scale.score.expr
Class NilExpr

java.lang.Object
  scale.common.Root
      scale.score.Note
          scale.score.expr.Expr
              scale.score.expr.ValueExpr
                  scale.score.expr.NilExpr

All Implemented Interfaces:

AnnotationInterface, DisplayNode

public class NilExpr
extends ValueExpr

This class represents the null or nil address.

$Id: NilExpr.java,v 1.33 2007-04-27 18:04:37 burrill Exp $

Copyright 2008 by the Scale Compiler Group,
Department of Computer Science
University of Massachusetts,
Amherst MA. 01003, USA
All Rights Reserved.

Field Summary

Fields inherited from class scale.score.expr.Expr

fpReorder, SE_DOMAIN, SE_NONE, SE_OVERFLOW, SE_STATE

Constructor Summary

NilExpr()
The expression type is generated.

NilExpr(Type t)

Method Summary

Expr	copy() Perform a deep copy of the expression tree.
int	executionCostEstimate() Return a relative cost estimate for executing the expression.
Literal	getConstantValue() Return the constant value of the expression.
Literal	getConstantValue(HashMap<Expr,Literal> cvMap) Return the constant value of the expression.
java.lang.String	getDisplayLabel() Return a String suitable for labeling this node in a graphical display.
boolean	optimizationCandidate() Return true if the expression can be moved without problems.
void	visit(Predicate p) Process a node by calling its associated routine.

Methods inherited from class scale.score.expr.ValueExpr

getDeclList, getExprList, getLoadExprList, getOperandArray, isLoopInvariant, numOperands, pushOperands, recordRefs, removeRefs, removeUseDef, replaceDecl, sideEffects

Methods inherited from class scale.score.expr.Expr

addCast, addCast, canonical, changeInDataEdge, conditionalCopy, conditionalUnlinkExpression, containsDeclaration, deleteOutDataEdge, dependsOnDeclaration, equivalent, executionOrder, executionOrdinal, findCriticalChord, findLinearCoefficient, findSubscriptExpr, getAffineExpr, getAffineRepresentation, getAliasAnnote, getCall, getCoreType, getCriticalChord, getDefExpr, getDisplayColorHint, getDisplayShapeHint, getDualExpr, getInDataEdge, getInDataEdgeArray, getLoopHeader, getLow, getLValue, getOperand, getOutDataEdge, getPointedToCore, getReference, getReuseLevel, getRValue, getType, getUseDef, hasTrueFalseResult, isCast, isDefined, isDefined, isLiteralExpr, isMatchExpr, isMemoryDef, isMemRefExpr, isScalar, isSimpleExpr, loopClean, mayGenerateCall, numInDataEdges, reduce, removeDualExprs, setCrossloopReuse, setOperand, setOutDataEdge, setSpatialReuse, setStep, setTemporalReuse, setType, setUseDef, toStringSpecial, unlinkExpression, validate, validLValue

Methods inherited from class scale.score.Note

getChord, getEssentialUse, setAnnotationLevel, setReportLevel, toString

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

NilExpr

public NilExpr(Type t)

NilExpr

public NilExpr()

The expression type is generated.

Method Detail

copy

public Expr copy()

Description copied from class: Expr

Perform a deep copy of the expression tree. By deep copy, we mean that copies are made of the expression tree.

Specified by:

copy in class Expr

Returns:

a copy of this expression

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

getDisplayLabel

public java.lang.String getDisplayLabel()

Description copied from class: Expr

Return a String suitable for labeling this node in a graphical display. This method should be over-ridden as it simplay returns the class name.

Specified by:

getDisplayLabel in interface DisplayNode

Overrides:

getDisplayLabel in class Expr

getConstantValue

public Literal getConstantValue(HashMap<Expr,Literal> cvMap)

Return the constant value of the expression. Follow use-def links.

Overrides:

getConstantValue in class Expr

See Also:

Lattice

getConstantValue

public Literal getConstantValue()

Return the constant value of the expression. Do not follow use-def links.

Overrides:

getConstantValue in class Expr

See Also:

Lattice

optimizationCandidate

public boolean optimizationCandidate()

Return true if the expression can be moved without problems. Expressions that reference global variables, non-atomic variables, etc are not optimization candidates.

Specified by:

optimizationCandidate in class Expr

executionCostEstimate

public int executionCostEstimate()

Return a relative cost estimate for executing the expression.

Specified by:

executionCostEstimate in class Note