how to use a named type?

Hi, all

I’m currently doing some minor change to a function argument list.

I want to add this named type to a function’s argument list.
%struct.ompi_request_t = type opaque

But I don’t know how to use it. I have already add it to the TypeSymbolTable of the Module, and I plan to add construct a argument of “struct.ompi_request_t” type, but there is no handle to this type, it is a StringRef, not a Type *, so what is the correct way to do this?
thanks a lot