soot.dava.toolkits.base.AST.traversals.CopyPropagation Maven / Gradle / Ivy

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

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 2005 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 soot.Local;
import soot.Value;
import soot.ValueBox;
import soot.dava.internal.AST.ASTAggregatedCondition;
import soot.dava.internal.AST.ASTBinaryCondition;
import soot.dava.internal.AST.ASTCondition;
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.ASTMethodNode;
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.ASTUnaryCondition;
import soot.dava.internal.AST.ASTWhileNode;
import soot.dava.internal.asg.AugmentedStmt;
import soot.dava.toolkits.base.AST.analysis.DepthFirstAdapter;
import soot.dava.toolkits.base.AST.structuredAnalysis.DavaFlowSet;
import soot.dava.toolkits.base.AST.structuredAnalysis.ReachingCopies;
import soot.jimple.DefinitionStmt;
import soot.jimple.Stmt;

/*
 * TODO: shouldnt this be a transformation and hence under the transformation package???
 This analysis uses the results from
 1 ReachingCopies
 2 uD and dU chains
 to eliminate extra copies


 ALGORITHM:
 When you encounter a copy stmt (a=b) find all uses of local a (using dU chain)

 if For ALL uses the ReachingCopies set contains copy stmt (a=b)
 Remove Copy Stmt
 Replace use of a with use of b

 Note:
 copy stmts can be encountered in:
 a, ASTStatementSequenceNode
 b, for loop init      -------> dont want to remove this
 c, for loop update   ---------> dont want to remove this

 */

public class CopyPropagation extends DepthFirstAdapter {
  public static boolean DEBUG = false;

  ASTNode AST;

  ASTUsesAndDefs useDefs;

  ReachingCopies reachingCopies;

  ASTParentNodeFinder parentOf;

  boolean someCopyStmtModified;

  // need to keep track of whenever we modify the AST
  // this flag is set to true whenever a stmt is removed or a local
  // substituted for another
  boolean ASTMODIFIED;

  public CopyPropagation(ASTNode AST) {
    super();
    someCopyStmtModified = false;
    this.AST = AST;
    ASTMODIFIED = false;
    setup();
  }

  public CopyPropagation(boolean verbose, ASTNode AST) {
    super(verbose);
    someCopyStmtModified = false;
    this.AST = AST;
    ASTMODIFIED = false;
    setup();
  }

  private void setup() {
    // create the uD and dU chains
    if (DEBUG) {
      System.out.println("computing usesAnd Defs");
    }
    useDefs = new ASTUsesAndDefs(AST);
    AST.apply(useDefs);

    if (DEBUG) {
      System.out.println("computing usesAnd Defs....done");
    }

    // apply the reaching copies Structural flow Analysis
    reachingCopies = new ReachingCopies(AST);

    parentOf = new ASTParentNodeFinder();
    AST.apply(parentOf);
  }

  /*
   * If any copy stmt was removed or any substitution made we might be able to get better results by redoing the analysis
   */
  public void outASTMethodNode(ASTMethodNode node) {
    if (ASTMODIFIED) {
      // need to rerun copy prop

      // before running a structured flow analysis have to do this one
      AST.apply(ClosestAbruptTargetFinder.v());

      // System.out.println("\n\n\nCOPY PROP\n\n\n\n");

      CopyPropagation prop1 = new CopyPropagation(AST);
      AST.apply(prop1);
    }
  }

  public void inASTStatementSequenceNode(ASTStatementSequenceNode node) {
    for (AugmentedStmt as : node.getStatements()) {
      Stmt s = as.get_Stmt();
      if (isCopyStmt(s)) {
        handleCopyStmt((DefinitionStmt) s);
      }
    }
  }

  /*
   * Method returns true if s is a copy stmt i.e. a = b where a and b are both locals
   */
  public boolean isCopyStmt(Stmt s) {
    if (!(s instanceof DefinitionStmt)) {
      // only definition stmts can be copy stmts
      return false;
    }

    // x = expr;
    // check if expr is a local in which case this is a copy
    Value leftOp = ((DefinitionStmt) s).getLeftOp();
    Value rightOp = ((DefinitionStmt) s).getRightOp();

    if (leftOp instanceof Local && rightOp instanceof Local) {
      // this is a copy statement
      return true;
    }
    return false;
  }

  /*
   * Given a copy stmt (a=b) find all uses of local a (using dU chain)
   *
   * if For ALL uses the ReachingCopies set contains copy stmt (a=b) Remove Copy Stmt Replace use of a with use of b
   */
  public void handleCopyStmt(DefinitionStmt copyStmt) {
    // System.out.println("COPY STMT FOUND-----------------------------------"+copyStmt);

    // get defined local...safe to cast since this is copyStmt
    Local definedLocal = (Local) copyStmt.getLeftOp();

    // get all uses of this local from the dU chain
    Object temp = useDefs.getDUChain(copyStmt);

    ArrayList uses = new ArrayList();
    if (temp != null) {
      uses = (ArrayList) temp;
    }

    // the uses list contains all stmts / nodes which use the definedLocal

    // check if uses is non-empty
    if (uses.size() != 0) {
      if (DEBUG) {
        System.out.println(">>>>The defined local:" + definedLocal + " is used in the following");
        System.out.println("\n numof uses:" + uses.size() + uses + ">>>>>>>>>>>>>>>\n\n");
      }

      // continuing with copy propagation algorithm

      // create localPair for copy stmt in question...same to cast as its
      // a copyStmt
      Local leftLocal = (Local) copyStmt.getLeftOp();
      Local rightLocal = (Local) copyStmt.getRightOp();

      ReachingCopies.LocalPair localPair = reachingCopies.new LocalPair(leftLocal, rightLocal);

      // check for all the non zero uses
      Iterator useIt = uses.iterator();
      while (useIt.hasNext()) {
        // check that the reaching copies of each use has the copy stmt
        // a use is either a statement or a node(condition, synch,
        // switch , for etc)
        Object tempUse = useIt.next();

        DavaFlowSet reaching = reachingCopies.getReachingCopies(tempUse);

        if (!reaching.contains(localPair)) {
          // this copy stmt does not reach this use
          // no copy elimination can be done
          return;
        }
      }

      // if we get here that means that the copy stmt reached each use

      // replace each use of a with b
      useIt = uses.iterator();
      while (useIt.hasNext()) {
        Object tempUse = useIt.next();
        if (DEBUG) {
          System.out.println("copy stmt reached this use" + tempUse);
        }
        replace(leftLocal, rightLocal, tempUse);
      }

      // remove copy stmt a=b
      removeStmt(copyStmt);

      if (someCopyStmtModified) {
        // get all the analyses re-set
        setup();
        someCopyStmtModified = false;
      }
    } else {
      // the copy stmt is usesless since the definedLocal is not being
      // used anywhere after definition
      // System.out.println("The defined local:"+definedLocal+" is not used anywhere");
      removeStmt(copyStmt);
    }
  }

  public void removeStmt(Stmt stmt) {
    Object tempParent = parentOf.getParentOf(stmt);
    if (tempParent == null) {
      // System.out.println("NO PARENT FOUND CANT DO ANYTHING");
      return;
    }

    // parents are always ASTNodes, hence safe to cast
    ASTNode parent = (ASTNode) tempParent;

    // REMOVING STMT
    if (!(parent instanceof ASTStatementSequenceNode)) {
      // parent of a statement should always be a ASTStatementSequenceNode
      throw new RuntimeException("Found a stmt whose parent is not an ASTStatementSequenceNode");
    }
    ASTStatementSequenceNode parentNode = (ASTStatementSequenceNode) parent;

    ArrayList newSequence = new ArrayList();

    for (AugmentedStmt as : parentNode.getStatements()) {
      Stmt s = as.get_Stmt();
      if (s.toString().compareTo(stmt.toString()) != 0) {
        // this is not the stmt to be removed
        newSequence.add(as);
      }
    }
    // System.out.println("STMT REMOVED---------------->"+stmt);
    parentNode.setStatements(newSequence);

    ASTMODIFIED = true;
    return;
  }

  /*
   * Method goes depth first into the condition tree and finds any use of local "from" If it finds the use it replaces it
   * with the use of local "to"
   */
  public void modifyUses(Local from, Local to, ASTCondition cond) {
    if (cond instanceof ASTAggregatedCondition) {
      // ArrayList useList = new ArrayList();
      modifyUses(from, to, ((ASTAggregatedCondition) cond).getLeftOp());
      modifyUses(from, to, ((ASTAggregatedCondition) cond).getRightOp());

    } else if (cond instanceof ASTUnaryCondition) {
      // get uses from unary condition
      Value val = ((ASTUnaryCondition) cond).getValue();
      if (val instanceof Local) {
        Local local = (Local) val;
        if (local.getName().compareTo(from.getName()) == 0) {
          // replace the name with the one in "to"
          ((ASTUnaryCondition) cond).setValue(to);
          ASTMODIFIED = true;
        }
      } else {
        Iterator it = val.getUseBoxes().iterator();
        while (it.hasNext()) {
          ValueBox valBox = (ValueBox) it.next();
          Value tempVal = valBox.getValue();
          if (tempVal instanceof Local) {
            Local local = (Local) tempVal;
            if (local.getName().compareTo(from.getName()) == 0) {
              // replace the name with the one in "to"
              valBox.setValue(to);
              ASTMODIFIED = true;
            }
          }
        }
      }
    } // end unary condition
    else if (cond instanceof ASTBinaryCondition) {
      // get uses from binaryCondition
      Value val = ((ASTBinaryCondition) cond).getConditionExpr();
      Iterator it = val.getUseBoxes().iterator();
      while (it.hasNext()) {
        ValueBox valBox = (ValueBox) it.next();
        Value tempVal = valBox.getValue();
        if (tempVal instanceof Local) {
          Local local = (Local) tempVal;
          if (local.getName().compareTo(from.getName()) == 0) {
            // replace the name with the one in "to"
            valBox.setValue(to);
            ASTMODIFIED = true;
          }
        }
      }
    } else {
      throw new RuntimeException("Method getUseList in CopyPropagation encountered unknown condition type");
    }
  }

  public void modifyUseBoxes(Local from, Local to, List useBoxes) {

    Iterator it = useBoxes.iterator();
    while (it.hasNext()) {
      ValueBox valBox = (ValueBox) it.next();
      Value tempVal = valBox.getValue();
      if (tempVal instanceof Local) {
        Local local = (Local) tempVal;
        if (local.getName().compareTo(from.getName()) == 0) {
          // replace the name with the one in "to"
          valBox.setValue(to);
          ASTMODIFIED = true;
        }
      }
    }
  }

  /*
   * Invoked by handleCopyStmt to replace the use of local  to the use of local  in 
   *
   * Notice  can be a stmt or an ASTNode
   */

  public void replace(Local from, Local to, Object use) {
    if (use instanceof Stmt) {
      Stmt s = (Stmt) use;
      if (isCopyStmt(s)) {
        someCopyStmtModified = true;
      }
      List useBoxes = s.getUseBoxes();
      if (DEBUG) {
        System.out.println("Printing uses for stmt" + useBoxes);
      }

      // TODO
      modifyUseBoxes(from, to, useBoxes);

    } else if (use instanceof ASTNode) {
      if (use instanceof ASTSwitchNode) {
        ASTSwitchNode temp = (ASTSwitchNode) use;
        Value val = temp.get_Key();
        if (val instanceof Local) {
          if (((Local) val).getName().compareTo(from.getName()) == 0) {
            // replace the name with the one in "to"
            ASTMODIFIED = true;
            temp.set_Key(to);
          }
        } else {
          List useBoxes = val.getUseBoxes();
          // TODO
          modifyUseBoxes(from, to, useBoxes);
        }
      } else if (use instanceof ASTSynchronizedBlockNode) {
        ASTSynchronizedBlockNode temp = (ASTSynchronizedBlockNode) use;
        Local local = temp.getLocal();
        if (local.getName().compareTo(from.getName()) == 0) {
          // replace the name with the one in "to"
          temp.setLocal(to);
          ASTMODIFIED = true;
        }
      } else if (use instanceof ASTIfNode) {
        if (DEBUG) {
          System.out.println("Use is an instanceof if node");
        }

        ASTIfNode temp = (ASTIfNode) use;
        ASTCondition cond = temp.get_Condition();
        modifyUses(from, to, cond);
      } else if (use instanceof ASTIfElseNode) {
        ASTIfElseNode temp = (ASTIfElseNode) use;
        ASTCondition cond = temp.get_Condition();
        modifyUses(from, to, cond);
      } else if (use instanceof ASTWhileNode) {
        ASTWhileNode temp = (ASTWhileNode) use;
        ASTCondition cond = temp.get_Condition();
        modifyUses(from, to, cond);
      } else if (use instanceof ASTDoWhileNode) {
        ASTDoWhileNode temp = (ASTDoWhileNode) use;
        ASTCondition cond = temp.get_Condition();
        modifyUses(from, to, cond);
      } else if (use instanceof ASTForLoopNode) {
        ASTForLoopNode temp = (ASTForLoopNode) use;

        // init
        for (AugmentedStmt as : temp.getInit()) {
          Stmt s = as.get_Stmt();
          replace(from, to, s);
        }

        // update
        for (AugmentedStmt as : temp.getUpdate()) {
          Stmt s = as.get_Stmt();
          replace(from, to, s);
        }

        // condition
        ASTCondition cond = temp.get_Condition();
        modifyUses(from, to, cond);
      } else {
        throw new RuntimeException("Encountered an unknown ASTNode in copyPropagation method replace");
      }
    } else {
      throw new RuntimeException("Encountered an unknown use in copyPropagation method replace");
    }

  }

}