Function drreg_unreserve_register 

pub unsafe extern "C" fn drreg_unreserve_register(
    drcontext: *mut c_void,
    ilist: *mut instrlist_t,
    where_: *mut instr_t,
    reg: reg_id_t,
) -> drreg_status_t

Terminates exclusive use of the register \p reg. Restores the application value at \p where in \p ilist, if necessary. If called during drmgr’s insertion phase, \p where must be the current application instruction.

@return whether successful or an error code on failure.