Date: Sun, 12 Aug 2012 23:01:33 -0000 From: Peter Jeremy <peter@rulingia.com> To: Steve Kargl <sgk@troutmask.apl.washington.edu> Cc: Diane Bruce <db@db.net>, John Baldwin <jhb@freebsd.org>, David Chisnall <theraven@freebsd.org>, Stephen Montgomery-Smith <stephen@missouri.edu>, Bruce Evans <bde@freebsd.org>, Bruce Evans <brde@optusnet.com.au>, David Schultz <das@freebsd.org>, Warner Losh <imp@bsdimp.com> Subject: Re: Use of C99 extra long double math functions after r236148 Message-ID: <20120722233134.GB8033@server.rulingia.com> Resent-Message-ID: <20120812230125.GV20453@server.rulingia.com> In-Reply-To: <20120722231056.GA84338@troutmask.apl.washington.edu> References: <20120717042125.GF66913@server.rulingia.com> <20120717043848.GB87001@troutmask.apl.washington.edu> <20120717225328.GA86902@server.rulingia.com> <20120717232740.GA95026@troutmask.apl.washington.edu> <20120718001337.GA87817@server.rulingia.com> <20120718123627.D1575@besplex.bde.org> <20120722121219.GC73662@server.rulingia.com> <20120722220031.GA7791@server.rulingia.com> <20120722221614.GB53450@zim.MIT.EDU> <20120722231056.GA84338@troutmask.apl.washington.edu>
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On 2012-Jul-22 16:10:56 -0700, Steve Kargl <sgk@troutmask.apl.washington.edu> wrote:
>The above isn't necessarily true. The Fortran standards from
>2003 and 2008, very care about NaN. Under certain conditions,
>if one has something like
>
> x = sin(NaN)
>
>in Fortran, then the returned NaN must be the one in the function
>call.
Even if it was a SNaN? My understanding is that SNaN should be
quietened if they are used in any further floating point operations.
> Having libm, do
>
> if (x == NaN)
> return (x + x);
>
>does/may not return the correct NaN.
I presume you mean
if (isnan(x))
return (x + x);
Do you have a test case that shows that? As far as I can tell, all
the FPUs I have access to will return a quietened variant of the
input NaN in this case (ie, only the signalling bit is altered).
--
Peter Jeremy
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