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From: "crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug tree-optimization/102131] [12 Regression] wrong code at -O1 and
 above on x86_64-linux-gnu since r12-3136
Date: Tue, 25 Jan 2022 01:28:35 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102131

Hongtao.liu <crazylht at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |crazylht at gmail dot com

--- Comment #13 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to CVS Commits from comment #11)
> The master branch has been updated by Richard Biener <rguenth@gcc.gnu.org=
>:
>=20
> https://gcc.gnu.org/g:f1af8528d34418bc874ae9d993ee0dc3559972d2
>=20
> commit r12-6844-gf1af8528d34418bc874ae9d993ee0dc3559972d2
> Author: Richard Biener <rguenther@suse.de>
> Date:   Mon Jan 24 11:50:06 2022 +0100
>=20
>     tree-optimization/102131 - fix niter analysis wrt overflow
>=20=20=20=20=20
>     This fixes the overflow issues seen with analyzing
>     BASE0 + STEP0 cmp BASE1 + STEP1 as BASE0 + STEP0 - STEP1 cmp BASE1
>     by following the logic we have when simplifying comparisons.
>=20=20=20=20=20
>     2022-01-24  Richard Biener  <rguenther@suse.de>
>                 Jiufu Guo  <guojiufu@linux.ibm.com>
>=20=20=20=20=20
>             PR tree-optimization/100740
>             PR tree-optimization/101508
>             PR tree-optimization/101972
>             PR tree-optimization/102131
>             * tree-ssa-loop-niter.cc (number_of_iterations_cond): Properly
>             constrain BASE0 + STEP0 cmp BASE1 + STEP1 to
>             BASE0 + STEP0 - STEP1 cmp BASE1 transform.
>=20=20=20=20=20
>             * gcc.dg/torture/pr100740.c: New testcase.
>             * gcc.dg/torture/pr101508.c: Likewise.
>             * gcc.dg/torture/pr101972.c: Likewise.
>             * gcc.dg/torture/pr102131-1.c: Likewise.
>             * gcc.dg/torture/pr102131-2.c: Likewise.
>             * gcc.dg/torture/pr102131-3.c: Likewise.
>             * gcc.dg/torture/pr102131-4.c: Likewise.

It regresses
https://gcc.gnu.org/pipermail/gcc-regression/2022-January/076279.html=