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From: "rdapp at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/111760] risc-v regression: COND_LEN_*
 incorrect fold/simplify in middle-end
Date: Tue, 10 Oct 2023 21:02:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D111760

Robin Dapp <rdapp at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rdapp at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org

--- Comment #2 from Robin Dapp <rdapp at gcc dot gnu.org> ---
https://gcc.gnu.org/pipermail/gcc-patches/2023-September/629904.html

prevents the wrong code but still leaves us with a redundant negation (and =
it
is not the only missed optimization of that kind):

  vect_neg_xi_14.4_23 =3D -vect_xi_13.3_22;
  vect_res_2.5_24 =3D .COND_LEN_ADD ({ -1, ... }, vect_res_1.0_17,
vect_neg_xi_14.4_23, vect_res_1.0_17, _29, 0);

That's because my "hackaround" doesn't recognize a valueized sequence
_30 =3D vect_res_1.0_17 - vect_xi_13.3_22;

Of course I could (reverse valueize) recognize that again and convert it to=
 a
COND_LEN... but that doesn't seem elegant at all.  There must be a simpler =
way
that I'm missing entirely right now.  That said, converting the last statem=
ent
of such a sequence should be sufficient?=