[Bug tree-optimization/126028] GCC trunk vs ICX : Missed SLP vectorization

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126028

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
The testcase is now vectorized.  What's missing is more optimal handling of


  pj_x_0 = p_1[jprev0].position.x;  pj_x_1 = p_1[jprev1].position.x;
  pj_y_0 = p_1[jprev0].position.y;  pj_y_1 = p_1[jprev1].position.y;
..
  for (;;)
...
     pj_x_0 = p_1[jprev0].position.x;  pj_x_1 = p_1[jprev1].position.x;
     pj_y_0 = p_1[jprev0].position.y;  pj_y_1 = p_1[jprev1].position.y;

where the three vectors {pj_x_1, pj_x_0}, {pj_y_1, pj_y_0} and {pj_z_1, pj_z_0
}
are constructed from scalar loads (because the vector SLP involves two
distinct load groups).  It's not clear whether two V2DF loads plus
shuffling would be more efficient.  I have a heuristic patch that moves
the CTORs to the latch and the preheader instead of constructing from the
PHI which removes an IV.