https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77848
--- Comment #17 from Richard Biener <rguenth at gcc dot gnu.org> --- Nono, you misunderstood -- I meant for the if-converter to produce if (LOOP_VECTORIZED) { for (;;) // outer loop for (;;) // if-converted inner loop } else { for (;;) // outer loop for (;;) // inner loop } if (and only if) the outer loop CFG shape matches what the vectorizer will later eventually handle. You still need adjustments to the vectorizer but only in its handling of eliminating the LOOP_VECTORIZED conditional.