public inbox for gcc-patches@gcc.gnu.org
 help / color / mirror / Atom feed
From: Joseph Myers <joseph@codesourcery.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>
Cc: Andrew Pinski <pinskia@gmail.com>
Subject: Re: [PATCH] fold a * (a > 0 ? 1 : -1) to abs(a) and related optimizations
Date: Mon, 26 Jun 2017 15:02:00 -0000	[thread overview]
Message-ID: <alpine.DEB.2.20.1706261500460.30222@digraph.polyomino.org.uk> (raw)
In-Reply-To: <alpine.DEB.2.20.1706240811460.2551@stedding.saclay.inria.fr>

On Sat, 24 Jun 2017, Marc Glisse wrote:

> * if X is NaN, we may get a qNaN with the wrong sign bit. We probably don't
> care much though...

The sign bit from a multiplication involving a NaN is not specified.  
*But* making any of these transformations with a qNaN loses the "invalid" 
exception from an ordered comparison involving a qNaN, so isn't valid in 
the case of (qNaNs respected and trapping-math).

-- 
Joseph S. Myers
joseph@codesourcery.com

      parent reply	other threads:[~2017-06-26 15:02 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-24  3:59 Andrew Pinski
2017-06-24  3:59 ` Andrew Pinski
2017-06-24  6:50 ` Marc Glisse
2017-06-24 18:51   ` Andrew Pinski
2017-06-24 19:47     ` Marc Glisse
2017-06-24 20:53       ` Andrew Pinski
2017-06-26 15:02   ` Joseph Myers [this message]

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=alpine.DEB.2.20.1706261500460.30222@digraph.polyomino.org.uk \
    --to=joseph@codesourcery.com \
    --cc=gcc-patches@gcc.gnu.org \
    --cc=pinskia@gmail.com \
    /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).