org.jikesrvm.mm.mminterface

Class GCMapIterator

java.lang.Object

org.jikesrvm.mm.mminterface.GCMapIterator

Direct Known Subclasses:

BaselineGCMapIterator, HardwareTrapGCMapIterator, JNIGCMapIterator, OptGenericGCMapIterator

public abstract class GCMapIterator
extends Object

Base class for iterators that identify object references and JSR return addresses held in stackframes produced by each of our compilers (baseline, opt, etc.). All compiler specific GCMapIterators extend this abstract class.

See Also:

GCMapIteratorGroup

Field Summary

Fields

Modifier and Type	Field and Description
protected Address	framePtr address of stackframe currently being scanned
AddressArray	registerLocations address where each gpr register was saved by previously scanned stackframe(s)
protected RVMThread	thread thread whose stack is currently being scanned

Constructor Summary

Constructors

Constructor and Description
GCMapIterator(AddressArray registerLocations)

Method Summary

Modifier and Type	Method and Description
abstract void	cleanupPointers() Iteration is complete, release any internal data structures including locks acquired during setupIterator for jsr maps.
abstract Address	getNextReferenceAddress() Get address of next object reference held by current stackframe.
abstract Address	getNextReturnAddressAddress() Get address of next JSR return address held by current stackframe.
abstract int	getType() Get the type of this iterator (BASELINE, OPT, etc.).
void	newStackWalk(RVMThread thread) Prepare to scan a thread's stack and saved registers for object references.
abstract void	reset() Prepare to re-iterate on same stackframe, and to switch between "reference" iteration and "JSR return address" iteration.
abstract void	setupIterator(CompiledMethod compiledMethod, Offset instructionOffset, Address framePtr) Prepare to iterate over object references and JSR return addresses held by a stackframe.

Methods inherited from class java.lang.Object

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

Field Detail

thread

protected RVMThread thread

thread whose stack is currently being scanned

framePtr

protected Address framePtr

address of stackframe currently being scanned

registerLocations

public final AddressArray registerLocations

address where each gpr register was saved by previously scanned stackframe(s)

Constructor Detail

GCMapIterator

public GCMapIterator(AddressArray registerLocations)

Method Detail

newStackWalk

public void newStackWalk(RVMThread thread)

Prepare to scan a thread's stack and saved registers for object references.

Parameters:

thread - Thread whose stack is being scanned

setupIterator

public abstract void setupIterator(CompiledMethod compiledMethod,
                                   Offset instructionOffset,
                                   Address framePtr)

Prepare to iterate over object references and JSR return addresses held by a stackframe.

Parameters:

compiledMethod - method running in the stackframe

instructionOffset - offset of current instruction within that method's code

framePtr - address of stackframe to be visited

getNextReferenceAddress

public abstract Address getNextReferenceAddress()

Get address of next object reference held by current stackframe. Returns zero when there are no more references to report.

Side effect: registerLocations[] updated at end of iteration. TODO: registerLocations[] update should be done via separately called method instead of as side effect.

Returns:

address of word containing an object reference zero if no more references to report

getNextReturnAddressAddress

public abstract Address getNextReturnAddressAddress()

Get address of next JSR return address held by current stackframe.

Returns:

address of word containing a JSR return address zero if no more return addresses to report

reset

public abstract void reset()

Prepare to re-iterate on same stackframe, and to switch between "reference" iteration and "JSR return address" iteration.

cleanupPointers

public abstract void cleanupPointers()

Iteration is complete, release any internal data structures including locks acquired during setupIterator for jsr maps.

getType

public abstract int getType()

Get the type of this iterator (BASELINE, OPT, etc.). Called from GCMapIteratorGroup to select which iterator to use for a stackframe. The possible types are specified in CompiledMethod.

Returns:

type code for this iterator