public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "dave at hiauly1 dot hia dot nrc dot ca" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/17578] Missed optimization--failure of gcc.c-torture/execute/ieee/compare-fp-3.c at -O1 and above Date: Tue, 21 Sep 2004 06:20:00 -0000 [thread overview] Message-ID: <20040921062055.14104.qmail@sourceware.org> (raw) In-Reply-To: <20040921015638.17578.danglin@gcc.gnu.org> ------- Additional Comments From dave at hiauly1 dot hia dot nrc dot ca 2004-09-21 06:20 ------- Subject: Re: Missed optimization--failure of gcc > ------- Additional Comments From pinskia at gcc dot gnu dot org 2004-09-21 > 04:35 ------- > Actually by the C standard, compares do not trap at all. C99 indicates that relational operations may raise the invalid exception when argument values are NaNs. This includes both quiet and signalling NaNs. 5.2.4.2.2 paragraph 3 states that a signalling NaN generally raises an exception when used as an arithmetic operand. As far as I can tell, there is no exception in this regard for the equality operators. They are analogous to the relational operators except for being lower in precedence. Treating relational operators and equality operators differently with respect to signalling NaNs would present a significant problem on the PA-RISC architecture as all floating point comparisons behave in the same manner. >From the C standard, it's somewhat ambiguous whether a quiet NaN should raise an exception in an equality operation. We currently don't raise an exception on the PA. The C standard allows for various floating point models but I don't think it was intended to be incompatible with IEC 60559:1989. There are various "is" macros which don't raise the invalid exception. Dave -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17578
next prev parent reply other threads:[~2004-09-21 6:20 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2004-09-21 1:56 [Bug tree-optimization/17578] New: " danglin at gcc dot gnu dot org 2004-09-21 4:33 ` [Bug tree-optimization/17578] " danglin at gcc dot gnu dot org 2004-09-21 4:35 ` pinskia at gcc dot gnu dot org 2004-09-21 6:20 ` dave at hiauly1 dot hia dot nrc dot ca [this message] 2004-09-23 3:18 ` danglin at gcc dot gnu dot org 2004-12-23 2:11 ` pinskia at gcc dot gnu dot org 2004-12-26 20:49 ` cvs-commit at gcc dot gnu dot org 2004-12-26 21:00 ` danglin at gcc dot gnu dot org 2005-01-07 14:15 ` pinskia at gcc dot gnu dot org 2005-01-15 5:26 ` pinskia at gcc dot gnu dot 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=20040921062055.14104.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).