The checks are done outside of the loop though (unless you mean ≥two nested loops, with a small-ish inner one, at which point things indeed get less nice, but also this is less common).

Yeah, autovectorization of a manual tail loop can be annoying, but there is "#pragma clang loop unroll(disable)" and "#pragma clang loop vectorize(disable)" for clang, and for gcc "#pragma GCC unroll 1" and, from gcc 14, "#pragma GCC novector".