[Bug target/86019] Unref implementation using atomic_thread_fence generates worse code on x86-64 in gcc 8.1 than 7.3

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86019

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |x86_64
                URL|                            |missed-optimization
          Component|c++                         |target

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I suspect memory_order_acquire is being treated as a compiler memory barrier
and that is causing an empty basic block (it is not truly empty).