jist.runtime
Class RewriterFlow

java.lang.Object
  jist.runtime.RewriterFlow

public final class RewriterFlow
extends java.lang.Object

Perform data flow analysis.

Since:

JIST1.0

Version:

$Id: RewriterFlow.java,v 1.22 2005/01/25 16:33:47 barr Exp $

Author:

Rimon Barr <barr+jist@cs.cornell.edu>

Nested Class Summary

static class	RewriterFlow.FlowInfoMap An accessor class to conveniently query data flow information.
private static class	RewriterFlow.WildcardReturnaddressType Utility class to replace BCEL's ReturnaddressType and ignore the return address when checking for type equality for stack merging purposes.

Field Summary

private org.apache.bcel.verifier.structurals.ExecutionVisitor	ev instruction execution visitor.
private org.apache.bcel.verifier.structurals.ExceptionHandlers	exInfo exception handler lookup.
private java.util.HashMap	frames frame information.
private java.util.HashMap	pointsTo pointsTo information.
private java.util.Vector	remaining remaining instructions to process.

Constructor Summary

RewriterFlow()
Create new rewriter data flow analysis object.

Method Summary

RewriterFlow.FlowInfoMap	doFlow(org.apache.bcel.generic.ClassGen cg, org.apache.bcel.generic.MethodGen mg) Perform data flow analysis to determine the frame at each execution point in the method.
private org.apache.bcel.generic.InstructionHandle[]	execute(org.apache.bcel.generic.InstructionHandle ih, org.apache.bcel.verifier.structurals.Frame f) Helper flow analysis method: "executes" a given instruction to produce the next frame, and returns all successors of this instruction.
static void	main(java.lang.String[] args) Small utility program to dump the methods of a given class file with flow information between every instruction.
private boolean	merge(org.apache.bcel.generic.InstructionHandle ih, org.apache.bcel.verifier.structurals.Frame f, org.apache.bcel.classfile.ConstantPool cp) Helper flow analysis method: merges two frames ala the VM spec, and stores result.
private org.apache.bcel.verifier.structurals.OperandStack	removeRetTargets(org.apache.bcel.verifier.structurals.OperandStack os) Replace any ReturnaddressTypes (placed on the stack by JSR) with WildcardReturnaddressTypes, so as to pass the verification performed during stack merge.
private org.apache.bcel.verifier.structurals.OperandStack	reverseStack(org.apache.bcel.verifier.structurals.OperandStack os) Reverse the operand stack.
private void	updatePointsTo(org.apache.bcel.generic.InstructionHandle from, org.apache.bcel.generic.InstructionHandle[] to) Update table of which instructions "point to" which.

Methods inherited from class java.lang.Object

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

Field Detail

remaining

private java.util.Vector remaining

remaining instructions to process.

ev

private org.apache.bcel.verifier.structurals.ExecutionVisitor ev

instruction execution visitor.

exInfo

private org.apache.bcel.verifier.structurals.ExceptionHandlers exInfo

exception handler lookup.

frames

private java.util.HashMap frames

frame information.

pointsTo

private java.util.HashMap pointsTo

pointsTo information.

Constructor Detail

RewriterFlow

public RewriterFlow()

Create new rewriter data flow analysis object.

Method Detail

doFlow

public RewriterFlow.FlowInfoMap doFlow(org.apache.bcel.generic.ClassGen cg,
                                       org.apache.bcel.generic.MethodGen mg)

Perform data flow analysis to determine the frame at each execution point in the method.

Parameters:

cg - BCEL class object

mg - BCEL method object

Returns:

flow information

execute

private org.apache.bcel.generic.InstructionHandle[] execute(org.apache.bcel.generic.InstructionHandle ih,
                                                            org.apache.bcel.verifier.structurals.Frame f)

Helper flow analysis method: "executes" a given instruction to produce the next frame, and returns all successors of this instruction.

Parameters:

ih - handle of instruction to execute

f - pre-instruction state (is modified to post-instruction state)

Returns:

list of instruction successors

merge

private boolean merge(org.apache.bcel.generic.InstructionHandle ih,
                      org.apache.bcel.verifier.structurals.Frame f,
                      org.apache.bcel.classfile.ConstantPool cp)

Helper flow analysis method: merges two frames ala the VM spec, and stores result.

Parameters:

ih - location to merge information into

f - frame to merge in

cp - class constant pool

Returns:

whether merging actually changed anything

removeRetTargets

private org.apache.bcel.verifier.structurals.OperandStack removeRetTargets(org.apache.bcel.verifier.structurals.OperandStack os)

Replace any ReturnaddressTypes (placed on the stack by JSR) with WildcardReturnaddressTypes, so as to pass the verification performed during stack merge.

Parameters:

os - input operand stack, not modified

Returns:

modified operand stack

reverseStack

private org.apache.bcel.verifier.structurals.OperandStack reverseStack(org.apache.bcel.verifier.structurals.OperandStack os)

Reverse the operand stack.

Parameters:

os - input operand stack, not modified

Returns:

reversed operand stack

updatePointsTo

private void updatePointsTo(org.apache.bcel.generic.InstructionHandle from,
                            org.apache.bcel.generic.InstructionHandle[] to)

Update table of which instructions "point to" which.

Parameters:

from - predecessor instruction

to - list of successor instructions

main

public static void main(java.lang.String[] args)

Small utility program to dump the methods of a given class file with flow information between every instruction.

Parameters:

args - list of filenames to process