Class Liveness

java.lang.Object

EDU.purdue.cs.bloat.codegen.Liveness

public class Liveness
extends Object

Liveness represents the interference graph of the local variables contained in a control flow graph. When the liveness of two variables overlap each other, the two variables are said to interfere with each other. The interference graph represents this relationship between variables. There is an (un-directed) edge between variables a and b in the interference graph if variable a interferes with variable b.

Field Summary

Fields

Modifier and Type	Field	Description
static final boolean	AFTER
static final boolean	BEFORE
static boolean	DEBUG
static boolean	UNIQUE

Constructor Summary

Constructors

Constructor	Description
Liveness(FlowGraph cfg)	Constructor.

Method Summary

Modifier and Type	Method	Description
Collection	defs()	Returns the LocalExprs (variables) that occur in the CFG.
Iterator	intersections(VarExpr a)	Returns an Iterator of LocalExprs that interfere with a given VarExpr.
boolean	liveAtEndOfBlock(VarExpr isLive, Block block)	Should not be called.
boolean	liveAtStartOfBlock(VarExpr isLive, Block block)	Should not be called.
boolean	liveAtUse(VarExpr isLive, VarExpr at, boolean after)	Should not be called.
boolean	liveRangesIntersect(VarExpr a, VarExpr b)	Determines whether or not two variables interfere with one another.
void	removeVar(LocalExpr expr)	Removes a local expression from the interference graph.

Methods inherited from class Object

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

Field Details

DEBUG

public static boolean DEBUG

UNIQUE

public static boolean UNIQUE

BEFORE

public static final boolean BEFORE

See Also:

• Constant Field Values

AFTER

public static final boolean AFTER

See Also:

• Constant Field Values

Constructor Details

Liveness

public Liveness(FlowGraph cfg)

Constructor.

Parameters:

cfg - Control flow graph on which to perform liveness analysis.

Method Details

removeVar

public void removeVar(LocalExpr expr)

Removes a local expression from the interference graph.

liveAtUse

public boolean liveAtUse(VarExpr isLive,
 VarExpr at,
 boolean after)

Should not be called.

liveAtStartOfBlock

public boolean liveAtStartOfBlock(VarExpr isLive,
 Block block)

Should not be called.

liveAtEndOfBlock

public boolean liveAtEndOfBlock(VarExpr isLive,
 Block block)

Should not be called.

defs

public Collection defs()

Returns the LocalExprs (variables) that occur in the CFG. They correspond to nodes in the interference graph.

intersections

public Iterator intersections(VarExpr a)

Returns an Iterator of LocalExprs that interfere with a given VarExpr.

liveRangesIntersect

public boolean liveRangesIntersect(VarExpr a,
 VarExpr b)

Determines whether or not two variables interfere with one another.