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/* Soot - a J*va Optimization Framework
* Copyright (C) 1997-1999 Raja Vallee-Rai
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/*
* Modified by the Sable Research Group and others 1997-1999.
* See the 'credits' file distributed with Soot for the complete list of
* contributors. (Soot is distributed at http://www.sable.mcgill.ca/soot)
*/
package soot.toolkits.scalar;
import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.TreeSet;
import soot.options.Options;
import soot.toolkits.graph.DirectedGraph;
import soot.toolkits.graph.PseudoTopologicalOrderer;
import soot.toolkits.graph.interaction.FlowInfo;
import soot.toolkits.graph.interaction.InteractionHandler;
/**
* Abstract class that provides the fixed point iteration functionality
* required by all BackwardFlowAnalyses.
*
*/
public abstract class BackwardFlowAnalysis extends FlowAnalysis
{
/** Construct the analysis from a DirectedGraph representation of a Body. */
public BackwardFlowAnalysis(DirectedGraph graph)
{
super(graph);
}
protected boolean isForward()
{
return false;
}
protected void doAnalysis()
{
final Map numbers = new HashMap();
List orderedUnits = constructOrderer().newList(graph,true);
int i = 1;
for( Iterator uIt = orderedUnits.iterator(); uIt.hasNext(); ) {
final N u = uIt.next();
numbers.put(u, new Integer(i));
i++;
}
Collection changedUnits = constructWorklist(numbers);
// Set initial Flows and nodes to visit.
{
Iterator it = graph.iterator();
while(it.hasNext())
{
N s = it.next();
changedUnits.add(s);
unitToBeforeFlow.put(s, newInitialFlow());
unitToAfterFlow.put(s, newInitialFlow());
}
}
List tails = graph.getTails();
// Feng Qian: March 07, 2002
// init entry points
{
Iterator it = tails.iterator();
while (it.hasNext()) {
N s = it.next();
// this is a backward flow analysis
unitToAfterFlow.put(s, entryInitialFlow());
}
}
// Perform fixed point flow analysis
{
A previousBeforeFlow = newInitialFlow();
while(!changedUnits.isEmpty())
{
A beforeFlow;
A afterFlow;
//get the first object
N s = changedUnits.iterator().next();
changedUnits.remove(s);
boolean isTail = tails.contains(s);
copy(unitToBeforeFlow.get(s), previousBeforeFlow);
// Compute and store afterFlow
{
List succs = graph.getSuccsOf(s);
afterFlow = unitToAfterFlow.get(s);
if(succs.size() == 1)
copy(unitToBeforeFlow.get(succs.get(0)), afterFlow);
else if(succs.size() != 0)
{
Iterator succIt = succs.iterator();
copy(unitToBeforeFlow.get(succIt.next()), afterFlow);
while(succIt.hasNext())
{
A otherBranchFlow = unitToBeforeFlow.get(succIt.next());
mergeInto(s, afterFlow, otherBranchFlow);
}
if(isTail && succs.size() != 0)
mergeInto(s, afterFlow, entryInitialFlow());
}
}
// Compute beforeFlow and store it.
{
beforeFlow = unitToBeforeFlow.get(s);
if (Options.v().interactive_mode()){
A savedFlow = newInitialFlow();
if (filterUnitToAfterFlow != null){
savedFlow = filterUnitToAfterFlow.get(s);
copy(filterUnitToAfterFlow.get(s), savedFlow);
}
else {
copy(afterFlow, savedFlow);
}
FlowInfo fi = new FlowInfo(savedFlow, s, false);
if (InteractionHandler.v().getStopUnitList() != null && InteractionHandler.v().getStopUnitList().contains(s)){
InteractionHandler.v().handleStopAtNodeEvent(s);
}
InteractionHandler.v().handleAfterAnalysisEvent(fi);
}
flowThrough(afterFlow, s, beforeFlow);
if (Options.v().interactive_mode()){
A bSavedFlow = newInitialFlow();
if (filterUnitToBeforeFlow != null){
bSavedFlow = filterUnitToBeforeFlow.get(s);
copy(filterUnitToBeforeFlow.get(s), bSavedFlow);
}
else {
copy(beforeFlow, bSavedFlow);
}
FlowInfo fi = new FlowInfo(bSavedFlow, s, true);
InteractionHandler.v().handleBeforeAnalysisEvent(fi);
}
}
// Update queue appropriately
if(!beforeFlow.equals(previousBeforeFlow))
{
Iterator predIt = graph.getPredsOf(s).iterator();
while(predIt.hasNext())
{
N pred = predIt.next();
changedUnits.add(pred);
}
}
}
}
}
protected Collection constructWorklist(final Map numbers) {
return new TreeSet( new Comparator() {
public int compare(N o1, N o2) {
Integer i1 = numbers.get(o1);
Integer i2 = numbers.get(o2);
return (i1.intValue() - i2.intValue());
}
} );
}
}
