[Bug target/86869] ICE when taking address of array member of __memx struct pointer

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86869

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
#ifndef POINTERS_EXTEND_UNSIGNED
  gcc_assert (GET_MODE (x) == to_mode || GET_MODE (x) == VOIDmode);
  return x;
#else /* defined(POINTERS_EXTEND_UNSIGNED) */
  scalar_int_mode pointer_mode, address_mode, from_mode;
  rtx temp;

So clearly avr has to define POINTERS_EXTEND_UNSIGNED in the correct way
and/or the assert needs to be ajdusted for pointer/address_mode of as.