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
prev 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]
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