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Re: riscv: fmax/fmin sNaN fix
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Szabolcs Nagy <szabolcs dot nagy at arm dot com>
- Cc: DJ Delorie <dj at redhat dot com>, <libc-alpha at sourceware dot org>, <nd at arm dot com>
- Date: Tue, 20 Feb 2018 23:11:47 +0000
- Subject: Re: riscv: fmax/fmin sNaN fix
- Authentication-results: sourceware.org; auth=none
- References: <xnk1v8jrki.fsf@greed.delorie.com> <b680364d-83ef-48ba-1885-71e50ccc4845@arm.com>
On Tue, 20 Feb 2018, Szabolcs Nagy wrote:
> On 20/02/18 02:57, DJ Delorie wrote:
> >
> > RISC-V's FPU follows the IEEE spec, not the POSIX spec. This patch
> ^^^^^^^^^
> which one?
> (the next ieee revision will have different min/max operations)
The point (as per
<https://sourceware.org/ml/libc-alpha/2018-01/msg01084.html>) is that fmax
and fmin in TS 18661-1 bind to maxNum and minNum. Those operations are to
be removed in IEEE 754-2018 so the C functions will have semantics that no
longer have a corresponding IEEE operation (much like e.g. nextafter /
nexttoward, which correspond to the Nextafter operation recommended in
IEEE 754-1985 but removed in IEEE 754-2008). Instead, the new minimum,
minimumNumber, maximum and maximumNumber operations are proposed to have
new functions fminimum, fminimum_num, fmaximum, fmaximum_num (and likewise
*mag* functions) - but so far there is no public draft of those proposed
TS changes (which might in any case more likely be dealt with in the C2x
process rather than through a new revision of the TS being produced).
--
Joseph S. Myers
joseph@codesourcery.com