dk.brics.xact.analysis.transformations
Class ReachingDefinitionsAnalysis

java.lang.Object
  dk.brics.xact.analysis.transformations.ReachingDefinitionsAnalysis

All Implemented Interfaces:

AnalysisInterface<Map<Variable,Set<Assignment>>>

public class ReachingDefinitionsAnalysis
extends Object
implements AnalysisInterface<Map<Variable,Set<Assignment>>>

Lattice and transfer functions for reaching definitions analysis. Maps each variable to a set of all statements that may assign to that variable.

Constructor Summary

ReachingDefinitionsAnalysis()
Constructs a new analysis object.

Method Summary

Set<Statement>	getInitial(FlowGraph g) Returns the set of statements to start the analysis at.
boolean	isForward() Returns true if this is a forwards analysis, and false if it is a backwards analysis.
boolean	merge(Map<Variable,Set<Assignment>> source, VariableFilter filter, Map<Variable,Set<Assignment>> dest) Computes the least upper bound of two lattice elements.
Map<Variable,Set<Assignment>>	newBottomElement() Constructs a new lattice bottom element.
boolean	transfer(Map<Variable,Set<Assignment>> in, Statement s, Map<Variable,Set<Assignment>> out) Computes the lattice element resulting from flowing through the given statement.

Methods inherited from class java.lang.Object

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

Constructor Detail

ReachingDefinitionsAnalysis

public ReachingDefinitionsAnalysis()

Constructs a new analysis object.

Method Detail

getInitial

public Set<Statement> getInitial(FlowGraph g)

Description copied from interface: AnalysisInterface

Returns the set of statements to start the analysis at. For forwards analyses, the graph's entry points are usually the correct return value.

Specified by:

getInitial in interface AnalysisInterface<Map<Variable,Set<Assignment>>>

Parameters:

g - the flow graph about to be analyzed

Returns:

an unmodifiable set of statements.

isForward

public boolean isForward()

Description copied from interface: AnalysisInterface

Returns true if this is a forwards analysis, and false if it is a backwards analysis.

Specified by:

isForward in interface AnalysisInterface<Map<Variable,Set<Assignment>>>

merge

public boolean merge(Map<Variable,Set<Assignment>> source,
                     VariableFilter filter,
                     Map<Variable,Set<Assignment>> dest)

Description copied from interface: AnalysisInterface

Computes the least upper bound of two lattice elements.

Specified by:

merge in interface AnalysisInterface<Map<Variable,Set<Assignment>>>

Parameters:

source - the first element

filter - the filter to merge through

dest - the second element and destination for the result

Returns:

true if the new value of dest is changed

newBottomElement

public Map<Variable,Set<Assignment>> newBottomElement()

Description copied from interface: AnalysisInterface

Constructs a new lattice bottom element.

Specified by:

newBottomElement in interface AnalysisInterface<Map<Variable,Set<Assignment>>>

transfer

public boolean transfer(Map<Variable,Set<Assignment>> in,
                        Statement s,
                        Map<Variable,Set<Assignment>> out)

Description copied from interface: AnalysisInterface

Computes the lattice element resulting from flowing through the given statement.

Specified by:

transfer in interface AnalysisInterface<Map<Variable,Set<Assignment>>>

Parameters:

in - the flow before the statement

out - destination for the result

Returns:

true if the new value of out is changed