[PATCH][risc-v] libstdc++: Preserve signbit of nan when converting float to double [PR113578]

[Jonathan Wakely]

On Tue, 7 May 2024 at 14:57, Jeff Law wrote:
>
>
>
> On 5/7/24 7:49 AM, Jonathan Wakely wrote:
> > Do we want this change for RISC-V, to fix PR113578?
> >
> > I haven't tested it on RISC-V, only on x86_64-linux (where it doesn't do
> > anything).
> >
> > -- >8 --
> >
> > libstdc++-v3/ChangeLog:
> >
> >       PR libstdc++/113578
> >       * include/std/ostream (operator<<(basic_ostream&, float)):
> >       Restore signbit after converting to double.
> No strong opinion.     One could argue that the existence of a
> conditional like that inherently implies the generic code is dependent
> on specific processor behavior which probably is unwise.  But again, no
> strong opinion.

Yes, but I'm not aware of any other processors that lose the signbit
like this, so in practice it's always worked fine to cast the float to
double.