scale.score.chords
Class NullChord

java.lang.Object
  scale.common.Root
      scale.score.Note
          scale.score.chords.Chord
              scale.score.chords.SequentialChord
                  scale.score.chords.NullChord

All Implemented Interfaces:

AnnotationInterface, DisplayNode

public class NullChord
extends SequentialChord

This class is used as a place holder in the construction of the CFG.

$Id: NullChord.java,v 1.23 2005-02-07 21:28:36 burrill Exp $

Copyright 2005 by the Scale Compiler Group,
Department of Computer Science
University of Massachusetts,
Amherst MA. 01003, USA
All Rights Reserved.

This class represents a non-action. We really don't want null actions in Score, but having this class simplifies the translation from Clef to Scribble. These nodes are removed from Score (Scribble) as soon as the initial, complete Cfg is generated.

Field Summary

Fields inherited from class scale.score.chords.Chord

lineNumber

Constructor Summary

NullChord()

NullChord(Chord next)
Create a NullChord.

Method Summary

Chord	copy() Make a copy of this CFG node with the same out-going CFG edges.
boolean	isSpecial() Return true if this is chord was added for the convenience of the compiler and does not correspond to actual source code in the user program.
void	visit(Predicate p) Process a node by calling its associated routine.

Methods inherited from class scale.score.chords.SequentialChord

changeOutCfgEdge, clearEdge, clearEdgeMarkers, deleteInDataEdges, deleteOutCfgEdges, edgeMarked, executionCostEstimate, getDeclList, getExprList, getLoadExprList, getNextChord, getOutCfgEdge, getOutCfgEdgeArray, getTarget, indexOfOutCfgEdge, isLastInBasicBlock, isSequential, linkSubgraph, linkTo, markEdge, numOutCfgEdges, pushAllOutCfgEdges, pushOutCfgEdges, pushOutCfgEdges, pushSortedOutCfgEdges, pushSortedOutCfgEdges, removeUseDef, replaceDecl, replaceOutCfgEdge, setTarget, setTargetUnsafe

Methods inherited from class scale.score.chords.Chord

addInCfgEdge, changeInDataEdge, changeParentOutCfgEdge, copySourceLine, deadCFGNodes, deletedCFGNodes, deleteInCfgEdge, executionOrder, expungeFromCfg, extractFromCfg, findLoopExit, findPhiChords, firstInBasicBlock, getCall, getDefExpr, getDisplayColorHint, getDisplayLabel, getDisplayShapeHint, getFirstInCfgEdge, getInCfgEdge, getInCfgEdge, getInCfgEdgeArray, getInDataEdge, getInDataEdgeArray, getLabel, getLoopHeader, getLoopHeader, getLoopNumber, getSourceLineNumber, gotoCFGNodes, inBasicBlock, indexOfInCfgEdge, insertAfterOutCfg, insertBeforeInCfg, isAssignChord, isBranch, isExprChord, isFirstInBasicBlock, isLoopExit, isLoopHeader, isLoopPreHeader, isLoopTail, isMarker, isPhiExpr, lastInBasicBlock, loopClean, nextVisit, nthIndexOfInCfgEdge, nullCFGNodes, numInCfgEdges, numInDataEdges, numOfInCfgEdge, parentsFinished, parentsVisited, pushAllInCfgEdges, pushChordWhenReady, pushChordWhenReady, pushInCfgEdges, pushInCfgEdges, pushInDataEdges, recordRefs, removeDeadCode, removeDualExprs, removeFromCfg, removeRefs, reorderInCfgEdgesOfCopy, replaceInCfgEdge, setLabel, setSourceLineNumber, setVisited, toStringSpecial, unlinkChord, visited

Methods inherited from class scale.score.Note

getChord, getEssentialUse, setAnnotationLevel, setReportLevel, toString, validate

Methods inherited from class scale.common.Root

addAnnotation, allAnnotations, allMatchingAnnotations, getAnnotation, getDisplayName, getDisplayString, getNodeCount, getNodeID, hasAnnotation, hasEqualAnnotation, hashCode, removeAnnotation, removeAnnotations, toStringAnnotations, toStringClass, trace, trace, trace

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

NullChord

public NullChord(Chord next)

Create a NullChord.

Parameters:

next - is the out-going CFG edge and may be null

NullChord

public NullChord()

Method Detail

copy

public Chord copy()

Description copied from class: Chord

Make a copy of this CFG node with the same out-going CFG edges. The validity of the CFG graph is maintained.

Specified by:

copy in class Chord

Returns:

a copy of this node

isSpecial

public boolean isSpecial()

Return true if this is chord was added for the convenience of the compiler and does not correspond to actual source code in the user program.

Overrides:

isSpecial in class Chord

visit

public void visit(Predicate p)

Description copied from class: Note

Process a node by calling its associated routine. See the "visitor" design pattern in Design Patterns: Elements of Reusable Object-Oriented Software by E. Gamma, et al, Addison Wesley, ISBN 0-201-63361-2.

Each class has a visit(Predicate p) method. For example, in class ABC:

   public void visit(Predicate p)
   {
     p.visitABC(this);
   }
 

and the class that implements Predicate has a method

   public void visitABC(Note n)
   {
     ABC a = (ABC) n;
     ...
   }
 

Thus, the class that implements Predicate can call

   n.visit(this);
 

where n is a Note sub-class without determining which specific sub-class n is. The visit pattern basically avoids implementing a large switch statement or defining different methods in each class for some purpose.

Specified by:

visit in class Note

See Also:

Predicate