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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/99412] s352 benchmark of TSVC is vectorized
 by clang and not by gcc
Date: Thu, 12 Jan 2023 09:30:07 +0000
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X-Bugzilla-Component: tree-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99412

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #3)
> (In reply to Jan Hubicka from comment #2)
> > This is also seen with zen4 comparing gcc and aocc. (about 2.3 times
> > differnece)
>=20
> Disabling
>=20
> @@ -6877,7 +6887,7 @@ reassociate_bb (basic_block bb)
>                           binary op are chosen wisely.  */
>                        int len =3D ops.length ();
>                        if (len >=3D 3)
>                          swap_ops_for_binary_stmt (ops, len - 3, stmt);
>=20
> will naturally create the reduction chain (or leave it in place) given the
> current rank computation.  We do have (somewhat) robust fallback from
> reduction chain to reduction (via reduction path support), so I think this
> change would be OK.

The code originated from r0-111616-gdf7b0cc4aae062, the reassoc rewrite by
Jeff back in 2005 for GCC 4.3 (or 4.2, don't have that tree around anymore)=
.=