public override bool Optimize(OptimizationContext context)
{
var changed = false;
for (var i = context.Count - 1; i >= 0; i--)
{
var instructionCount = context.Count;
var instruction = context[i];
switch (instruction.Type)
{
case InstructionType.Char:
case InstructionType.BoundsCheck:
var backtracerView = new BacktracerView(context.Backtracer, i - 1, false);
switch (instruction.Type == InstructionType.Char ? backtracerView.CheckChars(instruction, instruction.Offset) : backtracerView.CheckBounds(instruction.Offset))
{
case EvaluationResult.Fail:
context.NonDestructiveUpdate(i, Instruction.Jump(instruction.Label));
changed = true;
break;
case EvaluationResult.Success:
context.RemoveAt(i, true);
changed = true;
break;
case EvaluationResult.Inconclusive:
var targetPosition = -1;
if (context[i + 1].Matches(InstructionType.MarkLabel, out var markedLabel))
{
targetPosition = i + 2;
}
else if (context[i + 1].Matches(InstructionType.Jump, out var jumpTarget))
{
targetPosition = context.GetLabelPosition(jumpTarget) + 1;
}
if (targetPosition >= 0)
{
var normalPosition = InstructionHelper.FindJumpTarget(context, new BacktracerView(context.Backtracer, i - 1, false), context.GetLabelPosition(instruction.Label), FullPathSearch);
if (normalPosition == targetPosition)
{
// Label will be replaced in next step.
context.NonDestructiveUpdate(i, Instruction.Jump(instruction.Label));
changed = true;
}
}
break;
default: throw new NotImplementedException();
}
break;
}
if (i + 1 < context.Count)
{
var backtracerView = new BacktracerView(context.Backtracer, i, false);
var result = InstructionHelper.FindJumpTargetEx(context, backtracerView, i + 1, FullPathSearch, false);
if (result.Position != InstructionHelper.TracePath(context, null, i + 1))
{
if (context[result.Position - 1].Matches(InstructionType.MarkLabel, out var newTarget))
{
context.Insert(i + 1, Instruction.Jump(newTarget));
}
else
{
var newLabel = context.LabelAllocator++;
context.Insert(i + 1, Instruction.Jump(newLabel));
context.Insert(result.Position + (result.Position >= i + 1 ? 1 : 0), Instruction.MarkLabel(newLabel), true);
}
changed = true;
}
}
}
return(changed);
}
