org.jikesrvm.compilers.baseline

Class BuildBB

java.lang.Object

org.jikesrvm.compilers.baseline.BuildBB

final class BuildBB
extends Object

Analyze the byte codes and determine the boundaries of the basic blocks. Used for building the reference maps for a method.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private static class	BuildBB.InstructionType Types of Instructions

Field Summary

Fields

Modifier and Type	Field and Description
(package private) BasicBlock[]	basicBlocks
(package private) BasicBlockFactory	bbf basic blocks of the byte code
(package private) int	bytelength
(package private) short[]	byteToBlockMap identify which block a byte is part of
(package private) int	gcPointCount Number of GC points found
(package private) int	numJsrs Number of unique jsr targets processed

Constructor Summary

Constructors

Constructor and Description
BuildBB(NormalMethod method) Analyzes the bytecodes and builds the basic blocks with their predecessors.

Method Summary

Modifier and Type	Method and Description
private void	addBasicBlock(BasicBlock newBB) Adds a basic block.
private void	findAndSetJSRCallSite(int pred, BasicBlock retBB, int otherRetCount, boolean[] seenAlready) Scans back from ret instruction to jsr call sites.
private void	markTryBlocks(ExceptionHandlerMap exceptions) Mark all the blocks within try range as being Try blocks used for determining the stack maps for Handler blocks Only called when exceptions is not null.
private void	processAthrow(ExceptionHandlerMap exceptions, int athrowIndex) Check if an athrow is within a try block, if it is, then handlers have this block as their predecessor; which is registered in "processExceptionHandlers" Otherwise, the athrow acts as a branch to the exit and that should be marked here.
private void	processBackwardBranch(int index, int branchtarget) A backwards branch has been found from the byte code at location "index" to a target location of "branchtarget".
private void	processBranchTarget(int index, int branchtarget) Processing a branch that appears at location index in the byte code and has a target index of branchtarget in the byte code.
private void	processExceptionHandlers(ExceptionHandlerMap exceptions) For every handler, mark the blocks in its try block as its predecessors.
private void	processRetList(int[] retList, int nextRetList) process the effect of the ret instructions on the precedance table
private void	setupHandlerBBs(ExceptionHandlerMap exceptions) For every handler, make a block that starts with the handler PC Only called when exceptions is not null.
private void	setupJSRCallSite(BasicBlock entryBB, BasicBlock retBB) Does the setup for a jsr call site.
private void	setupTryStartBBs(ExceptionHandlerMap exceptions) For every try start, make a block that starts with the Try start, mark it as a try start.

Methods inherited from class java.lang.Object

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

Field Detail

bbf

final BasicBlockFactory bbf

basic blocks of the byte code

basicBlocks

BasicBlock[] basicBlocks

byteToBlockMap

short[] byteToBlockMap

identify which block a byte is part of

numJsrs

int numJsrs

Number of unique jsr targets processed

gcPointCount

int gcPointCount

Number of GC points found

bytelength

int bytelength

Constructor Detail

BuildBB

BuildBB(NormalMethod method)

Analyzes the bytecodes and builds the basic blocks with their predecessors. The results will be used by BuildReferenceMaps

Parameters:

method - the method whose bytecodes will be analyzed

Method Detail

processBranchTarget

private void processBranchTarget(int index,
                                 int branchtarget)

Processing a branch that appears at location index in the byte code and has a target index of branchtarget in the byte code. The target of a branch must start a basic block. So if the byteToBlockMap doesn't already show a basic block at the target, make one start there. If a basic block is already set up and this is a branch forward then only need to adjust predecessor list (we know it is not a branch into the middle of a block as only starts are marked in byte code beyond "index"). If the basic block is already set up and this is a backward branch then we must check if the block needs splitting, branching to the middle of a block is not allowed.

Parameters:

index - the byte index of the branch instruction

branchtarget - the target byte index

processBackwardBranch

private void processBackwardBranch(int index,
                                   int branchtarget)

A backwards branch has been found from the byte code at location "index" to a target location of "branchtarget". Need to make sure that the branchtarget location is the start of a block (and if not, then split the existing block into two) Need to register the block that ends at "index" as a predecessor of the block that starts at branchtarget.

Parameters:

index - the byte index of the branch instruction

branchtarget - the target byte index

processRetList

private void processRetList(int[] retList,
                            int nextRetList)

process the effect of the ret instructions on the precedance table

Parameters:

retList - a list of basic blocks with return instructions. Each block is represented by its basic block number.

nextRetList - maximum index in the list

findAndSetJSRCallSite

private void findAndSetJSRCallSite(int pred,
                                   BasicBlock retBB,
                                   int otherRetCount,
                                   boolean[] seenAlready)

Scans back from ret instruction to jsr call sites.

Parameters:

pred - the basic block number of the predecessor block

retBB - the basic block that contains the return

otherRetCount - the number of other returns (i.e. non-matching) returns that were found on the path

seenAlready - list of blocks that have already been seen

setupJSRCallSite

private void setupJSRCallSite(BasicBlock entryBB,
                              BasicBlock retBB)

Does the setup for a jsr call site.

Parameters:

entryBB - a basic block with a jsr entry

retBB - a basic block with a matching return

setupHandlerBBs

private void setupHandlerBBs(ExceptionHandlerMap exceptions)

For every handler, make a block that starts with the handler PC Only called when exceptions is not null.

Parameters:

exceptions - exception handler information

setupTryStartBBs

private void setupTryStartBBs(ExceptionHandlerMap exceptions)

For every try start, make a block that starts with the Try start, mark it as a try start. Only called when exceptions is not null.

Parameters:

exceptions - exception handler information

processExceptionHandlers

private void processExceptionHandlers(ExceptionHandlerMap exceptions)

For every handler, mark the blocks in its try block as its predecessors. Only called when exceptions is not null.

Parameters:

exceptions - exception handler information

markTryBlocks

private void markTryBlocks(ExceptionHandlerMap exceptions)

Mark all the blocks within try range as being Try blocks used for determining the stack maps for Handler blocks Only called when exceptions is not null.

Parameters:

exceptions - exception handler information

processAthrow

private void processAthrow(ExceptionHandlerMap exceptions,
                           int athrowIndex)

Check if an athrow is within a try block, if it is, then handlers have this block as their predecessor; which is registered in "processExceptionHandlers" Otherwise, the athrow acts as a branch to the exit and that should be marked here. Note exceptions may be null.

Parameters:

exceptions - exception handler information

athrowIndex - byte index of the athrow

addBasicBlock

private void addBasicBlock(BasicBlock newBB)

Adds a basic block.

Parameters:

newBB - the block to add