WALA/com.ibm.wala.core/src/com/ibm/wala/ssa/SSAAddressOfInstruction.java

/*******************************************************************************
 * Copyright (c) 2007 IBM Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package com.ibm.wala.ssa;

import com.ibm.wala.ssa.SSAIndirectionData.Name;
import com.ibm.wala.types.FieldReference;
import com.ibm.wala.types.TypeReference;
import com.ibm.wala.util.debug.Assertions;

/**
 * An {@link SSAAddressOfInstruction} represents storing the address of some "source" level entity (@see {@link Name}) into an SSA
 * value number.
 */
public class SSAAddressOfInstruction extends SSAInstruction {

  /**
   * The value number which is def'ed ... this instruction assigns this value to hold an address.
   */
  private final int lval;

  /**
   * The SSA value number that represents the entity whose address is being taken.
   * 
   * If we're taking the address of a local variable, this is the value number representing that local variable immediately before
   * this instruction.
   * 
   * If we're taking the address of an array element or a field of an object, then this is the base pointer.
   */
  private final int addressVal;

  /**
   * If we're taking the address of an array element, this is the array index. Otherwise, this is -1.
   */
  private final int indexVal;

  /**
   * If we're taking the address of a field, this is the field reference. Otherwise, this is null.
   */
  private final FieldReference field;

  private final TypeReference pointeeType;
  
  /**
   * Use this constructor when taking the address of a local variable.
   */
  public SSAAddressOfInstruction(int index, int lval, int local, TypeReference pointeeType) {
    super(index);
    if (local <= 0) {
      throw new IllegalArgumentException("Invalid local address load of " + local);
    }
    this.lval = lval;
    this.addressVal = local;
    this.indexVal = -1;
    this.field = null;
    this.pointeeType = pointeeType;
  }

  /**
   * Use this constructor when taking the address of an array element.
   */
  public SSAAddressOfInstruction(int index, int lval, int basePointer, int indexVal, TypeReference pointeeType) {
    super(index);
    this.lval = lval;
    this.addressVal = basePointer;
    this.indexVal = indexVal;
    this.field = null;
    this.pointeeType = pointeeType;
  }

  /**
   * Use this constructor when taking the address of a field in an object.
   */
  public SSAAddressOfInstruction(int index, int lval, int basePointer, FieldReference field, TypeReference pointeeType) {
    super(index);
    this.lval = lval;
    this.addressVal = basePointer;
    this.indexVal = -1;
    this.field = field;
    this.pointeeType = pointeeType;
  }

  public TypeReference getType() {
    return pointeeType;
  }
  
  @Override
  public SSAInstruction copyForSSA(SSAInstructionFactory insts, int[] defs, int[] uses) {
    Assertions.UNREACHABLE("not yet implemented.  to be nuked");
    return null;
  }

  @Override
  public int hashCode() {
    return lval * 99701 + addressVal;
  }

  @Override
  public boolean isFallThrough() {
    return true;
  }

  @Override
  public String toString(SymbolTable symbolTable) {
    return getValueString(symbolTable, lval)
        + " (" + pointeeType.getName() + ") " 
        + " = &"
        + getValueString(symbolTable, addressVal)
        + ((indexVal != -1) ? "[" + getValueString(symbolTable, indexVal) + "]" : (field != null) ? "."
            + field.getName().toString() : "");
  }

  @Override
  public void visit(IVisitor v) {
    assert (v instanceof IVisitorWithAddresses) : "expected an instance of IVisitorWithAddresses";
    ((IVisitorWithAddresses) v).visitAddressOf(this);
  }

  @Override
  public int getNumberOfDefs() {
    return 1;
  }

  @Override
  public int getDef(int i) {
    assert i == 0;
    return lval;
  }

  @Override
  public int getDef() {
    return lval;
  }

  @Override
  public int getNumberOfUses() {
    return (indexVal == -1) ? 1 : 2;
  }

  @Override
  public int getUse(int i) {
    assert i == 0 || (i == 1 && indexVal != -1);
    if (i == 0) {
      return addressVal;
    } else {
      return indexVal;
    }
  }
}