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.instrsched;
014    
015    import java.util.Enumeration;
016    
017    import org.jikesrvm.compilers.opt.ir.BasicBlock;
018    import org.jikesrvm.compilers.opt.ir.Instruction;
019    
020    /**
021     * Default (IR-order) instruction list.
022     * Used by the scheduler to enumerate over instructions.
023     *
024     * @see Priority
025     * @see Scheduler
026     */
027    class DefaultPriority extends Priority {
028      // Underlying enumeration.
029      private final BasicBlock bb;
030      private Instruction i;
031      private Enumeration<Instruction> instr;
032    
033      /**
034       * Creates new priority object for a given basic block
035       *
036       * @param bb basic block
037       */
038      public DefaultPriority(BasicBlock bb) {
039        this.bb = bb;
040      }
041    
042      @Override
043      public final void reset() {
044        i = bb.firstInstruction();
045        instr = bb.forwardRealInstrEnumerator();
046      }
047    
048      @Override
049      public final boolean hasMoreElements() {
050        return i != null || instr.hasMoreElements();
051      }
052    
053      @Override
054      public final Instruction nextElement() {
055        if (i != null) {
056          Instruction r = i;
057          i = null;
058          return r;
059        }
060        return instr.nextElement();
061      }
062    }