[Bug target/107456] std::atomic::fetch_xxx generate LOCK CMPXCHG instead of simpler LOCK instructions

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107456

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I was going to say the exact same comment as on LLVM bug report:
https://github.com/llvm/llvm-project/issues/58685#issuecomment-1295829030

There is no way atomically fetch and add without xadd.

There is no "x"and/"x"or  instruction on x86 (note the x here stands for
exchange rather than exclusive as there is an xor but that is an "exclusive
or").