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 6FD34385E004; Tue, 29 Mar 2022 05:54:36 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 6FD34385E004
From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/104971] [9/10/11 Regression] Optimisation for
 __builtin_ia32_readeflags corrupts the stack
Date: Tue, 29 Mar 2022 05:54:35 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 12.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: cvs-commit at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 9.5
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-104971-4-iVPO0VPHTv@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-104971-4@http.gcc.gnu.org/bugzilla/>
References: <bug-104971-4@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, 29 Mar 2022 05:54:36 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D104971

--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-11 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:be64c349e7312a4e89c569d42c4e2284610d4908

commit r11-9733-gbe64c349e7312a4e89c569d42c4e2284610d4908
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Mar 19 13:53:12 2022 +0100

    i386: Don't emit pushf;pop for __builtin_ia32_readeflags_u* with unused=
 lhs
[PR104971]

    __builtin_ia32_readeflags_u* aren't marked const or pure I think
    intentionally, so that they aren't CSEd from different regions of a
function
    etc. because we don't and can't easily track all dependencies between
    it and surrounding code (if somebody looks at the condition flags, it is
    dependent on the vast majority of instructions).
    But the builtin itself doesn't have any side-effects, so if we ignore t=
he
    result of the builtin, there is no point to emit anything.

    There is a LRA bug that miscompiles the testcase which this patch makes
    latent, which is certainly worth fixing too, but IMHO this change
    (and maybe ix86_gimple_fold_builtin too which would fold it even earlier
    when it looses lhs) is worth it as well.

    2022-03-19  Jakub Jelinek  <jakub@redhat.com>

            PR middle-end/104971
            * config/i386/i386-expand.c
            (ix86_expand_builtin) <case IX86_BUILTIN_READ_FLAGS>: If ignore,
            don't push/pop anything and just return const0_rtx.

            * gcc.target/i386/pr104971.c: New test.

    (cherry picked from commit b60bc913cca7439d29a7ec9e9a7f448d8841b43c)=