public QuantifierExpr RewriteMatchingLoops(QuantifierWithTriggers q)
{
// rewrite quantifier to avoid matching loops
// before:
// assert forall i :: 0 <= i < a.Length-1 ==> a[i] <= a[i+1];
// after:
// assert forall i,j :: j == i+1 ==> 0 <= i < a.Length-1 ==> a[i] <= a[j];
substMap = new List <Tuple <Expression, IdentifierExpr> >();
foreach (var m in q.LoopingMatches)
{
var e = m.OriginalExpr;
if (TriggersCollector.IsPotentialTriggerCandidate(e) && triggersCollector.IsTriggerKiller(e))
{
foreach (var sub in e.SubExpressions)
{
if (triggersCollector.IsTriggerKiller(sub) && (!TriggersCollector.IsPotentialTriggerCandidate(sub)))
{
var entry = substMap.Find(x => ExprExtensions.ExpressionEq(sub, x.Item1));
if (entry == null)
{
var newBv = new BoundVar(sub.tok, "_t#" + substMap.Count, sub.Type);
var ie = new IdentifierExpr(sub.tok, newBv.Name);
ie.Var = newBv;
ie.Type = newBv.Type;
substMap.Add(new Tuple <Expression, IdentifierExpr>(sub, ie));
}
}
}
}
}
var expr = (QuantifierExpr)q.quantifier;
if (substMap.Count > 0)
{
var s = new Translator.ExprSubstituter(substMap);
expr = s.Substitute(q.quantifier) as QuantifierExpr;
}
else
{
// make a copy of the expr
if (expr is ForallExpr)
{
expr = new ForallExpr(expr.tok, expr.TypeArgs, expr.BoundVars, expr.Range, expr.Term, TriggerUtils.CopyAttributes(expr.Attributes))
{
Type = expr.Type, Bounds = expr.Bounds
};
}
else
{
expr = new ExistsExpr(expr.tok, expr.TypeArgs, expr.BoundVars, expr.Range, expr.Term, TriggerUtils.CopyAttributes(expr.Attributes))
{
Type = expr.Type, Bounds = expr.Bounds
};
}
}
return(expr);
}
void CollectWithoutShareTriggers(TriggersCollector triggersCollector)
{
foreach (var q in quantifiers)
{
var candidates = triggersCollector.CollectTriggers(q.quantifier).Deduplicate(TriggerTerm.Eq);
q.CandidateTerms = candidates; // The list of candidate terms is immutable
q.Candidates = TriggerUtils.AllNonEmptySubsets(candidates, SubsetGenerationPredicate, q.quantifier.BoundVars).Select(set => set.ToTriggerCandidate()).ToList();
}
}
internal void ComputeTriggers(TriggersCollector triggersCollector)
{
CollectAndShareTriggers(triggersCollector);
TrimInvalidTriggers();
BuildDependenciesGraph();
if (SuppressMatchingLoops() && RewriteMatchingLoop())
{
CollectWithoutShareTriggers(triggersCollector);
TrimInvalidTriggers();
SuppressMatchingLoops();
}
SelectTriggers();
CombineSplitQuantifier();
}
/// <summary>
/// Collect triggers from the body of each quantifier, and share them
/// between all quantifiers. This method assumes that all quantifiers
/// actually come from the same context, and were the result of a split that
/// gave them all the same variables.
/// </summary>
/// <param name="triggersCollector"></param>
void CollectAndShareTriggers(TriggersCollector triggersCollector)
{
List <TriggerTerm> pool = new List <TriggerTerm>();
foreach (var q in quantifiers)
{
var candidates = triggersCollector.CollectTriggers(q.quantifier).Deduplicate(TriggerTerm.Eq);
// filter out the candidates that was "second-class"
var filtered = TriggerUtils.Filter(candidates, tr => tr, (tr, _) => !tr.IsTranslatedToFunctionCall(), (tr, _) => { }).ToList();
// if there are only "second-class" candidates, add them back.
if (filtered.Count == 0)
{
filtered = candidates;
}
pool.AddRange(filtered);
}
var distinctPool = pool.Deduplicate(TriggerTerm.Eq);
foreach (var q in quantifiers)
{
q.CandidateTerms = distinctPool; // The list of candidate terms is immutable
q.Candidates = TriggerUtils.AllNonEmptySubsets(distinctPool, SubsetGenerationPredicate, q.quantifier.BoundVars).Select(set => set.ToTriggerCandidate()).ToList();
}
}
internal bool IsTranslatedToFunctionCall()
{
return((TriggersCollector.TranslateToFunctionCall(this.Expr)) ? true : false);
}
