[Bug tree-optimization/92819] [10 Regression] Worse code generated on avx2 due to simplify_vector_constructor

[rsandifo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92819

--- Comment #5 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> 
---
Sorry for the dribble of messages, but how about just
changing the "else" in:

            if (sel.series_p (1, 1, nelts + 1, 1))
              {
                /* After canonicalizing the first elt to come from the
                   first vector we only can insert the first elt from
                   the first vector.  */
                at = 0;
                if ((ins = fold_read_from_vector (cop0, sel[0])))
                  op0 = op1;
              }
            else

to "if (!ins)"?