coins.alias
Class AliasAnalHir1

java.lang.Object
  coins.alias.AliasAnalHir1

All Implemented Interfaces:

AliasAnal

Direct Known Subclasses:

AliasAnalHir2

public class AliasAnalHir1

extends java.lang.Object

implements AliasAnal

Alias analysis level 1 implementation.

Alias analysis level 1 is a flow-insensitive intraprocedural analysis.

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

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) Tag[]	fBitAssignedTags Array of Tags that are assigned bits.
(package private) TagVector	fCurFrame TagVector that corresponds to the current frame (automatic variables that are in scope).
protected int	fDbgLevel
(package private) TagVector	fExternOpt TagVector that corresponds to the area visible from the outside of the current subprogram.
(package private) TagVector	fExternPes TagVector that corresponds to the area visible from the outside of the current subprogram.
(package private) AliasFactory	fFactory Factory object used to create other objects.
(package private) TagVector	fGlobals TagVector that corresponds to global variables.
(package private) TagVector	fHeap TagVector that corresponds to the heap (allocated) area.
(package private) java.util.Map	fHIRTomallocTag Map that maps malloc invocation nodes to corresponding tags.
(package private) java.util.Map	fHIRToTag Map that maps HIR nodes to tags.
(package private) boolean	fIsOptimistic Alias analysis option.
(package private) TagVector	fOther TagVector that corresponds to the area that is not included in fCurFrame or fStatic or fHeap, and includes frames from subprograms that called the currrent subprogram, global variables that do not appear in the current subprogram, and area allocated by the subprograms that called the current subprogram.
(package private) TagVector[]	fPointsTo The points-to graph represented as an array of TagVectors.
protected java.util.Set	fPredefined Set of predefined functions.
(package private) TagVector	fStatic TagVector that corresponds to the static area.
(package private) int	fTagBitCount Number of bit-allocated tags.
protected AliasUtil	fUtil AliasUtil object used to access utility methods.
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 interface coins.alias.AliasAnal

CATEGORY_NAME

Constructor Summary

AliasAnalHir1(boolean pIsOptimistic, HirRoot pHirRoot)
Creats a new instance of AliasAnalHir1 that performs alias analysis with the specified assumptions (pIsOptimistic) about aliasing.

AliasAnalHir1(HirRoot pHirRoot)
Creates a new instance of AliasAnalHir1 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).
void	dbg(int pLevel, java.lang.String pHeader, java.lang.Object pBody) Prints out the String representation of the pBody object headed by pHeader if the debug level for this alias analysis category is greater than or equal to pLevel.
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.
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.
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.
(package private) void	prepareTags(SubpDefinition pSubpDef) Instantiates tags and TagVectors, builds the tree structure between the tags and assigns TagVector bits to these tags.
void	printAliasPairs(SubpDefinition pSubpDef) Prints out alias pairs in IoRoot.printOut object.
void	printAliasPairsDetail(SubpDefinition pSubpDef) Prints out alias pairs in IoRoot.printOut object in somewhat more detailed format than in printAliasPairs.

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.

fHIRToTag

java.util.Map fHIRToTag

Map that maps HIR nodes to tags.

fHIRTomallocTag

java.util.Map fHIRTomallocTag

Map that maps malloc invocation nodes to corresponding tags.

fTagBitCount

int fTagBitCount

Number of bit-allocated tags. This determines the length of the TagVector.

fBitAssignedTags

Tag[] fBitAssignedTags

Array of Tags that are assigned bits.

fPointsTo

TagVector[] fPointsTo

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

fCurFrame

TagVector fCurFrame

TagVector that corresponds to the current frame (automatic variables that are in scope).

fStatic

TagVector fStatic

TagVector that corresponds to the static area.

fHeap

TagVector fHeap

TagVector that corresponds to the heap (allocated) area.

fOther

TagVector fOther

TagVector that corresponds to the area that is not included in fCurFrame or fStatic or fHeap, and includes frames from subprograms that called the currrent subprogram, global variables that do not appear in the current subprogram, and area allocated by the subprograms that called the current subprogram.

fGlobals

TagVector fGlobals

TagVector that corresponds to global variables. This is a subset of fStatic.

fExternPes

TagVector fExternPes

TagVector that corresponds to the area visible from the outside of the current subprogram. This is the complement of fCurFrame.

fExternOpt

TagVector fExternOpt

TagVector that corresponds to the area visible from the outside of the current subprogram. This is the sum of fGlobals and fOther.

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:

AliasAnalHir1(boolean, HirRoot)

fFactory

final AliasFactory fFactory

Factory object used to create other objects.

fUtil

protected final AliasUtil fUtil

AliasUtil object used to access utility methods.

fDbgLevel

protected int fDbgLevel

Constructor Detail

AliasAnalHir1

public AliasAnalHir1(HirRoot pHirRoot)

Creates a new instance of AliasAnalHir1 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:

AliasAnalHir1(boolean, HirRoot)

AliasAnalHir1

public AliasAnalHir1(boolean pIsOptimistic,
                     HirRoot pHirRoot)

Creats a new instance of AliasAnalHir1 that performs alias analysis with the specified assumptions (pIsOptimistic) about aliasing. The difference between optimistic and pessimistic assumptions are:

1. Whether vector (array) subscripts can get out of the declared range for the vector (in which case "storage promotion" is applied).
2. Whether storage promotion will be applied to pointer arithmetic. If an arithmetic operation was performed on a pointer that is pointing to an object that is of a certain storage class, storage promotion may be applied, resulting in the result of the operation possibly pointing to any objects in the same storage class.
3. Whether inconsistent object access (access by an object whose type differs from that of the stored object) may happen
.

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 AliasAnalHir1 object has to be newly created.

Specified by:

prepareForAliasAnalHir in interface AliasAnal

Parameters:

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

prepareTags

void prepareTags(SubpDefinition pSubpDef)

Instantiates tags and TagVectors, builds the tree structure between the tags and assigns TagVector bits to these tags.

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).

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

Parameters:

pExp - the lvalue node to check for aliasing.

Returns:

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

Throws:

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

printAliasPairs

public void printAliasPairs(SubpDefinition pSubpDef)

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

Specified by:

printAliasPairs in interface AliasAnal

Parameters:

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

printAliasPairsDetail

public void printAliasPairsDetail(SubpDefinition pSubpDef)

Prints out alias pairs in IoRoot.printOut object in somewhat more detailed format than in printAliasPairs.

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.

Specified by:

mayAlias in interface AliasAnal

Parameters:

pExp - lvalue node to check for aliasing.

pExp0 - lvalue node to check for aliasing.

Returns:

true if the two arguments may refer to an overlapping area in memory.

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.

Specified by:

mustAlias in interface AliasAnal

Parameters:

pExp - lvalue node to check for aliasing.

pExp0 - lvalue node to check for aliasing.

Returns:

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

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.

Specified by:

isLvalue in interface AliasAnal

Returns:

true if the specified argument is lvalue.

dbg

public void dbg(int pLevel,
                java.lang.String pHeader,
                java.lang.Object pBody)

Prints out the String representation of the pBody object headed by pHeader if the debug level for this alias analysis category is greater than or equal to pLevel.

Parameters:

pLevel - the debug level required to actually print the debug information.

pHeader - header for the information

pBody - body of the information

See Also:

Debug.printObject(int, String, Object)