org.jikesrvm.compilers.opt.runtimesupport
Class OptGCMap

java.lang.Object
  org.jikesrvm.compilers.opt.runtimesupport.OptGCMap

All Implemented Interfaces:

ArchitectureSpecificOpt.OptGCMapIteratorConstants, PhysicalRegisterConstants, OptGCMapIteratorConstants, RegisterConstants

public final class OptGCMap
extends Object
implements ArchitectureSpecificOpt.OptGCMapIteratorConstants

A class that encapsulates the GCMap portion of the machine code maps. An instance of this class is created to encode and instance of a GCIRMap into an int[]. The int[] is stored persistently, but the instance of the OptGCMap is NOT.

• each map will be a sequence of 1 or more ints
• the first int in each map is a bit map of registers that contain references (the MSB is used for chaining, we assume it will never contain a reference)
• the remaining ints will be spill locations
• the sequence will continue as long as the most significant bit is set to 1

• 1) methods called during compilation to create the GC maps these methods are virtual
• 2) methods called at GC time (no allocation allowed!) these methods are static

NO_MAP_ENTRY

public static final int NO_MAP_ENTRY

See Also:

Constant Field Values

ERROR

public static final int ERROR

See Also:

Constant Field Values

INITIAL_MAP_SIZE

public static final int INITIAL_MAP_SIZE

The initial allocation size for a map

See Also:

Constant Field Values

NEXT_BIT

private static final int NEXT_BIT

bit pattern for the "next" bit in the GC maps array

See Also:

Constant Field Values

lastGCMapEntry

private int lastGCMapEntry

the index of the last map entry in use

gcMapInformation

private int[] gcMapInformation

The gc map array, a sequence of gc maps. Each sequence starts with a register bit mask and is followed by a list of spills. The most significant bit of the spill location is used to chain the list.

DEBUG

public static final boolean DEBUG

See Also:

Constant Field Values

OptGCMap

OptGCMap()

Constructor, called during compilation

finish

public int[] finish()

Called to complete the encoding and return the final int[]

generateGCMapEntry

public int generateGCMapEntry(GCIRMapElement irMapElem)

Construct the GCMap for the argument GCIRMapElement

Parameters:

irMapElem - The IR Map element to create a GCMap for

Returns:

the GCMap index.

gcMapInformation

public static int gcMapInformation(int entry,
                                   int[] gcMap)

Returns the GC map information for the GC map information entry passed

Parameters:

entry - map entry

gcMap - the gc map

registerIsSet

public static boolean registerIsSet(int entry,
                                    int registerNumber,
                                    int[] gcMap)

Determines if the register map information for the entry passed is true

Parameters:

entry - map entry

registerNumber - the register number

gcMap - the encoded GCMap

nextLocation

public static int nextLocation(int currentIndex,
                               int[] gcMap)

Parameters:

gcMap - the encoded GCMap

Returns:

the next (relative) location or -1 for no more locations

getRegBitPosition

private static int getRegBitPosition(int registerNumber)

This method maps a register number to its bit position

Parameters:

registerNumber - the register number of interest

nextBitSet

private static boolean nextBitSet(int entry,
                                  int[] gcMap)

Determines if the next bit is set for the entry passed in the gc map passed

Parameters:

entry - the entry (index) to check

gcMap - the gcmap

Returns:

whether the next bit is set

dumpMap

public static void dumpMap(int entry,
                           int[] gcMap)

Dumps the GCmap that starts at entry.

Parameters:

entry - the entry where the map begins

gcMap - the encoded GCmaps

getNextMapEntry

private int getNextMapEntry()

Returns the next GC map entry for use

Returns:

the entry in the map table that can be used

resizeMapInformation

private void resizeMapInformation(int newSize)

Resize the map array

Parameters:

newSize - the new size for the map array

setRegisterBitMap

private int setRegisterBitMap(int bitMap)

Sets the register map information at the next available entry

Parameters:

bitMap - map entry

Returns:

The index of that entry.

addAllSpills

private void addAllSpills(int[] spillArray)

If we will be looking for missed references we need to sort the list of spills and then add them to the map, otherwise, nothing to do

Parameters:

spillArray - an array of spills

addSpillLocation

private void addSpillLocation(int spill)

Adds the passed spill value to the current map

Parameters:

spill - the spill location

endCurrentMap

private int endCurrentMap(int firstIndex)

Ends the current map

Parameters:

firstIndex - the index of the beginning of the map

Returns:

the index of the beginning of the map (may be different)