soot.toolkits.graph.PostDominatorAnalysis Maven / Gradle / Ivy

package soot.toolkits.graph;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 2003 Jennifer Lhotak
 * %%
 * This program 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 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 Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 * #L%
 */

import java.util.Iterator;
import java.util.List;

import soot.Unit;
import soot.jimple.Stmt;
import soot.toolkits.scalar.ArraySparseSet;
import soot.toolkits.scalar.BackwardFlowAnalysis;
import soot.toolkits.scalar.FlowSet;

// STEP 1: What are we computing?
// SETS OF Units that are post-dominators => Use ArraySparseSet.
//
// STEP 2: Precisely define what we are computing.
// For each statement compute the set of stmts that post-dominate it 
// 
// STEP 3: Decide whether it is a backwards or forwards analysis.
// FORWARDS
//
//
/**
 * @deprecated use {@link MHGPostDominatorsFinder} instead
 */
@Deprecated
public class PostDominatorAnalysis extends BackwardFlowAnalysis> {

  private UnitGraph g;
  private FlowSet allNodes;

  public PostDominatorAnalysis(UnitGraph g) {
    super(g);
    this.g = g;

    initAllNodes();

    doAnalysis();

  }

  private void initAllNodes() {
    allNodes = new ArraySparseSet();
    Iterator it = g.iterator();
    while (it.hasNext()) {
      allNodes.add(it.next());
    }
  }

  // STEP 4: Is the merge operator union or intersection?
  // INTERSECTION

  @Override
  protected void merge(FlowSet in1, FlowSet in2, FlowSet out) {
    in1.intersection(in2, out);
  }

  @Override
  protected void copy(FlowSet source, FlowSet dest) {
    source.copy(dest);

  }

  // STEP 5: Define flow equations.
  // dom(s) = s U ( ForAll Y in pred(s): Intersection (dom(y)))
  // ie: dom(s) = s and whoever dominates all the predeccessors of s
  //
  @Override
  protected void flowThrough(FlowSet in, Unit s, FlowSet out) {
    if (isUnitEndNode(s)) {
      // System.out.println("s: "+s+" is end node");
      out.clear();
      out.add(s);
      // System.out.println("in: "+in+" out: "+out);
    } else {

      // System.out.println("s: "+s+" is not start node");
      // FlowSet domsOfSuccs = (FlowSet) allNodes.clone();

      // for each pred of s
      Iterator succsIt = g.getSuccsOf(s).iterator();
      while (succsIt.hasNext()) {
        Unit succ = succsIt.next();
        // get the unitToBeforeFlow and find the intersection
        // System.out.println("succ: "+succ);
        FlowSet next = getFlowBefore(succ);
        // System.out.println("next: "+next);
        // System.out.println("in before intersect: "+in);
        in.intersection(next, in);
        // System.out.println("in after intersect: "+in);
      }

      // intersected with in

      // System.out.println("out init: "+out);
      out.intersection(in, out);
      out.add(s);
      // System.out.println("out after: "+out);
    }
  }

  private boolean isUnitEndNode(Unit s) {
    // System.out.println("head: "+g.getHeads().get(0));
    if (g.getTails().contains(s)) {
      return true;
    }
    return false;
  }

  // STEP 6: Determine value for start/end node, and
  // initial approximation.
  // dom(startNode) = startNode
  // dom(node) = allNodes
  //
  @Override
  protected FlowSet entryInitialFlow() {

    FlowSet fs = new ArraySparseSet();
    List tails = g.getTails();
    // if (tails.size() != 1) {
    // throw new RuntimeException("Expect one end node only.");
    // }
    fs.add(tails.get(0));
    return fs;
  }

  @Override
  protected FlowSet newInitialFlow() {
    return allNodes.clone();
  }

  /**
   * Returns true if s post-dominates t.
   */
  public boolean postDominates(Stmt s, Stmt t) {
    return getFlowBefore(t).contains(s);
  }

}