[Bug tree-optimization/91201] [7/8/9/10 Regression] SIMD not generated for horizontal sum of bytes in array

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91201

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2

--- Comment #25 from Richard Biener <rguenth at gcc dot gnu.org> ---
We unroll the loop completely but our basic-block vectorization capabilities do
not include reductions.  We see the following there:

  <bb 2> [local count: 357878154]:
  temp_33 = bytes[0];
  _34 = temp_33 >> 32;
  temp_35 = temp_33 + _34;
  _36 = temp_35 >> 16;
  temp_37 = temp_35 + _36;
  _38 = temp_37 >> 8;
  temp_44 = bytes[1];
  _45 = temp_44 >> 32;
  temp_46 = temp_44 + _45;
  _47 = temp_46 >> 16;
  temp_48 = temp_46 + _47;
  _40 = temp_37 + temp_48;
  _49 = temp_48 >> 8;
  _51 = _38 + _40;
  result_29 = _49 + _51;
  _20 = (unsigned char) result_29;
  b ={v} {CLOBBER};
  return _20;