/* Soot - a J*va Optimization Framework
 * Copyright (C) 2003 Ondrej Lhotak
 *
 * 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.
 */

package soot.jimple.toolkits.pointer;
import soot.*;
import soot.tagkit.*;
import soot.jimple.*;

import java.util.*;

/** Adds colour tags to indicate potential aliasing between method parameters. */
public class ParameterAliasTagger extends BodyTransformer {
    public ParameterAliasTagger( Singletons.Global g ) {}
    public static ParameterAliasTagger v() { return G.v().soot_jimple_toolkits_pointer_ParameterAliasTagger(); }

    protected void internalTransform(
            Body b, String phaseName, Map options)
    {
        PointsToAnalysis pa = Scene.v().getPointsToAnalysis();
        Set<IdentityStmt> parms = new HashSet<IdentityStmt>();

        for( Iterator sIt = b.getUnits().iterator(); sIt.hasNext(); ) {

            final Stmt s = (Stmt) sIt.next();
            if( !(s instanceof IdentityStmt) ) continue;
            IdentityStmt is = (IdentityStmt) s;
            ValueBox vb = is.getRightOpBox();
            if( !(vb.getValue() instanceof ParameterRef) ) continue;
            ParameterRef pr = (ParameterRef) vb.getValue();
            if( !(pr.getType() instanceof RefLikeType) ) continue;
            parms.add(is);
        }

        int colour = 0;
        while( !parms.isEmpty() ) {
            fill( parms, parms.iterator().next(), colour++, pa );
        }
    }
    private void fill( Set<IdentityStmt> parms, IdentityStmt parm, int colour, PointsToAnalysis pa ) {
        if( !parms.contains(parm) ) return;
        parm.getRightOpBox().addTag( new ColorTag(colour, "Parameter Alias") );
        parms.remove( parm );
        PointsToSet ps = pa.reachingObjects( (Local) parm.getLeftOp() );
        for( Iterator<IdentityStmt> parm2It = (new LinkedList<IdentityStmt>(parms)).iterator(); parm2It.hasNext(); ) {
            final IdentityStmt parm2 = parm2It.next();
            if( ps.hasNonEmptyIntersection(
                        pa.reachingObjects( (Local) parm2.getLeftOp() ) ) ) {
                fill( parms, parm2, colour, pa );
            }
        }
    }
}