/// <summary>
/// For an if statement with an unreachable end point and no else block,
/// inverts to match IL order of the first statement of each branch
/// </summary>
private void ImproveILOrdering(Block block, IfInstruction ifInst, Block continueTarget)
{
if (!block.HasFlag(InstructionFlags.EndPointUnreachable) ||
!ifInst.TrueInst.HasFlag(InstructionFlags.EndPointUnreachable) ||
!ifInst.FalseInst.MatchNop())
{
return;
}
Debug.Assert(ifInst != block.Instructions.Last());
var trueRangeStart = ConditionDetection.GetStartILOffset(ifInst.TrueInst, out bool trueRangeIsEmpty);
var falseRangeStart = ConditionDetection.GetStartILOffset(block.Instructions[block.Instructions.IndexOf(ifInst) + 1], out bool falseRangeIsEmpty);
if (trueRangeIsEmpty || falseRangeIsEmpty || falseRangeStart >= trueRangeStart)
{
return;
}
if (block.Instructions.Last() is Leave leave && !leave.IsLeavingFunction && leave.TargetContainer.Kind == ContainerKind.Normal)
{
// non-keyword leave. Can't move out of the last position in the block (fall-through) without introducing goto, unless it can be replaced with a keyword (return/continue)
if (!CanDuplicateExit(block.Instructions.Last(), continueTarget, out var keywordExit))
{
return;
}
context.Step("Replace leave with keyword exit", ifInst.TrueInst);
block.Instructions.Last().ReplaceWith(keywordExit.Clone());
}
ConditionDetection.InvertIf(block, ifInst, context);
}
/// <summary>
/// For an if statement with an unreachable end point and no else block,
/// inverts to match IL order of the first statement of each branch
/// </summary>
private void ImproveILOrdering(Block block, IfInstruction ifInst)
{
if (!block.HasFlag(InstructionFlags.EndPointUnreachable) ||
!ifInst.TrueInst.HasFlag(InstructionFlags.EndPointUnreachable) ||
!ifInst.FalseInst.MatchNop())
{
return;
}
Debug.Assert(ifInst != block.Instructions.Last());
var trueRangeStart = ConditionDetection.GetStartILOffset(ifInst.TrueInst, out bool trueRangeIsEmpty);
var falseRangeStart = ConditionDetection.GetStartILOffset(block.Instructions[block.Instructions.IndexOf(ifInst) + 1], out bool falseRangeIsEmpty);
if (!trueRangeIsEmpty && !falseRangeIsEmpty && falseRangeStart < trueRangeStart)
{
ConditionDetection.InvertIf(block, ifInst, context);
}
}
