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); }