Hello, I am wondering how to define a blackbox data type in gcc. It can be too wide and irregular to be represented by current data types. It needs to be assigned to special register files. I don't care and don't want to touch its content except using intrinsics (builtin) functions. An example of such data type is to represent value in a MAC register. Is there are convenient way to do that? Thanks in advance, Cheers, Bingfeng Mei Broadcom UK