flag-setting instruction

An instruction that updates the status flags. On ARM64 only some do, marked by an s on the end, like adds and subs.

x86-64 arithmetic and logic instructions (add, sub, neg, and, or, xor and others) set flags as a side effect while mov and lea do not; ARM64 arithmetic leaves NZCV alone unless the S-suffixed form (adds, subs, ands) is used.