https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94420
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- I'm not sure about the invalid, of course if one uses a global register var for a fixed reg and stores something into it, then it is clearly UB, but this case is ont about changing it, just inspecting, and I believe users use both global and local register vars for various fixed regs quite often, whether it is a stack pointer, hard frame pointer, _GLOBAL_OFFSET_TABLE_ etc.
