[Bug tree-optimization/98138] BB vect fail to SLP one case

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98138

--- Comment #17 from Kewen Lin <linkw at gcc dot gnu.org> ---
ccp1:

  t0_83 = a0_79 + a1_80;
  t1_84 = a0_79 - a1_80;
  t2_85 = a2_81 + a3_82;
  t3_86 = a2_81 - a3_82;
  _63 = t0_83 + t2_85;
  tmp[i_71][0] = _63;
  _64 = t0_83 - t2_85;
  tmp[i_71][2] = _64;
  _65 = t1_84 + t3_86;
  tmp[i_71][1] = _65;
  _66 = t1_84 - t3_86;
  tmp[i_71][3] = _66;
  i_91 = i_71 + 1;

=> 

forwprop1:

  t0_83 = a0_79 + a1_80;
  t1_84 = a0_79 - a1_80;
  t2_85 = a2_81 + a3_82;
  t3_86 = a2_81 - a3_82;
  _63 = t0_83 + t2_85;
  tmp[i_71][0] = _63;
  _64 = t0_83 - t2_85;
  tmp[i_71][2] = _64;
  _65 = t1_84 + t3_86;
  tmp[i_71][1] = _65;
  _73 = a3_82 - a2_81;
  _66 = _73 + t1_84;  // changed from t1_84 - t3_86;
  tmp[i_71][3] = _66;
  i_91 = i_71 + 1;

due to match.pd rule:

/* A - B -> A + (-B) if B is easily negatable.  */
(simplify
 (minus @0 negate_expr_p@1)
 (if (!FIXED_POINT_TYPE_P (type))
 (plus @0 (negate @1))))