GCC never evaluates __atomic_is_lock_free to 0. (gcc/builtins.c:fold_builtin_atomic_always_lock_free) I'd like to change clang to eagerly evaluate __atomic_is_lock_free to 0 for apparently oversized types. This helps some platforms to avoid a dependency on libatomic.
Either of the following choices can move my patch https://reviews.llvm.org/D72579 forward: * GCC will like do the same * GCC is committed to not extend __atomic_is_lock_free in a clang incompatible way.
