[Bug tree-optimization/66142] Loop is not vectorized because not sufficient support for GOMP_SIMD_LANE

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66142

--- Comment #17 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ok, so even with PR63916 rudimentary fixed we hit the issue that in

  _9 = &D.3665[_11].org;
  MEM[(struct vec_ *)_9] = 1.0e+0;
  MEM[(struct vec_ *)_9 + 4B] = _8;
...
  _24 = MEM[(const struct Ray *)&D.3665][_11].org.x;

the store to MEM[(struct vec_ *)_9 + 4B] aliases MEM[(const struct Ray
*)&D.3665][_11].org.x.

And the rudimentary fix for PR63916 doesn't allow for the forwarding to succeed
into MEM[(struct vec_ *)_9 + 4B] either.

Without SRA we get

  D.3665[_11].org = p;
  D.3665[_11].dir.x = x_12;
  D.3665[_11].dir.y = y_13;
  D.3664[_11].t = 1.0e+10;
  D.3664[_11].h = 0;
  _25 = MEM[(const struct Ray *)&D.3665][_11].org.x;

and the look-through-aggregate-copy code bails out at

      /* See if the assignment kills REF.  */
      base2 = ao_ref_base (&lhs_ref);
      offset2 = lhs_ref.offset;
      size2 = lhs_ref.size;
      maxsize2 = lhs_ref.max_size;
      if (maxsize2 == -1
          || (base != base2
              && (TREE_CODE (base) != MEM_REF
                  || TREE_CODE (base2) != MEM_REF
                  || TREE_OPERAND (base, 0) != TREE_OPERAND (base2, 0)
                  || !tree_int_cst_equal (TREE_OPERAND (base, 1),
                                          TREE_OPERAND (base2, 1))))
          || offset2 > offset
          || offset2 + size2 < offset + maxsize)
        return (void *)-1;

stmt_kills_ref_p fails to compare
MEM[(const struct Ray *)&D.3665][_15].org and D.3665[_15].org
equal via operand_equal_p.