Class UnconditionalValueDerefAnalysis

java.lang.Object

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

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

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

edu.umd.cs.findbugs.ba.deref.UnconditionalValueDerefAnalysis

All Implemented Interfaces:

DataflowAnalysis<UnconditionalValueDerefSet>

public class UnconditionalValueDerefAnalysis
extends BackwardDataflowAnalysis<UnconditionalValueDerefSet>

Dataflow analysis to find values unconditionally dereferenced in the future.

Field Summary

Fields

Modifier and Type	Field	Description
private final AssertionMethods	assertionMethods
static final boolean	ASSUME_NONZERO_TRIP_LOOPS
private final CFG	cfg
static final boolean	CHECK_ANNOTATIONS
static final boolean	CHECK_CALLS
static final boolean	DEBUG
static final boolean	DEBUG_CHECK_CALLS
static final boolean	IGNORE_DEREF_OF_NCP
private IsNullValueDataflow	invDataflow
private final org.apache.bcel.classfile.Method	method
private final org.apache.bcel.generic.MethodGen	methodGen
private static final int[]	NULLCHECK1
private static final int[]	NULLCHECK2
private TypeDataflow	typeDataflow
static final boolean	VERBOSE_NULLARG_DEBUG
private final ValueNumberDataflow	vnaDataflow

Constructor Summary

Constructors

Constructor	Description
UnconditionalValueDerefAnalysis(ReverseDepthFirstSearch rdfs, DepthFirstSearch dfs, CFG cfg, org.apache.bcel.classfile.Method method, org.apache.bcel.generic.MethodGen methodGen, ValueNumberDataflow vnaDataflow, AssertionMethods assertionMethods)	Constructor.

Method Summary

Modifier and Type	Method	Description
private static boolean	check(org.apache.bcel.generic.InstructionHandle h, int[] opcodes)
static Set<ValueNumber>	checkAllNonNullParams(Location location, ValueNumberFrame vnaFrame, org.apache.bcel.generic.ConstantPoolGen constantPool, org.apache.bcel.classfile.Method method, IsNullValueDataflow invDataflow, TypeDataflow typeDataflow)
private void	checkInstance(Location location, ValueNumberFrame vnaFrame, UnconditionalValueDerefSet fact)	Check to see if the instruction has a null check associated with it, and if so, add a dereference.
private void	checkNonNullParams(Location location, ValueNumberFrame vnaFrame, UnconditionalValueDerefSet fact)	If this is a method call instruction, check to see if any of the parameters are @NonNull, and treat them as dereferences.
static Set<ValueNumber>	checkNonNullParams(Location location, ValueNumberFrame vnaFrame, org.apache.bcel.generic.ConstantPoolGen constantPool, org.apache.bcel.classfile.Method method, IsNullValueFrame invFrame)
private void	checkNonNullPutField(Location location, ValueNumberFrame vnaFrame, UnconditionalValueDerefSet fact)	If this is a putfield or putstatic instruction, check to see if the field is @NonNull, and treat it as dereferences.
private void	checkNonNullReturnValue(XMethod thisMethod, Location location, ValueNumberFrame vnaFrame, UnconditionalValueDerefSet fact)	If this is a method call instruction, check to see if any of the parameters are @NonNull, and treat them as dereferences.
private void	checkUnconditionalDerefDatabase(Location location, ValueNumberFrame vnaFrame, UnconditionalValueDerefSet fact)	Check method call at given location to see if it unconditionally dereferences a parameter.
static Set<ValueNumber>	checkUnconditionalDerefDatabase(Location location, ValueNumberFrame vnaFrame, org.apache.bcel.generic.ConstantPoolGen constantPool, IsNullValueFrame invFrame, TypeDataflow typeDataflow)
void	clearDerefsOnNonNullBranches(IsNullValueDataflow invDataflow)	HACK: use the given is-null dataflow to clear deref sets for values that are known to be definitely non-null on a branch.
void	copy(UnconditionalValueDerefSet source, UnconditionalValueDerefSet dest)	Copy dataflow facts.
UnconditionalValueDerefSet	createFact()	Create empty (uninitialized) dataflow facts for one program point.
private UnconditionalValueDerefSet	duplicateFact(UnconditionalValueDerefSet fact)	Return a duplicate of given dataflow fact.
private ValueNumber	findValueKnownNonnullOnBranch(UnconditionalValueDerefSet fact, Edge edge)	Clear deref sets of values if this edge is the non-null branch of an if comparison.
int	getLastUpdateTimestamp(UnconditionalValueDerefSet fact)
private void	handleNullCheck(Location location, ValueNumberFrame vnaFrame, UnconditionalValueDerefSet fact)
void	initEntryFact(UnconditionalValueDerefSet result)	Initialize the "entry" fact for the graph.
private boolean	isAssertion(org.apache.bcel.generic.InstructionHandle handle)	Return whether or not given instruction is an assertion.
private boolean	isExceptionEdge(Edge edge)	Determine whether dataflow should be propagated on given edge.
boolean	isFactValid(UnconditionalValueDerefSet fact)	Determine whether the given fact is valid (neither top nor bottom).
static boolean	isNullCheck(org.apache.bcel.generic.InstructionHandle h, org.apache.bcel.generic.ConstantPoolGen cpg)
boolean	isTop(UnconditionalValueDerefSet fact)	Is the given fact the top value.
void	makeFactTop(UnconditionalValueDerefSet fact)	Make given fact the top value.
void	meetInto(UnconditionalValueDerefSet fact, Edge edge, UnconditionalValueDerefSet result)	Meet a dataflow fact associated with an incoming edge into another fact.
void	meetInto(UnconditionalValueDerefSet fact, Edge edge, UnconditionalValueDerefSet result, boolean onlyEdge)
private UnconditionalValueDerefSet	propagateDerefSetsToMergeInputValues(UnconditionalValueDerefSet fact, Edge edge)	Find out if any VNs in the source block contribute to unconditionally dereferenced VNs in the target block.
private static boolean	reportDereference(IsNullValue value)
private static boolean	reportDereference(IsNullValueFrame invFrameAtNullCheck, int instance)
static boolean	reportPotentialDereference(Location location, IsNullValueFrame invFrame)
boolean	same(UnconditionalValueDerefSet fact1, UnconditionalValueDerefSet fact2)	Are given dataflow facts the same?
void	setLastUpdateTimestamp(UnconditionalValueDerefSet fact, int lastUpdate)
void	setTypeDataflow(TypeDataflow typeDataflow)
void	startIteration()	Called before beginning an iteration of analysis.
String	toString()
void	transferInstruction(org.apache.bcel.generic.InstructionHandle handle, BasicBlock basicBlock, UnconditionalValueDerefSet fact)	Transfer function for a single instruction.

Methods inherited from class BackwardDataflowAnalysis

getBlockOrder, getReverseDepthFirstSearch, isForwards

Methods inherited from class AbstractDataflowAnalysis

getFactAfterLocation, getFactAtLocation, transfer

Methods inherited from class BasicAbstractDataflowAnalysis

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

Methods inherited from class Object

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

Field Details

DEBUG

public static final boolean DEBUG

ASSUME_NONZERO_TRIP_LOOPS

public static final boolean ASSUME_NONZERO_TRIP_LOOPS

IGNORE_DEREF_OF_NCP

public static final boolean IGNORE_DEREF_OF_NCP

CHECK_ANNOTATIONS

public static final boolean CHECK_ANNOTATIONS

CHECK_CALLS

public static final boolean CHECK_CALLS

DEBUG_CHECK_CALLS

public static final boolean DEBUG_CHECK_CALLS

NULLCHECK1

private static final int[] NULLCHECK1

NULLCHECK2

private static final int[] NULLCHECK2

cfg

private final CFG cfg

method

private final org.apache.bcel.classfile.Method method

methodGen

private final org.apache.bcel.generic.MethodGen methodGen

vnaDataflow

private final ValueNumberDataflow vnaDataflow

assertionMethods

private final AssertionMethods assertionMethods

invDataflow

private IsNullValueDataflow invDataflow

typeDataflow

private TypeDataflow typeDataflow

VERBOSE_NULLARG_DEBUG

public static final boolean VERBOSE_NULLARG_DEBUG

Constructor Details

UnconditionalValueDerefAnalysis

public UnconditionalValueDerefAnalysis(ReverseDepthFirstSearch rdfs,
 DepthFirstSearch dfs,
 CFG cfg,
 org.apache.bcel.classfile.Method method,
 org.apache.bcel.generic.MethodGen methodGen,
 ValueNumberDataflow vnaDataflow,
 AssertionMethods assertionMethods)

Constructor.

Parameters:

rdfs - the reverse depth-first-search (for the block order)

cfg - the CFG for the method

methodGen - the MethodGen for the method

vnaDataflow -

assertionMethods - AssertionMethods for the analyzed class

Method Details

toString

public String toString()

Overrides:

toString in class Object

clearDerefsOnNonNullBranches

public void clearDerefsOnNonNullBranches(IsNullValueDataflow invDataflow)

HACK: use the given is-null dataflow to clear deref sets for values that are known to be definitely non-null on a branch.

Parameters:

invDataflow - the IsNullValueDataflow to use

setTypeDataflow

public void setTypeDataflow(TypeDataflow typeDataflow)

isFactValid

public boolean isFactValid(UnconditionalValueDerefSet fact)

Description copied from class: AbstractDataflowAnalysis

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

Specified by:

isFactValid in class AbstractDataflowAnalysis<UnconditionalValueDerefSet>

check

private static boolean check(org.apache.bcel.generic.InstructionHandle h,
 int[] opcodes)

isNullCheck

public static boolean isNullCheck(org.apache.bcel.generic.InstructionHandle h,
 org.apache.bcel.generic.ConstantPoolGen cpg)

handleNullCheck

private void handleNullCheck(Location location,
 ValueNumberFrame vnaFrame,
 UnconditionalValueDerefSet fact)
                      throws DataflowAnalysisException

Throws:

DataflowAnalysisException

reportPotentialDereference

public static boolean reportPotentialDereference(Location location,
 IsNullValueFrame invFrame)
                                          throws DataflowAnalysisException

Throws:

DataflowAnalysisException

transferInstruction

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

Description copied from class: AbstractDataflowAnalysis

Transfer function for a single instruction.

Specified by:

transferInstruction in class AbstractDataflowAnalysis<UnconditionalValueDerefSet>

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

checkUnconditionalDerefDatabase

private void checkUnconditionalDerefDatabase(Location location,
 ValueNumberFrame vnaFrame,
 UnconditionalValueDerefSet fact)
                                      throws DataflowAnalysisException

Check method call at given location to see if it unconditionally dereferences a parameter. Mark any such arguments as derefs.

Parameters:

location - the Location of the method call

vnaFrame - ValueNumberFrame at the Location

fact - the dataflow value to modify

Throws:

DataflowAnalysisException

checkUnconditionalDerefDatabase

public static Set<ValueNumber> checkUnconditionalDerefDatabase(Location location,
 ValueNumberFrame vnaFrame,
 org.apache.bcel.generic.ConstantPoolGen constantPool,
 @CheckForNull
 IsNullValueFrame invFrame,
 TypeDataflow typeDataflow)
                                                        throws DataflowAnalysisException

Throws:

DataflowAnalysisException

checkNonNullReturnValue

private void checkNonNullReturnValue(XMethod thisMethod,
 Location location,
 ValueNumberFrame vnaFrame,
 UnconditionalValueDerefSet fact)
                              throws DataflowAnalysisException

If this is a method call instruction, check to see if any of the parameters are @NonNull, and treat them as dereferences.

Parameters:

location - the Location of the instruction

vnaFrame - the ValueNumberFrame at the Location of the instruction

fact - the dataflow value to modify

Throws:

DataflowAnalysisException

checkNonNullPutField

private void checkNonNullPutField(Location location,
 ValueNumberFrame vnaFrame,
 UnconditionalValueDerefSet fact)
                           throws DataflowAnalysisException

If this is a putfield or putstatic instruction, check to see if the field is @NonNull, and treat it as dereferences.

Parameters:

location - the Location of the instruction

vnaFrame - the ValueNumberFrame at the Location of the instruction

fact - the dataflow value to modify

Throws:

DataflowAnalysisException

checkNonNullParams

private void checkNonNullParams(Location location,
 ValueNumberFrame vnaFrame,
 UnconditionalValueDerefSet fact)
                         throws DataflowAnalysisException

If this is a method call instruction, check to see if any of the parameters are @NonNull, and treat them as dereferences.

Parameters:

location - the Location of the instruction

vnaFrame - the ValueNumberFrame at the Location of the instruction

fact - the dataflow value to modify

Throws:

DataflowAnalysisException

checkAllNonNullParams

public static Set<ValueNumber> checkAllNonNullParams(Location location,
 ValueNumberFrame vnaFrame,
 org.apache.bcel.generic.ConstantPoolGen constantPool,
 @CheckForNull
 org.apache.bcel.classfile.Method method,
 @CheckForNull
 IsNullValueDataflow invDataflow,
 TypeDataflow typeDataflow)
                                              throws DataflowAnalysisException

Throws:

DataflowAnalysisException

checkNonNullParams

public static Set<ValueNumber> checkNonNullParams(Location location,
 ValueNumberFrame vnaFrame,
 org.apache.bcel.generic.ConstantPoolGen constantPool,
 @CheckForNull
 org.apache.bcel.classfile.Method method,
 @CheckForNull
 IsNullValueFrame invFrame)
                                           throws DataflowAnalysisException

Throws:

DataflowAnalysisException

checkInstance

private void checkInstance(Location location,
 ValueNumberFrame vnaFrame,
 UnconditionalValueDerefSet fact)
                    throws DataflowAnalysisException

Check to see if the instruction has a null check associated with it, and if so, add a dereference.

Parameters:

location - the Location of the instruction

vnaFrame - ValueNumberFrame at the Location of the instruction

fact - the dataflow value to modify

Throws:

DataflowAnalysisException

reportDereference

private static boolean reportDereference(IsNullValueFrame invFrameAtNullCheck,
 int instance)

reportDereference

private static boolean reportDereference(IsNullValue value)

isAssertion

private boolean isAssertion(org.apache.bcel.generic.InstructionHandle handle)

Return whether or not given instruction is an assertion.

Parameters:

handle - the instruction

Returns:

true if instruction is an assertion, false otherwise

copy

public void copy(UnconditionalValueDerefSet source,
 UnconditionalValueDerefSet dest)

Description copied from interface: DataflowAnalysis

Copy dataflow facts.

createFact

public UnconditionalValueDerefSet 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(UnconditionalValueDerefSet result)
                   throws DataflowAnalysisException

Description copied from interface: DataflowAnalysis

Initialize the "entry" fact for the graph.

Throws:

DataflowAnalysisException

makeFactTop

public void makeFactTop(UnconditionalValueDerefSet fact)

Description copied from interface: DataflowAnalysis

Make given fact the top value.

isTop

public boolean isTop(UnconditionalValueDerefSet fact)

Description copied from interface: DataflowAnalysis

Is the given fact the top value.

meetInto

public void meetInto(UnconditionalValueDerefSet fact,
 Edge edge,
 UnconditionalValueDerefSet 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

meetInto

public void meetInto(UnconditionalValueDerefSet fact,
 Edge edge,
 UnconditionalValueDerefSet result,
 boolean onlyEdge)

propagateDerefSetsToMergeInputValues

private UnconditionalValueDerefSet propagateDerefSetsToMergeInputValues(UnconditionalValueDerefSet fact,
 Edge edge)

Find out if any VNs in the source block contribute to unconditionally dereferenced VNs in the target block. If so, the VN in the source block is also unconditionally dereferenced, and we must propagate the target VN's dereferences.

Parameters:

fact - a dataflow value

edge - edge to check for merge input values

Returns:

possibly-modified dataflow value

duplicateFact

private UnconditionalValueDerefSet duplicateFact(UnconditionalValueDerefSet fact)

Return a duplicate of given dataflow fact.

Parameters:

fact - a dataflow fact

Returns:

a duplicate of the input dataflow fact

findValueKnownNonnullOnBranch

@CheckForNull
private ValueNumber findValueKnownNonnullOnBranch(UnconditionalValueDerefSet fact,
 Edge edge)

Clear deref sets of values if this edge is the non-null branch of an if comparison.

Parameters:

fact - a datflow fact

edge - edge to check

Returns:

possibly-modified dataflow fact

isExceptionEdge

private boolean isExceptionEdge(Edge edge)

Determine whether dataflow should be propagated on given edge.

Parameters:

edge - the edge

Returns:

true if dataflow should be propagated on the edge, false otherwise

same

public boolean same(UnconditionalValueDerefSet fact1,
 UnconditionalValueDerefSet fact2)

Description copied from interface: DataflowAnalysis

Are given dataflow facts the same?

startIteration

public void startIteration()

Description copied from interface: DataflowAnalysis

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

Specified by:

startIteration in interface DataflowAnalysis<UnconditionalValueDerefSet>

Overrides:

startIteration in class BasicAbstractDataflowAnalysis<UnconditionalValueDerefSet>

getLastUpdateTimestamp

public int getLastUpdateTimestamp(UnconditionalValueDerefSet fact)

Specified by:

getLastUpdateTimestamp in interface DataflowAnalysis<UnconditionalValueDerefSet>

Overrides:

getLastUpdateTimestamp in class BasicAbstractDataflowAnalysis<UnconditionalValueDerefSet>

setLastUpdateTimestamp

public void setLastUpdateTimestamp(UnconditionalValueDerefSet fact,
 int lastUpdate)

Specified by:

setLastUpdateTimestamp in interface DataflowAnalysis<UnconditionalValueDerefSet>

Overrides:

setLastUpdateTimestamp in class BasicAbstractDataflowAnalysis<UnconditionalValueDerefSet>