caller``\ " ``catchswitch`` within a funclet pad that has an unwind
destination other than caller; it is undefined behavior for such a ``call``
or ``catchswitch`` to unwind.
+
+Finally, the funclet pads' unwind destinations cannot form a cycle. This
+ensures that EH lowering can construct "try regions" with a tree-like
+structure, which funclet-based personalities may require.