[Bug middle-end/40135] using alias-set zero for union accesses necessary because of RTL alias oracle

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=40135

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Eventually just removing the call to mems_in_disjoint_alias_sets_p fixes the
rest (rtx_refs_may_alias_p will apply TBAA as well, _after_ positively
bailing out on the union punning).