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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/105533] UBSAN: gcc/expmed.cc:3272:26: runtime error: signed integer overflow: -9223372036854775808 - 1 cannot be represented in type 'long int'
Date: Thu, 07 Mar 2024 07:32:00 +0000 [thread overview]
Message-ID: <bug-105533-4-IpOJoVFr2J@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-105533-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105533
--- Comment #10 from rguenther at suse dot de <rguenther at suse dot de> ---
On Wed, 6 Mar 2024, jakub at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105533
>
> Jakub Jelinek <jakub at gcc dot gnu.org> changed:
>
> What |Removed |Added
> ----------------------------------------------------------------------------
> CC| |rguenth at gcc dot gnu.org
>
> --- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
> The second UB is on
> #2 ao_ref_init_from_vn_reference (ref=<optimized out>, set=1, base_set=1,
> type=<optimized out>, ops=...) at ../../gcc/tree-ssa-sccvn.cc:1224
> 1224 offset += op->off << LOG2_BITS_PER_UNIT;
> where op->off is negative.
> Isn't this just an unnecessary optimization? I mean can't we just do
> offset += op->off * BITS_PER_UNIT;
> BITS_PER_UNIT is a constant 8 on all targets we support...
It's a habit from dealing with offset_int (but this is poly_int64)
where the multiply is possibly a lot more costly than a shift.
So yeah, a multiply is fine I guess.
next prev parent reply other threads:[~2024-03-07 7:32 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-09 11:27 [Bug tree-optimization/105533] New: " zsojka at seznam dot cz
2022-10-31 3:32 ` [Bug middle-end/105533] " pinskia at gcc dot gnu.org
2024-03-05 19:20 ` dcb314 at hotmail dot com
2024-03-06 9:30 ` dcb314 at hotmail dot com
2024-03-06 10:33 ` jakub at gcc dot gnu.org
2024-03-06 11:39 ` dcb314 at hotmail dot com
2024-03-06 13:37 ` jakub at gcc dot gnu.org
2024-03-06 13:45 ` jakub at gcc dot gnu.org
2024-03-06 13:56 ` jakub at gcc dot gnu.org
2024-03-06 15:16 ` jakub at gcc dot gnu.org
2024-03-07 7:32 ` rguenther at suse dot de [this message]
2024-03-07 9:08 ` cvs-commit at gcc dot gnu.org
2024-03-07 9:08 ` cvs-commit at gcc dot gnu.org
2024-03-08 8:28 ` dcb314 at hotmail dot com
2024-03-08 8:29 ` jakub at gcc dot gnu.org
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