soot.jimple.toolkits.base.Aggregator Maven / Gradle / Ivy

package soot.jimple.toolkits.base;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 1997 - 1999 Raja Vallee-Rai
 * %%
 * 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.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import soot.Body;
import soot.BodyTransformer;
import soot.G;
import soot.Local;
import soot.PhaseOptions;
import soot.Singletons;
import soot.Timers;
import soot.Unit;
import soot.Value;
import soot.ValueBox;
import soot.jimple.ArrayRef;
import soot.jimple.AssignStmt;
import soot.jimple.DefinitionStmt;
import soot.jimple.FieldRef;
import soot.jimple.InvokeExpr;
import soot.jimple.MonitorStmt;
import soot.jimple.Stmt;
import soot.jimple.StmtBody;
import soot.options.Options;
import soot.toolkits.graph.ExceptionalUnitGraph;
import soot.toolkits.graph.PseudoTopologicalOrderer;
import soot.toolkits.scalar.LocalDefs;
import soot.toolkits.scalar.LocalUses;
import soot.toolkits.scalar.UnitValueBoxPair;
import soot.util.Chain;

public class Aggregator extends BodyTransformer {
  private static final Logger logger = LoggerFactory.getLogger(Aggregator.class);

  public Aggregator(Singletons.Global g) {
  }

  public static Aggregator v() {
    return G.v().soot_jimple_toolkits_base_Aggregator();
  }

  /**
   * Traverse the statements in the given body, looking for aggregation possibilities; that is, given a def d and a use u, d
   * has no other uses, u has no other defs, collapse d and u.
   *
   * option: only-stack-locals; if this is true, only aggregate variables starting with $
   */
  protected void internalTransform(Body b, String phaseName, Map options) {
    StmtBody body = (StmtBody) b;
    boolean onlyStackVars = PhaseOptions.getBoolean(options, "only-stack-locals");

    if (Options.v().time()) {
      Timers.v().aggregationTimer.start();
    }

    int aggregateCount = 1;

    boolean changed = false;

    Map boxToZone = new HashMap(body.getUnits().size() * 2 + 1, 0.7f);

    // Determine the zone of every box
    {
      Zonation zonation = new Zonation(body);

      for (Unit u : body.getUnits()) {
        Zone zone = zonation.getZoneOf(u);

        for (ValueBox box : u.getUseBoxes()) {
          boxToZone.put(box, zone);
        }

        for (ValueBox box : u.getDefBoxes()) {
          boxToZone.put(box, zone);
        }
      }
    }

    do {
      if (Options.v().verbose()) {
        logger.debug("" + "[" + body.getMethod().getName() + "] Aggregating iteration " + aggregateCount + "...");
      }

      // body.printTo(new java.io.PrintWriter(G.v().out, true));

      changed = internalAggregate(body, boxToZone, onlyStackVars);

      aggregateCount++;
    } while (changed);

    if (Options.v().time()) {
      Timers.v().aggregationTimer.end();
    }

  }

  private static boolean internalAggregate(StmtBody body, Map boxToZone, boolean onlyStackVars) {
    boolean hadAggregation = false;
    Chain units = body.getUnits();

    ExceptionalUnitGraph graph = new ExceptionalUnitGraph(body);
    LocalDefs localDefs = LocalDefs.Factory.newLocalDefs(graph);
    LocalUses localUses = LocalUses.Factory.newLocalUses(body, localDefs);

    List unitList = new PseudoTopologicalOrderer().newList(graph, false);
    for (Unit u : unitList) {
      if (!(u instanceof AssignStmt)) {
        continue;
      }
      AssignStmt s = (AssignStmt) u;

      Value lhs = s.getLeftOp();
      if (!(lhs instanceof Local)) {
        continue;
      }
      Local lhsLocal = (Local) lhs;

      if (onlyStackVars && !lhsLocal.getName().startsWith("$")) {
        continue;
      }

      List lu = localUses.getUsesOf(s);
      if (lu.size() != 1) {
        continue;
      }

      UnitValueBoxPair usepair = lu.get(0);
      Unit use = usepair.unit;
      ValueBox useBox = usepair.valueBox;

      List ld = localDefs.getDefsOfAt(lhsLocal, use);
      if (ld.size() != 1) {
        continue;
      }

      // Check to make sure aggregation pair in the same zone
      if (boxToZone.get(s.getRightOpBox()) != boxToZone.get(usepair.valueBox)) {
        continue;
      }

      /* we need to check the path between def and use */
      /* to see if there are any intervening re-defs of RHS */
      /* in fact, we should check that this path is unique. */
      /*
       * if the RHS uses only locals, then we know what to do; if RHS has a method invocation f(a, b, c) or field access, we
       * must ban field writes, other method calls and (as usual) writes to a, b, c.
       */

      boolean cantAggr = false;
      boolean propagatingInvokeExpr = false;
      boolean propagatingFieldRef = false;
      boolean propagatingArrayRef = false;
      List fieldRefList = new ArrayList();

      List localsUsed = new ArrayList();
      for (ValueBox vb : s.getUseBoxes()) {
        Value v = vb.getValue();
        if (v instanceof Local) {
          localsUsed.add(v);
        } else if (v instanceof InvokeExpr) {
          propagatingInvokeExpr = true;
        } else if (v instanceof ArrayRef) {
          propagatingArrayRef = true;
        } else if (v instanceof FieldRef) {
          propagatingFieldRef = true;
          fieldRefList.add((FieldRef) v);
        }
      }

      // look for a path from s to use in graph.
      // only look in an extended basic block, though.

      List path = graph.getExtendedBasicBlockPathBetween(s, use);

      if (path == null) {
        continue;
      }

      Iterator pathIt = path.iterator();

      // skip s.
      if (pathIt.hasNext()) {
        pathIt.next();
      }

      while (pathIt.hasNext() && !cantAggr) {
        Stmt between = (Stmt) (pathIt.next());

        if (between != use) {
          // Check for killing definitions

          for (ValueBox vb : between.getDefBoxes()) {
            Value v = vb.getValue();
            if (localsUsed.contains(v)) {
              cantAggr = true;
              break;
            }

            if (propagatingInvokeExpr || propagatingFieldRef || propagatingArrayRef) {
              if (v instanceof FieldRef) {
                if (propagatingInvokeExpr) {
                  cantAggr = true;
                  break;
                } else if (propagatingFieldRef) {
                  // Can't aggregate a field access if passing
                  // a definition of a field
                  // with the same name, because they might be
                  // aliased
                  for (FieldRef fieldRef : fieldRefList) {
                    if (isSameField((FieldRef) v, fieldRef)) {
                      cantAggr = true;
                      break;
                    }
                  }
                }
              } else if (v instanceof ArrayRef) {
                if (propagatingInvokeExpr) {
                  // Cannot aggregate an invoke expr past an
                  // array write
                  cantAggr = true;
                  break;
                } else if (propagatingArrayRef) {
                  // cannot aggregate an array read past a
                  // write
                  // this is somewhat conservative
                  // (if types differ they may not be aliased)

                  cantAggr = true;
                  break;
                }
              }
            }
          }

          // Make sure not propagating past a {enter,exit}Monitor
          if (propagatingInvokeExpr && between instanceof MonitorStmt) {
            cantAggr = true;
          }
        }

        // Check for intervening side effects due to method calls
        if (propagatingInvokeExpr || propagatingFieldRef || propagatingArrayRef) {
          for (final ValueBox box : between.getUseBoxes()) {
            if (between == use && box == useBox) {
              // Reached use point, stop looking for
              // side effects
              break;
            }

            Value v = box.getValue();

            if (v instanceof InvokeExpr || (propagatingInvokeExpr && (v instanceof FieldRef || v instanceof ArrayRef))) {
              cantAggr = true;
              break;
            }

          }
        }
      }

      // we give up: can't aggregate.
      if (cantAggr) {
        continue;
      }
      /* assuming that the d-u chains are correct, */
      /* we need not check the actual contents of ld */

      Value aggregatee = s.getRightOp();

      if (usepair.valueBox.canContainValue(aggregatee)) {
        boolean wasSimpleCopy = isSimpleCopy(usepair.unit);
        usepair.valueBox.setValue(aggregatee);
        units.remove(s);
        hadAggregation = true;
        // clean up the tags. If s was not a simple copy, the new
        // statement should get
        // the tags of s.
        // OK, this fix was wrong. The condition should not be
        // "If s was not a simple copy", but rather "If usepair.unit
        // was a simple copy". This way, when there's a load of a
        // constant
        // followed by an invoke, the invoke gets the tags.
        if (wasSimpleCopy) {
          // usepair.unit.removeAllTags();
          usepair.unit.addAllTagsOf(s);
        }
      } else {
        /*
         * if(Options.v().verbose()) { logger.debug("[debug] failed aggregation");
         * logger.debug("[debug] tried to put "+aggregatee+ " into "+usepair.stmt + ": in particular, "+usepair.valueBox);
         * logger.debug("[debug] aggregatee instanceof Expr: " +(aggregatee instanceof Expr)); }
         */
      }
    }
    return hadAggregation;
  }

  /**
   * Checks whether two field references point to the same field
   *
   * @param ref1
   *          The first field reference
   * @param ref2
   *          The second reference
   * @return True if the two references point to the same field, otherwise false
   */
  private static boolean isSameField(FieldRef ref1, FieldRef ref2) {
    if (ref1 == ref2) {
      return true;
    }

    return ref1.getFieldRef().equals(ref2.getFieldRef());
  }

  private static boolean isSimpleCopy(Unit u) {
    if (!(u instanceof DefinitionStmt)) {
      return false;
    }
    DefinitionStmt defstmt = (DefinitionStmt) u;
    if (!(defstmt.getRightOp() instanceof Local)) {
      return false;
    }
    if (!(defstmt.getLeftOp() instanceof Local)) {
      return false;
    }
    return true;
  }

}