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From: "rguenther at suse dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/31178] VRP can infer a range for b in a >> b and a << b
Date: Wed, 23 Mar 2022 08:08:48 +0000 [thread overview]
Message-ID: <bug-31178-4-vfNT7LPACA@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-31178-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=31178
--- Comment #10 from rguenther at suse dot de <rguenther at suse dot de> ---
On Tue, 22 Mar 2022, amacleod at redhat dot com wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=31178
>
> Andrew Macleod <amacleod at redhat dot com> changed:
>
> What |Removed |Added
> ----------------------------------------------------------------------------
> CC| |amacleod at redhat dot com
>
> --- Comment #8 from Andrew Macleod <amacleod at redhat dot com> ---
> Is this always true?
>
> I implemented this for GCC13 in the new side-effect code, and its causing
> problems in fortran.
>
> In particular gfortran.dg/check_bits_1.f90 goes into an infinite loop. I am
> seeing things like
>
> nb = bit_size (i)
> do shift = 0, nb
> k = shiftl (i, shift) ! Fortran 2008
> i = shiftr (k, shift)
>
> So it appears to do shifts on [0, 32] rather than [0, 31], and when I go look
> for fortran 2008 info, i find:
>
> "Its value must be non-negative, and less than or equal to BIT_SIZE(I)"
>
> so it seem [0, N] for fortran rather than [0, N)? Are there other language
> issues as well?
Interesting. For GIMPLE we of course have to find common ground which
then means to allow N as well.
next prev parent reply other threads:[~2022-03-23 8:08 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-31178-4@http.gcc.gnu.org/bugzilla/>
2013-02-11 7:48 ` rguenth at gcc dot gnu.org
2013-02-11 8:00 ` jakub at gcc dot gnu.org
2022-03-22 14:21 ` amacleod at redhat dot com
2022-03-22 17:03 ` amacleod at redhat dot com
2022-03-23 8:08 ` rguenther at suse dot de [this message]
2022-03-23 8:26 ` jakub at gcc dot gnu.org
2022-03-23 8:31 ` jakub at gcc dot gnu.org
2022-04-05 17:58 ` amacleod at redhat dot com
2022-04-05 18:06 ` jakub at gcc dot gnu.org
2022-04-05 18:24 ` amacleod at redhat dot com
2022-04-06 6:00 ` rguenth at gcc dot gnu.org
2022-04-06 8:16 ` vincent-gcc at vinc17 dot net
2022-04-06 8:22 ` rguenther at suse dot de
2022-04-06 8:45 ` vincent-gcc at vinc17 dot net
2022-04-06 13:10 ` amacleod at redhat dot com
2022-04-06 13:13 ` jakub at gcc dot gnu.org
2022-04-06 13:16 ` rguenther at suse dot de
2024-06-20 16:07 ` pinskia at gcc dot gnu.org
2024-06-26 5:44 ` pinskia at gcc dot gnu.org
2007-03-14 21:13 [Bug tree-optimization/31178] New: " rguenth at gcc dot gnu dot org
2007-03-15 14:43 ` [Bug tree-optimization/31178] " rguenth at gcc dot gnu dot org
2009-02-08 14:21 ` steven at gcc dot gnu dot org
2009-02-08 14:47 ` rguenth at gcc dot gnu dot org
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