cetus.analysis

Class AliasAnalysis

java.lang.Object

cetus.analysis.AnalysisPass

cetus.analysis.AliasAnalysis

public class AliasAnalysis
extends AnalysisPass

Alias analysis is used to obtain alias sets i.e. sets of variable names that reference the same memory locations, in other words, aliases. Alias information can be flow and/or context sensitive or neither. The implementation of this analysis in Cetus provides two different levels.

Switch off alias analysis intentionally using option level 0 on the command line.

The default for alias analysis is to provide alias information using advanced interprocedural points-to analysis. See IPPointsToAnalysis. Points-to analysis in Cetus is flow as well as context sensitive i.e. the analysis provides pointer relationships at every program point using limited context information as well. Alias analysis can use the sets of pointer relationships at the relevant program point to create accurate alias sets. Interprocedural points-to analysis further helps crucial disambiguation, especially in the case of arrays.

The advanced interprocedural analyzer is supplemented by a simple array-argument disambiguation analysis, ArrayParameterAnalysis.

See Also:

PointsToAnalysis, IPPointsToAnalysis, ArrayParameterAnalysis

Constructor Summary

Constructors

Constructor and Description
AliasAnalysis(Program program)

Method Summary

Methods

Modifier and Type	Method and Description
void	displayAliasMap() Deprecated.
java.util.Set	get_alias_set(Statement cur_stmt, Symbol symbol) Returns the alias set for the given input symbol, which includes the input symbol itself.
java.lang.String	getPassName()
boolean	isAliased(Statement stmt, Symbol a, java.util.Set<Symbol> bset) Returns true if the given Symbol, a, is aliased to any symbol in the set of Symbols, bset.
boolean	isAliased(Statement stmt, Symbol a, Symbol b) Returns true if Symbol a is aliased to Symbol b at the given statement.
boolean	isAliasedToUniverse()
void	start() This provides the high-level driver for Alias analysis.

Methods inherited from class cetus.analysis.AnalysisPass

run

Methods inherited from class java.lang.Object

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

Constructor Detail

AliasAnalysis

public AliasAnalysis(Program program)

Method Detail

getPassName

public java.lang.String getPassName()

Specified by:

getPassName in class AnalysisPass

start

public void start()

This provides the high-level driver for Alias analysis. The default is to run interprocedural points-to analysis and use that information, hence a majority of this procedure is not executed in that case.

For other global alias analyses, this procedure traverses the IR and collects whole program alias sets. These can be supported by user-provided information regarding interprocedural assumptions.

Specified by:

start in class AnalysisPass

get_alias_set

public java.util.Set get_alias_set(Statement cur_stmt,
                          Symbol symbol)

Returns the alias set for the given input symbol, which includes the input symbol itself. This forms the interface API to other passes, for requested alias information.

For advanced analysis, it uses the interface to interprocedural points-to analysis. Alias sets are created from the map returned by the points-to analyzer.

Parameters:

cur_stmt - Statement used to request flow-sensitive alias information using advanced points-to analysis

symbol - The variable symbol for which alias sets are being requested.

Returns:

alias set for symbol, which includes the input symbol itself.

displayAliasMap

@Deprecated
public void displayAliasMap()

Deprecated.

Prints to standard out a pretty version of the global alias map.

isAliased

public boolean isAliased(Statement stmt,
                Symbol a,
                Symbol b)

Returns true if Symbol a is aliased to Symbol b at the given statement.

isAliased

public boolean isAliased(Statement stmt,
                Symbol a,
                java.util.Set<Symbol> bset)

Returns true if the given Symbol, a, is aliased to any symbol in the set of Symbols, bset.

isAliasedToUniverse

public boolean isAliasedToUniverse()