Re: [PATCH] Add support for floating point endpoints to frange.

[Toon Moene <toon@moene.org>]

On 8/29/22 15:54, Jakub Jelinek via Gcc-patches wrote:

> On Mon, Aug 29, 2022 at 03:45:33PM +0200, Aldy Hernandez wrote:

>> For convenience, singleton_p() returns false for a NAN.  IMO, it makes
>> the implementation cleaner, but I'm not wed to the idea if someone
>> objects.
> 
> If singleton_p() is used to decide whether one can just replace a variable
> with singleton range with a constant, then certainly.
> If MODE_HAS_SIGNED_ZEROS, zero has 2 representations (-0.0 and 0.0) and
> NaNs have lots of different representations (the sign bit is ignored
> except for stuff like copysign/signbit, there are qNaNs and sNaNs and
> except for the single case how Inf is represented, all other values of the
> mantissa mean different representations of NaN).  So, unless we track which
> exact form of NaN can appear, NaN or any [x, x] range with NaN property
> set can't be a singleton.  There could be programs that propagate something
> important in NaN mantissa and would be upset if frange kills that.
> Of course, one needs to take into account that when a FPU creates NaN, it
> will create the canonical qNaN.
> 
> 	Jakub
> 

But the NaNs are irrelevant with -ffinite-math-only, as are the various 
Infs (I do not know offhand which MODE_ that is) ...

Kind regards,

-- 
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