Well, if the function is marked "static", the compiler can actually check whether the function's address is taken in the current compilation unit or not and omit/emit ENDBR64 accordingly (passing pointers to static functions to code in another compilation units is legal, and should still work).
Good catch. Yeah, as long as the functions address is never taken the compiler has a lot of leeway with static functions; it can even avoid emitting code for them entirely if it can prove they're never called or if it's able to compute their results at compile-time.
