org.jikesrvm.compilers.opt.ssa

Class IndexPropagation.ObjectCell

java.lang.Object

org.jikesrvm.compilers.opt.dfsolver.DF_AbstractCell

org.jikesrvm.compilers.opt.ssa.IndexPropagation.ObjectCell

All Implemented Interfaces:

DF_LatticeCell, GraphNode

Enclosing class:

IndexPropagation

static final class IndexPropagation.ObjectCell
extends DF_AbstractCell

An ObjectCell is a lattice cell for the index propagation problem, used in redundant load elimination for fields.

An ObjectCell represents a set of value numbers, indicating that the elements indexed by these value numbers are available for a certain field type.

Note: this implementation does not scale, and is not terribly efficient.

Field Summary

Fields

Modifier and Type	Field and Description
private static int	CAPACITY a bound on the size of a lattice cell.
private HeapVariable<?>	key The heap variable this lattice cell tracks information for.
private int[]	numbers a set of value numbers comparising this lattice cell.
private int	size The number of value numbers in this cell.
private boolean	TOP Does this lattice cell represent TOP?

Constructor Summary

Constructors

Constructor and Description
ObjectCell(HeapVariable<?> key) Create a lattice cell corresponding to a heap variable.

Method Summary

Modifier and Type	Method and Description
(package private) void	add(int v) Add a value number to this cell.
(package private) void	clear() Clear all value numbers from this cell.
(package private) boolean	contains(int v) Does this cell contain the value number v?
(package private) int[]	copyValueNumbers() Return a deep copy of the value numbers in this cell.
(package private) HeapVariable<?>	getKey()
(package private) boolean	isBOTTOM() Does this cell represent the BOTTOM element in the dataflow lattice?
(package private) boolean	isTOP() Does this cell represent the TOP element in the dataflow lattice?
(package private) void	remove(int v) Remove a value number from this cell.
(package private) void	setBOTTOM() Set the value of this cell to BOTTOM.
static boolean	setsDiffer(int[] set1, int[] set2) Do two sets of value numbers differ?
(package private) void	setTOP(boolean b) Mark this cell as representing (or not) the TOP element in the dataflow lattice.
String	toString() Return a string representation of this cell

Methods inherited from class org.jikesrvm.compilers.opt.dfsolver.DF_AbstractCell

addDef, addUse, getDefs, getIndex, getUses, inNodes, outNodes, setIndex

Methods inherited from class java.lang.Object

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

Field Detail

CAPACITY

private static final int CAPACITY

a bound on the size of a lattice cell.

See Also:

Constant Field Values

numbers

private int[] numbers

a set of value numbers comparising this lattice cell.

size

private int size

The number of value numbers in this cell.

key

private final HeapVariable<?> key

The heap variable this lattice cell tracks information for.

TOP

private boolean TOP

Does this lattice cell represent TOP?

Constructor Detail

ObjectCell

ObjectCell(HeapVariable<?> key)

Create a lattice cell corresponding to a heap variable.

Parameters:

key - the heap variable associated with this cell.

Method Detail

getKey

HeapVariable<?> getKey()

isTOP

boolean isTOP()

Does this cell represent the TOP element in the dataflow lattice?

Returns:

true or false.

isBOTTOM

boolean isBOTTOM()

Does this cell represent the BOTTOM element in the dataflow lattice?

Returns:

true or false.

setTOP

void setTOP(boolean b)

Mark this cell as representing (or not) the TOP element in the dataflow lattice.

Parameters:

b - should this cell contain TOP?

setBOTTOM

void setBOTTOM()

Set the value of this cell to BOTTOM.

contains

boolean contains(int v)

Does this cell contain the value number v?

Parameters:

v - value number in question

Returns:

true or false

add

void add(int v)

Add a value number to this cell.

Parameters:

v - value number

remove

void remove(int v)

Remove a value number from this cell.

Parameters:

v - value number

clear

void clear()

Clear all value numbers from this cell.

copyValueNumbers

int[] copyValueNumbers()

Return a deep copy of the value numbers in this cell.

Returns:

a deep copy of the value numbers in this cell, null to represent empty set.

toString

public String toString()

Return a string representation of this cell

Specified by:

toString in interface DF_LatticeCell

Overrides:

toString in class Object

Returns:

a string representation of this cell

setsDiffer

public static boolean setsDiffer(int[] set1,
                                 int[] set2)

Do two sets of value numbers differ?

SIDE EFFECT: sorts the sets

Parameters:

set1 - first set to compare

set2 - second set to compare

Returns:

true iff the two sets are different