private void HandleSwitchExpression(BlockContainer container, SwitchInstruction switchInst)
{
if (!context.Settings.SwitchExpressions)
{
return;
}
Debug.Assert(container.Kind == ContainerKind.Switch);
Debug.Assert(container.ResultType == StackType.Void);
var defaultSection = switchInst.GetDefaultSection();
StackType resultType = StackType.Void;
BlockContainer leaveTarget = null;
ILVariable resultVariable = null;
foreach (var section in switchInst.Sections)
{
if (section != defaultSection)
{
// every section except for the default must have exactly 1 label
if (section.Labels.Count() != (section.HasNullLabel ? 0u : 1u))
{
return;
}
}
if (!section.Body.MatchBranch(out var sectionBlock))
{
return;
}
if (sectionBlock.IncomingEdgeCount != 1)
{
return;
}
if (sectionBlock.Parent != container)
{
return;
}
if (sectionBlock.Instructions.Count == 1)
{
if (sectionBlock.Instructions[0] is Throw)
{
// OK
}
else if (sectionBlock.Instructions[0] is Leave leave)
{
if (!leave.IsLeavingFunction)
{
return;
}
leaveTarget ??= leave.TargetContainer;
Debug.Assert(leaveTarget == leave.TargetContainer);
resultType = leave.Value.ResultType;
}
else
{
return;
}
}
else if (sectionBlock.Instructions.Count == 2)
{
if (!sectionBlock.Instructions[0].MatchStLoc(out var v, out _))
{
return;
}
if (!sectionBlock.Instructions[1].MatchLeave(container))
{
return;
}
resultVariable ??= v;
if (resultVariable != v)
{
return;
}
resultType = resultVariable.StackType;
}
else
{
return;
}
}
// Exactly one of resultVariable/leaveTarget must be null
if ((resultVariable == null) == (leaveTarget == null))
{
return;
}
if (switchInst.Value is StringToInt str2int)
{
// validate that each integer is used for exactly one value
var integersUsed = new HashSet <int>();
foreach ((string key, int val) in str2int.Map)
{
if (!integersUsed.Add(val))
{
return;
}
}
}
context.Step("Switch Expression", switchInst);
switchInst.SetResultType(resultType);
foreach (var section in switchInst.Sections)
{
var block = ((Branch)section.Body).TargetBlock;
if (block.Instructions.Count == 1)
{
if (block.Instructions[0] is Throw t)
{
t.resultType = resultType;
section.Body = t;
}
else if (block.Instructions[0] is Leave leave)
{
section.Body = leave.Value;
}
else
{
throw new InvalidOperationException();
}
}
else
{
section.Body = ((StLoc)block.Instructions[0]).Value;
}
}
if (resultVariable != null)
{
container.ReplaceWith(new StLoc(resultVariable, switchInst));
}
else
{
container.ReplaceWith(new Leave(leaveTarget, switchInst));
}
context.RequestRerun(); // new StLoc might trigger inlining
}
