/// <summary>
/// Adds yield target to the current try statement and returns the label
/// to which the outer code must jump to to route properly to this label.
/// </summary>
internal TargetLabel AddYieldTarget(TargetLabel label, int index) {
switch (State) {
case TryStatementState.Try:
return _statement.AddTryYieldTarget(label, index);
case TryStatementState.Handler:
return _statement.AddCatchYieldTarget(label, index, _handler);
case TryStatementState.Finally:
return _statement.AddFinallyYieldTarget(label, index);
default:
Debug.Assert(false, "Invalid try statement state " + State.ToString());
throw new System.InvalidOperationException();
}
}
protected internal override void PostWalk(YieldStatement node)
{
// Assign the yield statement index for codegen
int index = _topTargets.Count;
TargetLabel label = new TargetLabel();
node.Target = new YieldTarget(index, label);
foreach (ExceptionBlock eb in _tryBlocks) {
// The exception statement must determine
// the label for the enclosing code to jump to
// to return to the given yield target
label = eb.AddYieldTarget(label, index);
}
// Insert the top target to the top yields
Debug.Assert(_topTargets.Count == index);
_topTargets.Add(new YieldTarget(index, label));
}
public YieldTarget(int index, TargetLabel label)
{
_index = index;
_target = label;
}
private TargetLabel EnsureTopTarget()
{
if (_target == null) {
_target = new TargetLabel();
}
return _target;
}
internal TargetLabel AddTryYieldTarget(TargetLabel label, int index)
{
// Yield inside try stays inside try block, so we need to
// remember the target label.
AddYieldTarget(ref _tryYields, label, index);
return EnsureTopTarget();
}
internal TargetLabel AddFinallyYieldTarget(TargetLabel label, int index)
{
// Yields inside finally stay inside finally so we need to keep track
// of them.
AddYieldTarget(ref _finallyYields, label, index);
return EnsureTopTarget();
}
internal TargetLabel AddCatchYieldTarget(TargetLabel label, int index, int handler)
{
// Yields inside catch blocks are hoisted out of the catch.
// If the catch block has a finally, though, it will get wrapped in
// another try block, in which case the direct jump is not possible
// and code must route through the top target.
Debug.Assert(_handlers != null && handler < _handlers.Count);
CatchBlock cb = _handlers[handler];
cb.Yield = true;
_yieldInCatch = true;
if (_finally != null) {
AddYieldTarget(ref _catchYields, label, index);
return EnsureTopTarget();
} else {
return label;
}
}
internal static void AddYieldTarget(ref List<YieldTarget> list, TargetLabel target, int index)
{
if (list == null) {
list = new List<YieldTarget>();
}
list.Add(new YieldTarget(index, target));
}
public YieldTarget(int index, TargetLabel label)
{
_index = index;
_target = label;
}