// устранение переходов через переходы (пример из презентации Opt5.pdf слайд 32)
public static (bool wasChanged, IReadOnlyList <Instruction> instructions) RemoveGotoThroughGoto(IReadOnlyList <Instruction> instructions)
{
if (instructions is null)
{
throw new ArgumentNullException("instructions is null");
}
var wasChanged = false;
var newInstructions = new List <Instruction>();
for (var i = 0; i < instructions.Count; ++i)
{
if (instructions[i].Operation == "ifgoto" && 4 <= (instructions.Count - i))
{
var com0 = instructions[i];
var com1 = instructions[i + 1];
var com2 = instructions[i + 2];
var com3 = instructions[i + 3];
// только одна операция
if (com1.Operation == "goto" && com1.Label == "" && com2.Operation != "noop" && com0.Argument2 == com2.Label && com1.Argument1 == com3.Label)
{
var tmpName = ThreeAddressCodeTmp.GenTmpName();
newInstructions.Add(new Instruction(com0.Label, "NOT", com0.Argument1, "", tmpName));
newInstructions.Add(new Instruction("", "ifgoto", tmpName, com3.Label, ""));
var label = com2.Label.StartsWith("L") && uint.TryParse(com2.Label.Substring(1), out _) ? "" : com2.Label;
newInstructions.Add(new Instruction(label, com2.Operation, com2.Argument1, com2.Argument2, com2.Result));
newInstructions.Add(com3.Copy());
wasChanged = true;
i += 3;
continue;
}
}
newInstructions.Add(instructions[i].Copy());
}
return(wasChanged, newInstructions);
}
// устранение переходов через переходы (experimental)
#region
/*public static Tuple<bool, List<Instruction>> RemoveGotoThroughGoto(List<Instruction> instructions)
* {
* if (instructions is null)
* throw new ArgumentNullException("instructions is null");
*
* bool isChange = false;
* var newInstructions = new List<Instruction>();
*
* for (int i = 0; i < instructions.Count; ++i)
* {
* var com0 = instructions[i];
* if (instructions[i].Operation == "ifgoto" && 4 <= (instructions.Count - i))
* {
* var com1 = instructions[i + 1];
* var com2 = instructions[i + 2];
*
* //
* if (com1.Operation == "goto" && com1.Label == "" && com2.Operation != "noop" && com0.Argument2 == com2.Label)
* {
* // search end label with "noop" operation
* var endLabelIndex = FindLabelIndex(instructions, i + 2, com1.Argument1);
* if (0 < endLabelIndex || endLabelIndex < instructions.Count || instructions[endLabelIndex].Operation == "noop")
* {
* //
* string tmpName = ThreeAddressCodeTmp.GenTmpName();
* newInstructions.Add(new Instruction(com0.Label, "EQUAL", "False", com0.Argument1, tmpName)); // операция отрицания через EQUAL
* newInstructions.Add(new Instruction("", "ifgoto", tmpName, com1.Argument1, ""));
*
* // copy instructions for true branch
* newInstructions.Add(new Instruction("", com2.Operation, com2.Argument1, com2.Argument2, com2.Result));
* for (int k = i + 3; k < endLabelIndex; ++k)
* {
* var bla = instructions[k];
* newInstructions.Add(new Instruction(bla.Label, bla.Operation, bla.Argument1, bla.Argument2, bla.Result));
* }
*
* var endLabel = instructions[endLabelIndex];
* newInstructions.Add(new Instruction(endLabel.Label, endLabel.Operation, endLabel.Argument1, endLabel.Argument2, endLabel.Result));
* i = endLabelIndex;
* isChange = true;
* continue;
* }
* }
* }
*
* newInstructions.Add(new Instruction(com0.Label, com0.Operation, com0.Argument1, com0.Argument2, com0.Result));
* }
*
* return Tuple.Create(isChange, newInstructions);
* }*/
#endregion
// устранение переходов через переходы (пример из презентации Opt5.pdf слайд 32)
public static Tuple <bool, List <Instruction> > RemoveGotoThroughGoto(List <Instruction> instructions)
{
if (instructions is null)
{
throw new ArgumentNullException("instructions is null");
}
bool isChange = false;
var newInstructions = new List <Instruction>();
for (int i = 0; i < instructions.Count; ++i)
{
if (instructions[i].Operation == "ifgoto" && 4 <= (instructions.Count - i))
{
var com0 = instructions[i];
var com1 = instructions[i + 1];
var com2 = instructions[i + 2];
var com3 = instructions[i + 3];
// только одна операция
if (com1.Operation == "goto" && com1.Label == "" && com2.Operation != "noop" && com0.Argument2 == com2.Label && com1.Argument1 == com3.Label)
{
string tmpName = ThreeAddressCodeTmp.GenTmpName();
newInstructions.Add(new Instruction(com0.Label, "NOT", com0.Argument1, "", tmpName));
newInstructions.Add(new Instruction("", "ifgoto", tmpName, com3.Label, ""));
newInstructions.Add(new Instruction("", com2.Operation, com2.Argument1, com2.Argument2, com2.Result));
newInstructions.Add(new Instruction(com3.Label, com3.Operation, com3.Argument1, com3.Argument2, com3.Result));
isChange = true;
i += 3;
continue;
}
}
newInstructions.Add(new Instruction(instructions[i].Label, instructions[i].Operation, instructions[i].Argument1, instructions[i].Argument2, instructions[i].Result));
}
return(Tuple.Create(isChange, newInstructions));
}