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 C833B388F400; Tue,  5 May 2020 22:41:27 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C833B388F400
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
 s=default; t=1588718487;
 bh=VNjJ0SHqYRtxWbXK7FGaFDqWPWgEVZLmTiyKTOCdLao=;
 h=From:To:Subject:Date:From;
 b=CoAd6EaKO+s5KZvqH2TzAes0j953757pnCHpS1rGuAgMnw5jIvvqdW9xa5CxQCm01
 /MBZ3ySJaKr4xE7defrEywhuThws7QwKen8fVyGPHePxcK71uPuTJo0x9bUWerWb9k
 fCD7WnnZ6F4ENB4E35/WVos2mkIPlv8+x0Z0ndm0=
From: "jsm28 at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/94963] New: [11 Regression] Spurious
 uninitialized warning for static variable building glibc
Date: Tue, 05 May 2020 22:41:27 +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: jsm28 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
Message-ID: <bug-94963-4@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: <http://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: <http://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Tue, 05 May 2020 22:41:27 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94963

            Bug ID: 94963
           Summary: [11 Regression] Spurious uninitialized warning for
                    static variable building glibc
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jsm28 at gcc dot gnu.org
  Target Milestone: ---

r11-39-gf9e1ea10e657af9fb02fafecf1a600740fd34409 ("tree-optimization/39612 -
avoid issueing loads in SM when possible") introduces a spurious warning
building the following code (reduced from glibc) with -O2 -Wall (for
aarch64-linux-gnu at least, probably for other targets.  The warning is
obviously bogus because it relates to a field of a static variable, which is
always initialized.

uninit.c: In function 'f':
uninit.c:30:6: warning: 'var_field_lsm.8' may be used uninitialized in this
function [-Wmaybe-uninitialized]
   30 |   if (var.field !=3D 0)
      |      ^


Reduced testcase:

typedef struct
{
  int p1;
  int p2;
  int p3;
} P;
struct S
{
  int field;
};
extern int v2;
extern void foo (struct S *map);
static struct S var;
const P *pv;
int ps;
void
f (void)
{
  if (pv !=3D 0)
    for (const P *ph =3D pv; ph < &pv[ps]; ++ph)
      switch (ph->p1)
        {
        case 1:
          v2 =3D ph->p2;
          break;
        case 2:
          var.field =3D ph->p3;
          break;
        }
  if (var.field !=3D 0)
    foo (&var);
}=