/*******************************************************************************
* Copyright (c) 2007 IBM Corporation.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package com.ibm.wala.ssa;
import com.ibm.wala.util.collections.Pair;
/**
* A pi node policy with the following rule:
*
* If we have the following code:
* <p>
* <verbatim> S1: c = v1 instanceof T S2: if (c == 0) { ... } </verbatim>
*
* replace it with:
* <p>
* <verbatim> S1: c = v1 instanceof T S2: if (c == 0) { v2 = PI(v1, S1) .... } </verbatim>
*
* The same pattern holds if the test is c == 1. This renaming allows SSA-based analysis to reason about the type of v2 depending on
* the outcome of the branch.
*/
public class InstanceOfPiPolicy implements SSAPiNodePolicy {
private final static InstanceOfPiPolicy singleton = new InstanceOfPiPolicy();
public static InstanceOfPiPolicy createInstanceOfPiPolicy() {
return singleton;
}
private InstanceOfPiPolicy() {
}
/*
* @see com.ibm.wala.ssa.SSAPiNodePolicy#getPi(com.ibm.wala.ssa.SSAConditionalBranchInstruction, com.ibm.wala.ssa.SSAInstruction,
* com.ibm.wala.ssa.SSAInstruction, com.ibm.wala.ssa.SymbolTable)
*/
@Override
public Pair<Integer, SSAInstruction> getPi(SSAConditionalBranchInstruction cond, SSAInstruction def1, SSAInstruction def2,
SymbolTable symbolTable) {
if (def1 instanceof SSAInstanceofInstruction) {
if (symbolTable.isBooleanOrZeroOneConstant(cond.getUse(1))) {
return Pair.make(def1.getUse(0), def1);
}
}
if (def2 instanceof SSAInstanceofInstruction) {
if (symbolTable.isBooleanOrZeroOneConstant(cond.getUse(0))) {
return Pair.make(def2.getUse(0), def2);
}
}
return null;
}
@Override
public boolean equals(Object obj) {
return this == obj;
}
@Override
public int hashCode() {
return 12;
}
/*
* @see com.ibm.wala.ssa.SSAPiNodePolicy#getPi(com.ibm.wala.ssa.SSAAbstractInvokeInstruction, com.ibm.wala.ssa.SymbolTable)
*/
@Override
public Pair<Integer, SSAInstruction> getPi(SSAAbstractInvokeInstruction call, SymbolTable symbolTable) {
return null;
}
}