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];
if (instruction.Matches(InstructionType.Jump, out var targetLabel) && context.GetLabelPosition(targetLabel) < i)
{
var startPosition = context.GetLabelPosition(targetLabel);
var endPosition = i;
if (context[i + 1].Matches(InstructionType.MarkLabel))
{
endPosition++;
}
var labelMap = new ushort?[context.LabelAllocator];
var maxBoundsCheck = -1;
// By default, keep al labels the same
for (var j = 0; j < labelMap.Length; j++)
{
labelMap[j] = (ushort)j;
}
for (var j = startPosition; j <= endPosition; j++)
{
if (context[j].Matches(InstructionType.BoundsCheck, out var _, out var offset))
{
if (offset > maxBoundsCheck)
{
maxBoundsCheck = offset;
}
}
else if (context[j].Matches(InstructionType.MarkLabel, out var label))
{
// ... except for labels that are marked inside the loop...
labelMap[label] = null;
}
}
{
if (maxBoundsCheck >= 3 && (!context[startPosition + 1].Matches(InstructionType.BoundsCheck, out var _, out var offset) || offset < maxBoundsCheck))
{
var canMakeFastPath = true;
for (var j = 0; j < context.Count; j++)
{
if (context[j].CanJumpToLabel)
{
if (context[j].Matches(InstructionType.BoundsCheck, out var boundsCheckTargetLabel) && boundsCheckTargetLabel == targetLabel)
{
canMakeFastPath = false;
}
else if (j >= startPosition && j <= endPosition && context.GetLabelPosition(context[j].Label) < startPosition || context.GetLabelPosition(context[j].Label) > endPosition)
{
canMakeFastPath = false;
}
}
else if (j >= startPosition && j <= endPosition && context[j].Type == InstructionType.Call)
{
foreach (var(_, jumpTarget) in context.FailureLabelMap[context[j].Data2].Mapping)
{
if (context.GetLabelPosition(jumpTarget) < startPosition || context.GetLabelPosition(jumpTarget) > endPosition)
{
canMakeFastPath = false;
break;
}
}
}
}
if (canMakeFastPath && context.Backtracer.CheckBounds(startPosition, false, maxBoundsCheck) != Analyzers.EvaluationResult.Fail)
{
// Create fast path
var newInstructions = InstructionHelper.DuplicateLabels(context, context.Skip(startPosition).Take(endPosition - startPosition + 1).ToList(), labelMap).ToList();
var goToSlowPathLabel = context.LabelAllocator++;
newInstructions.Insert(1, Instruction.BoundsCheck(goToSlowPathLabel, (short)maxBoundsCheck));
newInstructions.Add(Instruction.MarkLabel(goToSlowPathLabel));
context.InsertRange(startPosition, newInstructions);
changed = true;
}
}
}
}
