coins.alias.alias2
Class AliasAnalHir2

java.lang.Object
  coins.alias.AliasAnalHir1
      coins.alias.alias2.AliasAnalHir2

All Implemented Interfaces:

AliasAnal

public class AliasAnalHir2

extends AliasAnalHir1

Alias analysis level 2 implementation.

Alias analysis level 2 is a flow-sensitive intraprocedural analysis.

This class drives the alias analysis and also implements AliasAnal interface.

Flow sensitive analysis is performed only for structured subprograms, which don't contain unstructed jumps (jumps that do not correpond to C's break/continue). If the subprogram is unstructured, the analysis is reverted to that of level 1 (flow-insensitive analysis).

Two modes (Optimistic and Pessimistic), or options, for the analysis are available, each of which uses different assumptions about aliasing.

Handling of source languages other than C is not supported in this version.

Field Summary

protected static int	AREA_INCLUDES
protected static int	AREA_OVERLAPS
(package private) java.util.Map	fElemToMask
(package private) TagVector2	fExternOpt TagVector2 that corresponds to the area visible from the outside of the current subprogram.
(package private) AliasFactory2	fFactory Factory object used to create other objects.
(package private) TagVector2	fGlobals TagVector2 that corresponds to global variables.
(package private) java.util.Map	fHIRToLoc Map that maps HIR nodes to TagVectors.
(package private) boolean	fIsOptimistic Alias analysis option.
(package private) TagVector2[]	fLocalRootVects
(package private) java.util.Map	fmallocToLoc
(package private) TagVector2[]	fPointsTo The points-to graph represented as an array of TagVector2s.
protected java.util.Set	fPredefined Set of predefined functions.
(package private) java.util.Map	fSubscriptToMask
(package private) int	fTagBitCount Number of bit-allocated memory objects.
protected AliasUtil	fUtil AliasUtil object used to access utility methods.
(package private) java.util.Map	fVarToLoc
HirRoot	hirRoot The HirRoot object shared by every module in the program.
IoRoot	ioRoot The IoRoot object shared by every module in the program.
protected static int	MAY_ALIAS
protected static int	MUST_ALIAS
protected static int	NOT_ALIAS
protected static java.lang.String	PREDEFINED

Fields inherited from class coins.alias.AliasAnalHir1

fDbgLevel

Fields inherited from interface coins.alias.AliasAnal

CATEGORY_NAME

Constructor Summary

AliasAnalHir2(boolean pIsOptimistic, HirRoot pHirRoot)
Creats a new instance of AliasAnalHir2 that performs alias analysis with the specified assumptions (pIsOptimistic) about aliasing.

AliasAnalHir2(HirRoot pHirRoot)
Creates a new instance of AliasAnalHir2 that performs alias analysis based on some set of assumptions about aliasing.

Method Summary

protected int	areAliased(Exp pExp, Exp pExp0) Returns one of the codes (MUST_ALIAS, MAY_ALIAS, NOT_ALIAS).
AliasGroup	getAliasGroupFor(Exp pExp) Returns the set of lvalue nodes the specified argument may be aliased to.
boolean	isLvalue(Exp pExp) Returns true if the specified argument is lvalue.
(package private) boolean	jumpCheck(SubpDefinition pSubpDef)
boolean	mayAlias(Exp pExp, Exp pExp0) Returns true if the two arguments may refer to the overlapping area in memory.
boolean	mustAlias(Exp pExp, Exp pExp0) Returns true if the two arguments definitely refer to the overlapping area in memory.
(package private) void	prepare(SubpDefinition pSubpDef) Instantiates TagVector2s and assigns TagVector2 objects to Var, malloced area, and external area.
void	prepareForAliasAnalHir(SubpDefinition pSubpDef) Performs alias analysis for the given SubpDefinition argument so that may/mustAlias methods for nodes contained in the SubpDefinition are ready.
void	printAliasPairs(SubpDefinition pSubpDef) Prints out alias pairs in IoRoot.printOut object.

Methods inherited from class coins.alias.AliasAnalHir1

dbg, printAliasPairsDetail

Methods inherited from class java.lang.Object

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

Field Detail

AREA_INCLUDES

protected static final int AREA_INCLUDES

See Also:

Constant Field Values

AREA_OVERLAPS

protected static final int AREA_OVERLAPS

See Also:

Constant Field Values

MUST_ALIAS

protected static final int MUST_ALIAS

See Also:

Constant Field Values

NOT_ALIAS

protected static final int NOT_ALIAS

See Also:

Constant Field Values

MAY_ALIAS

protected static final int MAY_ALIAS

See Also:

Constant Field Values

PREDEFINED

protected static final java.lang.String PREDEFINED

See Also:

Constant Field Values

fPredefined

protected java.util.Set fPredefined

Set of predefined functions.

fHIRToLoc

java.util.Map fHIRToLoc

Map that maps HIR nodes to TagVectors.

fLocalRootVects

TagVector2[] fLocalRootVects

fTagBitCount

int fTagBitCount

Number of bit-allocated memory objects. This determines the length of the TagVector2.

fPointsTo

TagVector2[] fPointsTo

The points-to graph represented as an array of TagVector2s.

fGlobals

TagVector2 fGlobals

TagVector2 that corresponds to global variables.

fExternOpt

TagVector2 fExternOpt

TagVector2 that corresponds to the area visible from the outside of the current subprogram.

hirRoot

public final HirRoot hirRoot

The HirRoot object shared by every module in the program.

ioRoot

public final IoRoot ioRoot

The IoRoot object shared by every module in the program.

fIsOptimistic

final boolean fIsOptimistic

Alias analysis option. This determines the set of assumptions on which the alias analysis is based.

See Also:

AliasAnalHir2(boolean, HirRoot)

fFactory

final AliasFactory2 fFactory

Factory object used to create other objects.

fUtil

protected final AliasUtil fUtil

AliasUtil object used to access utility methods.

fVarToLoc

java.util.Map fVarToLoc

fSubscriptToMask

java.util.Map fSubscriptToMask

fElemToMask

java.util.Map fElemToMask

fmallocToLoc

java.util.Map fmallocToLoc

Constructor Detail

AliasAnalHir2

public AliasAnalHir2(HirRoot pHirRoot)

Creates a new instance of AliasAnalHir2 that performs alias analysis based on some set of assumptions about aliasing. Two sets of assumptions (Pessimistic and Optimistic) are available, and which one to use is determined from the command line, and defaults to Pessimistic.

Parameters:

pHirRoot - the HirRoot object shared by every module in the program.

See Also:

AliasAnalHir2(boolean, HirRoot)

AliasAnalHir2

public AliasAnalHir2(boolean pIsOptimistic,
                     HirRoot pHirRoot)

Creats a new instance of AliasAnalHir2 that performs alias analysis with the specified assumptions (pIsOptimistic) about aliasing. The difference between optimistic and pessimistic assumptions are:

1. Whether inconsistent object access (access by an object whose type differs from that of the stored object) may happen
.
2. Whether parameters may initially pointing to objects that are elements of the same array object.

Method Detail

prepareForAliasAnalHir

public void prepareForAliasAnalHir(SubpDefinition pSubpDef)

Performs alias analysis for the given SubpDefinition argument so that may/mustAlias methods for nodes contained in the SubpDefinition are ready.

This method may be called only once in the lifetime of this analysis object; for analyses of different SubpDefinitions, the AliasAnalHir2 object has to be newly created.

Specified by:

prepareForAliasAnalHir in interface AliasAnal

Overrides:

prepareForAliasAnalHir in class AliasAnalHir1

Parameters:

pSubpDef - the SubpDefinition instance nodes contained in which are to be analyzed for aliasing.

jumpCheck

boolean jumpCheck(SubpDefinition pSubpDef)

prepare

void prepare(SubpDefinition pSubpDef)

Instantiates TagVector2s and assigns TagVector2 objects to Var, malloced area, and external area.

Parameters:

pSubpDef - SubpDefinition instance to analyze.

areAliased

protected int areAliased(Exp pExp,
                         Exp pExp0)

Returns one of the codes (MUST_ALIAS, MAY_ALIAS, NOT_ALIAS).

Overrides:

areAliased in class AliasAnalHir1

getAliasGroupFor

public AliasGroup getAliasGroupFor(Exp pExp)

Returns the set of lvalue nodes the specified argument may be aliased to. Each AliasGroup object for different argument (pExp) is distinct from one another, so it can be safely modified without affecting others.

Specified by:

getAliasGroupFor in interface AliasAnal

Overrides:

getAliasGroupFor in class AliasAnalHir1

Parameters:

pExp - the lvalue node to check for aliasing.

Returns:

the set of lvalue nodes the specified argument may be aliased to.

printAliasPairs

public void printAliasPairs(SubpDefinition pSubpDef)

Prints out alias pairs in IoRoot.printOut object. For debugging.

Specified by:

printAliasPairs in interface AliasAnal

Overrides:

printAliasPairs in class AliasAnalHir1

Parameters:

pSubpDef - the SubpDefinition object aliasing relation between nodes contained in which are to be printed.

mayAlias

public boolean mayAlias(Exp pExp,
                        Exp pExp0)

Returns true if the two arguments may refer to the overlapping area in memory. A CONTENTS node with uninitialized pointer value operand (undefined behavior in C) does not represent an object that inhabits the memory space, so it is not aliased even to itself.

This method has to be called after the prepareForAliasAnalHir method has been called.

Specified by:

mayAlias in interface AliasAnal

Overrides:

mayAlias in class AliasAnalHir1

Throws:

java.lang.IllegalArgumentException - if either of the arguments is not lvalue.

mustAlias

public boolean mustAlias(Exp pExp,
                         Exp pExp0)

Returns true if the two arguments definitely refer to the overlapping area in memory.

This method has to be called after the prepareForAliasAnalHir method has been called.

Specified by:

mustAlias in interface AliasAnal

Overrides:

mustAlias in class AliasAnalHir1

Throws:

java.lang.IllegalArgumentException - if either of the arguments is not lvalue.

isLvalue

public boolean isLvalue(Exp pExp)

Returns true if the specified argument is lvalue. As is the case for the query methods (mayAlias etc.) that is specified in the AliasAnal interface, this method also has to be called after the prepareForAliasAnalHir method for the corresponding SubpDefinition object has been called.

This method has to be called after the prepareForAliasAnalHir method has been called.

Specified by:

isLvalue in interface AliasAnal

Overrides:

isLvalue in class AliasAnalHir1

Returns:

true if the specified argument is lvalue.