__sync_fetch_and_{add,sub,and,or,xor}_16 and __sync_lock_test_and_set_16 are
cmpxchg16b loops returning the previous value, and __atomic_is_lock_free
answers by size and alignment, as in the libc.prx bundled with PPSA08427. Its
generic __atomic_load/store/exchange/compare_exchange are a ud2, so they throw.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Q8tinbP1MUpUaDsbNWnGnu
