fmax/fmin sNaN compatibility question

[Ulrich Weigand]

Joseph Myers wrote:
> On Tue, 10 Dec 2019, Ulrich Weigand wrote:
> 
> > Joseph Myers wrote:
> > > On Mon, 9 Dec 2019, Ulrich Weigand wrote:
> > > > Do you know why the sample implementation was even updated then?
> > > > If FP_SNANS_ALWAYS_SIGNAL is false, shouldn't the C11 method then
> > > > still be OK?
> > > 
> > > The canonicalize call is needed in general to avoid propagating 
> > > noncanonical DFP encodings, though not relevant for binary FP.
> > 
> > But it does change the behavior for binary FP as well, as far
> > as I can see: e.g. if both inputs are sNaNs, the C11 method
> > would return one of those sNaNs unchanged, while the C2x method
> > will return a qNaN (as the canonicalize call will quiet the
> > sNaN it receives as input), right?
> 
> The handling of sNaN is explicitly implementation-defined when 
> FE_SNANS_ALWAYS_SIGNAL is not defined, so that example implementation 
> should not be used to infer anything about how sNaN should be handled.

OK, got it.  I think it starts making sense now :-)

Thanks for your help!

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain
  Ulrich.Weigand@de.ibm.com