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Message-ID: <alpine.LRH.2.02.2108141354270.8681@key0.esi.com.au>
Date: Sat, 14 Aug 2021 14:07:34 +1000 (AEST)
From: Damian McGuckin <damianm@....com.au>
To: musl@...ts.openwall.com
Subject: Re: [PATCH #2] Properly simplified nextafter()
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?
Stay safe - Damian
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