https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80878
Alexander Monakov <amonakov at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
CC| |amonakov at gcc dot gnu.org
Resolution|--- |INVALID
--- Comment #6 from Alexander Monakov <amonakov at gcc dot gnu.org> ---
There's a bit of a misunderstanding here, the -mcx16 option remains supported,
and the compiler remains capable of issuing lock-cmpxchg16b for __sync
builtins, in particular for __sync_val_compare_and_swap. What changed in gcc-7
is that __atomic builtins that would previously get expanded to a sequence
involving cmpxchg16b now always yield a library call on x86, but libatomic
tries to support that efficiently by using cmpxchg16b internally, on CPUs that
have it and on targets that support IFUNC.
No bug here, rather a (non-obvious imho) design change.
