org.jikesrvm.compilers.opt.regalloc

Class ScratchMap

java.lang.Object

org.jikesrvm.compilers.opt.regalloc.ScratchMap

public final class ScratchMap
extends Object

This class holds information on scratch register usage, needed to adjust GC Maps.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private class	ScratchMap.Interval Super class of physical and symbolic intervals
private class	ScratchMap.PhysicalInterval An object that represents an interval where a physical register's contents are evicted so that the physical register can be used as a scratch.
private class	ScratchMap.SymbolicInterval An object that represents an interval where a symbolic register resides in a scratch register.

Field Summary

Fields

Modifier and Type	Field and Description
private static boolean	DEBUG
private HashMap<Instruction,HashSet<Register>>	dirtyMap For each GC Point s, a set of symbolic registers that are cached in dirty scratch registers before s.
private HashMap<Register,ArrayList<ScratchMap.Interval>>	map For each register, the set of intervals describing the register.
private HashMap<Register,ScratchMap.Interval>	pending For each register, a pending (incomplete) interval under construction.
private RegisterAllocatorState	regAllocState

Constructor Summary

Constructors

Constructor and Description
ScratchMap(RegisterAllocatorState regAllocState)

Method Summary

Modifier and Type	Method and Description
(package private) void	beginScratchInterval(Register r, Instruction begin) Begin a new interval of scratch-ness for a physical register.
(package private) void	beginSymbolicInterval(Register r, Register scratch, Instruction begin) Begin a new interval of scratch-ness for a symbolic register.
void	endScratchInterval(Register r, Instruction end) End an interval of scratch-ness for a physical register.
void	endSymbolicInterval(Register r, Instruction end) End an interval of scratch-ness for a symbolic register.
private ArrayList<ScratchMap.Interval>	findOrCreateIntervalSet(Register r) Find or create the set of intervals corresponding to a register r.
(package private) Register	getScratch(Register r, int n) Gets the scratch register if a matching one exists.
boolean	isDirty(Instruction s, Register r) At GC point s, is the value of register r cached in a dirty scratch register?
boolean	isEmpty()
(package private) boolean	isScratch(Register r, int n) Is the given physical register being used as a scratch register in the given instruction?
void	markDirty(Instruction s, Register symb) Records that the real value of a symbolic register is cached in a dirty scratch register at a given instruction that is a GC point.
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

DEBUG

private static final boolean DEBUG

See Also:

Constant Field Values

map

private final HashMap<Register,ArrayList<ScratchMap.Interval>> map

For each register, the set of intervals describing the register.

pending

private final HashMap<Register,ScratchMap.Interval> pending

For each register, a pending (incomplete) interval under construction.

dirtyMap

private final HashMap<Instruction,HashSet<Register>> dirtyMap

For each GC Point s, a set of symbolic registers that are cached in dirty scratch registers before s.

regAllocState

private final RegisterAllocatorState regAllocState

Constructor Detail

ScratchMap

public ScratchMap(RegisterAllocatorState regAllocState)

Method Detail

beginSymbolicInterval

void beginSymbolicInterval(Register r,
                           Register scratch,
                           Instruction begin)

Begin a new interval of scratch-ness for a symbolic register.

Parameters:

r - the symbolic register being moved into scratch

scratch - the physical register being used as a scratch

begin - the instruction before which the physical register is vacated.

endSymbolicInterval

public void endSymbolicInterval(Register r,
                                Instruction end)

End an interval of scratch-ness for a symbolic register.

Parameters:

r - the symbolic register being moved into scratch

end - the instruction before which the scratch interval ends

beginScratchInterval

void beginScratchInterval(Register r,
                          Instruction begin)

Begin a new interval of scratch-ness for a physical register.

Parameters:

r - the physical register being used as a scratch

begin - the instruction before which the physical register is vacated.

endScratchInterval

public void endScratchInterval(Register r,
                               Instruction end)

End an interval of scratch-ness for a physical register.

Parameters:

r - the physical register being used as a scratch

end - the instruction before which the physical register is vacated.

findOrCreateIntervalSet

private ArrayList<ScratchMap.Interval> findOrCreateIntervalSet(Register r)

Find or create the set of intervals corresponding to a register r.

Parameters:

r - the register to check

Returns:

a possibly empty list of intervals

isScratch

boolean isScratch(Register r,
                  int n)

Is the given physical register being used as a scratch register in the given instruction?

Parameters:

r - a physical register

n - the instruction's number

Returns:

true if the register is used as a scratch register in the instruction, false otherwise

getScratch

Register getScratch(Register r,
                    int n)

Gets the scratch register if a matching one exists.

Parameters:

r - a symbolic register

n - the instruction number

Returns:

if a symbolic register resides in a scratch register at an instruction with the given number, then return the scratch register. Else, return null.

isEmpty

public boolean isEmpty()

markDirty

public void markDirty(Instruction s,
                      Register symb)

Records that the real value of a symbolic register is cached in a dirty scratch register at a given instruction that is a GC point.

Parameters:

s - an instruction that is a GC point. Note: it is the caller's responsibility to check this

symb - the symbolic register

isDirty

public boolean isDirty(Instruction s,
                       Register r)

At GC point s, is the value of register r cached in a dirty scratch register?

Parameters:

s - an instruction that is a GC point

r - register to check

Returns:

true if the register is in a scratch register and the scratch register is dirty, false otherwise

toString

public String toString()

Overrides:

toString in class Object