soot.jimple.toolkits.pointer
Class LocalMustNotAliasAnalysis

java.lang.Object
  soot.toolkits.scalar.AbstractFlowAnalysis<N,A>
      soot.toolkits.scalar.FlowAnalysis<N,A>
          soot.toolkits.scalar.ForwardFlowAnalysis
              soot.jimple.toolkits.pointer.LocalMustNotAliasAnalysis

public class LocalMustNotAliasAnalysis
extends ForwardFlowAnalysis

LocalNotMayAliasAnalysis attempts to determine if two local variables (at two potentially different program points) definitely point to different objects. The underlying abstraction is that of definition expressions. When a local variable gets assigned a new object (unlike LocalMust, only NewExprs), the analysis tracks the source of the value. If two variables have different sources, then they are different. See Sable TR 2007-8 for details.

Author:

Patrick Lam

Field Summary

protected Set<Local>	locals
protected static Object	UNKNOWN

Fields inherited from class soot.toolkits.scalar.FlowAnalysis

filterUnitToAfterFlow, unitToAfterFlow

Fields inherited from class soot.toolkits.scalar.AbstractFlowAnalysis

filterUnitToBeforeFlow, graph, unitToBeforeFlow

Constructor Summary

LocalMustNotAliasAnalysis(UnitGraph g)

Method Summary

protected void	copy(Object source, Object dest) Creates a copy of the source flow object in dest.
protected Object	entryInitialFlow() Returns the initial flow value for entry/exit graph nodes.
protected void	flowThrough(Object inValue, Object unit, Object outValue) Given the merge of the out sets, compute the in set for s (or in to out, depending on direction).
boolean	hasInfoOn(Local l, Stmt s) Returns true if this analysis has any information about local l at statement s (i.e.
protected void	merge(Object in1, Object in2, Object o) Compute the merge of the in1 and in2 sets, putting the result into out.
protected Object	newInitialFlow() Returns the flow object corresponding to the initial values for each graph node.
boolean	notMayAlias(Local l1, Stmt s1, Local l2, Stmt s2)

Methods inherited from class soot.toolkits.scalar.ForwardFlowAnalysis

constructWorklist, doAnalysis, isForward

Methods inherited from class soot.toolkits.scalar.FlowAnalysis

constructOrderer, getFlowAfter

Methods inherited from class soot.toolkits.scalar.AbstractFlowAnalysis

getFlowBefore, merge, mergeInto, treatTrapHandlersAsEntries

Methods inherited from class java.lang.Object

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

Field Detail

UNKNOWN

protected static final Object UNKNOWN

locals

protected Set<Local> locals

Constructor Detail

LocalMustNotAliasAnalysis

public LocalMustNotAliasAnalysis(UnitGraph g)

Method Detail

merge

protected void merge(Object in1,
                     Object in2,
                     Object o)

Description copied from class: AbstractFlowAnalysis

Compute the merge of the in1 and in2 sets, putting the result into out. The behavior of this function depends on the implementation ( it may be necessary to check whether in1 and in2 are equal or aliased ). Used by the doAnalysis method.

Specified by:

merge in class AbstractFlowAnalysis

flowThrough

protected void flowThrough(Object inValue,
                           Object unit,
                           Object outValue)

Description copied from class: FlowAnalysis

Given the merge of the out sets, compute the in set for s (or in to out, depending on direction). This function often causes confusion, because the same interface is used for both forward and backward flow analyses. The first parameter is always the argument to the flow function (i.e. it is the "in" set in a forward analysis and the "out" set in a backward analysis), and the third parameter is always the result of the flow function (i.e. it is the "out" set in a forward analysis and the "in" set in a backward analysis).

Specified by:

flowThrough in class FlowAnalysis

copy

protected void copy(Object source,
                    Object dest)

Description copied from class: AbstractFlowAnalysis

Creates a copy of the source flow object in dest.

Specified by:

copy in class AbstractFlowAnalysis

entryInitialFlow

protected Object entryInitialFlow()

Description copied from class: AbstractFlowAnalysis

Returns the initial flow value for entry/exit graph nodes.

Specified by:

entryInitialFlow in class AbstractFlowAnalysis

newInitialFlow

protected Object newInitialFlow()

Description copied from class: AbstractFlowAnalysis

Returns the flow object corresponding to the initial values for each graph node.

Specified by:

newInitialFlow in class AbstractFlowAnalysis

hasInfoOn

public boolean hasInfoOn(Local l,
                         Stmt s)

Returns true if this analysis has any information about local l at statement s (i.e. it is not UNKNOWN). In particular, it is safe to pass in locals/statements that are not even part of the right method. In those cases false will be returned. Permits s to be null, in which case false will be returned.

notMayAlias

public boolean notMayAlias(Local l1,
                           Stmt s1,
                           Local l2,
                           Stmt s2)

Returns:

true if values of l1 (at s1) and l2 (at s2) are known to point to different objects