.*; |
| import proguard.classfile.instruction.visitor.InstructionVisitor; |
| import proguard.classfile.util.SimplifiedVisitor; |
| |
| import java.util.Arrays; |
| |
| /** |
| * This AttributeVisitor finds all instruction offsets, branch targets, and |
| * exception targets in the CodeAttribute objects that it visits. |
| * |
| * @author Eric Lafortune |
| */ |
| public class ReachableCodeMarker |
| extends SimplifiedVisitor |
| implements AttributeVisitor, |
| InstructionVisitor, |
| ExceptionInfoVisitor |
| { |
| private boolean[] isReachable = new boolean[ClassConstants.TYPICAL_CODE_LENGTH]; |
| |
| private boolean next; |
| private boolean evaluateExceptions; |
| |
| |
| /** |
| * Returns whether the instruction at the given offset is reachable in |
| * the CodeAttribute that was visited most recently. |
| */ |
| public boolean isReachable(int offset) |
| { |
| return isReachable[offset]; |
| } |
| |
| |
| /** |
| * Returns whether any of the instructions at the given offsets are |
| * reachable in the CodeAttribute that was visited most recently. |
| */ |
| public boolean isReachable(int startOffset, int endOffset) |
| { |
| // Check if any of the instructions is reachable. |
| for (int offset = startOffset; offset < endOffset; offset++) |
| { |
| if (isReachable[offset]) |
| { |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| |
| // Implementations for AttributeVisitor. |
| |
| public void visitAnyAttribute(Clazz clazz, Attribute attribute) {} |
| |
| |
| public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) |
| { |
| // Make sure there is a sufficiently large array. |
| int codeLength = codeAttribute.u4codeLength; |
| if (isReachable.length < codeLength) |
| { |
| // Create a new array. |
| isReachable = new boolean[codeLength]; |
| } |
| else |
| { |
| // Reset the array. |
| Arrays.fill(isReachable, 0, codeLength, false); |
| } |
| |
| // Mark the code, starting at the entry point. |
| markCode(clazz, method, codeAttribute, 0); |
| |
| // Mark the exception handlers, iterating as long as necessary. |
| do |
| { |
| evaluateExceptions = false; |
| |
| codeAttribute.exceptionsAccept(clazz, method, this); |
| } |
| while (evaluateExceptions); |
| } |
| |
| |
| // Implementations for InstructionVisitor. |
| |
| public void visitSimpleInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, SimpleInstruction simpleInstruction) |
| { |
| byte opcode = simpleInstruction.opcode; |
| if (opcode == InstructionConstants.OP_IRETURN || |
| opcode == InstructionConstants.OP_LRETURN || |
| opcode == InstructionConstants.OP_FRETURN || |
| opcode == InstructionConstants.OP_DRETURN || |
| opcode == InstructionConstants.OP_ARETURN || |
| opcode == InstructionConstants.OP_RETURN || |
| opcode == InstructionConstants.OP_ATHROW) |
| { |
| next = false; |
| } |
| } |
| |
| |
| public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction) |
| { |
| } |
| |
| |
| public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, VariableInstruction variableInstruction) |
| { |
| if (variableInstruction.opcode == InstructionConstants.OP_RET) |
| { |
| next = false; |
| } |
| } |
| |
| |
| public void visitBranchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, BranchInstruction branchInstruction) |
| { |
| // Mark the branch target. |
| markBranchTarget(clazz, |
| method, |
| codeAttribute, |
| offset + branchInstruction.branchOffset); |
| |
| byte opcode = branchInstruction.opcode; |
| if (opcode == InstructionConstants.OP_GOTO || |
| opcode == InstructionConstants.OP_GOTO_W) |
| { |
| next = false; |
| } |
| } |
| |
| |
| public void visitAnySwitchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, SwitchInstruction switchInstruction) |
| { |
| // Mark the branch targets of the default jump offset. |
| markBranchTarget(clazz, |
| method, |
| codeAttribute, |
| offset + switchInstruction.defaultOffset); |
| |
| // Mark the branch targets of the jump offsets. |
| markBranchTargets(clazz, |
| method, |
| codeAttribute, |
| offset, |
| switchInstruction.jumpOffsets); |
| |
| next = false; |
| } |
| |
| |
| // Implementations for ExceptionInfoVisitor. |
| |
| public void visitExceptionInfo(Clazz clazz, Method method, CodeAttribute codeAttribute, ExceptionInfo exceptionInfo) |
| { |
| // Mark the exception handler if it's relevant. |
| if (!isReachable(exceptionInfo.u2handlerPC) && |
| isReachable(exceptionInfo.u2startPC, exceptionInfo.u2endPC)) |
| { |
| markCode(clazz, method, codeAttribute, exceptionInfo.u2handlerPC); |
| |
| evaluateExceptions = true; |
| } |
| } |
| |
| |
| // Small utility methods. |
| |
| /** |
| * Marks the branch targets of the given jump offsets for the instruction |
| * at the given offset. |
| */ |
| private void markBranchTargets(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, int[] jumpOffsets) |
| { |
| for (int index = 0; index < jumpOffsets.length; index++) |
| { |
| markCode(clazz, method, codeAttribute, offset + jumpOffsets[index]); |
| } |
| } |
| |
| |
| /** |
| * Marks the branch target at the given offset. |
| */ |
| private void markBranchTarget(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset) |
| { |
| boolean oldNext = next; |
| |
| markCode(clazz, method, codeAttribute, offset); |
| |
| next = oldNext; |
| } |
| |
| |
| /** |
| * Marks the code starting at the given offset. |
| */ |
| private void markCode(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset) |
| { |
| boolean oldNext = next; |
| |
| byte[] code = codeAttribute.code; |
| |
| // Continue with the current instruction as long as we haven't marked it |
| // yet. |
| while (!isReachable[offset]) |
| { |
| // Get the current instruction. |
| Instruction instruction = InstructionFactory.create(code, offset); |
| |
| // Mark it as reachable. |
| isReachable[offset] = true; |
| |
| // By default, we'll assume we can continue with the next |
| // instruction in a moment. |
| next = true; |
| |
| // Mark the branch targets, if any. |
| instruction.accept(clazz, method, codeAttribute, offset, this); |
| |
| // Can we really continue with the next instruction? |
| if (!next) |
| { |
| break; |
| } |
| |
| // Go to the next instruction. |
| offset += instruction.length(offset); |
| } |
| |
| next = oldNext; |
| } |
| } |