[Bug tree-optimization/102806] [x86] Suboptimal codegen for v4hi vector concat under -mavx512bw and -mavx512vl

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102806
Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2021-10-18
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
           Severity|normal                      |enhancement
          Component|target                      |tree-optimization

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
It is because we don't optimize:

  _1 = {a_3(D), { 0, 0, 0, 0 }};
  _2 = {b_4(D), { 0, 0, 0, 0 }};
  _5 = VEC_PERM_EXPR <_1, _2, { 0, 1, 2, 3, 8, 9, 10, 11 }>;

To just
_5 = {a_3(D), b_4(D)};