kilim.analysis

Class Usage

java.lang.Object

kilim.analysis.Usage

public class Usage
extends java.lang.Object

Each BasicBlock owns one instance of Usage. This class maintains, in essence, three vectors of booleans, indexed by the local variable number. Since it is very rare for a method to have more than 31 local variables, the vectors are represented by int bitmaps. For more than this, the basic block creates an instance of BigUsage that is functionally identical (TODO) Note that we don't need to track usage of operand stack. All elements of the operand stack are always live, and always need to be stored and restored (during stack switching). This is not true of local vars; a var may have a valid value which may not be used downstream, so we track which vars must be taken seriously.

See Also:

BasicBlock

Constructor Summary

Constructors

Constructor and Description
Usage(int numLocals)

Method Summary

Modifier and Type	Method and Description
void	born(int var)
boolean	evalLiveIn(java.util.ArrayList<Usage> succUsage, java.util.ArrayList<Handler> handUsage) This is the standard liveness calculation (Dragon Book, section 10.6).
boolean	isLiveIn(int var) return true if var is live at the entrance to this BB.
void	read(int var)
void	setBornIn(int var) This is purely for testing purposes.
void	setLiveIn(int var) This is purely for testing purposes.
java.lang.String	toString()
java.lang.String	toStringBits(java.lang.String sep)
void	write(int var)

Methods inherited from class java.lang.Object

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

Constructor Detail

Usage

public Usage(int numLocals)

Method Detail

read

public void read(int var)

write

public void write(int var)

born

public void born(int var)

isLiveIn

public boolean isLiveIn(int var)

return true if var is live at the entrance to this BB.

evalLiveIn

public boolean evalLiveIn(java.util.ArrayList<Usage> succUsage,
                          java.util.ArrayList<Handler> handUsage)

This is the standard liveness calculation (Dragon Book, section 10.6). At each BB (and its corresponding usage), we evaluate "in" using use and def. in = use U (out \ def) where out = U succ.in, for all successors this algorithm has been modified to treat catch blocks as occurring anywhere ie, that vars defined in a try may never be set however, this only applies to vars that have been defined at least once (ie, born)

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

toStringBits

public java.lang.String toStringBits(java.lang.String sep)

setLiveIn

public void setLiveIn(int var)

This is purely for testing purposes.

Parameters:

var - local var index

setBornIn

public void setBornIn(int var)

This is purely for testing purposes.

Parameters:

var - local var index