From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id DCE3E3857C6F; Fri, 16 Apr 2021 07:22:35 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org DCE3E3857C6F From: "zhendong.su at inf dot ethz.ch" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/100112] New: missed optimization for dead code elimination at -O3, -Os (vs. -O1, -O2) Date: Fri, 16 Apr 2021 07:22:35 +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: unknown X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: zhendong.su at inf dot ethz.ch 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: 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 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 16 Apr 2021 07:22:36 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100112 Bug ID: 100112 Summary: missed optimization for dead code elimination at -O3, -Os (vs. -O1, -O2) Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: zhendong.su at inf dot ethz.ch Target Milestone: --- [545] % gcctk -v Using built-in specs. COLLECT_GCC=3Dgcctk COLLECT_LTO_WRAPPER=3D/local/suz-local/software/local/gcc-trunk/libexec/gcc= /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 20210416 (experimental) [master revision 89c863488bc:10ed13839be:76c7e7d6b003a17d183d0571bf9b34c691819d25] (GCC)=20 [546] %=20 [546] % gcctk -O1 -S -o O1.s small.c [547] % gcctk -O3 -S -o O3.s small.c [548] %=20 [548] % wc O1.s O3.s 17 38 365 O1.s 37 78 633 O3.s 54 116 998 total [549] %=20 [549] % grep foo O1.s [550] % grep foo O3.s call foo [551] %=20 [551] % cat small.c extern void foo(void); static int e, *a =3D &e, b, *c =3D &b; static int d(int f, int i) { if (f ^ i) foo(); } int main() { int **g =3D &c; (*a)++; *g =3D c; d(1, c !=3D 0); return 0; }=