[Bug libstdc++/99277] C++2a synchronisation is inefficient in GCC 11

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99277

--- Comment #20 from Jonathan Wakely <redi at gcc dot gnu.org> ---
We've already done it with other C++20 types, and we did it with C++17 types
before that.