From: Szabolcs Nagy <nsz@port70.net>
To: Damian McGuckin <damianm@esi.com.au>
Cc: musl@lists.openwall.com
Subject: Re: [musl] [PATCH #2] Properly simplified nextafter()
Date: Sun, 15 Aug 2021 00:45:12 +0200 [thread overview]
Message-ID: <20210814224512.GG37904@port70.net> (raw)
In-Reply-To: <alpine.LRH.2.02.2108141354270.8681@key0.esi.com.au>
* Damian McGuckin <damianm@esi.com.au> [2021-08-14 14:07:34 +1000]:
> On Fri, 13 Aug 2021, Stefan Kanthak wrote:
> > > It may be possible to reduce the number of such ops too; not sure. But
> > > there's no way to eliminate them.
>
> Replacing the second FORCE'd expression with
>
> FORCE((ux.f + x) * (0x1.0p-52 * 0.25));
>
> eliminates one floating point OP, assuming the optimiser does the right
> thing to
>
> epsilon / 4
>
> in the expression. Some preliminary testing seems to suggest that the same
> exceptions get raised.
>
> > It's definitely possible to do a strength reduction and get rid of the
> > multiplications.
>
> But then how is the exception still raised, or are we talking soft FP?
that does not work, i think.
but the subnormal result case is not worth optimizing.
(or rather, i prefer to optimize cold code paths for size)
next prev parent reply other threads:[~2021-08-14 22:45 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-10 6:23 [musl] [PATCH] " Stefan Kanthak
2021-08-10 21:34 ` Szabolcs Nagy
2021-08-10 22:53 ` Stefan Kanthak
2021-08-11 2:40 ` Rich Felker
2021-08-11 15:44 ` Stefan Kanthak
2021-08-11 16:09 ` Rich Felker
2021-08-11 16:50 ` Stefan Kanthak
2021-08-11 17:57 ` Rich Felker
2021-08-11 22:16 ` Szabolcs Nagy
2021-08-11 22:43 ` Stefan Kanthak
2021-08-12 0:59 ` Rich Felker
2021-08-11 8:23 ` Szabolcs Nagy
2021-08-13 12:04 ` [musl] [PATCH #2] " Stefan Kanthak
2021-08-13 15:59 ` Rich Felker
2021-08-13 18:30 ` Stefan Kanthak
2021-08-14 4:07 ` Damian McGuckin
2021-08-14 22:45 ` Szabolcs Nagy [this message]
2021-08-14 23:46 ` Szabolcs Nagy
2021-08-15 7:04 ` Stefan Kanthak
2021-08-15 7:46 ` Ariadne Conill
2021-08-15 13:59 ` Rich Felker
2021-08-15 14:57 ` Ariadne Conill
2021-08-15 8:24 ` Damian McGuckin
2021-08-15 14:03 ` Rich Felker
2021-08-15 15:10 ` Damian McGuckin
2021-08-15 14:56 ` Szabolcs Nagy
2021-08-15 15:19 ` Stefan Kanthak
2021-08-15 15:48 ` Rich Felker
2021-08-15 16:29 ` Stefan Kanthak
2021-08-15 16:49 ` Rich Felker
2021-08-15 20:52 ` Stefan Kanthak
2021-08-15 21:48 ` Rich Felker
2021-08-15 15:52 ` Ariadne Conill
2021-08-15 16:09 ` Rich Felker
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