public bool HasSinglePredecessor(APC ppoint, out APC singlePredecessor, bool skipContracts)
{
CallAdaption.Push <IEdgeSubroutineAdaptor>(this);
try
{
return(underlying.HasSinglePredecessor(ppoint, out singlePredecessor, skipContracts));
}
finally {
CallAdaption.Pop(this);
}
}
protected APC VisitBlock(APC pc, AElement preCondition, out AElement newPrecondition)
{
var pcHead = pc.FirstInBlock();
newPrecondition = preCondition;
APC prePC;
while (CFG.HasSinglePredecessor(pc, out prePC))
{
// We found the head!
if (pc.Equals(pcHead))
{
return(pcHead);
}
// nothing to do, kill search
if (this.Mdriver.BasicFacts.IsUnreachable(pc))
{
Trace("Killing path as pc is unreachable", newPrecondition);
newPrecondition = this.NoCondition;
return(pc);
}
newPrecondition = this.Mdriver.BackwardTransfer(pc, prePC, newPrecondition, this);
if (this.IsNoCondition(newPrecondition))
{
Trace("Killing path as we the underlyng analysis returned bottom", newPrecondition);
return(pc);
}
pc = prePC;
}
return(pc);
}
private void FixpointComputation(APC entry, Postconditions initialState)
{
var todo = new List <Tuple <APC, Preconditions> >()
{
new Tuple <APC, Preconditions>(entry, initialState)
};
var stable = new Set <APC>();
while (todo.Count != 0)
{
this.timeout.CheckTimeOut("backwards postcondition propagation");
var next = todo.ExtractFirst();
var nextPC = next.Item1;
var nextState = next.Item2;
var newPre = nextState;
// do the block
{
APC pred;
while (CFG.HasSinglePredecessor(nextPC, out pred) && !CFG.IsJoinPoint(nextPC))
{
this.timeout.CheckTimeOut("backwards postcondition propagation (block)");
//var post = CFG.Predecessors(nextPC).First();
newPre = this.Mdriver.BackwardTransfer(nextPC, pred, newPre, this);
// no pre, killing the path
if (newPre == null)
{
break;
}
// TODO: check for contraddictions
nextPC = pred;
}
}
if (nextPC.Equals(CFG.EntryAfterRequires) || nextPC.Equals(CFG.Entry))
{
this.invariants = newPre;
continue;
}
var fixpointReached = false;
if (CFG.IsJoinPoint(nextPC))
{
Preconditions prev;
if (this.joinPoints.TryGetValue(nextPC, out prev))
{
newPre = Join(prev, newPre, CFG.IsForwardBackEdgeTarget(nextPC.Block.First), out fixpointReached);
if (fixpointReached)
{
stable.Add(nextPC.Block.First);
}
}
joinPoints[nextPC] = newPre;
}
// Split in the backwards analysis
foreach (var pred in CFG.Predecessors(nextPC))
{
if (fixpointReached && CFG.IsForwardBackEdge(pred, nextPC))
{
continue;
}
if (this.Mdriver.IsUnreachable(nextPC))
{
continue;
}
var transf = this.Mdriver.BackwardTransfer(nextPC, pred, newPre, this);
if (transf != null)
{
todo.Add(new Tuple <APC, Preconditions>(pred, transf));
}
}
}
}
