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/*
* ProGuard -- shrinking, optimization, obfuscation, and preverification
* of Java bytecode.
*
* Copyright (c) 2002-2009 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.info;
import proguard.classfile.*;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.constant.*;
import proguard.classfile.constant.visitor.ConstantVisitor;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.classfile.visitor.*;
/**
* This class can tell whether an instruction has any side effects. Return
* instructions can be included or not.
*
* @see ReadWriteFieldMarker
* @see NoSideEffectMethodMarker
* @see SideEffectMethodMarker
* @author Eric Lafortune
*/
public class SideEffectInstructionChecker
extends SimplifiedVisitor
implements InstructionVisitor,
ConstantVisitor,
MemberVisitor
{
private final boolean includeReturnInstructions;
// A return value for the visitor methods.
private boolean hasSideEffects;
public SideEffectInstructionChecker(boolean includeReturnInstructions)
{
this.includeReturnInstructions = includeReturnInstructions;
}
public boolean hasSideEffects(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction)
{
hasSideEffects = false;
instruction.accept(clazz, method, codeAttribute, offset, this);
return hasSideEffects;
}
// Implementations for InstructionVisitor.
public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, Instruction instruction) {}
public void visitSimpleInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, SimpleInstruction simpleInstruction)
{
byte opcode = simpleInstruction.opcode;
// Check for instructions that might cause side effects.
if (opcode == InstructionConstants.OP_IASTORE ||
opcode == InstructionConstants.OP_LASTORE ||
opcode == InstructionConstants.OP_FASTORE ||
opcode == InstructionConstants.OP_DASTORE ||
opcode == InstructionConstants.OP_AASTORE ||
opcode == InstructionConstants.OP_BASTORE ||
opcode == InstructionConstants.OP_CASTORE ||
opcode == InstructionConstants.OP_SASTORE ||
opcode == InstructionConstants.OP_ATHROW ||
opcode == InstructionConstants.OP_MONITORENTER ||
opcode == InstructionConstants.OP_MONITOREXIT ||
(includeReturnInstructions &&
(opcode == InstructionConstants.OP_IRETURN ||
opcode == InstructionConstants.OP_LRETURN ||
opcode == InstructionConstants.OP_FRETURN ||
opcode == InstructionConstants.OP_DRETURN ||
opcode == InstructionConstants.OP_ARETURN ||
opcode == InstructionConstants.OP_RETURN)))
{
// These instructions always cause a side effect.
hasSideEffects = true;
}
}
public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, VariableInstruction variableInstruction)
{
byte opcode = variableInstruction.opcode;
// Check for instructions that might cause side effects.
if (includeReturnInstructions &&
opcode == InstructionConstants.OP_RET)
{
hasSideEffects = true;
}
}
public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction)
{
byte opcode = constantInstruction.opcode;
// Check for instructions that might cause side effects.
if (opcode == InstructionConstants.OP_PUTSTATIC ||
opcode == InstructionConstants.OP_PUTFIELD ||
opcode == InstructionConstants.OP_INVOKEVIRTUAL ||
opcode == InstructionConstants.OP_INVOKESPECIAL ||
opcode == InstructionConstants.OP_INVOKESTATIC ||
opcode == InstructionConstants.OP_INVOKEINTERFACE)
{
// Check if the field is write-only or volatile, or if the invoked
// method is causing any side effects.
clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
}
}
public void visitBranchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, BranchInstruction branchInstruction)
{
byte opcode = branchInstruction.opcode;
// Check for instructions that might cause side effects.
if (includeReturnInstructions &&
(opcode == InstructionConstants.OP_JSR ||
opcode == InstructionConstants.OP_JSR_W))
{
hasSideEffects = true;
}
}
// Implementations for ConstantVisitor.
public void visitFieldrefConstant(Clazz clazz, FieldrefConstant fieldrefConstant)
{
// We'll have to assume accessing an unknown field has side effects.
hasSideEffects = true;
// Check the referenced field.
fieldrefConstant.referencedMemberAccept(this);
}
public void visitAnyMethodrefConstant(Clazz clazz, RefConstant refConstant)
{
Member referencedMember = refConstant.referencedMember;
// Do we have a reference to the method?
if (referencedMember == null)
{
// We'll have to assume invoking the unknown method has side effects.
hasSideEffects = true;
}
else
{
// First check the referenced method itself.
refConstant.referencedMemberAccept(this);
// If the result isn't conclusive, check down the hierarchy.
if (!hasSideEffects)
{
Clazz referencedClass = refConstant.referencedClass;
Method referencedMethod = (Method)referencedMember;
// Check all other implementations of the method down the class
// hierarchy.
if ((referencedMethod.getAccessFlags() & ClassConstants.INTERNAL_ACC_PRIVATE) == 0)
{
clazz.hierarchyAccept(false, false, false, true,
new NamedMethodVisitor(referencedMethod.getName(referencedClass),
referencedMethod.getDescriptor(referencedClass),
this));
}
}
}
}
// Implementations for MemberVisitor.
public void visitProgramField(ProgramClass programClass, ProgramField programField)
{
hasSideEffects = ReadWriteFieldMarker.isRead(programField);
}
public void visitProgramMethod(ProgramClass programClass, ProgramMethod programMethod)
{
hasSideEffects = hasSideEffects ||
SideEffectMethodMarker.hasSideEffects(programMethod);
}
public void visitLibraryField(LibraryClass libraryClass, LibraryField libraryField)
{
hasSideEffects = true;
}
public void visitLibraryMethod(LibraryClass libraryClass, LibraryMethod libraryMethod)
{
hasSideEffects = hasSideEffects ||
!NoSideEffectMethodMarker.hasNoSideEffects(libraryMethod);
}
}
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