gov.nasa.jpf.jvm.bytecode

Class IfInstruction

java.lang.Object

gov.nasa.jpf.vm.Instruction

gov.nasa.jpf.jvm.bytecode.IfInstruction

All Implemented Interfaces:

JVMInstruction, Attributable, InstructionInterface, java.lang.Cloneable

Direct Known Subclasses:

IF_ACMPEQ, IF_ACMPNE, IF_ICMPEQ, IF_ICMPGE, IF_ICMPGT, IF_ICMPLE, IF_ICMPLT, IF_ICMPNE, IFEQ, IFGE, IFGT, IFLE, IFLT, IFNE, IFNONNULL, IFNULL

public abstract class IfInstruction
extends Instruction
implements JVMInstruction

abstraction for all comparison instructions

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	conditionValue
protected Instruction	target
protected int	targetPosition

Fields inherited from class gov.nasa.jpf.vm.Instruction

attr, insnIndex, mi, position

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	IfInstruction(int targetPosition) value of last evaluation of branch condition

Method Summary

Modifier and Type	Method and Description
void	accept(JVMInstructionVisitor insVisitor)
Instruction	execute(ThreadInfo ti) this is the real workhorse returns next instruction to enter in this thread <2do> it's unfortunate we roll every side effect into this method, because it diminishes the value of the 'executeInstruction' notification: all insns that require some sort of late binding (InvokeVirtual, GetField, ..) are not yet fully analyzable (e.g.
protected Instruction	executeBothBranches(SystemState ss, KernelState ks, ThreadInfo ti) use this as a delegatee in overridden executes of derived IfInstructions (e.g.
boolean	getConditionValue() return which branch was taken.
int	getLength() return the length in bytes of this instruction.
Instruction	getTarget()
boolean	isBackJump() Added so that SimpleIdleFilter can detect do-while loops when the while statement evaluates to true.
abstract boolean	popConditionValue(StackFrame frame) retrieve value of jump condition from operand stack (not ideal to have this public, but some listeners might need it for skipping the insn, plus we require it for subclass factorization)
java.lang.String	toString()
Instruction	typeSafeClone(MethodInfo mi) this is overridden by any Instruction that use a cache for class or method to provide a type safe cloning

Methods inherited from class gov.nasa.jpf.vm.Instruction

addAttr, asInstruction, attrIterator, attrIterator, cleanupTransients, getAttr, getAttr, getFileLocation, getFilePos, getInstructionIndex, getLineNumber, getMethodInfo, getMnemonic, getNext, getNext, getNextAttr, getPosition, getPrev, getSourceLine, getSourceLocation, getSourceOrLocation, hasAttr, hasAttr, init, isCompleted, isExtendedInstruction, isFirstInstruction, isMonitorEnterPrologue, isSchedulingRelevant, removeAttr, replaceAttr, requiresClinitExecution, setAttr, setContext, setLocation, setMethodInfo, toPostExecString

Methods inherited from class java.lang.Object

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

Methods inherited from interface gov.nasa.jpf.vm.bytecode.InstructionInterface

asInstruction, getByteCode, getFileLocation, getFilePos, getInstructionIndex, getLineNumber, getMethodInfo, getMnemonic, getNext, getNext, getPosition, getPrev, getSourceLine, getSourceLocation, isCompleted, isExtendedInstruction, isFirstInstruction, toPostExecString

Methods inherited from interface gov.nasa.jpf.util.Attributable

addAttr, attrIterator, attrIterator, getAttr, getAttr, getNextAttr, hasAttr, hasAttr, removeAttr, replaceAttr, setAttr

Field Detail

targetPosition

protected int targetPosition

target

protected Instruction target

conditionValue

protected boolean conditionValue

Constructor Detail

IfInstruction

protected IfInstruction(int targetPosition)

value of last evaluation of branch condition

Method Detail

getConditionValue

public boolean getConditionValue()

return which branch was taken. Only useful after instruction got executed WATCH OUT - 'true' means the jump condition is met, which logically is the 'false' branch

isBackJump

public boolean isBackJump()

Added so that SimpleIdleFilter can detect do-while loops when the while statement evaluates to true.

Specified by:

isBackJump in interface InstructionInterface

Overrides:

isBackJump in class Instruction

popConditionValue

public abstract boolean popConditionValue(StackFrame frame)

retrieve value of jump condition from operand stack (not ideal to have this public, but some listeners might need it for skipping the insn, plus we require it for subclass factorization)

getTarget

public Instruction getTarget()

execute

public Instruction execute(ThreadInfo ti)

Description copied from class: Instruction

this is the real workhorse returns next instruction to enter in this thread <2do> it's unfortunate we roll every side effect into this method, because it diminishes the value of the 'executeInstruction' notification: all insns that require some sort of late binding (InvokeVirtual, GetField, ..) are not yet fully analyzable (e.g. the callee of InvokeVirtuals is not known yet), putting the burden of duplicating the related code of enter() in the listener. It would be better if we factor this 'prepareExecution' out of enter()

Specified by:

execute in interface InstructionInterface

Specified by:

execute in class Instruction

executeBothBranches

protected Instruction executeBothBranches(SystemState ss,
                                          KernelState ks,
                                          ThreadInfo ti)

use this as a delegatee in overridden executes of derived IfInstructions (e.g. for symbolic execution)

toString

public java.lang.String toString()

Overrides:

toString in class Instruction

getLength

public int getLength()

Description copied from class: Instruction

return the length in bytes of this instruction. override if this is not 1

Specified by:

getLength in interface InstructionInterface

Overrides:

getLength in class Instruction

accept

public void accept(JVMInstructionVisitor insVisitor)

Specified by:

accept in interface JVMInstruction

typeSafeClone

public Instruction typeSafeClone(MethodInfo mi)

Description copied from class: Instruction

this is overridden by any Instruction that use a cache for class or method to provide a type safe cloning

Overrides:

typeSafeClone in class Instruction