[Bug target/87598] [8/9 Regression] Rejects "%a0" with constant

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87598

--- Comment #2 from Segher Boessenkool <segher at gcc dot gnu.org> ---
rs6000.c print_operand_address does not like (const_int 0) or any other
const_int.  Power *can* actually have constant numbers as data addresses,
but only for instructions that have some D form; and GCC does not support
such constant addresses currently.

We could do output_operand_lossage, or we could do as most targets do here:
call output_addr_const and hope for the best (it will output just "0" with
this testcase).  Is that preferred?