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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/103544] [11/12 Regression] compiler crashes
 when trying to vectorize loop
Date: Mon, 06 Dec 2021 09:52:39 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103544

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

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

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
  if (!single_defuse_cycle
      && !lane_reduc_code_p
      && reduction_type !=3D FOLD_LEFT_REDUCTION)
    {
      stmt_vec_info tem
        =3D vect_stmt_to_vectorize (STMT_VINFO_REDUC_DEF (phi_info));
      if (slp_node && REDUC_GROUP_FIRST_ELEMENT (tem))
        {
          gcc_assert (!REDUC_GROUP_NEXT_ELEMENT (tem));
          tem =3D REDUC_GROUP_FIRST_ELEMENT (tem);
        }
      STMT_VINFO_DEF_TYPE (vect_orig_stmt (tem)) =3D vect_internal_def;
      STMT_VINFO_DEF_TYPE (tem) =3D vect_internal_def;

fails to work here, because we end up visiting the reduction stmt before the
reduction PHI because we have a hybrid use that makes another entry into the
SLP graph, reaching the reduction stmt over the backedge.

But the above relies on us doing the reduction analysis on the PHI node bef=
ore
the analysis of the reduction stmt.=