On Tue, Sep 6, 2022 at 2:06 PM Jakub Jelinek <ja...@redhat.com> wrote:
>
> On Tue, Sep 06, 2022 at 01:47:43PM +0200, Aldy Hernandez wrote:
> > Question...for !HONOR_NANS or !HONOR_INFINITIES or whatever, say the
> > range for the domain is [-MIN, +MAX] for the min and max representable
> > numbers. What happens for MAX+1? Is that undefined? I wonder what
> > real.cc does for that.
>
> I'm afraid I have no idea.
>
> The formats without Inf/NaN are:
> spu_single_format
> vax_{f,d,g}_format
> arm_half_format
>
> Never had the "pleasure" to work with any of these.
> Looking at encode_vax_*, it seems both GCC internal inf and nan are
> most likely are encoded as maximum or minimum representable numbers
> (depending on sign), and encode_ieee_half for !fmt->has_inf does too
> (for !fmt->has_nans it seems to "encode" the nan mantissa bits into
> highest possible exponent). encode_ieee_single (for spu) uses
> maximum or minimum representable numbers for any infinities or nans.
> What they actually do at runtime is something I can't really check,
> but one would hope it is saturating...
I'd simply do what we do for -ffinite-math-only - just pretend you don't
cross the maximum/minmum value and effectively saturate the range.
Richard.
> Jakub
>
