Package edu.umd.cs.findbugs.ba

Interface DataflowAnalysis<Fact>

All Known Implementing Classes:

AbstractDataflowAnalysis, AbstractDominatorsAnalysis, BackwardDataflowAnalysis, BackwardTypeQualifierDataflowAnalysis, BasicAbstractDataflowAnalysis, BlockTypeAnalysis, CallListAnalysis, ConstantAnalysis, DominatorsAnalysis, FieldSetAnalysis, ForwardDataflowAnalysis, ForwardTypeQualifierDataflowAnalysis, FrameDataflowAnalysis, IsNullValueAnalysis, LiveLocalStoreAnalysis, LoadAnalysis, LockAnalysis, NonExceptionPostdominatorsAnalysis, NonImplicitExceptionPostDominatorsAnalysis, ObligationAnalysis, PostDominatorsAnalysis, ResourceValueAnalysis, ReturnPathAnalysis, ReturnPathTypeAnalysis, StackDepthAnalysis, StoreAnalysis, TypeAnalysis, TypeQualifierDataflowAnalysis, UnconditionalValueDerefAnalysis, ValueNumberAnalysis

public interface DataflowAnalysis<Fact>

A dataflow analysis to be used with the Dataflow class.

In order to avoid duplicating functionality (such as caching of start and result facts), most analyses should extend the BasicAbstractDataflowAnalysis or AbstractDataflowAnalysis classes rather than directly implementing this interface.

Author:

David Hovemeyer

See Also:

Dataflow

Method Summary

Modifier and Type	Method	Description
void	copy(Fact source, Fact dest)	Copy dataflow facts.
Fact	createFact()	Create empty (uninitialized) dataflow facts for one program point.
void	edgeTransfer(Edge edge, Fact fact)	Edge transfer function.
java.lang.String	factToString(Fact fact)	Return a String representation of given Fact.
void	finishIteration()	Called after finishing an iteration of analysis.
BlockOrder	getBlockOrder(CFG cfg)	Return the BlockOrder specifying the order in which BasicBlocks should be visited in the main dataflow loop.
Fact	getFactAfterLocation(Location location)	Get the dataflow fact representing the point just after given Location.
Fact	getFactAtLocation(Location location)	Get dataflow fact at (just before) given Location.
Fact	getFactOnEdge(Edge edge)	Get the fact that is true on the given control edge.
int	getLastUpdateTimestamp(Fact fact)
Fact	getResultFact(BasicBlock block)	Get the result fact for given basic block.
Fact	getStartFact(BasicBlock block)	Get the start fact for given basic block.
void	initEntryFact(Fact result)	Initialize the "entry" fact for the graph.
boolean	isForwards()	Returns true if the analysis is forwards, false if backwards.
boolean	isTop(Fact fact)	Is the given fact the top value.
void	makeFactTop(Fact fact)	Make given fact the top value.
void	meetInto(Fact fact, Edge edge, Fact result)	Meet a dataflow fact associated with an incoming edge into another fact.
boolean	same(Fact fact1, Fact fact2)	Are given dataflow facts the same?
void	setLastUpdateTimestamp(Fact fact, int timestamp)
void	startIteration()	Called before beginning an iteration of analysis.
void	transfer(BasicBlock basicBlock, org.apache.bcel.generic.InstructionHandle end, Fact start, Fact result)	Transfer function for the analysis.

Method Detail

createFact

Fact createFact()

Create empty (uninitialized) dataflow facts for one program point. A valid value will be copied into it before it is used.

getStartFact

Fact getStartFact(BasicBlock block)

Get the start fact for given basic block.

Parameters:

block - the basic block

getResultFact

Fact getResultFact(BasicBlock block)

Get the result fact for given basic block.

Parameters:

block - the basic block

getFactAtLocation

Fact getFactAtLocation(Location location)
                throws DataflowAnalysisException

Get dataflow fact at (just before) given Location. Note "before" is meant in the logical sense, so for backward analyses, before means after the location in the control flow sense.

Parameters:

location - the Location

Returns:

the dataflow value at given Location

Throws:

DataflowAnalysisException

getFactAfterLocation

Fact getFactAfterLocation(Location location)
                   throws DataflowAnalysisException

Get the dataflow fact representing the point just after given Location. Note "after" is meant in the logical sense, so for backward analyses, after means before the location in the control flow sense.

Parameters:

location - the Location

Returns:

the dataflow value after given Location

Throws:

DataflowAnalysisException

getFactOnEdge

Fact getFactOnEdge(Edge edge)
            throws DataflowAnalysisException

Get the fact that is true on the given control edge.

Parameters:

edge - the edge

Returns:

the fact that is true on the edge

Throws:

DataflowAnalysisException

copy

void copy(Fact source,
          Fact dest)

Copy dataflow facts.

initEntryFact

void initEntryFact(Fact result)
            throws DataflowAnalysisException

Initialize the "entry" fact for the graph.

Throws:

DataflowAnalysisException

makeFactTop

void makeFactTop(Fact fact)

Make given fact the top value.

isTop

boolean isTop(Fact fact)

Is the given fact the top value.

isForwards

boolean isForwards()

Returns true if the analysis is forwards, false if backwards.

getBlockOrder

BlockOrder getBlockOrder(CFG cfg)

Return the BlockOrder specifying the order in which BasicBlocks should be visited in the main dataflow loop.

Parameters:

cfg - the CFG upon which we're performing dataflow analysis

same

boolean same(Fact fact1,
             Fact fact2)

Are given dataflow facts the same?

transfer

void transfer(BasicBlock basicBlock,
              @CheckForNull
              org.apache.bcel.generic.InstructionHandle end,
              Fact start,
              Fact result)
       throws DataflowAnalysisException

Transfer function for the analysis. Taking dataflow facts at start (which might be either the entry or exit of the block, depending on whether the analysis is forwards or backwards), modify result to be the facts at the other end of the block.

Parameters:

basicBlock - the basic block

end - if nonnull, stop before considering this instruction; otherwise, consider all of the instructions in the basic block

start - dataflow facts at beginning of block (if forward analysis) or end of block (if backwards analysis)

result - resulting dataflow facts at other end of block

Throws:

DataflowAnalysisException

edgeTransfer

void edgeTransfer(Edge edge,
                  Fact fact)
           throws DataflowAnalysisException

Edge transfer function. Modify the given fact that is true on the (logical) edge source to modify it so that it is true at the (logical) edge target.

A do-nothing implementation is legal, and appropriate for analyses where branches are not significant.

Parameters:

edge - the Edge

fact - a dataflow fact

Throws:

DataflowAnalysisException

meetInto

void meetInto(Fact fact,
              Edge edge,
              Fact result)
       throws DataflowAnalysisException

Meet a dataflow fact associated with an incoming edge into another fact. This is used to determine the start fact for a basic block.

Parameters:

fact - the predecessor fact (incoming edge)

edge - the edge from the predecessor

result - the result fact

Throws:

DataflowAnalysisException

startIteration

void startIteration()

Called before beginning an iteration of analysis. Each iteration visits every basic block in the CFG.

finishIteration

void finishIteration()

Called after finishing an iteration of analysis.

getLastUpdateTimestamp

int getLastUpdateTimestamp(Fact fact)

setLastUpdateTimestamp

void setLastUpdateTimestamp(Fact fact,
                            int timestamp)

factToString

java.lang.String factToString(Fact fact)

Return a String representation of given Fact. For debugging purposes.

Parameters:

fact - a dataflow fact

Returns:

String representation of the fact