Yep. It should (hopefully!) be self-evident that "hot loops" in which single-digit nanosecond performance differences are meaningful, are (a) exceptional; and,

Yep. It should (hopefully!) be self-evident that "hot loops" in which single-digit nanosecond performance differences are meaningful, are (a) exceptional; and, more importantly, (b) not a place where you'd make any kind of function call in the first place!