Yes, there's been a recommendation floating around for a long time that branch/call targets should be 16-byte aligned. However, my experience is that modern x86 is basically almost completely insensitive to alignment in general (there are some small exceptions, like avoiding crossing cacheline boundaries in a loop.) It wouldn't surprise me if the NOPs only helped on earlier models, had no effect or even a negative effect on more recent CPUs, and were just left in out of tradition.