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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/100171] autovectorizer
Date: Wed, 21 Apr 2021 08:25:13 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100171

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Compared to the non-self case where we see

  <bb 2> [local count: 357878152]:
  _19 =3D MEM <const double[2]> [(const value_type &)arg1_3(D)][0];
  _20 =3D MEM <const double[2]> [(const value_type &)arg2_4(D)][0];
  _21 =3D _19 + _20;
  _26 =3D MEM <const double[2]> [(const value_type &)arg1_3(D)][1];
  _27 =3D MEM <const double[2]> [(const value_type &)arg2_4(D)][1];
  _28 =3D _26 + _27;
  res =3D{v} {CLOBBER};
  MEM[(struct value_type *)out_2(D)][0].value._M_elems[0] =3D _21;
  MEM[(struct value_type *)out_2(D)][0].value._M_elems[1] =3D _28;
  return;

here intermediate optimizations have elided 'res'.=