ScratchMap (Jikes RVM API)

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org.jikesrvm.compilers.opt.regalloc
Class ScratchMap

java.lang.Object
  org.jikesrvm.compilers.opt.regalloc.ScratchMap

public final class ScratchMap
extends Object
extends Object

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

Nested Class Summary
`private static class`	`ScratchMap.Interval` Super class of physical and symbolic intervals
`(package private) static 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.
`(package private) static class`	`ScratchMap.SymbolicInterval` An object that represents an interval where a symbolic register resides in a scratch register.

Field Summary
`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.

Constructor Summary
`ScratchMap()`

Method Summary
`(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)` If a symbolic register resides in a scratch register at an instruction numbered n, then return the scratch register.
`boolean`	`isDirty(Instruction s, Register r)` At GC point s, is the value of register r cached in a dirty scratch register?
`boolean`	`isEmpty()` Is this map empty?
`(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)` Note that at GC point s, the real value of register symb is cached in a dirty scratch register.
`String`	`toString()` Return a String representation.

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.

Constructor Detail

ScratchMap

public ScratchMap()

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.

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)

If a symbolic register resides in a scratch register at an instruction numbered n, then return the scratch register. Else, return null.

isEmpty

public boolean isEmpty()

Is this map empty?

markDirty

public void markDirty(Instruction s,
                      Register symb)

Note that at GC point s, the real value of register symb is cached in a dirty scratch 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?

toString

public String toString()

Return a String representation.

Overrides:: toString in class Object