[Bug sanitizer/84340] [8 regression] g++.dg/asan/use-after-scope-types-1.C (and others) fails after r257585

[bonzini at gnu dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84340

--- Comment #14 from Paolo Bonzini <bonzini at gnu dot org> ---
I'll just revert the original PR84307 patch.  Changing the fnspec has way too
many ramifications.  PR84307 can either be fixed with an early UNPOISON
elimination pass, or delayed to GCC 9 where we can play with pass reordering.