void AnalyseAssignment(Variable variable, List <Tuple <IRegion, Expr> > defs, Graph <Block> cfg, HashSet <Variable> modSet)
{
// Ensure defs[0] refers to the definition from the outermost region
// This also checks that the definitions are in different regions
if (!OrderDefs(defs, cfg))
{
return;
}
var regionId = defs[1].Item1.Identifier();
var varDefAnalysis = verifier.varDefAnalysesRegion[impl];
var varDef = varDefAnalysis.GetPossibleInductionVariableDefintion(variable.Name, regionId);
if (varDef == null)
{
return;
}
HashSet <string> loopFreeVars;
var defInd = varDefAnalysis.SubstDefinitions(varDef, impl.Name, out loopFreeVars);
if (loopFreeVars.Any(i => i != variable.Name))
{
return;
}
var modSetLoop = LoopInvariantGenerator.GetModifiedVariables(defs[1].Item1);
var v = new VariablesOccurringInExpressionVisitor();
v.Visit(defs[0].Item2);
if (v.GetVariables().Intersect(modSetLoop).Any())
{
return;
}
AddDefinitionPair(variable, defInd, defs[0].Item2, regionId, modSet);
}
void AnalyseRegion(IRegion region, Graph <Block> cfg)
{
var header = region.Header();
var blockVarDefs = new Dictionary <Block, VarDefs>();
var blocks = region.SubBlocks().Where(i => i != header);
var modSet = LoopInvariantGenerator.GetModifiedVariables(region);
blockVarDefs[header] = new VarDefs(header, cfg.BackEdgeNodes(header), modSet);
blockVarDefs[header].Initialize();
foreach (var b in blocks)
{
blockVarDefs[b] = new VarDefs(b, cfg.Predecessors(b), modSet);
}
var changed = true;
while (changed)
{
changed = false;
foreach (var b in blocks)
{
if (blockVarDefs[b].ComputeTransfer(blockVarDefs))
{
changed = true;
}
}
}
possibleInductionVarDefs[region.Identifier()]
= blockVarDefs[header].FindSelfReferentialVariables(blockVarDefs)
.ToDictionary(i => i.Item1.Name, i => i.Item2);
}
void Analyse()
{
var cfg = verifier.Program.ProcessLoops(impl);
var modSet = LoopInvariantGenerator.GetModifiedVariables(verifier.RootRegion(impl));
var multiDefMap = new VarDefMap();
FindAssignments(verifier.RootRegion(impl), multiDefMap);
foreach (var e in multiDefMap.Where(i => i.Value.Count == 2))
{
AnalyseAssignment(e.Key, e.Value, cfg, modSet);
}
}