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From: "juzhe.zhong at rivai dot ai" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/113441] [14 Regression] Fail to fold the last
 element with multiple loop
Date: Tue, 23 Jan 2024 08:15:33 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113441

--- Comment #12 from JuzheZhong <juzhe.zhong at rivai dot ai> ---
(In reply to Richard Biener from comment #11)
> (In reply to Tamar Christina from comment #9)
> > There is a weird costing going on in the PHI nodes though:
> >=20
> > m_108 =3D PHI <m_92(16), m_111(5)> 1 times vector_stmt costs 0 in body=
=20
> > m_108 =3D PHI <m_92(16), m_111(5)> 2 times scalar_to_vec costs 0 in pro=
logue
> >=20
> > they have collapsed to 0. which can't be right..
>=20
> Note this is likely because of the backend going wrong.
>=20
> bool
> vectorizable_phi (vec_info *,
>                   stmt_vec_info stmt_info, gimple **vec_stmt,
>                   slp_tree slp_node, stmt_vector_for_cost *cost_vec)
> {
> ..
>=20
>       /* For single-argument PHIs assume coalescing which means zero cost
>          for the scalar and the vector PHIs.  This avoids artificially
>          favoring the vector path (but may pessimize it in some cases).  =
*/
>       if (gimple_phi_num_args (as_a <gphi *> (stmt_info->stmt)) > 1)
>         record_stmt_cost (cost_vec, SLP_TREE_NUMBER_OF_VEC_STMTS (slp_nod=
e),
>                           vector_stmt, stmt_info, vectype, 0, vect_body);
>=20
> You could check if we call this with sane values.

Do you mean it's RISC-V backend cost model issue ?=