public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "bangerth at dealii dot org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/33611] [4.1/4.2/4.3 regression] Optimizations generate incorrect code Date: Mon, 01 Oct 2007 17:16:00 -0000 [thread overview] Message-ID: <20071001171644.30293.qmail@sourceware.org> (raw) In-Reply-To: <bug-33611-15175@http.gcc.gnu.org/bugzilla/> ------- Comment #3 from bangerth at dealii dot org 2007-10-01 17:16 ------- For once a real floating point bug. In this code double p = 0.422244 * f[a.e]; if (f[0] < p) with a.e=1, f[1]=0.285433, we should calculate p=0.285433. Since f[0]=0.0461109, we shouldn't enter the if-clause, but we do when optimization is on. Since the numbers aren't even close, this isn't due to excess precision or any other floating point instability but a real bug. Funny enough, this was already broken in 2.95, 3.2.3 and 3.3.6 but then worked in 3.4.6 and 4.0.x only to be broken again in 4.1.2. W. -- bangerth at dealii dot org changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |bangerth at dealii dot org Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 Keywords| |wrong-code Known to fail| |2.95 3.2.3 3.3.6 4.1.2 Known to work| |3.4.6 4.0.4 Last reconfirmed|0000-00-00 00:00:00 |2007-10-01 17:16:44 date| | Summary|Optimizations generate |[4.1/4.2/4.3 regression] |incorrect code |Optimizations generate | |incorrect code http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33611
next prev parent reply other threads:[~2007-10-01 17:16 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-10-01 17:02 [Bug c++/33611] New: " macracan at yahoo dot com 2007-10-01 17:05 ` [Bug c++/33611] " macracan at yahoo dot com 2007-10-01 17:10 ` [Bug middle-end/33611] " pinskia at gcc dot gnu dot org 2007-10-01 17:16 ` bangerth at dealii dot org [this message] 2007-10-01 17:43 ` [Bug middle-end/33611] [4.1/4.2/4.3 regression] " macracan at yahoo dot com 2007-10-01 17:43 ` macracan at yahoo dot com
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=20071001171644.30293.qmail@sourceware.org \ --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).