public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/100080] missed optimization for dead code elimination at -O3 (vs. -O2)
Date: Fri, 02 Jun 2023 05:03:35 +0000 [thread overview]
Message-ID: <bug-100080-4-yk70XfdIgD@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-100080-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100080
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> Confirmed. At -O2 combine manages to drop the call to foo () (indirectly),
> at -O3 it does not. There's not much difference on the GIMPLE level
For the gimple level it comes down to:
_5 = (unsigned int) l_20(D);
if (_5 > 1)
goto <bb 5>; [50.00%]
else
goto <bb 6>; [50.00%]
What should we do there, l_20(D) is definitely uninitialized?
We even get a warning about it:
In function 'e',
inlined from 'main' at <source>:17:5:
<source>:9:20: warning: 'l' may be used uninitialized [-Wmaybe-uninitialized]
9 | d = c >= (*j = b | *k) && b & (*i == 0);
| ~~^~~~
<source>: In function 'main':
<source>:16:9: note: 'l' was declared here
16 | int l;
| ^
next prev parent reply other threads:[~2023-06-02 5:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-14 14:14 [Bug tree-optimization/100080] New: " zhendong.su at inf dot ethz.ch
2021-04-15 6:43 ` [Bug rtl-optimization/100080] " rguenth at gcc dot gnu.org
2023-06-02 5:03 ` pinskia at gcc dot gnu.org [this message]
2023-08-18 6:52 ` pinskia 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-100080-4-yk70XfdIgD@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).