https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49244
--- Comment #7 from dhowells at redhat dot com <dhowells at redhat dot com> --- We should also be able to reduce: bool test_bit (int *a, int bit) { uint mask = (1u << bit); return (__atomic_load_n (a, __ATOMIC_xxx) & mask) != 0; } to a BT instruction on x86.