org.jikesrvm.compilers.common.assembler
Class ForwardReference

java.lang.Object
  org.jikesrvm.compilers.common.assembler.ForwardReference

Direct Known Subclasses:

ForwardReference.ConditionalBranch, ForwardReference.LoadReturnAddress, ForwardReference.ShortBranch, ForwardReference.SwitchCase, ForwardReference.UnconditionalBranch

public abstract class ForwardReference
extends Object

A forward reference has a machine-code-index source and optionally a bytecode-index target. The idea is to fix up the instruction at the source when the machine-code-index of the target is known. There need not be an explicit target, if the reference is used (by the compiler) within the machine-code for one bytecode. There are three kinds of forward reference: 1) unconditional branches 2) conditional branches 3) switch cases Each subclass must be able to resolve itself. This class also includes the machinery for maintaining a priority queue of forward references, priorities being target bytecode addresses. The head of this priority queue is maintained by a Assembler object. The priority queue is implemented as a one-way linked list of forward references with strictly increasing targets. The link for this list is "next". A separate linked list ("other" is the link) contains all forward references with the same target.

sourceMachinecodeIndex

final int sourceMachinecodeIndex

targetBytecodeIndex

final int targetBytecodeIndex

next

ForwardReference next

Has next larger targetBytecodeIndex

other

ForwardReference other

Has the same targetBytecodeIndex

ForwardReference

protected ForwardReference(int source,
                           int btarget)

ForwardReference

protected ForwardReference(int source)

No target; for use within cases of the main compiler loop

resolve

public abstract void resolve(AbstractAssembler asm)

Rewrite source to reference current machine code (in asm's machineCodes)

enqueue

public static ForwardReference enqueue(ForwardReference q,
                                       ForwardReference r)

Add a new reference r to a priority queue q

Returns:

the updated queue

resolveMatching

public static ForwardReference resolveMatching(AbstractAssembler asm,
                                               ForwardReference q,
                                               int bi)

Resolve any forward references on priority queue q to bytecode index bi

Returns:

queue of unresolved references