private static void GenerateCandidateForEnabledness(GPUVerifier verifier, Implementation impl, IRegion region)
{
Block header = region.Header();
if (verifier.UniformityAnalyser.IsUniform(impl.Name, header))
{
return;
}
var cfg = Program.GraphFromImpl(impl);
Dictionary <Block, HashSet <Block> > controlDependence = cfg.ControlDependence();
controlDependence.TransitiveClosure();
cfg.ComputeLoops();
var loopNodes = cfg.BackEdgeNodes(header).Select(item => cfg.NaturalLoops(header, item)).SelectMany(item => item);
Expr guardEnclosingLoop = null;
foreach (var b in controlDependence.Keys.Where(item => controlDependence[item].Contains(region.Header())))
{
foreach (var succ in cfg.Successors(b).Where(item => cfg.DominatorMap.DominatedBy(header, item)))
{
var guard = MaybeExtractGuard(verifier, impl, succ);
if (guard != null)
{
guardEnclosingLoop = guardEnclosingLoop == null ? guard : Expr.And(guardEnclosingLoop, guard);
break;
}
}
}
if (guardEnclosingLoop != null)
{
verifier.AddCandidateInvariant(
region,
Expr.Imp(Expr.Ident(verifier.FindOrCreateEnabledVariable()), guardEnclosingLoop),
"conditionsImpliedByEnabledness");
}
var cfgDual = cfg.Dual(new Block());
Block loopConditionDominator = header;
// The dominator might have multiple successors
while (cfg.Successors(loopConditionDominator).Count(item => loopNodes.Contains(item)) > 1)
{
// Find the immediate post-dominator of the successors
Block block = null;
foreach (var succ in cfg.Successors(loopConditionDominator).Where(item => loopNodes.Contains(item)))
{
if (block == null)
{
block = succ;
}
else
{
block = cfgDual.DominatorMap.LeastCommonAncestor(block, succ);
}
}
// Use the immediate post-dominator
loopConditionDominator = block;
}
Expr guardIncludingLoopCondition = null;
foreach (var succ in cfg.Successors(loopConditionDominator).Where(item => loopNodes.Contains(item)))
{
var guard = MaybeExtractGuard(verifier, impl, succ);
if (guard != null)
{
// There is at most one successor, so it's safe not use GuardIncludingLoopCondition on the rhs
guardIncludingLoopCondition = guardEnclosingLoop == null ? guard : Expr.And(guardEnclosingLoop, guard);
break;
}
}
if (guardIncludingLoopCondition != null)
{
verifier.AddCandidateInvariant(
region, Expr.Imp(guardIncludingLoopCondition, Expr.Ident(verifier.FindOrCreateEnabledVariable())), "conditionsImplyingEnabledness", "do_not_predicate");
}
}