[Bug libstdc++/51798] [4.7 regression] libstdc++ atomicity performance regression due to __sync_fetch_and_add

[dje at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51798

--- Comment #3 from David Edelsohn <dje at gcc dot gnu.org> 2012-01-09 17:11:32 UTC ---
Another alternative is to modify __gnu_cxx::_atomic_add() to perform acquire
semantics for positive increments and release semantics for negative
increments.  That avoid creating a new function in the __gnu_cxx space.