001    /*
002     *  This file is part of the Jikes RVM project (http://jikesrvm.org).
003     *
004     *  This file is licensed to You under the Eclipse Public License (EPL);
005     *  You may not use this file except in compliance with the License. You
006     *  may obtain a copy of the License at
007     *
008     *      http://www.opensource.org/licenses/eclipse-1.0.php
009     *
010     *  See the COPYRIGHT.txt file distributed with this work for information
011     *  regarding copyright ownership.
012     */
013    package org.jikesrvm.compilers.opt.ir.operand;
014    
015    
016    /**
017     * This operand represents, in a phi function, a control-flow path that is
018     * actually unreachable.
019     *
020     * @see Operand
021     */
022    public final class UnreachableOperand extends ConstantOperand {
023    
024      /**
025       * Return a new operand that is semantically equivalent to <code>this</code>.
026       *
027       * @return a copy of <code>this</code>
028       */
029      public Operand copy() {
030        return new UnreachableOperand();
031      }
032    
033      /**
034       * Are two operands semantically equivalent?
035       *
036       * @param op other operand
037       * @return   <code>true</code> if <code>this</code> and <code>op</code>
038       *           are semantically equivalent or <code>false</code>
039       *           if they are not.
040       */
041      public boolean similar(Operand op) {
042        return op instanceof UnreachableOperand;
043      }
044    
045      /**
046       * Returns the string representation of this operand.
047       *
048       * @return a string representation of this operand.
049       */
050      public String toString() {
051        return "<unreachable>";
052      }
053    }