scale.score.expr
Class CompareExpr

java.lang.Object
  scale.common.Root
      scale.score.Note
          scale.score.expr.Expr
              scale.score.expr.BinaryExpr
                  scale.score.expr.CompareExpr

All Implemented Interfaces:

AnnotationInterface, DisplayNode

public class CompareExpr
extends BinaryExpr

This class represents three-valued comparison functions.

$Id: CompareExpr.java,v 1.26 2007-04-27 18:04:35 burrill Exp $

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

If the left argument is less than the right argument, a -1 is returned. If the left argument is greater than the right argument, a 1 is returned. Otherwise, a 0 is returned. If the arguments are floating point and either is Nan, then either a -1 or a 1 is returned depending on the mode setting.

We use instances of this class instead of generating comparisons and IfThenElseChords directly in the CFG. There is no benefit to generating the decision points in the CFG and doing so makes the CFG unnecessarily complex. Also, there is no easy way to test for a NaN in C code so a function call would have to be made to do that test anyway.

By using this class, Scribble2C can generate a function call for floating point arguments and use the C conditional operator inline for integer arguments.

When going direct to machine code, an instance of this class can be converted directly into machine instructions that test for NaN.

Field Summary

static int	FloatG If either argument is Nan, return 1.
static int	FloatL If either argument is Nan, return -1.
static java.lang.String[]	modes String representation of the compare mode.
static int	Normal Use normal compare.

Fields inherited from class scale.score.expr.Expr

fpReorder, SE_DOMAIN, SE_NONE, SE_OVERFLOW, SE_STATE

Constructor Summary

CompareExpr(Expr la, Expr ra, int mode)
The expression type is integer two's complement.

CompareExpr(Type type, Expr la, Expr ra, int mode)

Method Summary

Expr	copy() Perform a deep copy of the expression tree.
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.
int	getMode() Return the mode of the comparison operation.
void	visit(Predicate p) Process a node by calling its associated routine.

Methods inherited from class scale.score.expr.BinaryExpr

associativeSwapOperands, containsDeclaration, dependsOnDeclaration, equivalent, executionCostEstimate, getAliasAnnote, getDeclList, getExprList, getLeftArg, getLoadExprList, getOperand, getOperandArray, getRightArg, isAssociative, isCommutative, isLeftDistributive, isRightDistributive, loopClean, numOperands, optimizationCandidate, pushOperands, recordRefs, removeRefs, removeUseDef, replaceDecl, setLeftArg, setOperand, setRightArg, sideEffects, swapOperands, unlinkExpression, validate

Methods inherited from class scale.score.expr.Expr

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

Field Detail

Normal

public static final int Normal

Use normal compare.

See Also:

Constant Field Values

FloatL

public static final int FloatL

If either argument is Nan, return -1.

See Also:

Constant Field Values

FloatG

public static final int FloatG

If either argument is Nan, return 1.

See Also:

Constant Field Values

modes

public static final java.lang.String[] modes

String representation of the compare mode.

Constructor Detail

CompareExpr

public CompareExpr(Type type,
                   Expr la,
                   Expr ra,
                   int mode)

Parameters:

type - is the expression type

la - is the left operand

ra - is the right operand

mode - determines the type of comparison

CompareExpr

public CompareExpr(Expr la,
                   Expr ra,
                   int mode)

The expression type is integer two's complement.

Parameters:

la - is the left operand

ra - is the right operand

mode - determines the type of comparison

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

getMode

public int getMode()

Return the mode of the comparison operation.

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