public static void DeleteDeadCode(ControlFlowGraph graph)
{
var usedVars = CreateUsedVarsSets(graph);
var info = new ReachingDefinitions().Execute(graph);
var usedDefinitions = new HashSet <Instruction>(
info[graph.GetCurrentBasicBlocks()[graph.GetCurrentBasicBlocks().Count - 1]].In,
new InstructionComparer());
var possibleOperationTypes = new[] { "assign", "input", "PLUS" };
var wasChanged = true;
while (wasChanged)
{
wasChanged = false;
foreach (var block in graph.GetCurrentBasicBlocks())
{
var deadDefinitions = info[block].In.Except(info[block].Out);
foreach (var oldDef in deadDefinitions)
{
var variable = oldDef.Result;
// find first assign in current block that rewrites variable
var newDefIndex = block.GetInstructions()
.Select((t, i) => (Instruction: t, Index: i))
.First(t => possibleOperationTypes.Contains(t.Instruction.Operation) && t.Instruction.Result == variable)
.Index;
var blockWithOldDef = graph.GetCurrentBasicBlocks()
.Single(z => z.GetInstructions().Any(t => t == oldDef));
var oldDefIndex = blockWithOldDef.GetInstructions()
.Select((t, i) => (Instruction: t, Index: i))
.Single(t => t.Instruction == oldDef)
.Index;
if (usedDefinitions.Contains(oldDef) ||
IsUsedInCurrentBlock(block, variable, newDefIndex) ||
IsUsedInOriginalBlock(blockWithOldDef, variable, oldDefIndex) ||
IsUsedInOtherBlocks(graph, blockWithOldDef, oldDef, usedVars, info))
{
_ = usedDefinitions.Add(oldDef);
continue;
}
// remove useless definition
blockWithOldDef.RemoveInstructionByIndex(oldDefIndex);
if (!string.IsNullOrEmpty(oldDef.Label))
{
blockWithOldDef.InsertInstruction(oldDefIndex, new Instruction(oldDef.Label, "noop", null, null, null));
}
info = new ReachingDefinitions().Execute(graph);
wasChanged = true;
}
}
}
}
public ReachingTransferFunc(ControlFlowGraph g)
{
var basicBlocks = g.GetCurrentBasicBlocks();
GetDefs(basicBlocks);
GetGenKill(basicBlocks);
}
/// <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 Dictionary <BasicBlock, HashSet <string> > CreateUsedVarsSets(ControlFlowGraph graph)
{
var result = new Dictionary <BasicBlock, HashSet <string> >();
foreach (var block in graph.GetCurrentBasicBlocks())
{
result[block] = new HashSet <string>();
foreach (var instruction in block.GetInstructions())
{
if (IsVariable(instruction.Argument1))
{
_ = result[block].Add(instruction.Argument1);
}
if (IsVariable(instruction.Argument2))
{
_ = result[block].Add(instruction.Argument2);
}
}
}
return(result);
}