soot.shimple
Interface PhiExpr

All Superinterfaces:

EquivTo, Expr, Serializable, ShimpleExpr, Switchable, UnitBoxOwner, Value

All Known Implementing Classes:

SPhiExpr

public interface PhiExpr
extends ShimpleExpr

A fully defined PhiExpr usually consists of a list of Values for the arguments alongst with the corresponding control flow predecessor for each argument. This may be provided either as a Soot CFG Block or more directly as the Unit at the end of the corresponding CFG block.

As much as possible we try to conform to the semantics as described by Cytron et al., TOPLAS Oct. 91. A Phi node such as "x_1 = Phi(x_2, x_3)" is eliminated by respectively adding the statements "x_1 = x_2" and "x_1 = x_3" at the end of the corresponding control flow predecessor.

However, due to the fact that each argument is explicitly associated with the control flow predecessor, there may be some subtle differences. We tried to make the behaviour as robust and transparent as possible by handling the common cases of Unit chain manipulations in the Shimple internal implementation of PatchingChain.

Author:

Navindra Umanee

See Also:

Efficiently Computing Static Single Assignment Form and the Control Dependence Graph, Shimple.newPhiExpr(List, List), Shimple.newPhiExpr(Local, List)

Method Summary

boolean	addArg(Value arg, Block pred) Add the given argument associated with the given CFG predecessor.
boolean	addArg(Value arg, Unit predTailUnit) Add the given argument associated with the given CFG predecessor.
void	apply(Switch sw) Called when this object is visited.
ValueUnitPair	getArgBox(Block pred) Returns the argument pair corresponding to the given CFG predecessor.
ValueUnitPair	getArgBox(int index) Returns the argument pair for the given index.
ValueUnitPair	getArgBox(Unit predTailUnit) Returns the argument pair corresponding to the given CFG predecessor.
int	getArgCount() Returns the number of arguments in this PhiExpr.
int	getArgIndex(Block pred) Returns the index of the argument associated with the given control flow predecessor.
int	getArgIndex(Unit predTailUnit) Returns the index of the argument associated with the given control flow predecessor Unit.
List	getArgs() Returns an unmodifiable, backed view of the arguments to this PhiExpr.
int	getBlockId() Returns the id number of the block from which the Phi node originated from.
Unit	getPred(int index) Returns the control flow predecessor Unit for the given index into the PhiExpr.
List<Unit>	getPreds() Returns a list of the control flow predecessor Units being tracked by this PhiExpr
Type	getType() The type of the PhiExpr is usually the same as the type of its arguments.
Value	getValue(Block pred) Get the PhiExpr argument corresponding to the given control flow predecessor, returns null if not available.
Value	getValue(int index) Returns the value for the given index into the PhiExpr.
Value	getValue(Unit predTailUnit) Get the PhiExpr argument corresponding to the given control flow predecessor, returns null if not available.
List<Value>	getValues() Returns a list of the values used by this PhiExpr.
boolean	removeArg(Block pred) Remove the argument corresponding to the given CFG predecessor.
boolean	removeArg(int index) Remove the argument at the given index.
boolean	removeArg(Unit predTailUnit) Remove the argument corresponding to the given CFG predecessor.
boolean	removeArg(ValueUnitPair arg) Remove the given argument.
boolean	setArg(int index, Value arg, Block pred) Modify the PhiExpr argument at the given index with the given information.
boolean	setArg(int index, Value arg, Unit predTailUnit) Modify the PhiExpr argument at the given index with the given information.
void	setBlockId(int blockId) Set the block number of the Phi node.
boolean	setPred(int index, Block pred) Update the CFG predecessor associated with the PhiExpr argument at the given index.
boolean	setPred(int index, Unit predTailUnit) Update the CFG predecessor associated with the PhiExpr argument at the given index.
boolean	setValue(Block pred, Value arg) Locate the argument assocatiated with the given CFG predecessor and set the value.
boolean	setValue(int index, Value arg) Set the value at the given index into the PhiExpr.
boolean	setValue(Unit predTailUnit, Value arg) Locate the argument assocatiated with the given CFG predecessor unit and set the value.

Methods inherited from interface soot.Value

clone, getUseBoxes, toString

Methods inherited from interface soot.EquivTo

equivHashCode, equivTo

Methods inherited from interface soot.UnitBoxOwner

clearUnitBoxes, getUnitBoxes

Method Detail

getArgs

List getArgs()

Returns an unmodifiable, backed view of the arguments to this PhiExpr. Each argument is a ValueUnitPair.

See Also:

ValueUnitPair

getValues

List<Value> getValues()

Returns a list of the values used by this PhiExpr.

getPreds

List<Unit> getPreds()

Returns a list of the control flow predecessor Units being tracked by this PhiExpr

getArgCount

int getArgCount()

Returns the number of arguments in this PhiExpr.

getArgBox

ValueUnitPair getArgBox(int index)

Returns the argument pair for the given index. Null if out-of-bounds.

getValue

Value getValue(int index)

Returns the value for the given index into the PhiExpr. Null if out-of-bounds.

getPred

Unit getPred(int index)

Returns the control flow predecessor Unit for the given index into the PhiExpr. Null if out-of-bounds.

getArgIndex

int getArgIndex(Unit predTailUnit)

Returns the index of the argument associated with the given control flow predecessor Unit. Returns -1 if not found.

getArgBox

ValueUnitPair getArgBox(Unit predTailUnit)

Returns the argument pair corresponding to the given CFG predecessor. Returns null if not found.

getValue

Value getValue(Unit predTailUnit)

Get the PhiExpr argument corresponding to the given control flow predecessor, returns null if not available.

getArgIndex

int getArgIndex(Block pred)

Returns the index of the argument associated with the given control flow predecessor. Returns -1 if not found.

getArgBox

ValueUnitPair getArgBox(Block pred)

Returns the argument pair corresponding to the given CFG predecessor. Returns null if not found.

getValue

Value getValue(Block pred)

Get the PhiExpr argument corresponding to the given control flow predecessor, returns null if not available.

setArg

boolean setArg(int index,
               Value arg,
               Unit predTailUnit)

Modify the PhiExpr argument at the given index with the given information. Returns false on failure.

setArg

boolean setArg(int index,
               Value arg,
               Block pred)

Modify the PhiExpr argument at the given index with the given information. Returns false on failure.

setValue

boolean setValue(int index,
                 Value arg)

Set the value at the given index into the PhiExpr. Returns false on failure.

setValue

boolean setValue(Unit predTailUnit,
                 Value arg)

Locate the argument assocatiated with the given CFG predecessor unit and set the value. Returns false on failure.

setValue

boolean setValue(Block pred,
                 Value arg)

Locate the argument assocatiated with the given CFG predecessor and set the value. Returns false on failure.

setPred

boolean setPred(int index,
                Unit predTailUnit)

Update the CFG predecessor associated with the PhiExpr argument at the given index. Returns false on failure.

setPred

boolean setPred(int index,
                Block pred)

Update the CFG predecessor associated with the PhiExpr argument at the given index. Returns false on failure.

removeArg

boolean removeArg(int index)

Remove the argument at the given index. Returns false on failure.

removeArg

boolean removeArg(Unit predTailUnit)

Remove the argument corresponding to the given CFG predecessor. Returns false on failure.

removeArg

boolean removeArg(Block pred)

Remove the argument corresponding to the given CFG predecessor. Returns false on failure.

removeArg

boolean removeArg(ValueUnitPair arg)

Remove the given argument. Returns false on failure.

addArg

boolean addArg(Value arg,
               Block pred)

Add the given argument associated with the given CFG predecessor. Returns false on failure.

addArg

boolean addArg(Value arg,
               Unit predTailUnit)

Add the given argument associated with the given CFG predecessor. Returns false on failure.

setBlockId

void setBlockId(int blockId)

Set the block number of the Phi node.

getBlockId

int getBlockId()

Returns the id number of the block from which the Phi node originated from.

getType

Type getType()

The type of the PhiExpr is usually the same as the type of its arguments.

Specified by:

getType in interface Value

apply

void apply(Switch sw)

Description copied from interface: Switchable

Called when this object is visited.

Specified by:

apply in interface Switchable