GCMapIterator (Jikes RVM API)

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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
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
`Address`	`framePtr` address of stackframe currently being scanned
`WordArray`	`registerLocations` address where each gpr register was saved by previously scanned stackframe(s)
`RVMThread`	`thread` thread whose stack is currently being scanned

Constructor Summary
`GCMapIterator()`

Method Summary
`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

public RVMThread thread

thread whose stack is currently being scanned

framePtr

public Address framePtr

address of stackframe currently being scanned

registerLocations

public WordArray registerLocations

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

Constructor Detail

GCMapIterator

public GCMapIterator()

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