[Bug c++/81906] [7/8 Regression] Calls to rint() wrongly optimized away starting in g++ 6

["vz-gcc at zeitlins dot org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81906

--- Comment #5 from Vadim Zeitlin <vz-gcc at zeitlins dot org> ---
Yes, I did find this documentation myself in the meanwhile and I agree that
you're formally correct, just as gcc developers are formally correct in the
long discussion at #34678 (which I really wouldn't want to reopen), but this is
not very helpful in practice because this information is completely
undiscoverable, i.e. you can only find it if you already know what you're
looking for (or enjoy reading compiler optimization options documentation as a
hobby, of course).

Perhaps you could consider this as a QoI issue, but it would be really great if
gcc could give a warning if the code tries to use fesetround() without
-frounding-math being on.