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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/110754] assume create spurious load for volatile variable
Date: Thu, 20 Jul 2023 22:42:02 +0000	[thread overview]
Message-ID: <bug-110754-4-Xehf0sR34c@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-110754-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110754

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2023-07-20
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
           Keywords|                            |wrong-code
          Component|c++                         |middle-end

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Xi Ruoyao from comment #1)
> Is this a bug?  The standard defines accessing volatile objects as
> side-effects so it's not allowed to merge volatile loads, AFAIU.

Yes because assume attribute is defined not to have any side effects.

Confirmed.

gimplifier produces:

  [[assume (D.2786)]]
    {
      {
        int n.0;

        n.0 = n;
        D.2786 = n.0 == 1;
      }
    }

And then lowering produces:
  _2 = n;
  .ASSUME (_Z3bari._assume.0, _2);

But really it should have passed the address of n rather than the value since n
is volatile here .

  parent reply	other threads:[~2023-07-20 22:42 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-20 19:16 [Bug c++/110754] New: " muecker at gwdg dot de
2023-07-20 22:34 ` [Bug c++/110754] " xry111 at gcc dot gnu.org
2023-07-20 22:42 ` pinskia at gcc dot gnu.org [this message]
2023-07-20 22:44 ` [Bug middle-end/110754] " pinskia at gcc dot gnu.org
2023-07-20 22:45 ` xry111 at gcc dot gnu.org
2023-07-21  6:44 ` rguenth at gcc dot gnu.org
2023-07-21  8:33 ` muecker at gwdg dot de
2024-02-09  9:15 ` jakub at gcc dot gnu.org
2024-02-09 15:00 ` jakub at gcc dot gnu.org
2024-02-10 10:28 ` cvs-commit at gcc dot gnu.org
2024-03-02  0:38 ` cvs-commit at gcc dot gnu.org
2024-03-04 12:09 ` jakub at gcc dot gnu.org

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