[Bug c++/82496] Optimization breaks duration_cast

[jeff.benshetler at stackpath dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82496

--- Comment #2 from Jeff Benshetler <jeff.benshetler at stackpath dot com> ---
I confirmed that the identical problem exists on Linux for both gcc-6.4.0 and
gcc-7.2.0.