Package soot.shimple.internal

Class PhiNodeManager

java.lang.Object

soot.shimple.internal.PhiNodeManager

public class PhiNodeManager
extends Object

Author:

Navindra Umanee

See Also:

ShimpleBody, Efficiently Computing Static Single Assignment Form and the Control Dependence Graph

Field Summary

Fields

Modifier and Type	Field	Description
protected ShimpleBody	body
protected BlockGraph	cfg
protected ShimpleFactory	sf
protected Map<Unit,Block>	unitToBlock
protected MultiMap<Local,Block>	varToBlocks

Constructor Summary

Constructors

Constructor	Description
PhiNodeManager(ShimpleBody body, ShimpleFactory sf)

Method Summary

Modifier and Type	Method	Description
boolean	doEliminatePhiNodes()	Eliminate Phi nodes in block by naively replacing them with shimple assignment statements in the control flow predecessors.
boolean	dominates(Unit champ, Unit challenger)	Returns true if champ dominates challenger.
static Map<Unit,Block>	getUnitToBlockMap(BlockGraph blocks)	Convenience function that maps units to blocks.
boolean	insertTrivialPhiNodes()	Phi node Insertion Algorithm from Cytron et al 91, P24-5,
void	prependTrivialPhiNode(Local local, Block frontierBlock)	Inserts a trivial Phi node with the appropriate number of arguments.
void	trimExceptionalPhiNodes()	Exceptional Phi nodes have a huge number of arguments and control flow predecessors by default.
void	trimPhiNode(PhiExpr phiExpr)
void	update()

Methods inherited from class java.lang.Object

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

Field Detail

body

protected final ShimpleBody body

sf

protected final ShimpleFactory sf

cfg

protected BlockGraph cfg

varToBlocks

protected MultiMap<Local,Block> varToBlocks

unitToBlock

protected Map<Unit,Block> unitToBlock

Constructor Detail

PhiNodeManager

public PhiNodeManager(ShimpleBody body,
                      ShimpleFactory sf)

Method Detail

update

public void update()

insertTrivialPhiNodes

public boolean insertTrivialPhiNodes()

Phi node Insertion Algorithm from Cytron et al 91, P24-5,

Special Java case: If a variable is not defined along all paths of entry to a node, a Phi node is not needed.

prependTrivialPhiNode

public void prependTrivialPhiNode(Local local,
                                  Block frontierBlock)

Inserts a trivial Phi node with the appropriate number of arguments.

trimExceptionalPhiNodes

public void trimExceptionalPhiNodes()

Exceptional Phi nodes have a huge number of arguments and control flow predecessors by default. Since it is useless trying to keep the number of arguments and control flow predecessors in synch, we might as well trim out all redundant arguments and eliminate a huge number of copy statements when we get out of SSA form in the process.

trimPhiNode

public void trimPhiNode(PhiExpr phiExpr)

See Also:

trimExceptionalPhiNodes()

dominates

public boolean dominates(Unit champ,
                         Unit challenger)

Returns true if champ dominates challenger. Note that false doesn't necessarily mean that challenger dominates champ.

doEliminatePhiNodes

public boolean doEliminatePhiNodes()

Eliminate Phi nodes in block by naively replacing them with shimple assignment statements in the control flow predecessors. Returns true if new locals were added to the body during the process, false otherwise.

getUnitToBlockMap

public static Map<Unit,Block> getUnitToBlockMap(BlockGraph blocks)

Convenience function that maps units to blocks. Should probably be in BlockGraph.