public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "zhendong.su at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
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 [thread overview]
Message-ID: <bug-100112-4@http.gcc.gnu.org/bugzilla/> (raw)
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100112
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=gcctk
COLLECT_LTO_WRAPPER=/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=/local/suz-local/software/local/gcc-trunk --enable-languages=c,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)
[546] %
[546] % gcctk -O1 -S -o O1.s small.c
[547] % gcctk -O3 -S -o O3.s small.c
[548] %
[548] % wc O1.s O3.s
17 38 365 O1.s
37 78 633 O3.s
54 116 998 total
[549] %
[549] % grep foo O1.s
[550] % grep foo O3.s
call foo
[551] %
[551] % cat small.c
extern void foo(void);
static int e, *a = &e, b, *c = &b;
static int d(int f, int i) {
if (f ^ i)
foo();
}
int main() {
int **g = &c;
(*a)++;
*g = c;
d(1, c != 0);
return 0;
}
next reply other threads:[~2021-04-16 7:22 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-16 7:22 zhendong.su at inf dot ethz.ch [this message]
2021-04-20 8:14 ` [Bug ipa/100112] " rguenth at gcc dot gnu.org
2021-09-25 7:51 ` [Bug tree-optimization/100112] " pinskia at gcc dot gnu.org
2021-09-25 9:40 ` pinskia at gcc dot gnu.org
2021-09-27 7:02 ` rguenth at gcc dot gnu.org
2021-09-27 7:06 ` pinskia at gcc dot gnu.org
2021-09-27 7:26 ` rguenth at gcc dot gnu.org
2021-09-27 7:28 ` rguenth at gcc dot gnu.org
2021-09-27 7:28 ` rguenth at gcc dot gnu.org
2021-09-27 7:31 ` rguenth at gcc dot gnu.org
2021-09-28 10:32 ` cvs-commit at gcc dot gnu.org
2021-09-28 10:32 ` rguenth at gcc dot gnu.org
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=bug-100112-4@http.gcc.gnu.org/bugzilla/ \
--to=gcc-bugzilla@gcc.gnu.org \
--cc=gcc-bugs@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).