/// <summary>
/// Принимает Граф потока данных и по нему ищет все естественные циклы
/// </summary>
/// <param name="cfg">Граф потока управления</param>
/// <returns>
/// Вернёт все натуральные циклы
/// </returns>
public static IReadOnlyList <IReadOnlyList <BasicBlock> > GetAllNaturalLoops(ControlFlowGraph cfg)
{
if (cfg.IsReducibleGraph())
{
var natLoops = new List <List <BasicBlock> >();
var ForwardEdges = cfg.GetCurrentBasicBlocks();
foreach (var(From, To) in cfg.GetBackEdges())
{
if (cfg.VertexOf(To) > 0)
{
var tmp = new List <BasicBlock>();
for (var i = cfg.VertexOf(To); i < cfg.VertexOf(From) + 1; i++)
{
if (!tmp.Contains(ForwardEdges[i]))
{
tmp.Add(ForwardEdges[i]);
}
}
natLoops.Add(tmp);
}
}
return(natLoops.Where(loop => IsNaturalLoop(loop, cfg)).ToList());
}
else
{
Console.WriteLine("Граф не приводим");
return(new List <List <BasicBlock> >());
}
}
private static bool IsUsedInOtherBlocks(
ControlFlowGraph graph,
BasicBlock blockWithDefinition,
Instruction definitionToCheck,
Dictionary <BasicBlock, HashSet <string> > usedVars,
InOutInfo info)
{
var queue = new Queue <BasicBlock>();
queue.Enqueue(blockWithDefinition);
while (queue.Count != 0)
{
var block = queue.Dequeue();
foreach (var child in graph.GetChildrenBasicBlocks(graph.VertexOf(block)).Select(z => z.block))
{
var isRewritten = !info[child].Out.Contains(definitionToCheck);
var isUsed = usedVars[block].Contains(definitionToCheck.Result);
if (!isRewritten)
{
if (isUsed)
{
return(true);
}
else
{
queue.Enqueue(child);
}
}
else
{
if (!isUsed)
{
continue;
}
else
{
// we need to check instructions before definitionToCheck is rewritten
foreach (var instruction in child.GetInstructions())
{
if (instruction.Argument1 == definitionToCheck.Result ||
instruction.Argument2 == definitionToCheck.Result)
{
return(true);
}
if (instruction.Result == definitionToCheck.Result)
{
break;
}
}
}
}
}
}
return(false);
}
/// <summary>
/// Проверка цикла на естественность
/// </summary>
/// <param name="loop">Проверяемый цикл</param>
/// <param name="cfg">Граф потока управления</param>
/// <returns>
/// Вернёт флаг, естественнен ли он
/// </returns>
private static bool IsNaturalLoop(IReadOnlyCollection <BasicBlock> loop, ControlFlowGraph cfg)
{
foreach (var bblock in loop.Skip(1))
{
var parents = cfg.GetParentsBasicBlocks(cfg.VertexOf(bblock));
if (parents.Count > 1)
{
foreach (var parent in parents.Select(x => x.block))
{
if (!loop.Contains(parent))
{
return(false);
}
}
}
}
return(true);
}
