soot.dava.toolkits.base.AST.structuredAnalysis.UnreachableCodeFinder Maven / Gradle / Ivy

package soot.dava.toolkits.base.AST.structuredAnalysis;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 2006 Nomair A. Naeem
 * %%
 * 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.Iterator;
import java.util.List;
import java.util.Map;

import soot.Local;
import soot.Value;
import soot.dava.DecompilationException;
import soot.dava.internal.AST.ASTDoWhileNode;
import soot.dava.internal.AST.ASTForLoopNode;
import soot.dava.internal.AST.ASTIfElseNode;
import soot.dava.internal.AST.ASTIfNode;
import soot.dava.internal.AST.ASTLabeledBlockNode;
import soot.dava.internal.AST.ASTNode;
import soot.dava.internal.AST.ASTStatementSequenceNode;
import soot.dava.internal.AST.ASTSwitchNode;
import soot.dava.internal.AST.ASTSynchronizedBlockNode;
import soot.dava.internal.AST.ASTTryNode;
import soot.dava.internal.AST.ASTUnaryBinaryCondition;
import soot.dava.internal.AST.ASTUnconditionalLoopNode;
import soot.dava.internal.AST.ASTWhileNode;
import soot.dava.internal.SET.SETNodeLabel;
import soot.dava.internal.javaRep.DAbruptStmt;
import soot.jimple.RetStmt;
import soot.jimple.ReturnStmt;
import soot.jimple.ReturnVoidStmt;
import soot.jimple.Stmt;
import soot.toolkits.scalar.FlowSet;

/*
 * Sort of the mark phase of a mark and sweep dead code eliminator.
 * Carry NOPATH information through the flowsets
 *
 * Will need to over ride the processAbruptStatement method of parent
 * class since we plan to do something special with abrupt stmts
 *
 * ONLY PROCESS A CONSTRUCT IF ITS INSET HOLDS TRUE i.e. it is REACHABLE otherwise
 * simply pass on the inset
 *
 * TODO:
 *   1, The child after any loop is always reachable (even for a while(true) which returns)
 *      Will probably have to override loop process methods, invoke the super process method and then change the outset
 *   2, handleBreak would need to see if there is any break stmt then set the out to contain true
 */

public class UnreachableCodeFinder extends StructuredAnalysis {
  public static boolean DEBUG = false;

  public class UnreachableCodeFlowSet extends DavaFlowSet {

    public UnreachableCodeFlowSet clone() {
      if (this.size() != 1) {
        throw new DecompilationException("unreachableCodeFlow set size should always be 1");
      }
      Boolean temp = (Boolean) this.elements[0];
      UnreachableCodeFlowSet toReturn = new UnreachableCodeFlowSet();
      toReturn.add(new Boolean(temp.booleanValue()));
      toReturn.copyInternalDataFrom(this);
      return toReturn;
    }

    @Override
    public void intersection(FlowSet otherFlow, FlowSet destFlow) {
      if (DEBUG) {
        System.out.println("In intersection");
      }
      if (!(otherFlow instanceof UnreachableCodeFlowSet) || !(destFlow instanceof UnreachableCodeFlowSet)) {
        super.intersection(otherFlow, destFlow);
        return;
      }

      UnreachableCodeFlowSet other = (UnreachableCodeFlowSet) otherFlow;
      UnreachableCodeFlowSet dest = (UnreachableCodeFlowSet) destFlow;

      UnreachableCodeFlowSet workingSet;

      if (dest == other || dest == this) {
        workingSet = new UnreachableCodeFlowSet();
      } else {
        workingSet = dest;
        workingSet.clear();
      }

      if (other.size() != 1 || this.size() != 1) {
        System.out.println("Other size = " + other.size());
        System.out.println("This size = " + this.size());
        throw new DecompilationException("UnreachableCodeFlowSet size should always be one");
      }

      Boolean thisPath = (Boolean) this.elements[0];
      Boolean otherPath = (Boolean) other.elements[0];
      if (!thisPath.booleanValue() && !otherPath.booleanValue()) {
        // both say there is no path
        workingSet.add((new Boolean(false)));
      } else {
        workingSet.add((new Boolean(true)));
      }
      (workingSet).copyInternalDataFrom(this);
      if (otherFlow instanceof DavaFlowSet) {
        (workingSet).copyInternalDataFrom((DavaFlowSet) otherFlow);
      }

      if (workingSet != dest) {
        workingSet.copy(dest);
      }

      if (DEBUG) {
        System.out.println("destFlow contains size:" + ((UnreachableCodeFlowSet) destFlow).size());
      }
    }

  } // end UnreachableCodeFlowSet

  public UnreachableCodeFinder(Object analyze) {
    super();
    // the input to the process method is newInitialFlow
    DavaFlowSet temp = (DavaFlowSet) process(analyze, newInitialFlow());
  }

  /*
   * Merge is intersection but our SPECIALIZED intersection hence creating our own specialize flow set with overriding the
   * intersection method
   */
  public void setMergeType() {
    MERGETYPE = INTERSECTION;
  }

  /*
   * For catch bodies.
   *
   * If you are processing the catch body that means you can reach to the try Since you can always come to a catchbody the
   * inset to the catch body to should be that there is a path
   */
  public DavaFlowSet newInitialFlow() {
    DavaFlowSet newSet = emptyFlowSet();
    newSet.add(new Boolean(true));
    return newSet;
  }

  public DavaFlowSet emptyFlowSet() {
    return new UnreachableCodeFlowSet();
  }

  @Override
  public UnreachableCodeFlowSet cloneFlowSet(DavaFlowSet flowSet) {
    if (flowSet instanceof UnreachableCodeFlowSet) {
      return ((UnreachableCodeFlowSet) flowSet).clone();
    }
    throw new RuntimeException("Clone only implemented for UnreachableCodeFlowSet");
  }

  @Override
  public DavaFlowSet processUnaryBinaryCondition(ASTUnaryBinaryCondition cond, DavaFlowSet input) {
    return input;
  }

  @Override
  public DavaFlowSet processSynchronizedLocal(Local local, DavaFlowSet input) {
    return input;
  }

  @Override
  public DavaFlowSet processSwitchKey(Value key, DavaFlowSet input) {
    return input;
  }

  @Override
  public DavaFlowSet processStatement(Stmt s, DavaFlowSet input) {
    return input;
  }

  @Override
  public DavaFlowSet processAbruptStatements(Stmt s, DavaFlowSet input) {
    if (DEBUG) {
      System.out.println("processing stmt " + s);
    }
    if (s instanceof ReturnStmt || s instanceof RetStmt || s instanceof ReturnVoidStmt) {
      // dont need to remember this path
      UnreachableCodeFlowSet toReturn = new UnreachableCodeFlowSet();
      toReturn.add(new Boolean(false));
      toReturn.copyInternalDataFrom(input);
      // false indicates NOPATH
      if (DEBUG) {
        System.out.println("\tstmt is a return stmt. Hence sending forward false");
      }
      return toReturn;
    } else if (s instanceof DAbruptStmt) {
      DAbruptStmt abStmt = (DAbruptStmt) s;

      // see if its a break or continue
      if (!(abStmt.is_Continue() || abStmt.is_Break())) {
        // DAbruptStmt is of only two kinds
        throw new RuntimeException("Found a DAbruptStmt which is neither break nor continue!!");
      }

      DavaFlowSet temp = new UnreachableCodeFlowSet();
      SETNodeLabel nodeLabel = abStmt.getLabel();

      // notice we ignore continues for this analysis
      if (abStmt.is_Break()) {
        if (nodeLabel != null && nodeLabel.toString() != null) {
          // explicit break stmt
          temp.addToBreakList(nodeLabel.toString(), input);
        } else {
          // found implicit break
          temp.addToImplicitBreaks(abStmt, input);
        }
      }
      temp.add(new Boolean(false));
      temp.copyInternalDataFrom(input);
      if (DEBUG) {
        System.out.println("\tstmt is an abrupt stmt. Hence sending forward false");
      }
      return temp;
    } else {
      if (DEBUG) {
        System.out.println("\tstmt is not an abrupt stmt.");
      }
      return processStatement(s, input);
    }
  }

  /*
   * If a particular node is targeted by a break statement then that means there is always a path to it Hence if there is
   * even a single entry in the implicit or explicit break set return a flow set which contains true since there is a path to
   * this point
   */
  @Override
  public DavaFlowSet handleBreak(String label, DavaFlowSet output, ASTNode node) {
    if (DEBUG) {
      System.out.println("Handling break. Output contains" + ((UnreachableCodeFlowSet) output).size());
    }
    if (!(output instanceof UnreachableCodeFlowSet)) {
      throw new RuntimeException("handleBreak is only implemented for UnreachableCodeFlowSet type");
    }

    DavaFlowSet out = (DavaFlowSet) output;

    // get the explicit list with this label from the breakList
    List explicitSet = out.getBreakSet(label);

    // getting the implicit list now
    if (node == null) {
      throw new RuntimeException("ASTNode sent to handleBreak was null");
    }

    List implicitSet = out.getImplicitlyBrokenSets(node);
    // System.out.println("\n\nImplicit set is"+implicitSet);

    DavaFlowSet toReturn = emptyFlowSet();
    toReturn.copyInternalDataFrom(output);
    if ((explicitSet != null && explicitSet.size() > 0) || (implicitSet != null && implicitSet.size() > 0)) {
      if (DEBUG) {
        System.out.println("\tBreak sets (implicit and explicit are nonempty hence forwarding true");
      }
      // some break targets node
      toReturn.add(new Boolean(true));
      return toReturn;
    } else {
      // no break targets node, maybe output was true though hence use merge
      toReturn.add(new Boolean(false));
      if (DEBUG) {
        System.out.println("\tBreak sets (implicit and explicit are empty hence forwarding merge of false with inset");
      }
      return merge(toReturn, output);
    }
  }

  public boolean isReachable(Object input) {
    if (!(input instanceof UnreachableCodeFlowSet)) {
      throw new DecompilationException("Implemented only for UnreachableCodeFlowSet");
    }

    UnreachableCodeFlowSet checking = (UnreachableCodeFlowSet) input;
    if (checking.size() != 1) {
      throw new DecompilationException("unreachableCodeFlow set size should always be 1");
    }

    if (((Boolean) checking.elements[0]).booleanValue()) {
      // it is reachable
      if (DEBUG) {
        System.out.println("\t Reachable");
      }
      return true;
    } else {
      if (DEBUG) {
        System.out.println("\t NOT Reachable");
      }
      return false;
    }
  }

  @Override
  public DavaFlowSet processASTStatementSequenceNode(ASTStatementSequenceNode node, DavaFlowSet input) {
    if (DEBUG) {
      System.out.println("Processing statement sequence node");
    }
    if (!isReachable(input)) {
      // this sequence is not reachable hence simply return inset
      return input;
    } else {
      return super.processASTStatementSequenceNode(node, input);
    }
  }

  @Override
  public DavaFlowSet processASTLabeledBlockNode(ASTLabeledBlockNode node, DavaFlowSet input) {
    if (DEBUG) {
      System.out.println("Processing labeled block node node");
    }
    if (!isReachable(input)) {
      // this sequence is not reachable hence simply return inset
      return input;
    } else {
      return super.processASTLabeledBlockNode(node, input);
    }
  }

  @Override
  public DavaFlowSet processASTSynchronizedBlockNode(ASTSynchronizedBlockNode node, DavaFlowSet input) {
    if (DEBUG) {
      System.out.println("Processing synchronized block node");
    }
    if (!isReachable(input)) {
      // this sequence is not reachable hence simply return inset
      return input;
    } else {
      return super.processASTSynchronizedBlockNode(node, input);
    }
  }

  @Override
  public DavaFlowSet processASTIfElseNode(ASTIfElseNode node, DavaFlowSet input) {
    if (DEBUG) {
      System.out.println("Processing ifelse node");
    }
    if (!isReachable(input)) {
      // this sequence is not reachable hence simply return inset
      return input;
    } else {
      // the output will be false if both branches are abrupt
      // and also there is no break targetting this construct
      return super.processASTIfElseNode(node, input);
    }
  }

  public DavaFlowSet ifNotReachableReturnInputElseProcessBodyAndReturnTrue(ASTNode node, DavaFlowSet input) {
    if (DEBUG) {
      System.out.println("Processing " + node.getClass() + " node");
    }
    if (!isReachable(input)) {
      // this sequence is not reachable hence simply return inset
      return input;
    } else {
      DavaFlowSet output = processSingleSubBodyNode(node, input);

      UnreachableCodeFlowSet toReturn = new UnreachableCodeFlowSet();
      toReturn.add(new Boolean(true));
      toReturn.copyInternalDataFrom(output);
      return toReturn;
    }

  }

  /*
   * If the if stmt is reachable the outset if always reachable
   */
  @Override
  public DavaFlowSet processASTIfNode(ASTIfNode node, DavaFlowSet input) {
    return ifNotReachableReturnInputElseProcessBodyAndReturnTrue(node, input);
  }

  /*
   * No need to process Condition No need to do fixed point No need to handleContinues since they dont change reachability
   */
  @Override
  public DavaFlowSet processASTWhileNode(ASTWhileNode node, DavaFlowSet input) {
    return ifNotReachableReturnInputElseProcessBodyAndReturnTrue(node, input);
  }

  /*
   * Same as while loop
   */
  @Override
  public DavaFlowSet processASTDoWhileNode(ASTDoWhileNode node, DavaFlowSet input) {
    return ifNotReachableReturnInputElseProcessBodyAndReturnTrue(node, input);
  }

  @Override
  public DavaFlowSet processASTUnconditionalLoopNode(ASTUnconditionalLoopNode node, DavaFlowSet input) {
    return ifNotReachableReturnInputElseProcessBodyAndReturnTrue(node, input);
  }

  /*
   * No need to process Init No need to process Condition No need to process Update No need to handle continue
   */
  @Override
  public DavaFlowSet processASTForLoopNode(ASTForLoopNode node, DavaFlowSet input) {
    return ifNotReachableReturnInputElseProcessBodyAndReturnTrue(node, input);
  }

  /*
   * No need to process SwitchKey TODO test and reason
   */
  @Override
  public DavaFlowSet processASTSwitchNode(ASTSwitchNode node, DavaFlowSet input) {
    if (DEBUG) {
      System.out.println("Processing switch node");
    }
    if (!isReachable(input)) {
      // this sequence is not reachable hence simply return inset
      return input;
    }
    // if reachable
    List