scale.score.chords
Class LoopTailChord

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

All Implemented Interfaces:

AnnotationInterface, DisplayNode

public class LoopTailChord
extends SequentialChord

This class is used to collect the loop edges so that the loop header has two and only two in-coming CFG edges.

$Id: LoopTailChord.java,v 1.33 2007-10-04 19:58:23 burrill Exp $

Copyright 2007 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. No code is generated for this node.

We need to mark the end of a loop so that there are only two in-coming CFG edges to a LoopHeaderChord instance. For example, consider the following C code:

 void tail(int k)
 {
   int i;
   i = 0;
   while (i++ < k) {
     if (i == 2)
       continue;
     ftn(i);
   }
 }
 

We want to represent this as

See Also:

LoopHeaderChord, LoopPreHeaderChord, LoopExitChord, LoopInitChord

Field Summary

Fields inherited from class scale.score.chords.Chord

lineNumber

Constructor Summary

LoopTailChord()

LoopTailChord(Chord next)

Method Summary

Chord	copy() Make a copy of this CFG node with the same out-going CFG edges.
DColor	getDisplayColorHint() Return a String specifying the color to use for coloring this node in a graphical display.
LoopHeaderChord	getLoopHeader() Return the LoopHeaderChord associated with this loop tail.
boolean	isLastInBasicBlock() Return true if this is the last Chord in this Basic Block.
boolean	isLoopTail() Return true if this CFG node is a LoopTailChord instance.
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	unlinkChord() Break any un-needed links from a Chord that is being deleted.
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, 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, getDisplayLabel, getDisplayShapeHint, getFirstInCfgEdge, getInCfgEdge, getInCfgEdge, getInCfgEdgeArray, getInDataEdge, getInDataEdgeArray, getLabel, getLoopHeader, getLoopNumber, getSourceLineNumber, gotoCFGNodes, inBasicBlock, indexOfInCfgEdge, insertAfterOutCfg, insertBeforeInCfg, isAssignChord, isBranch, isExprChord, isFirstInBasicBlock, isLoopExit, isLoopHeader, isLoopPreHeader, 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, 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

LoopTailChord

public LoopTailChord(Chord next)

LoopTailChord

public LoopTailChord()

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

getLoopHeader

public LoopHeaderChord getLoopHeader()

Return the LoopHeaderChord associated with this loop tail.

Overrides:

getLoopHeader in class Chord

isLastInBasicBlock

public boolean isLastInBasicBlock()

Return true if this is the last Chord in this Basic Block.

Overrides:

isLastInBasicBlock in class SequentialChord

See Also:

Chord.lastInBasicBlock(), Chord.isFirstInBasicBlock(), Chord.firstInBasicBlock()

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

isLoopTail

public boolean isLoopTail()

Return true if this CFG node is a LoopTailChord instance.

Overrides:

isLoopTail in class Chord

unlinkChord

public void unlinkChord()

Break any un-needed links from a Chord that is being deleted.

Overrides:

unlinkChord 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

getDisplayColorHint

public DColor getDisplayColorHint()

Return a String specifying the color to use for coloring this node in a graphical display.

Specified by:

getDisplayColorHint in interface DisplayNode

Overrides:

getDisplayColorHint in class Chord

See Also:

DColor