sandmark.util.controlflowgraph
Class LiveVariable

java.lang.Object
  |
  +--sandmark.util.controlflowgraph.LiveVariable

All Implemented Interfaces:

java.lang.Cloneable, java.lang.Comparable

public class LiveVariable

extends java.lang.Object

implements java.lang.Comparable, java.lang.Cloneable

LiveVariable encapsulates information about a variable in the local variable table.

Field Summary

boolean	immutable Denotes that changes to this live variable should not change the acutal code.
(package private) boolean	movable
(package private) int	myVarNum

Constructor Summary

(package private)

LiveVariable(int varNum) Constructs a new live variable.

Method Summary

void	addDef(de.fub.bytecode.generic.InstructionHandle ih) Adds another definition (the instruction handle for the def instruction) to the definition list for this variable.
void	addInterference(LiveVariable other) Adds a fake interference between this variable and the parameter, so that calls to interferesWith will return true, regardless of the contents of their live ranges.
(package private) void	addRange(InterferenceGraph.RangeNode live) Adds another node to the live range for this variable.
void	addUse(de.fub.bytecode.generic.InstructionHandle ih) Adds another use (the instruction handle for the use instruction) to the use list for this variable.
java.lang.Object	clone()
int	compareTo(java.lang.Object o) Compares two live variables based on the order of definition (earlier defined variables first) the local variable number of parameters
boolean	equals(java.lang.Object o)
java.util.Iterator	getDefIterator() Returns an iterator of InstructionHandles for each definition of this variable.
java.util.Iterator	getUseIterator() Returns an iterator of InstructionHandles for each use of this variable.
int	getVarNum() Returns the current slot in the local variable table where this variable is assigned.
boolean	hasFakeInterference() Returns true if there is a fake edge added to this variable.
boolean	interferesWith(LiveVariable other) Returns true if the live ranges for these variables intersect, or if there is a fake interference added between these nodes (by the addInterference method).
boolean	isMovable() Checks to see if this variable can be moved from its current slot in the local variable table.
boolean	isSameAs(LiveVariable other) Returns true if these variables share any uses or defs.
(package private) static LiveVariable	merge(LiveVariable v1, LiveVariable v2)
boolean	removeInterference(LiveVariable other) Removes a fake interference between this variable and the parameter, if it existed.
void	setMovable(boolean move) Sets whether or not this variable can be moved from its current slot in the local variable table.
void	setVarNum(int index) Changes the current slot in the local variable table where this variable is assigned and changes the bytecode where this variable is referenced.
java.lang.String	toString()

Methods inherited from class java.lang.Object

finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

myVarNum

int myVarNum

immutable

public boolean immutable

Denotes that changes to this live variable should not change the acutal code.

movable

boolean movable

Constructor Detail

LiveVariable

LiveVariable(int varNum)

Constructs a new live variable. This method should only be used to for analysis.

Method Detail

clone

public java.lang.Object clone()

Overrides:

clone in class java.lang.Object

addRange

void addRange(InterferenceGraph.RangeNode live)

Adds another node to the live range for this variable. This method should only be used to for analysis.

addUse

public void addUse(de.fub.bytecode.generic.InstructionHandle ih)

Adds another use (the instruction handle for the use instruction) to the use list for this variable. This method should only be used to for analysis.

setMovable

public void setMovable(boolean move)

Sets whether or not this variable can be moved from its current slot in the local variable table.

isMovable

public boolean isMovable()

Checks to see if this variable can be moved from its current slot in the local variable table. A variable will not be movable if its definition is from a parameter, or if the programmer has called setMovable(false) on this variable.

Returns:

true if the variable can be moved, false if not

getUseIterator

public java.util.Iterator getUseIterator()

Returns an iterator of InstructionHandles for each use of this variable.

getDefIterator

public java.util.Iterator getDefIterator()

Returns an iterator of InstructionHandles for each definition of this variable.

isSameAs

public boolean isSameAs(LiveVariable other)

Returns true if these variables share any uses or defs. This method should only be used to for analysis, to remove duplicate variables.

compareTo

public int compareTo(java.lang.Object o)

Compares two live variables based on

• the order of definition (earlier defined variables first)
• the local variable number of parameters

Specified by:

compareTo in interface java.lang.Comparable

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

addDef

public void addDef(de.fub.bytecode.generic.InstructionHandle ih)

Adds another definition (the instruction handle for the def instruction) to the definition list for this variable. This method should only be used to for analysis.

getVarNum

public int getVarNum()

Returns the current slot in the local variable table where this variable is assigned.

setVarNum

public void setVarNum(int index)

Changes the current slot in the local variable table where this variable is assigned and changes the bytecode where this variable is referenced. This method does not verify if the new assignment interferes with other variables, use interferesWith to check that. This modifies the Instructions in the InstructionHandles in the MethodGen in the ControlFlowGraph passed to the constructor of InterferenceGraph. Do not forget to commit these changes to the ClassFileCollection you are working with.

Parameters:

index - the new local variable number

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

addInterference

public void addInterference(LiveVariable other)

Adds a fake interference between this variable and the parameter, so that calls to interferesWith will return true, regardless of the contents of their live ranges.

Parameters:

other - the variable that this variable should always appear to interfere with

removeInterference

public boolean removeInterference(LiveVariable other)

Removes a fake interference between this variable and the parameter, if it existed.

Returns:

false if there was no fake edge between the two variables, true if the removal succeeded

hasFakeInterference

public boolean hasFakeInterference()

Returns true if there is a fake edge added to this variable.

interferesWith

public boolean interferesWith(LiveVariable other)

Returns true if the live ranges for these variables intersect, or if there is a fake interference added between these nodes (by the addInterference method).

merge

static LiveVariable merge(LiveVariable v1,
                          LiveVariable v2)