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 A047C398B436; Fri,  9 Apr 2021 11:37:46 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A047C398B436
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/99862] [meta-issue] various missed optimizations for dead
 code elimination
Date: Fri, 09 Apr 2021 11:37:46 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: ipa
X-Bugzilla-Version: unknown
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth 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: 
Message-ID: <bug-99862-4-iisooouKX4@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-99862-4@http.gcc.gnu.org/bugzilla/>
References: <bug-99862-4@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: Fri, 09 Apr 2021 11:37:46 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99862

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Zhendong Su from comment #0)
> [561] % gcctk -v
> Using built-in specs.
> COLLECT_GCC=3Dgcctk
> COLLECT_LTO_WRAPPER=3D/local/suz-local/software/local/gcc-trunk/libexec/g=
cc/
> x86_64-pc-linux-gnu/11.0.1/lto-wrapper
> Target: x86_64-pc-linux-gnu
> Configured with: ../gcc-trunk/configure --disable-bootstrap
> --prefix=3D/local/suz-local/software/local/gcc-trunk --enable-languages=
=3Dc,c++
> --disable-werror --enable-multilib --with-system-zlib
> Thread model: posix
> Supported LTO compression algorithms: zlib
> gcc version 11.0.1 20210401 (experimental) [master revision
> e4bb1bd60a9:c23a685bf70:95d217ab52d31dc06fda42fc136dea165909e88b] (GCC)=20
> [562] %=20
> [562] % gcctk -O1 -S -o O1.s small.c
> [563] % gcctk -O3 -S -o O3.s small.c
> [564] %=20
> [564] % wc O1.s O3.s
>   23   45  420 O1.s
>   39   74  669 O3.s
>   62  119 1089 total
> [565] %=20
> [565] % grep foo O1.s
> [566] % grep foo O3.s
>         call    foo
> [567] %=20
> [567] % cat small.c
> extern void foo(void);
> static int a, b;
> static int c() {
>   foo();
>   while (1)
>     while (b)
>       foo();
> }
> void d() {
>   if (a)
>     c();
> }
> int main() {
>   d();
>   return 0;
> }

I filed this as PR99991.=