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 78AC83858429; Tue,  5 Oct 2021 14:51:33 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 78AC83858429
From: "law at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/102608] New: [12 regression] Recent change to
 VN causes bogus Wuninitialized warnings & kernel build failures
Date: Tue, 05 Oct 2021 14:51:33 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 11.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: law at gcc dot gnu.org
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
 attachments.created
Message-ID: <bug-102608-4@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
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <https://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <https://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Tue, 05 Oct 2021 14:51:33 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102608

            Bug ID: 102608
           Summary: [12 regression] Recent change to VN causes bogus
                    Wuninitialized warnings & kernel build failures
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: law at gcc dot gnu.org
  Target Milestone: ---

Created attachment 51555
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D51555&action=3Dedit
Testcase

This change:
55a3be2f5255d69e740d61b2c5aaba1ccbc643b8 is the first bad commit
commit 55a3be2f5255d69e740d61b2c5aaba1ccbc643b8
Author: Richard Biener <rguenther@suse.de>
Date:   Mon Oct 4 10:57:45 2021 +0200

    tree-optimization/102570 - teach VN about internal functions

    We're now using internal functions for a lot of stuff but there's
    still missing VN support out of laziness.  The following instantiates
    support and adds testcases for FRE and PRE (hoisting).

Is causing mips64-linux-gnu and mips64el-linux-gnu kernel build failures du=
e to
a bogus uninitialized warning with the attached file when compiled with -O2
-ftrivial-auto-var-init=3Dzero:

../arch/mips/kernel/cmpxchg.c: In function '__xchg_small':
../arch/mips/kernel/cmpxchg.c:44:36: warning: 'old32' is used uninitialized
[-Wuninitialized]
../arch/mips/kernel/cmpxchg.c:12:6: note: 'old32' was declared here
 __cmpxchg_small
../arch/mips/kernel/cmpxchg.c: In function '__cmpxchg_small':
../arch/mips/kernel/cmpxchg.c:100:36: warning: 'mask' may be used uninitial=
ized
[-Wmaybe-uninitialized]
../arch/mips/kernel/cmpxchg.c:53:6: note: 'mask' was declared here


I haven't tracked this down any further.=