org.jikesrvm.mm.mminterface
Class GCMapIteratorGroup

java.lang.Object
  org.jikesrvm.mm.mminterface.GCMapIteratorGroup

All Implemented Interfaces:

SizeConstants

public final class GCMapIteratorGroup
extends Object
implements SizeConstants

Maintains a collection of compiler specific GCMapIterators that are used by collection threads when scanning thread stacks to locate object references in those stacks. Each collector thread has its own GCMapIteratorGroup.

The group contains a GCMapIterator for each type of stack frame that may be found while scanning a stack during garbage collection, including frames for baseline compiled methods, OPT compiled methods, and frames for transitions from Java into JNI native code. These iterators are responsible for reporting the location of references in the stack or register save areas.

See Also:

GCMapIterator, CompiledMethod, CollectorThread

registerLocations

private final WordArray registerLocations

current location (memory address) of each gpr register

baselineIterator

private final GCMapIterator baselineIterator

iterator for baseline compiled frames

optIterator

private final GCMapIterator optIterator

iterator for opt compiled frames

hardwareTrapIterator

private final GCMapIterator hardwareTrapIterator

iterator for HardwareTrap stackframes

jniIterator

private final GCMapIterator jniIterator

iterator for JNI Java -> C stackframes

GCMapIteratorGroup

public GCMapIteratorGroup()

newStackWalk

public void newStackWalk(RVMThread thread,
                         Address registerLocation)

Prepare to scan a thread's stack for object references. Called by collector threads when beginning to scan a threads stack. Calls newStackWalk for each of the contained GCMapIterators.

Assumption: the thread is currently suspended, ie. its saved gprs[] contain the thread's full register state.

Side effect: registerLocations[] initialized with pointers to the thread's saved gprs[] (in thread.contextRegisters.gprs)

Parameters:

thread - Thread whose registers and stack are to be scanned

selectIterator

public GCMapIterator selectIterator(CompiledMethod compiledMethod)

Select iterator for scanning for object references in a stackframe. Called by collector threads while scanning a threads stack.

Parameters:

compiledMethod - CompiledMethod for the method executing in the stack frame

Returns:

GCMapIterator to use

getJniIterator

public GCMapIterator getJniIterator()

get the GCMapIterator used for scanning JNI native stack frames.

Returns:

jniIterator