does gcc support multiple sizes, or not?

[DJ Delorie]

In cp/cvt.c we have this code in cp_convert_to_pointer:

  if (INTEGRAL_CODE_P (form))
    {
      if (TYPE_PRECISION (intype) == POINTER_SIZE)
        return build1 (CONVERT_EXPR, type, expr);
      expr = cp_convert (c_common_type_for_size (POINTER_SIZE, 0), expr);
      /* Modes may be different but sizes should be the same.  There
         is supposed to be some integral type that is the same width
         as a pointer.  */
      gcc_assert (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (expr)))
                  == GET_MODE_SIZE (TYPE_MODE (type)));

      return convert_to_pointer (type, expr);
    }

Note that it always converts to a POINTER_SIZE pointer, regardless of
the size of TYPE (the target type), then asserts that the result is
the same size as TYPE.

However, in s390.c, we have:

static bool
s390_valid_pointer_mode (enum machine_mode mode)
{
  return (mode == SImode || (TARGET_64BIT && mode == DImode));
}

Note that more than one mode is supported simultaneously.  Thus, it's
legal for the application to specify SI or DI mode for pointer (via
__attribute__((mode))), but cc1plus then aborts.

So... who is right?  Are we supposed to support multiple pointer sizes
in the same compilation unit, or not?