SubclassData in SDNode

hi,everyone.

i notice that theres a subclassdata field in SDNode class but it seems
that there no any method to access subclassdata, so i want to encode
some information into it in my backend, and going to add the access
function for it.

is the way using it like this subclassdata recommanded? or the
subclassdata is designed to use for other purpose?

thanks very much.

--ether