https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63704
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Oh, no. It's actually a genuine bug.
__attribute__((optimize("O3"))) enables -fstrict-aliasing, so if the
rest of the TU is compiled with -fno-strict-aliasing it depends on
prue luck if 'int' (as in this case) gets alias-set zero (a function
compiled with -fno-strict-aliasing calls get_alias_set on it) or
a non-zero alias-set (the -O3 function calls get_alias_set on 'int').
Of course LTO just makes it more likely to trigger.
-> -fstrict-aliasing may not be altered via attribute((optimize())).
