edu.jmu.decaf

Class LocalRegisterAllocator

java.lang.Object

edu.jmu.decaf.LocalRegisterAllocator

All Implemented Interfaces:

ILOCProcessor

Direct Known Subclasses:

MyLocalRegisterAllocator

public abstract class LocalRegisterAllocator
extends Object
implements ILOCProcessor

Performs register allocation for an ILOC program.

Field Summary

Fields

Modifier and Type	Field and Description
ILOCBasicBlock	currentBlock Basic block that is currently being allocated
ILOCFunction	currentFunction Function that is currently being allocated
Set<ILOCBasicBlock>	handled Collection of basic blocks that have already been allocated
int	numPhysicalRegs Number of physical registers available for allocation

Constructor Summary

Constructors

Constructor and Description
LocalRegisterAllocator(int numRegisters) Initialize register allocator

Method Summary

Modifier and Type	Method and Description
void	allocateRegisters(ILOCBasicBlock block) Perform local register allocation for a single basic block.
void	emitSpillLoad(int idx, int offset, int reg, String comment) Emit a new instruction at the given index.
int	emitSpillStore(int idx, int reg, String comment) Emit a new instruction at the given index.
void	process(ILOCBasicBlock block) Perform register allocation for a basic block and all basic blocks reachable from it.
void	process(ILOCProgram program) Perform register allocation on each function.

Methods inherited from class java.lang.Object

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

Field Detail

numPhysicalRegs

public int numPhysicalRegs

Number of physical registers available for allocation

currentFunction

public ILOCFunction currentFunction

Function that is currently being allocated

currentBlock

public ILOCBasicBlock currentBlock

Basic block that is currently being allocated

handled

public Set<ILOCBasicBlock> handled

Collection of basic blocks that have already been allocated

Constructor Detail

LocalRegisterAllocator

public LocalRegisterAllocator(int numRegisters)

Initialize register allocator

Parameters:

numRegisters - Number of physical registers

Method Detail

process

public void process(ILOCProgram program)

Perform register allocation on each function.

Specified by:

process in interface ILOCProcessor

Parameters:

program - ILOCProgram to process

process

public void process(ILOCBasicBlock block)

Perform register allocation for a basic block and all basic blocks reachable from it.

Parameters:

block - Entry block

allocateRegisters

public void allocateRegisters(ILOCBasicBlock block)

Perform local register allocation for a single basic block. This should be overridden in actual implementations.

Parameters:

block - Block to allocate

emitSpillLoad

public void emitSpillLoad(int idx,
                          int offset,
                          int reg,
                          String comment)

Emit a new instruction at the given index. The instruction will load the value from BP-offset into the desired register.

Parameters:

idx - Block index at which to insert the instruction

offset - Spill value offset

reg - Destination register

comment - Comment for new instruction (can be blank)

emitSpillStore

public int emitSpillStore(int idx,
                          int reg,
                          String comment)

Emit a new instruction at the given index. The instruction will store the value from the given register to a new spot on the stack (BP-offset). Essentially, it adds a new "local" variable to the current stack frame.

Parameters:

idx - Block index at which to insert the instruction

reg - Source register

comment - Comment for new instruction (can be blank)

Returns:

Destination offset from base pointer