ObjectModel (Jikes RVM API)

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org.jikesrvm.objectmodel
Class ObjectModel

java.lang.Object
  org.jikesrvm.objectmodel.ObjectModel

All Implemented Interfaces:: JavaHeaderConstants, SizeConstants

public class ObjectModel
extends Object
implements JavaHeaderConstants, SizeConstants
extends Object
implements JavaHeaderConstants, SizeConstants

The interface to the object model definition accessible to the virtual machine.

Conceptually each Java object is composed of the following pieces:

The JavaHeader defined by JavaHeader. This portion of the object supports language-level functions such as locking, hashcodes, dynamic type checking, virtual function invocation, and array length.
The GCHeader defined by MemoryManager. This portion of the object supports allocator-specific requirements such as mark/barrier bits, reference counts, etc.
The MiscHeader defined by MiscHeader. This portion supports various other clients that want to add bits/words to all objects. Typical uses are profiling and instrumentation (basically this is a way to add an instance field to java.lang.Object).
The instance fields. Currently defined by various classloader classes. Factoring this code out and making it possible to lay out the instance fields in different ways is a todo item.

Every object's header contains the three portions outlined above.

 |<- lo memory                                        hi memory ->|

   SCALAR LAYOUT:
 |<---------- scalar header --------->|
 +----------+------------+------------+------+------+------+--------+
 | GCHeader | MiscHeader | JavaHeader | fldO | fld1 | fldx | fldN-1 |
 +----------+------------+------------+------+------+------+--------+
                         ^ JHOFF             ^objref
                                             .
    ARRAY LAYOUT:                            .
 |<---------- array header ----------------->|
 +----------+------------+------------+------+------+------+------+------+
 | GCHeader | MiscHeader | JavaHeader | len  | elt0 | elt1 | ...  |eltN-1|
 +----------+------------+------------+------+------+------+------+------+
                         ^ JHOFF             ^objref

Assumptions:

Each portion of the header (JavaHeader, GCHeader, MiscHeader) is some multiple of 4 bytes (possibly 0). This simplifies access, since we can access each portion independently without having to worry about word tearing.
The JavaHeader exports k (>=0) unused contiguous bits that can be used by the GCHeader and MiscHeader. The GCHeader gets first dibs on these bits. The GCHeader should use buts 0..i, MiscHeader should use bits i..k.
JHOFF is a constant for a given configuration.

This model allows efficient array access: the array pointer can be used directly in the base+offset subscript calculation, with no additional constant required.

This model allows free null pointer checking for most reads: a small offset from that reference will wrap around to either very high or very low unmapped memory in the case of a null pointer. As long as these segments of memory are not mapped to the current process, loads/stores through such a pointer will cause a trap that we can catch with a unix signal handler.

Note that on AIX we are forced to perform explicit null checks on scalar field accesses as we are unable to protect low memory.

Note the key invariant that all elements of the header are available at the same offset from an objref for both arrays and scalar objects.

Note that this model allows for arbitrary growth of the GC header to the left of the object. A possible TODO item is to modify the necessary interfaces within this class and JavaHeader to allow moveObject, bytesUsed, bytesRequiredWhenCopied, etc. to tell this class how many GC header bytes have been allocated. As these calls would be constant within the constant of the call the optimising compiler should be able to allow this at minimal cost.

Another possible TODO item is to include support for linear scanning, where it is possible to move from one object to the next under contiguous allocation. At the moment this is in conflict with object alignment code for objects with long/double fields. We could possibly include the code anyway but require that the alignment code is switched off, or that all objects are aligned. Linear scanning is used in several GC algorithms including card-marking and compaction.

See Also:: JavaHeader, MiscHeader, MemoryManager

Field Summary
`static boolean`	`HASH_STATS` Should we gather stats on hash code state transitions for address-based hashing?
`static int`	`hashRequests` count number of Object.hashCode() operations
`static int`	`hashTransition1` count transitions from UNHASHED to HASHED
`static int`	`hashTransition2` count transitions from HASHED to HASHED_AND_MOVED
`private static FieldLayout`	`layout` Layout widget
`private static boolean`	`PACKED` Whether to pack bytes and shorts into 32bit fields

Fields inherited from interface org.jikesrvm.objectmodel.JavaHeaderConstants
ADDRESS_BASED_HASHING, ALIGNMENT_MASK, ALIGNMENT_VALUE, ALLOWS_LINEAR_SCAN, ARRAY_BASE_OFFSET, ARRAY_LENGTH_BYTES, ARRAY_LENGTH_OFFSET, DYNAMIC_HASH_OFFSET, FIELD_ZERO_OFFSET, FORWARDING_PTR_OVERLAYS_TIB, GC_HEADER_BYTES, GC_HEADER_OFFSET, HASH_STATE_HASHED, HASH_STATE_HASHED_AND_MOVED, HASH_STATE_MASK, HASH_STATE_UNHASHED, HASHCODE_BYTES, HASHCODE_OFFSET, JAVA_HEADER_BYTES, JAVA_HEADER_OFFSET, LOG_MIN_ALIGNMENT, MISC_HEADER_BYTES, MISC_HEADER_OFFSET, NUM_AVAILABLE_BITS, OTHER_HEADER_BYTES, SEGREGATE_ARRAYS_FOR_LINEAR_SCAN, STATUS_BYTES, TIB_BYTES

Fields inherited from interface org.jikesrvm.objectmodel.JavaHeaderConstants

ADDRESS_BASED_HASHING, ALIGNMENT_MASK, ALIGNMENT_VALUE, ALLOWS_LINEAR_SCAN, ARRAY_BASE_OFFSET, ARRAY_LENGTH_BYTES, ARRAY_LENGTH_OFFSET, DYNAMIC_HASH_OFFSET, FIELD_ZERO_OFFSET, FORWARDING_PTR_OVERLAYS_TIB, GC_HEADER_BYTES, GC_HEADER_OFFSET, HASH_STATE_HASHED, HASH_STATE_HASHED_AND_MOVED, HASH_STATE_MASK, HASH_STATE_UNHASHED, HASHCODE_BYTES, HASHCODE_OFFSET, JAVA_HEADER_BYTES, JAVA_HEADER_OFFSET, LOG_MIN_ALIGNMENT, MISC_HEADER_BYTES, MISC_HEADER_OFFSET, NUM_AVAILABLE_BITS, OTHER_HEADER_BYTES, SEGREGATE_ARRAYS_FOR_LINEAR_SCAN, STATUS_BYTES, TIB_BYTES

Fields inherited from interface org.jikesrvm.SizeConstants
BITS_IN_ADDRESS, BITS_IN_BOOLEAN, BITS_IN_BYTE, BITS_IN_CHAR, BITS_IN_DOUBLE, BITS_IN_EXTENT, BITS_IN_FLOAT, BITS_IN_INT, BITS_IN_LONG, BITS_IN_OFFSET, BITS_IN_PAGE, BITS_IN_SHORT, BITS_IN_WORD, BYTES_IN_ADDRESS, BYTES_IN_BOOLEAN, BYTES_IN_BYTE, BYTES_IN_CHAR, BYTES_IN_DOUBLE, BYTES_IN_EXTENT, BYTES_IN_FLOAT, BYTES_IN_INT, BYTES_IN_LONG, BYTES_IN_OFFSET, BYTES_IN_PAGE, BYTES_IN_SHORT, BYTES_IN_WORD, LOG_BITS_IN_ADDRESS, LOG_BITS_IN_BOOLEAN, LOG_BITS_IN_BYTE, LOG_BITS_IN_CHAR, LOG_BITS_IN_DOUBLE, LOG_BITS_IN_EXTENT, LOG_BITS_IN_FLOAT, LOG_BITS_IN_INT, LOG_BITS_IN_LONG, LOG_BITS_IN_OFFSET, LOG_BITS_IN_PAGE, LOG_BITS_IN_SHORT, LOG_BITS_IN_WORD, LOG_BYTES_IN_ADDRESS, LOG_BYTES_IN_BOOLEAN, LOG_BYTES_IN_BYTE, LOG_BYTES_IN_CHAR, LOG_BYTES_IN_DOUBLE, LOG_BYTES_IN_EXTENT, LOG_BYTES_IN_FLOAT, LOG_BYTES_IN_INT, LOG_BYTES_IN_LONG, LOG_BYTES_IN_OFFSET, LOG_BYTES_IN_PAGE, LOG_BYTES_IN_SHORT, LOG_BYTES_IN_WORD

Fields inherited from interface org.jikesrvm.SizeConstants

BITS_IN_ADDRESS, BITS_IN_BOOLEAN, BITS_IN_BYTE, BITS_IN_CHAR, BITS_IN_DOUBLE, BITS_IN_EXTENT, BITS_IN_FLOAT, BITS_IN_INT, BITS_IN_LONG, BITS_IN_OFFSET, BITS_IN_PAGE, BITS_IN_SHORT, BITS_IN_WORD, BYTES_IN_ADDRESS, BYTES_IN_BOOLEAN, BYTES_IN_BYTE, BYTES_IN_CHAR, BYTES_IN_DOUBLE, BYTES_IN_EXTENT, BYTES_IN_FLOAT, BYTES_IN_INT, BYTES_IN_LONG, BYTES_IN_OFFSET, BYTES_IN_PAGE, BYTES_IN_SHORT, BYTES_IN_WORD, LOG_BITS_IN_ADDRESS, LOG_BITS_IN_BOOLEAN, LOG_BITS_IN_BYTE, LOG_BITS_IN_CHAR, LOG_BITS_IN_DOUBLE, LOG_BITS_IN_EXTENT, LOG_BITS_IN_FLOAT, LOG_BITS_IN_INT, LOG_BITS_IN_LONG, LOG_BITS_IN_OFFSET, LOG_BITS_IN_PAGE, LOG_BITS_IN_SHORT, LOG_BITS_IN_WORD, LOG_BYTES_IN_ADDRESS, LOG_BYTES_IN_BOOLEAN, LOG_BYTES_IN_BYTE, LOG_BYTES_IN_CHAR, LOG_BYTES_IN_DOUBLE, LOG_BYTES_IN_EXTENT, LOG_BYTES_IN_FLOAT, LOG_BYTES_IN_INT, LOG_BYTES_IN_LONG, LOG_BYTES_IN_OFFSET, LOG_BYTES_IN_PAGE, LOG_BYTES_IN_SHORT, LOG_BYTES_IN_WORD

Constructor Summary
`ObjectModel()`

Method Summary
`static Address`	`allocateArray(BootImageInterface bootImage, RVMArray array, int numElements, boolean needsIdentityHash, int identityHashValue, int alignCode)` Allocate and initialize space in the bootimage (at bootimage writing time) to be an uninitialized instance of the (array) type specified by array.
`static Address`	`allocateArray(BootImageInterface bootImage, RVMArray array, int numElements, boolean needsIdentityHash, int identityHashValue, int align, int alignCode)` Allocate and initialize space in the bootimage (at bootimage writing time) to be an uninitialized instance of the (array) type specified by array.
`static Address`	`allocateCode(BootImageInterface bootImage, RVMArray array, int numElements)` Allocate and initialize space in the bootimage (at bootimage writing time) to be an uninitialized instance of the (array) type specified by array.
`static Address`	`allocateScalar(BootImageInterface bootImage, RVMClass klass, boolean needsIdentityHash, int identityHashValue)` Allocate and initialize space in the bootimage (at bootimage writing time) to be an uninitialized instance of the (scalar) type specified by klass.
`static void`	`allocateThinLock(RVMType t)` Allocate a thin lock word for instances of the type (if they already have one, then has no effect).
`static boolean`	`attemptAvailableBits(Object o, Word oldVal, Word newVal)` An attempt on the word containing the available bits
`static void`	`baselineEmitLoadTIB(ArchitectureSpecific.Assembler asm, int dest, int object)` The following method will emit code that moves a reference to an object's TIB into a destination register.
`static int`	`bytesRequiredWhenCopied(Object obj)` how many bytes are required when the object is copied by GC?
`static int`	`bytesRequiredWhenCopied(Object fromObj, RVMArray type, int numElements)` how many bytes are needed when the array object is copied by GC?
`static int`	`bytesRequiredWhenCopied(Object fromObj, RVMClass type)` how many bytes are needed when the scalar object is copied by GC?
`static int`	`bytesUsed(Object obj)` how many bytes are used by the object?
`static int`	`bytesUsed(Object obj, RVMArray type, int numElements)` how many bytes are used by the array?
`static int`	`bytesUsed(Object obj, RVMClass type)` how many bytes are used by the scalar?
`static int`	`computeArrayHeaderSize(RVMArray type)` Compute the header size of an instance of the given type.
`static int`	`computeHeaderSize(Object ref)` Compute the header size of an object
`static int`	`computeHeaderSize(Object[] tib)` Given a TIB, compute the header size of an instance of the TIB's class
`static int`	`computeHeaderSize(RVMType type)` Compute the header size of an instance of the given type.
`static int`	`computeScalarHeaderSize(RVMClass type)` Compute the header size of an instance of the given type.
`static Offset`	`defaultThinLockOffset()` what is the default offset for a thin lock?
`static void`	`describeObject(ObjectReference addr)` For debugging.
`static void`	`dumpHeader(Object ref)` For low level debugging of GC subsystem.
`static void`	`dumpHeader(ObjectReference ptr)` For low level debugging of GC subsystem.
`static void`	`fillAlignmentGap(BootImageInterface bootImage, Address address, Extent size)` Fill an alignment gap with the alignment value
`static void`	`genericLock(Object o)` Generic lock
`static void`	`genericUnlock(Object o)` Generic unlock
`static int`	`getAlignment(RVMArray t)` Return the desired alignment of the alignment point returned by getOffsetForAlignment in instances of the argument RVMArray.
`static int`	`getAlignment(RVMArray t, Object obj)` Return the desired alignment of the alignment point returned by getOffsetForAlignment in instances of the argument RVMArray.
`static int`	`getAlignment(RVMClass t)` Return the desired aligment of the alignment point in the object returned by getScalarOffsetForAlignment.
`static int`	`getAlignment(RVMClass t, Object obj)` Return the desired alignment of the alignment point returned by getOffsetForAlignment in instances of the argument RVMClass.
`static ObjectReference`	`getArrayFromStartAddress(Address start)` Get an object reference from the address the lowest word of the object was allocated.
`static int`	`getArrayLength(Object o)` Get the length of an array
`static Offset`	`getArrayLengthOffset()` Return the offset of the array length field from an object reference (in bytes)
`static int`	`getHeaderEndOffset()` For a reference to an object, what is the offset in bytes to the last word of the header from an out-to-in perspective for the object?
`static Lock`	`getHeavyLock(Object o, boolean create)` Obtains the heavy-weight lock, if there is one, associated with the indicated object.
`static ObjectReference`	`getNextObject(ObjectReference obj)` Get the next object in the heap under contiguous allocation.
`static ObjectReference`	`getNextObject(ObjectReference obj, RVMArray type, int numElements)` Get the next object after this array under contiguous allocation.
`static ObjectReference`	`getNextObject(ObjectReference obj, RVMClass type)` Get the next object after this scalar under contiguous allocation.
`static Address`	`getObjectEndAddress(Object obj)` Get the pointer just past an object
`static Address`	`getObjectEndAddress(Object object, RVMArray type, int elements)` Get the pointer just past an object
`static Address`	`getObjectEndAddress(Object object, RVMClass type)` Get the pointer just past an object
`static ObjectReference`	`getObjectFromStartAddress(Address start)` Get an object reference from the address the lowest word of the object was allocated.
`static int`	`getObjectHashCode(Object o)` Get the hash code of an object.
`static RVMType`	`getObjectType(Object o)` Get the type of an object.
`static int`	`getOffsetForAlignment(RVMArray t, boolean needsIdentityHash)` Return the offset relative to physical beginning of object that must be aligned.
`static int`	`getOffsetForAlignment(RVMArray t, ObjectReference obj)` Return the offset relative to physical beginning of object that must be aligned.
`static int`	`getOffsetForAlignment(RVMClass t, boolean needsIdentityHash)` Return the offset relative to physical beginning of object that must be aligned.
`static int`	`getOffsetForAlignment(RVMClass t, ObjectReference obj)` Return the offset relative to physical beginning of object that must be aligned.
`static Address`	`getPointerInMemoryRegion(ObjectReference ref)` Given a reference, return an address which is guaranteed to be inside the memory region allocated to the object.
`static Object`	`getReferenceWhenCopiedTo(Object obj, Address to)` how many bytes are used by the object?
`static Object`	`getReferenceWhenCopiedTo(Object obj, Address region, RVMArray type)` Get the reference of an object after copying to a specified region.
`static Object`	`getReferenceWhenCopiedTo(Object obj, Address region, RVMClass type)` Get the reference of an object after copying to a specified region.
`static ObjectReference`	`getScalarFromStartAddress(Address start)` Get an object reference from the address the lowest word of the object was allocated.
`static Offset`	`getThinLockOffset(Object o)` Get the offset of the thin lock word in this object
`static TIB`	`getTIB(Object o)` Get the TIB for an object.
`static TIB`	`getTIB(ObjectReference ptr)` Get the TIB for an object.
`static boolean`	`holdsLock(Object obj, RVMThread thread)`
`static Object`	`initializeArray(Address ptr, TIB tib, int numElems, int size)` Initialize raw storage with low memory word ptr of size bytes to be an uninitialized instance of the array type specific by tib with numElems elements.
`static void`	`initializeAvailableByte(Object o)` Freeze the other bits in the byte containing the available bits so that it is safe to update them using setAvailableBits.
`static Object`	`initializeScalar(Address ptr, TIB tib, int size)` Initialize raw storage with low memory word ptr of size bytes to be an uninitialized instance of the (scalar) type specified by tib.
`static void`	`layoutInstanceFields(RVMClass klass)` Layout the instance fields declared in this class.
`static Address`	`maximumObjectRef(Address regionHighAddr)` Given the largest base address in a region, return the largest object reference that could refer to an object in the region.
`static Address`	`minimumObjectRef(Address regionBaseAddr)` Given the smallest base address in a region, return the smallest object reference that could refer to an object in the region.
`static Object`	`moveObject(Address toAddress, Object fromObj, int numBytes, RVMArray type)` Copy an array object to the given raw storage address
`static Object`	`moveObject(Address toAddress, Object fromObj, int numBytes, RVMClass type)` Copy a scalar object to the given raw storage address
`static Object`	`moveObject(Object fromObj, Object toObj, int numBytes, RVMArray type)` Copy an array object to the given raw storage address
`static Object`	`moveObject(Object fromObj, Object toObj, int numBytes, RVMClass type)` Copy a scalar object to the given raw storage address
`static int`	`objectStartOffset(RVMClass t)` For a reference to an object, what is the offset in bytes to the bottom word of the object?
`static Address`	`objectStartRef(ObjectReference obj)` Map from the object ref to the lowest address of the storage associated with the object
`static Word`	`prepareAvailableBits(Object o)` A prepare on the word containing the available bits
`static Word`	`readAvailableBitsWord(Object o)` Non-atomic read of word containing available bits
`static byte`	`readAvailableByte(Object o)` Non-atomic read of byte containing available bits
`static void`	`setArrayLength(Object o, int len)` Set the length of an array
`static void`	`setAvailableBit(Object o, int idx, boolean flag)` Set argument bit to 1 if flag is true, 0 if flag is false
`static void`	`setTIB(BootImageInterface bootImage, Address refAddress, Address tibAddr, RVMType type)` Set the TIB for an object.
`static void`	`setTIB(ObjectReference ptr, TIB tib)` Set the TIB for an object.
`static void`	`setTIB(Object ref, TIB tib)` Set the TIB for an object.
`static boolean`	`testAvailableBit(Object o, int idx)` Return true if argument bit is 1, false if it is 0
`static void`	`writeAvailableBitsWord(Object o, Word val)` Non-atomic write of word containing available bits
`static void`	`writeAvailableByte(Object o, byte val)` Non-atomic write of byte containing available bits

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

HASH_STATS

public static final boolean HASH_STATS

Should we gather stats on hash code state transitions for address-based hashing?

See Also:: Constant Field Values

hashRequests

public static int hashRequests

count number of Object.hashCode() operations

hashTransition1

public static int hashTransition1

count transitions from UNHASHED to HASHED

hashTransition2

public static int hashTransition2

count transitions from HASHED to HASHED_AND_MOVED

PACKED

private static final boolean PACKED

Whether to pack bytes and shorts into 32bit fields

See Also:: Constant Field Values

layout

private static final FieldLayout layout

Layout widget

Constructor Detail

ObjectModel

public ObjectModel()

Method Detail

layoutInstanceFields

public static void layoutInstanceFields(RVMClass klass)

Layout the instance fields declared in this class.

Parameters:: klass - the class to layout

getPointerInMemoryRegion

public static Address getPointerInMemoryRegion(ObjectReference ref)

Given a reference, return an address which is guaranteed to be inside the memory region allocated to the object.

getArrayLengthOffset

public static Offset getArrayLengthOffset()

Return the offset of the array length field from an object reference (in bytes)

getTIB

public static TIB getTIB(ObjectReference ptr)

Get the TIB for an object.

getTIB

public static TIB getTIB(Object o)

Get the TIB for an object.

setTIB

public static void setTIB(ObjectReference ptr,
                          TIB tib)

Set the TIB for an object.

setTIB

public static void setTIB(Object ref,
                          TIB tib)

Set the TIB for an object.

setTIB

public static void setTIB(BootImageInterface bootImage,
                          Address refAddress,
                          Address tibAddr,
                          RVMType type)

Set the TIB for an object.

getObjectEndAddress

public static Address getObjectEndAddress(Object obj)

Get the pointer just past an object

getObjectEndAddress

public static Address getObjectEndAddress(Object object,
                                          RVMClass type)

Get the pointer just past an object

getObjectEndAddress

public static Address getObjectEndAddress(Object object,
                                          RVMArray type,
                                          int elements)

Get the pointer just past an object

getObjectFromStartAddress

public static ObjectReference getObjectFromStartAddress(Address start)

Get an object reference from the address the lowest word of the object was allocated.

getScalarFromStartAddress

public static ObjectReference getScalarFromStartAddress(Address start)

Get an object reference from the address the lowest word of the object was allocated.

getArrayFromStartAddress

public static ObjectReference getArrayFromStartAddress(Address start)

Get an object reference from the address the lowest word of the object was allocated.

getNextObject

public static ObjectReference getNextObject(ObjectReference obj)

Get the next object in the heap under contiguous allocation.

getNextObject

public static ObjectReference getNextObject(ObjectReference obj,
                                            RVMClass type)

Get the next object after this scalar under contiguous allocation.

getNextObject

public static ObjectReference getNextObject(ObjectReference obj,
                                            RVMArray type,
                                            int numElements)

Get the next object after this array under contiguous allocation.

getReferenceWhenCopiedTo

public static Object getReferenceWhenCopiedTo(Object obj,
                                              Address to)

how many bytes are used by the object?

bytesUsed

public static int bytesUsed(Object obj)

how many bytes are used by the object?

bytesUsed

public static int bytesUsed(Object obj,
                            RVMClass type)

how many bytes are used by the scalar?

bytesUsed

public static int bytesUsed(Object obj,
                            RVMArray type,
                            int numElements)

how many bytes are used by the array?

bytesRequiredWhenCopied

public static int bytesRequiredWhenCopied(Object obj)

how many bytes are required when the object is copied by GC?

bytesRequiredWhenCopied

public static int bytesRequiredWhenCopied(Object fromObj,
                                          RVMClass type)

how many bytes are needed when the scalar object is copied by GC?

bytesRequiredWhenCopied

public static int bytesRequiredWhenCopied(Object fromObj,
                                          RVMArray type,
                                          int numElements)

how many bytes are needed when the array object is copied by GC?

objectStartRef

public static Address objectStartRef(ObjectReference obj)

Map from the object ref to the lowest address of the storage associated with the object

getReferenceWhenCopiedTo

public static Object getReferenceWhenCopiedTo(Object obj,
                                              Address region,
                                              RVMClass type)

Get the reference of an object after copying to a specified region.

getReferenceWhenCopiedTo

public static Object getReferenceWhenCopiedTo(Object obj,
                                              Address region,
                                              RVMArray type)

Get the reference of an object after copying to a specified region.

moveObject

public static Object moveObject(Object fromObj,
                                Object toObj,
                                int numBytes,
                                RVMClass type)

Copy a scalar object to the given raw storage address

moveObject

public static Object moveObject(Object fromObj,
                                Object toObj,
                                int numBytes,
                                RVMArray type)

Copy an array object to the given raw storage address

moveObject

public static Object moveObject(Address toAddress,
                                Object fromObj,
                                int numBytes,
                                RVMClass type)

Copy a scalar object to the given raw storage address

moveObject

public static Object moveObject(Address toAddress,
                                Object fromObj,
                                int numBytes,
                                RVMArray type)

Copy an array object to the given raw storage address

getObjectType

public static RVMType getObjectType(Object o)

Get the type of an object.

getArrayLength

public static int getArrayLength(Object o)

Get the length of an array

setArrayLength

public static void setArrayLength(Object o,
                                  int len)

Set the length of an array

getObjectHashCode

public static int getObjectHashCode(Object o)

Get the hash code of an object.

getThinLockOffset

public static Offset getThinLockOffset(Object o)

Get the offset of the thin lock word in this object

defaultThinLockOffset

public static Offset defaultThinLockOffset()

what is the default offset for a thin lock?

allocateThinLock

public static void allocateThinLock(RVMType t)

Allocate a thin lock word for instances of the type (if they already have one, then has no effect).

genericLock

public static void genericLock(Object o)

Generic lock

genericUnlock

public static void genericUnlock(Object o)

Generic unlock

holdsLock

public static boolean holdsLock(Object obj,
                                RVMThread thread)

Parameters:: obj - an object; thread - a thread
Returns:: true if the lock on obj is currently owned by thread false if it is not.

getHeavyLock

public static Lock getHeavyLock(Object o,
                                boolean create)

Obtains the heavy-weight lock, if there is one, associated with the indicated object. Returns null, if there is no heavy-weight lock associated with the object.

Parameters:: o - the object from which a lock is desired; create - if true, create heavy lock if none found
Returns:: the heavy-weight lock on the object (if any)

readAvailableBitsWord

public static Word readAvailableBitsWord(Object o)

Non-atomic read of word containing available bits

readAvailableByte

public static byte readAvailableByte(Object o)

Non-atomic read of byte containing available bits

writeAvailableBitsWord

public static void writeAvailableBitsWord(Object o,
                                          Word val)

Non-atomic write of word containing available bits

writeAvailableByte

public static void writeAvailableByte(Object o,
                                      byte val)

Non-atomic write of byte containing available bits

testAvailableBit

public static boolean testAvailableBit(Object o,
                                       int idx)

Return true if argument bit is 1, false if it is 0

setAvailableBit

public static void setAvailableBit(Object o,
                                   int idx,
                                   boolean flag)

Set argument bit to 1 if flag is true, 0 if flag is false

initializeAvailableByte

public static void initializeAvailableByte(Object o)

Freeze the other bits in the byte containing the available bits so that it is safe to update them using setAvailableBits.

prepareAvailableBits

public static Word prepareAvailableBits(Object o)

A prepare on the word containing the available bits

attemptAvailableBits

public static boolean attemptAvailableBits(Object o,
                                           Word oldVal,
                                           Word newVal)

An attempt on the word containing the available bits

minimumObjectRef

public static Address minimumObjectRef(Address regionBaseAddr)

Given the smallest base address in a region, return the smallest object reference that could refer to an object in the region.

maximumObjectRef

public static Address maximumObjectRef(Address regionHighAddr)

Given the largest base address in a region, return the largest object reference that could refer to an object in the region.

computeHeaderSize

public static int computeHeaderSize(RVMType type)

Compute the header size of an instance of the given type.

computeHeaderSize

public static int computeHeaderSize(Object ref)

Compute the header size of an object

computeScalarHeaderSize

public static int computeScalarHeaderSize(RVMClass type)

Compute the header size of an instance of the given type.

computeArrayHeaderSize

public static int computeArrayHeaderSize(RVMArray type)

Compute the header size of an instance of the given type.

computeHeaderSize

public static int computeHeaderSize(Object[] tib)

Given a TIB, compute the header size of an instance of the TIB's class

getHeaderEndOffset

public static int getHeaderEndOffset()

For a reference to an object, what is the offset in bytes to the last word of the header from an out-to-in perspective for the object?

objectStartOffset

public static int objectStartOffset(RVMClass t)

For a reference to an object, what is the offset in bytes to the bottom word of the object?

getAlignment

public static int getAlignment(RVMClass t)

Return the desired aligment of the alignment point in the object returned by getScalarOffsetForAlignment.

Parameters:: t - RVMClass instance being created

getAlignment

public static int getAlignment(RVMClass t,
                               Object obj)

Return the desired alignment of the alignment point returned by getOffsetForAlignment in instances of the argument RVMClass.

Parameters:: t - RVMClass instance being copied; obj - the object being copied

getAlignment

public static int getAlignment(RVMArray t)

Return the desired alignment of the alignment point returned by getOffsetForAlignment in instances of the argument RVMArray.

Parameters:: t - RVMArray instance being created

getAlignment

public static int getAlignment(RVMArray t,
                               Object obj)

Return the desired alignment of the alignment point returned by getOffsetForAlignment in instances of the argument RVMArray.

Parameters:: t - RVMArray instance being copied; obj - the object being copied

getOffsetForAlignment

public static int getOffsetForAlignment(RVMClass t,
                                        boolean needsIdentityHash)

Return the offset relative to physical beginning of object that must be aligned.

Parameters:: t - RVMClass instance being created

getOffsetForAlignment

public static int getOffsetForAlignment(RVMClass t,
                                        ObjectReference obj)

Return the offset relative to physical beginning of object that must be aligned.

Parameters:: t - RVMClass instance being copied; obj - the object being copied

getOffsetForAlignment

public static int getOffsetForAlignment(RVMArray t,
                                        boolean needsIdentityHash)

Return the offset relative to physical beginning of object that must be aligned.

Parameters:: t - RVMArray instance being created

getOffsetForAlignment

public static int getOffsetForAlignment(RVMArray t,
                                        ObjectReference obj)

Return the offset relative to physical beginning of object that must be aligned.

Parameters:: t - RVMArray instance being copied; obj - the object being copied

initializeScalar

public static Object initializeScalar(Address ptr,
                                      TIB tib,
                                      int size)

Initialize raw storage with low memory word ptr of size bytes to be an uninitialized instance of the (scalar) type specified by tib.

Parameters:: ptr - address of raw storage; tib - the type information block; size - number of bytes of raw storage allocated.

allocateScalar

public static Address allocateScalar(BootImageInterface bootImage,
                                     RVMClass klass,
                                     boolean needsIdentityHash,
                                     int identityHashValue)

Allocate and initialize space in the bootimage (at bootimage writing time) to be an uninitialized instance of the (scalar) type specified by klass. NOTE: TIB is set by BootImageWriter2

Parameters:: bootImage - the bootimage to put the object in; klass - the RVMClass object of the instance to create.; needsIdentityHash - needs an identity hash value; identityHashValue - the value for the identity hash
Returns:: the offset of object in bootimage (in bytes)

fillAlignmentGap

public static void fillAlignmentGap(BootImageInterface bootImage,
                                    Address address,
                                    Extent size)

Fill an alignment gap with the alignment value

initializeArray

public static Object initializeArray(Address ptr,
                                     TIB tib,
                                     int numElems,
                                     int size)

Initialize raw storage with low memory word ptr of size bytes to be an uninitialized instance of the array type specific by tib with numElems elements.

Parameters:: ptr - address of raw storage; tib - the type information block; numElems - number of elements in the array; size - number of bytes of raw storage allocated.

allocateArray

public static Address allocateArray(BootImageInterface bootImage,
                                    RVMArray array,
                                    int numElements,
                                    boolean needsIdentityHash,
                                    int identityHashValue,
                                    int alignCode)

Allocate and initialize space in the bootimage (at bootimage writing time) to be an uninitialized instance of the (array) type specified by array. NOTE: TIB is set by BootimageWriter2

Parameters:: bootImage - the bootimage to put the object in; array - RVMArray object of array being allocated.; numElements - number of elements; needsIdentityHash - needs an identity hash value; identityHashValue - the value for the identity hash; alignCode - TODO
Returns:: Address of object in bootimage (in bytes)

allocateArray

public static Address allocateArray(BootImageInterface bootImage,
                                    RVMArray array,
                                    int numElements,
                                    boolean needsIdentityHash,
                                    int identityHashValue,
                                    int align,
                                    int alignCode)

Allocate and initialize space in the bootimage (at bootimage writing time) to be an uninitialized instance of the (array) type specified by array. NOTE: TIB is set by BootimageWriter2

Parameters:: bootImage - the bootimage to put the object in; array - RVMArray object of array being allocated.; numElements - number of elements; needsIdentityHash - needs an identity hash value; identityHashValue - the value for the identity hash; alignCode - TODO
Returns:: Address of object in bootimage (in bytes)

allocateCode

public static Address allocateCode(BootImageInterface bootImage,
                                   RVMArray array,
                                   int numElements)

Allocate and initialize space in the bootimage (at bootimage writing time) to be an uninitialized instance of the (array) type specified by array. NOTE: TIB is set by BootimageWriter2

Parameters:: bootImage - the bootimage to put the object in; array - RVMArray object of array being allocated.; numElements - number of elements
Returns:: Address of object in bootimage

dumpHeader

public static void dumpHeader(ObjectReference ptr)

For low level debugging of GC subsystem. Dump the header word(s) of the given object reference.

Parameters:: ptr - the object reference whose header should be dumped

dumpHeader

public static void dumpHeader(Object ref)

For low level debugging of GC subsystem. Dump the header word(s) of the given object reference.

Parameters:: ref - the object reference whose header should be dumped

describeObject

public static void describeObject(ObjectReference addr)

For debugging.

baselineEmitLoadTIB

public static void baselineEmitLoadTIB(ArchitectureSpecific.Assembler asm,
                                       int dest,
                                       int object)

The following method will emit code that moves a reference to an object's TIB into a destination register.

Parameters:: asm - the assembler object to emit code with; dest - the number of the destination register; object - the number of the register holding the object reference

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org.jikesrvm.objectmodel Class ObjectModel

HASH_STATS

hashRequests

hashTransition1

hashTransition2

PACKED

layout

ObjectModel

layoutInstanceFields

getPointerInMemoryRegion

getArrayLengthOffset

getTIB

getTIB

setTIB

setTIB

setTIB

getObjectEndAddress

getObjectEndAddress

getObjectEndAddress

getObjectFromStartAddress

getScalarFromStartAddress

getArrayFromStartAddress

getNextObject

getNextObject

getNextObject

getReferenceWhenCopiedTo

bytesUsed

bytesUsed

bytesUsed

bytesRequiredWhenCopied

bytesRequiredWhenCopied

bytesRequiredWhenCopied

objectStartRef

getReferenceWhenCopiedTo

getReferenceWhenCopiedTo

moveObject

moveObject

moveObject

moveObject

getObjectType

getArrayLength

setArrayLength

getObjectHashCode

getThinLockOffset

defaultThinLockOffset

allocateThinLock

genericLock

genericUnlock

holdsLock

getHeavyLock

readAvailableBitsWord

readAvailableByte

writeAvailableBitsWord

writeAvailableByte

testAvailableBit

setAvailableBit

initializeAvailableByte

prepareAvailableBits

attemptAvailableBits

minimumObjectRef

maximumObjectRef

computeHeaderSize

computeHeaderSize

computeScalarHeaderSize

computeArrayHeaderSize

computeHeaderSize

getHeaderEndOffset

objectStartOffset

getAlignment

getAlignment

getAlignment

getAlignment

getOffsetForAlignment

getOffsetForAlignment

getOffsetForAlignment

getOffsetForAlignment

initializeScalar

allocateScalar

fillAlignmentGap

initializeArray

org.jikesrvm.objectmodel
Class ObjectModel