Package edu.umd.cs.findbugs.ba.vna

Class ValueNumberAnalysis

java.lang.Object

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

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

edu.umd.cs.findbugs.ba.ForwardDataflowAnalysis<FrameType>

edu.umd.cs.findbugs.ba.FrameDataflowAnalysis<ValueNumber,ValueNumberFrame>

edu.umd.cs.findbugs.ba.vna.ValueNumberAnalysis

All Implemented Interfaces:

DataflowAnalysis<ValueNumberFrame>

public class ValueNumberAnalysis
extends FrameDataflowAnalysis<ValueNumber,ValueNumberFrame>

A dataflow analysis to track the production and flow of values in the Java stack frame. See the ValueNumber class for an explanation of what the value numbers mean, and when they can be compared.

This class is still experimental.

Author:

David Hovemeyer

See Also:

• ValueNumber
• DominatorsAnalysis

Field Summary

Fields

Modifier and Type	Field	Description
static final boolean	DEBUG

Constructor Summary

Constructors

Constructor	Description
ValueNumberAnalysis(org.apache.bcel.generic.MethodGen methodGen, DepthFirstSearch dfs, LoadedFieldSet loadedFieldSet, RepositoryLookupFailureCallback lookupFailureCallback)

Method Summary

Modifier and Type	Method	Description
void	compactValueNumbers(Dataflow<ValueNumberFrame,ValueNumberAnalysis> dataflow)	Deprecated.
ValueNumberFrame	createFact()	Create empty (uninitialized) dataflow facts for one program point.
Iterator<ValueNumberFrame>	factIterator()	Get an Iterator over all dataflow facts that we've recorded for the Locations in the CFG.
String	getClassName(ValueNumber v)
ValueNumber	getClassObjectValue(String className)
ValueNumber	getEntryValue(int local)	Get the value number assigned to the given local variable upon entry to the method.
ValueNumber	getEntryValueForParameter(int param)	Get the value number assigned to the given parameter upon entry to the method.
ValueNumberFrame	getFactAfterLocation(Location location)	Get the dataflow fact representing the point just after given Location.
ValueNumberFrame	getFactAtLocation(Location location)	Get the dataflow fact representing the point just before given Location.
ValueNumberFactory	getFactory()
MergeTree	getMergeTree()
int	getNumValuesAllocated()
ValueNumber	getThisValue()
void	initEntryFact(ValueNumberFrame result)	Initialize the "entry" fact for the graph.
boolean	isThisValue(ValueNumber value)
void	meetInto(ValueNumberFrame fact, Edge edge, ValueNumberFrame result)	Meet a dataflow fact associated with an incoming edge into another fact.
protected void	mergeInto(ValueNumberFrame frame, ValueNumberFrame result)	Merge one frame into another.
protected void	mergeValues(ValueNumberFrame otherFrame, ValueNumberFrame resultFrame, int slot)	Merge the values contained in a given slot of two Frames.
void	setMergeTree(MergeTree mergeTree)
void	transfer(BasicBlock basicBlock, org.apache.bcel.generic.InstructionHandle end, ValueNumberFrame start, ValueNumberFrame result)	Transfer function for the analysis.
void	transferInstruction(org.apache.bcel.generic.InstructionHandle handle, BasicBlock basicBlock, ValueNumberFrame fact)	Transfer function for a single instruction.

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

copy, getFactAtPC, getFactBeforeExceptionCheck, getLastUpdateTimestamp, isFactValid, isTop, makeFactTop, modifyFrame, same, setLastUpdateTimestamp

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

getBlockOrder, getDepthFirstSearch, isForwards

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

edgeTransfer, factToString, finishIteration, getFactOnEdge, getResultFact, getStartFact, resultFactIterator, startIteration

Methods inherited from class java.lang.Object

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

Field Details

DEBUG

public static final boolean DEBUG

Constructor Details

ValueNumberAnalysis

public ValueNumberAnalysis(org.apache.bcel.generic.MethodGen methodGen,
 DepthFirstSearch dfs,
 LoadedFieldSet loadedFieldSet,
 RepositoryLookupFailureCallback lookupFailureCallback)

Method Details

getClassObjectValue

public ValueNumber getClassObjectValue(String className)

setMergeTree

public void setMergeTree(MergeTree mergeTree)

getMergeTree

public MergeTree getMergeTree()

getFactory

public ValueNumberFactory getFactory()

getNumValuesAllocated

public int getNumValuesAllocated()

isThisValue

public boolean isThisValue(ValueNumber value)

getThisValue

public ValueNumber getThisValue()

getEntryValue

public ValueNumber getEntryValue(int local)

Get the value number assigned to the given local variable upon entry to the method.

Parameters:

local - local variable number

Returns:

ValueNumber assigned to the local variable

getEntryValueForParameter

public ValueNumber getEntryValueForParameter(int param)

Get the value number assigned to the given parameter upon entry to the method.

Parameters:

param - a parameter (0 == first parameter)

Returns:

the ValueNumber assigned to that parameter

createFact

public ValueNumberFrame 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.

initEntryFact

public void initEntryFact(ValueNumberFrame result)

Description copied from interface: DataflowAnalysis

Initialize the "entry" fact for the graph.

transfer

public void transfer(BasicBlock basicBlock,
 org.apache.bcel.generic.InstructionHandle end,
 ValueNumberFrame start,
 ValueNumberFrame result)
              throws DataflowAnalysisException

Description copied from interface: DataflowAnalysis

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.

Specified by:

transfer in interface DataflowAnalysis<ValueNumberFrame>

Overrides:

transfer in class AbstractDataflowAnalysis<ValueNumberFrame>

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

transferInstruction

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

Description copied from class: AbstractDataflowAnalysis

Transfer function for a single instruction.

Specified by:

transferInstruction in class AbstractDataflowAnalysis<ValueNumberFrame>

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

meetInto

public void meetInto(ValueNumberFrame fact,
 Edge edge,
 ValueNumberFrame 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.

Parameters:

fact - the predecessor fact (incoming edge)

edge - the edge from the predecessor

result - the result fact

Throws:

DataflowAnalysisException

mergeInto

protected void mergeInto(ValueNumberFrame frame,
 ValueNumberFrame result)
                  throws DataflowAnalysisException

Description copied from class: FrameDataflowAnalysis

Merge one frame into another.

Overrides:

mergeInto in class FrameDataflowAnalysis<ValueNumber,ValueNumberFrame>

Parameters:

frame - the frame to merge with the result

result - the result frame, which is modified to be the merge of the two frames

Throws:

DataflowAnalysisException

mergeValues

protected void mergeValues(ValueNumberFrame otherFrame,
 ValueNumberFrame resultFrame,
 int slot)
                    throws DataflowAnalysisException

Description copied from class: FrameDataflowAnalysis

Merge the values contained in a given slot of two Frames.

Specified by:

mergeValues in class FrameDataflowAnalysis<ValueNumber,ValueNumberFrame>

Parameters:

otherFrame - a Frame

resultFrame - a Frame which will contain the resulting merged value

slot - a slot in both frames

Throws:

DataflowAnalysisException

getFactAtLocation

public ValueNumberFrame getFactAtLocation(Location location)

Description copied from class: AbstractDataflowAnalysis

Get the dataflow fact representing the point 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.

Specified by:

getFactAtLocation in interface DataflowAnalysis<ValueNumberFrame>

Overrides:

getFactAtLocation in class AbstractDataflowAnalysis<ValueNumberFrame>

Parameters:

location - the location

Returns:

the fact at the point just before the location

getFactAfterLocation

public ValueNumberFrame getFactAfterLocation(Location location)

Description copied from class: AbstractDataflowAnalysis

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.

Specified by:

getFactAfterLocation in interface DataflowAnalysis<ValueNumberFrame>

Overrides:

getFactAfterLocation in class AbstractDataflowAnalysis<ValueNumberFrame>

Parameters:

location - the location

Returns:

the fact at the point just after the location

factIterator

public Iterator<ValueNumberFrame> factIterator()

Get an Iterator over all dataflow facts that we've recorded for the Locations in the CFG. Note that this does not include result facts (since there are no Locations corresponding to the end of basic blocks).

compactValueNumbers

@Deprecated
public void compactValueNumbers(Dataflow<ValueNumberFrame,ValueNumberAnalysis> dataflow)

Deprecated.

Compact the value numbers assigned. This should be done only after the dataflow algorithm has executed. This works by modifying the actual ValueNumber objects assigned. After this method is called, the getNumValuesAllocated() method of this object will return a value less than or equal to the value it would have returned before the call to this method.

This method should be called at most once.

Parameters:

dataflow - the Dataflow object which executed this analysis (and has all of the block result values)

getClassName

@CheckForNull
@DottedClassName
public String getClassName(ValueNumber v)