From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id 404FD3858CDB; Thu, 20 Jul 2023 19:16:39 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 404FD3858CDB
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1689880599;
	bh=9/EejJAAG4O6vt1VJuycSpljcWvTH+ZdnWKTxXUKuXs=;
	h=From:To:Subject:Date:From;
	b=jE4TrGYjqWHnck4OeVU90aMONHCUBBLO6G87+0mhuHtDCd+F8d9kwTV1lM9xqXs5+
	 dFWSvyRf/q14JhFb6Z++o7cGCnhNwYqsnmS2bz6ElvELVI1X2UxrHt5CtsHrSiqVmc
	 kOOJCoZ7z32ySodFil58E1SpzjxqmBBvG+j5SM0A=
From: "muecker at gwdg dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/110754] New: assume create spurious load for volatile
 variable
Date: Thu, 20 Jul 2023 19:16:39 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: muecker at gwdg dot de
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-110754-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110754

            Bug ID: 110754
           Summary: assume create spurious load for volatile variable
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: muecker at gwdg dot de
  Target Milestone: ---

With optimization, using assume with volatile create spurious loads:

int bar(int p)
{
    volatile int n =3D p;
    [[assume (1 =3D=3D n)]];
    return 1 + n;
}


bar(int):
        mov     DWORD PTR [rsp-4], edi
        mov     eax, DWORD PTR [rsp-4]
        mov     eax, DWORD PTR [rsp-4]
        add     eax, 1
        ret=