org.jikesrvm.objectmodel

Class TIBLayoutConstants

java.lang.Object

org.jikesrvm.objectmodel.TIBLayoutConstants

public final class TIBLayoutConstants
extends Object

Layout the TIB (Type Information Block).

  --------------------------------------------------------------------------------------------
                        Type Information Block (TIB) Layout Constants
  --------------------------------------------------------------------------------------------

                                 Object[] (type info block)        RVMType (class info)
                                    /                              /
            +--------------------+              +--------------+
            |    TIB pointer     |              |  TIB pointer |
            +--------------------+              +--------------+
            |      status        |              |    status    |
            +--------------------+              +--------------+
            |      length        |              |    field0    |
            +--------------------+              +--------------+
    TIB:  0:|       type         +------------> |     ...      |
            +--------------------+              +--------------+
          1:|   superclass ids   +-->           |   fieldN-1   |
            +--------------------+              +--------------+
          2:|  implements trits  +-->
            +--------------------+
          3:|  array element TIB +-->
            +--------------------+
          4:|     iTABLES/IMT    +-->
            +--------------------+
          5:|  specialized 0     +-->
            +--------------------+
            |       ...          +-->
            +--------------------+
         V0:|  virtual method 0  +-----+
            +--------------------+     |
            |       ...          |     |                         INSTRUCTION[] (machine code)
            +--------------------+     |                        /
       VN-1:| virtual method N-1 |     |        +--------------+
            +--------------------+     |        |  TIB pointer |
                                       |        +--------------+
                                       |        |    status    |
                                       |        +--------------+
                                       |        |    length    |
                                       |        +--------------+
                                       +------->|    code0     |
                                                +--------------+
                                                |      ...     |
                                                +--------------+
                                                |    codeN-1   |
                                                +--------------+

 

Field Summary

Fields

Modifier and Type	Field and Description
static int	IMT_METHOD_SLOTS Number of slots reserved for interface method pointers.
static int	NEEDS_DYNAMIC_LINK Special value returned by RVMClassLoader.getFieldOffset() or RVMClassLoader.getMethodOffset() to indicate fields or methods that must be accessed via dynamic linking code because their offset is not yet known or the class's static initializer has not yet been run.
static int	TIB_ARRAY_ELEMENT_TIB_INDEX The TIB of the elements type of an array (may be null in fringe cases when element type couldn't be resolved during array resolution).
static int	TIB_DOES_IMPLEMENT_INDEX Does this class implement the ith interface?
static int	TIB_FIRST_SPECIALIZED_METHOD_INDEX A set of 0 or more specialized methods used in the VM such as for GC scanning.
static int	TIB_FIRST_VIRTUAL_METHOD_INDEX Next group of slots point to virtual method code blocks (slots V1..VN in above diagram).
static int	TIB_INTERFACE_DISPATCH_TABLE_INDEX A pointer to either an ITable or InterfaceMethodTable (IMT) depending on which dispatch implementation we are using.
static int	TIB_SUPERCLASS_IDS_INDEX A vector of ids for classes that this one extends.
static int	TIB_TYPE_INDEX First slot of TIB points to RVMType (slot 0 in above diagram).

Constructor Summary

Constructors

Modifier	Constructor and Description
private	TIBLayoutConstants()

Method Summary

Methods inherited from class java.lang.Object

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

Field Detail

IMT_METHOD_SLOTS

public static final int IMT_METHOD_SLOTS

Number of slots reserved for interface method pointers.

See Also:

Constant Field Values

TIB_TYPE_INDEX

public static final int TIB_TYPE_INDEX

First slot of TIB points to RVMType (slot 0 in above diagram).

See Also:

Constant Field Values

TIB_SUPERCLASS_IDS_INDEX

public static final int TIB_SUPERCLASS_IDS_INDEX

A vector of ids for classes that this one extends. See DynamicTypeCheck.java

See Also:

Constant Field Values

TIB_DOES_IMPLEMENT_INDEX

public static final int TIB_DOES_IMPLEMENT_INDEX

Does this class implement the ith interface? See DynamicTypeCheck.java

See Also:

Constant Field Values

TIB_ARRAY_ELEMENT_TIB_INDEX

public static final int TIB_ARRAY_ELEMENT_TIB_INDEX

The TIB of the elements type of an array (may be null in fringe cases when element type couldn't be resolved during array resolution). Will be null when not an array.

See Also:

Constant Field Values

TIB_INTERFACE_DISPATCH_TABLE_INDEX

public static final int TIB_INTERFACE_DISPATCH_TABLE_INDEX

A pointer to either an ITable or InterfaceMethodTable (IMT) depending on which dispatch implementation we are using.

See Also:

Constant Field Values

TIB_FIRST_SPECIALIZED_METHOD_INDEX

public static final int TIB_FIRST_SPECIALIZED_METHOD_INDEX

A set of 0 or more specialized methods used in the VM such as for GC scanning.

See Also:

Constant Field Values

TIB_FIRST_VIRTUAL_METHOD_INDEX

public static final int TIB_FIRST_VIRTUAL_METHOD_INDEX

Next group of slots point to virtual method code blocks (slots V1..VN in above diagram).

NEEDS_DYNAMIC_LINK

public static final int NEEDS_DYNAMIC_LINK

Special value returned by RVMClassLoader.getFieldOffset() or RVMClassLoader.getMethodOffset() to indicate fields or methods that must be accessed via dynamic linking code because their offset is not yet known or the class's static initializer has not yet been run. We choose a value that will never match a valid jtoc-, instance-, or virtual method table- offset. Short.MIN_VALUE+1 is a good value:

• the jtoc offsets are aligned and this value should be too huge to address the table
• instance field offsets are always >= -4 (TODO check if this is still correct)
• virtual method offsets are always positive w.r.t. TIB pointer
• fits into a PowerPC 16bit immediate operand

See Also:

Constant Field Values

Constructor Detail

TIBLayoutConstants

private TIBLayoutConstants()