Re: [PATCH][RFT] Vectorization of first-order recurrences

[Richard Sandiford via Gcc-patches]

Richard Biener <rguent...@suse.de> writes:
> +  /* First-order recurrence autovectorization needs to handle permutation
> +     with indices = [nunits-1, nunits, nunits+1, ...].  */
> +  vec_perm_builder sel (nunits, 1, 3);
> +  for (int i = 0; i < 3; ++i)
> +    sel.quick_push (nunits - dist + i);
> +  vec_perm_indices indices (sel, 1, nunits * 2);

Should be:

  vec_perm_indices indices (sel, 2, nunits);

With that change, the patch passes testing on SVE.  vect-recurr-6.c
fails to vectorise, but I think that's because SVE doesn't yet support
the required permute.

Thanks,
Richard