com.android.dx.ssa.back
Class RegisterAllocator

java.lang.Object
  com.android.dx.ssa.back.RegisterAllocator

Direct Known Subclasses:

FirstFitAllocator, FirstFitLocalCombiningAllocator, NullRegisterAllocator

public abstract class RegisterAllocator
extends Object

Base class of all register allocators.

Field Summary

protected InterferenceGraph	interference interference graph, indexed by register in both dimensions
protected SsaMethod	ssaMeth method being processed

Constructor Summary

RegisterAllocator(SsaMethod ssaMeth, InterferenceGraph interference)
Creates an instance.

Method Summary

abstract RegisterMapper	allocateRegisters() Runs the algorithm.
protected int	getCategoryForSsaReg(int reg) Returns the category (width) of the definition site of the register.
protected RegisterSpec	getDefinitionSpecForSsaReg(int reg) Returns the RegisterSpec of the definition of the register.
protected RegisterSpec	insertMoveBefore(SsaInsn insn, RegisterSpec reg) Inserts a move instruction for a specified SSA register before a specified instruction, creating a new SSA register and adjusting the interference graph in the process.
protected boolean	isDefinitionMoveParam(int reg) Returns true if the definition site of this register is a move-param (ie, this is a method parameter).
abstract boolean	wantsParamsMovedHigh() Indicates whether the method params were allocated at the bottom of the namespace, and thus should be moved up to the top of the namespace after phi removal.

Methods inherited from class java.lang.Object

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

Field Detail

ssaMeth

protected final SsaMethod ssaMeth

method being processed

interference

protected final InterferenceGraph interference

interference graph, indexed by register in both dimensions

Constructor Detail

RegisterAllocator

public RegisterAllocator(SsaMethod ssaMeth,
                         InterferenceGraph interference)

Creates an instance. Call allocateRegisters to run.

Parameters:

ssaMeth - method to process.

interference - Interference graph, indexed by register in both dimensions.

Method Detail

wantsParamsMovedHigh

public abstract boolean wantsParamsMovedHigh()

Indicates whether the method params were allocated at the bottom of the namespace, and thus should be moved up to the top of the namespace after phi removal.

Returns:

true if params should be moved from low to high

allocateRegisters

public abstract RegisterMapper allocateRegisters()

Runs the algorithm.

Returns:

a register mapper to apply to the SsaMethod

getCategoryForSsaReg

protected final int getCategoryForSsaReg(int reg)

Returns the category (width) of the definition site of the register. Returns 1 for undefined registers.

Parameters:

reg - register

Returns:

1..2

getDefinitionSpecForSsaReg

protected final RegisterSpec getDefinitionSpecForSsaReg(int reg)

Returns the RegisterSpec of the definition of the register.

Parameters:

reg - >= 0; SSA register

Returns:

definition spec of the register or null if it is never defined (for the case of "version 0" SSA registers)

isDefinitionMoveParam

protected boolean isDefinitionMoveParam(int reg)

Returns true if the definition site of this register is a move-param (ie, this is a method parameter).

Parameters:

reg - register in question

Returns:

true if this is a method parameter

insertMoveBefore

protected final RegisterSpec insertMoveBefore(SsaInsn insn,
                                              RegisterSpec reg)

Inserts a move instruction for a specified SSA register before a specified instruction, creating a new SSA register and adjusting the interference graph in the process. The insn currently must be the last insn in a block.

Parameters:

insn - non-null; insn to insert move before, must be last insn in block

reg - non-null; SSA register to duplicate

Returns:

non-null; spec of new SSA register created by move