soot.dava.toolkits.base.AST.transformations.BooleanConditionSimplification Maven / Gradle / Ivy

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

/*-
 * #%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 soot.BooleanType;
import soot.Type;
import soot.Value;
import soot.dava.internal.AST.ASTBinaryCondition;
import soot.dava.internal.AST.ASTCondition;
import soot.dava.internal.AST.ASTDoWhileNode;
import soot.dava.internal.AST.ASTIfElseNode;
import soot.dava.internal.AST.ASTIfNode;
import soot.dava.internal.AST.ASTStatementSequenceNode;
import soot.dava.internal.AST.ASTUnaryCondition;
import soot.dava.internal.AST.ASTWhileNode;
import soot.dava.internal.javaRep.DIntConstant;
import soot.dava.internal.javaRep.DNotExpr;
import soot.dava.toolkits.base.AST.analysis.DepthFirstAdapter;
import soot.jimple.ConditionExpr;
import soot.jimple.EqExpr;
import soot.jimple.NeExpr;

/*
  TO MAKE CODE EFFECIENT BLOCK THE ANALYSIS TO GOING INTO STATEMENTS
  this is done by overriding the caseASTStatementSequenceNode
*/
public class BooleanConditionSimplification extends DepthFirstAdapter {

  public BooleanConditionSimplification(boolean verbose) {
    super(verbose);
  }

  public void caseASTStatementSequenceNode(ASTStatementSequenceNode node) {
  }

  public BooleanConditionSimplification() {
  }

  /*
   * The method checks whether a particular ASTBinaryCondition is a comparison of a local with a boolean If so the
   * ASTBinaryCondition is replaced by a ASTUnaryCondition
   */
  public void outASTIfNode(ASTIfNode node) {
    ASTCondition condition = node.get_Condition();
    if (condition instanceof ASTBinaryCondition) {
      ConditionExpr condExpr = ((ASTBinaryCondition) condition).getConditionExpr();
      Value unary = checkBooleanUse(condExpr);
      if (unary != null) {
        node.set_Condition(new ASTUnaryCondition(unary));
      }
    }
  }

  public void outASTIfElseNode(ASTIfElseNode node) {
    ASTCondition condition = node.get_Condition();
    if (condition instanceof ASTBinaryCondition) {
      ConditionExpr condExpr = ((ASTBinaryCondition) condition).getConditionExpr();
      Value unary = checkBooleanUse(condExpr);
      if (unary != null) {
        node.set_Condition(new ASTUnaryCondition(unary));
      }
    }
  }

  public void outASTWhileNode(ASTWhileNode node) {
    ASTCondition condition = node.get_Condition();
    if (condition instanceof ASTBinaryCondition) {
      ConditionExpr condExpr = ((ASTBinaryCondition) condition).getConditionExpr();
      Value unary = checkBooleanUse(condExpr);
      if (unary != null) {
        node.set_Condition(new ASTUnaryCondition(unary));
      }
    }
  }

  public void outASTDoWhileNode(ASTDoWhileNode node) {
    ASTCondition condition = node.get_Condition();
    if (condition instanceof ASTBinaryCondition) {
      ConditionExpr condExpr = ((ASTBinaryCondition) condition).getConditionExpr();
      Value unary = checkBooleanUse(condExpr);
      if (unary != null) {
        node.set_Condition(new ASTUnaryCondition(unary));
      }
    }
  }

  private Value checkBooleanUse(ConditionExpr condition) {
    // check whether the condition qualifies as a boolean use
    if (condition instanceof NeExpr || condition instanceof EqExpr) {
      Value op1 = condition.getOp1();
      Value op2 = condition.getOp2();
      if (op1 instanceof DIntConstant) {
        Type op1Type = ((DIntConstant) op1).type;
        if (op1Type instanceof BooleanType) {
          return decideCondition(op2, ((DIntConstant) op1).toString(), condition);
        }
      } else if (op2 instanceof DIntConstant) {
        Type op2Type = ((DIntConstant) op2).type;
        if (op2Type instanceof BooleanType) {
          return decideCondition(op1, ((DIntConstant) op2).toString(), condition);
        }
      } else {
        return null;// meaning no Value used as boolean found
      }
    }
    return null; // meaning no local used as boolean found
  }

  /*
   * Used to decide what the condition should be if we are converting from ConditionExpr to Value A != false/0 --> A A !=
   * true/1 --> !A A == false/0 --> !A A == true/1 --> A
   */
  private Value decideCondition(Value A, String truthString, ConditionExpr condition) {
    int truthValue = 0;
    boolean notEqual = false;

    // find out whether we are dealing with a false or true
    if (truthString.compareTo("false") == 0) {
      truthValue = 0;
    } else if (truthString.compareTo("true") == 0) {
      truthValue = 1;
    } else {
      throw new RuntimeException();
    }

    // find out whether the comparison operator is != or ==
    if (condition instanceof NeExpr) {
      notEqual = true;
    } else if (condition instanceof EqExpr) {
      notEqual = false;
    } else {
      throw new RuntimeException();
    }

    // decide and return
    if (notEqual && truthValue == 0) { // A != false -->A
      return A;
    } else if (notEqual && truthValue == 1) {
      // A != true --> !A
      if (A instanceof DNotExpr) {
        // A is actually !B
        return ((DNotExpr) A).getOp();
      } else {
        return (new DNotExpr(A));
      }
    } else if (!notEqual && truthValue == 0) {
      // A == false --> !A
      if (A instanceof DNotExpr) {
        // A is actually !B
        return ((DNotExpr) A).getOp();
      } else {
        return new DNotExpr(A);
      }
    } else if (!notEqual && truthValue == 1) {
      // A == true --> A
      return A;
    } else {
      throw new RuntimeException();
    }
  }

}