edu.umd.cs.findbugs.ba

Class LiveLocalStoreAnalysis

java.lang.Object

edu.umd.cs.findbugs.ba.BasicAbstractDataflowAnalysis<Fact>

edu.umd.cs.findbugs.ba.AbstractDataflowAnalysis<Fact>

edu.umd.cs.findbugs.ba.BackwardDataflowAnalysis<BitSet>

edu.umd.cs.findbugs.ba.LiveLocalStoreAnalysis

All Implemented Interfaces:

DataflowAnalysis<BitSet>, Debug

public class LiveLocalStoreAnalysis
extends BackwardDataflowAnalysis<BitSet>
implements Debug

Dataflow analysis to find live stores of locals. This is just a backward analysis to see which loads reach stores of the same local.

This analysis also computes which stores that were killed by a subsequent store on any subsequent reachable path. (The FindDeadLocalStores detector uses this information to reduce false positives.)

Author:

David Hovemeyer

Field Summary

Fields inherited from interface edu.umd.cs.findbugs.ba.Debug

VERIFY_INTEGRITY

Constructor Summary

Constructors

Constructor and Description
LiveLocalStoreAnalysis(org.apache.bcel.generic.MethodGen methodGen, ReverseDepthFirstSearch rdfs, DepthFirstSearch dfs)

Method Summary

Methods

Modifier and Type	Method and Description
void	copy(BitSet source, BitSet dest) Copy dataflow facts.
BitSet	createFact() Create empty (uninitialized) dataflow facts for one program point.
String	factToString(BitSet fact) Return a String representation of given Fact.
void	initEntryFact(BitSet result) Initialize the "entry" fact for the graph.
boolean	isFactValid(BitSet fact) Determine whether the given fact is valid (neither top nor bottom).
boolean	isStoreAlive(BitSet fact, int local) Return whether or not a store of given local is alive.
boolean	isTop(BitSet fact) Return whether or not given fact is the special TOP value.
boolean	killedByStore(BitSet fact, int local) Return whether or not a store of given local was killed by a subsequent (dominated) store.
void	makeFactTop(BitSet fact) Make given fact the top value.
void	meetInto(BitSet fact, Edge edge, BitSet result) Meet a dataflow fact associated with an incoming edge into another fact.
boolean	same(BitSet fact1, BitSet fact2) Are given dataflow facts the same?
void	transferInstruction(org.apache.bcel.generic.InstructionHandle handle, BasicBlock basicBlock, BitSet fact) Transfer function for a single instruction.

Methods inherited from class edu.umd.cs.findbugs.ba.BackwardDataflowAnalysis

getBlockOrder, getReverseDepthFirstSearch, isForwards

Methods inherited from class edu.umd.cs.findbugs.ba.AbstractDataflowAnalysis

getFactAfterLocation, getFactAtLocation, transfer

Methods inherited from class edu.umd.cs.findbugs.ba.BasicAbstractDataflowAnalysis

edgeTransfer, finishIteration, getFactOnEdge, getLastUpdateTimestamp, getResultFact, getStartFact, resultFactIterator, setLastUpdateTimestamp, startIteration

Methods inherited from class java.lang.Object

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

Constructor Detail

LiveLocalStoreAnalysis

public LiveLocalStoreAnalysis(org.apache.bcel.generic.MethodGen methodGen,
                      ReverseDepthFirstSearch rdfs,
                      DepthFirstSearch dfs)

Method Detail

createFact

public BitSet createFact()

Description copied from interface: DataflowAnalysis

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

Specified by:

createFact in interface DataflowAnalysis<BitSet>

copy

public void copy(BitSet source,
        BitSet dest)

Description copied from interface: DataflowAnalysis

Copy dataflow facts.

Specified by:

copy in interface DataflowAnalysis<BitSet>

initEntryFact

public void initEntryFact(BitSet result)
                   throws DataflowAnalysisException

Description copied from interface: DataflowAnalysis

Initialize the "entry" fact for the graph.

Specified by:

initEntryFact in interface DataflowAnalysis<BitSet>

Throws:

DataflowAnalysisException

makeFactTop

public void makeFactTop(BitSet fact)

Description copied from interface: DataflowAnalysis

Make given fact the top value.

Specified by:

makeFactTop in interface DataflowAnalysis<BitSet>

same

public boolean same(BitSet fact1,
           BitSet fact2)

Description copied from interface: DataflowAnalysis

Are given dataflow facts the same?

Specified by:

same in interface DataflowAnalysis<BitSet>

meetInto

public void meetInto(BitSet fact,
            Edge edge,
            BitSet result)
              throws DataflowAnalysisException

Description copied from interface: DataflowAnalysis

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

Specified by:

meetInto in interface DataflowAnalysis<BitSet>

Parameters:

fact - the predecessor fact (incoming edge)

edge - the edge from the predecessor

result - the result fact

Throws:

DataflowAnalysisException

transferInstruction

public void transferInstruction(org.apache.bcel.generic.InstructionHandle handle,
                       BasicBlock basicBlock,
                       BitSet fact)
                         throws DataflowAnalysisException

Description copied from class: AbstractDataflowAnalysis

Transfer function for a single instruction.

Specified by:

transferInstruction in class AbstractDataflowAnalysis<BitSet>

Parameters:

handle - the instruction

basicBlock - the BasicBlock containing the instruction; needed to disambiguate instructions in inlined JSR subroutines

fact - which should be modified based on the instruction

Throws:

DataflowAnalysisException

isFactValid

public boolean isFactValid(BitSet fact)

Description copied from class: AbstractDataflowAnalysis

Determine whether the given fact is valid (neither top nor bottom).

Specified by:

isFactValid in class AbstractDataflowAnalysis<BitSet>

factToString

public String factToString(BitSet fact)

Description copied from interface: DataflowAnalysis

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

Specified by:

factToString in interface DataflowAnalysis<BitSet>

Overrides:

factToString in class BasicAbstractDataflowAnalysis<BitSet>

Parameters:

fact - a dataflow fact

Returns:

String representation of the fact

isTop

public boolean isTop(BitSet fact)

Return whether or not given fact is the special TOP value.

Specified by:

isTop in interface DataflowAnalysis<BitSet>

isStoreAlive

public boolean isStoreAlive(BitSet fact,
                   int local)

Return whether or not a store of given local is alive.

Parameters:

fact - a dataflow fact created by this analysis

local - the local

killedByStore

public boolean killedByStore(BitSet fact,
                    int local)

Return whether or not a store of given local was killed by a subsequent (dominated) store.