public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/113265] [Regression] Missed optimization for redundancy computation elimination may be due to constant propagation about 0 too late Date: Tue, 09 Jan 2024 08:06:12 +0000 [thread overview] Message-ID: <bug-113265-4-qDDRgvzJCs@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-113265-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113265 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |pinskia at gcc dot gnu.org Status|UNCONFIRMED |NEW Ever confirmed|0 |1 Keywords| |missed-optimization Last reconfirmed| |2024-01-09 --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- We're somehow expanding -b as x - b. That's done by forwprop seeing <bb 2> : x.0_1 = x; a_8 = b_7(D) - x.0_1; y = 0; y.1_2 = y; _3 = a_8 + y.1_2; _4 = -a_8; _5 = _3 / _4; z = _5; this transform is done irrespectively of whether the non-negated expression is still used (its a 1:1 replacement, though unary to binary). We're thn missing folding of a_8 = b_7(D) - x.0_1; _4 = x.0_1 - b_7(D); _5 = a_8 / _4; failing to realize this is a_8 / -a_8. Reduced testcase which isn't optimized by GCC 7 either: int z; void func(int a, int b){ z=(a-b)/-(a-b); } void func1(int a, int b){ z=(a-b)/(b-a); }
next prev parent reply other threads:[~2024-01-09 8:06 UTC|newest] Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-01-08 8:25 [Bug tree-optimization/113265] New: " 652023330028 at smail dot nju.edu.cn 2024-01-09 8:06 ` rguenth at gcc dot gnu.org [this message] 2024-01-09 8:16 ` [Bug tree-optimization/113265] " rguenth at gcc dot gnu.org 2024-01-09 8:43 ` pinskia at gcc dot gnu.org 2024-01-09 22:55 ` [Bug tree-optimization/113265] [11/12/13/14 Regression] " pinskia at gcc dot gnu.org 2024-01-09 23:01 ` pinskia at gcc dot gnu.org 2024-03-07 20:52 ` law at gcc dot gnu.org 2024-05-26 5:43 ` [Bug tree-optimization/113265] [11/12/13/14/15 " pinskia at gcc dot gnu.org 2024-05-26 5:44 ` 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-113265-4-qDDRgvzJCs@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: linkBe 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).