Switch to hard-float by default?

[Warner Losh]

On Wed, Jan 10, 2018 at 5:49 PM, Alex Zepeda <mips at inferiorhumanorgans.com>
wrote:

> > On Wed, Jan 10, 2018 at 12:54 PM, John Baldwin <jhb at freebsd.org> wrote:
> >
> > > I have been working on LLVM libunwind patches for MIPS and the last
> round
> > > has
> > > been to teach the unwinder to handle hard-float.  As part of this I
> just
> > > fixed
> > > a bug which had broken HF support for N32 (in review now), and I have a
> > > working 'mipsn32hf' world that boots under qemu.  However, if I add
> > > 'mipsn32hf' to the list of known targets that is yet another world to
> add
> > > to make universe.  I wonder if instead we should consider switching
> MIPS to
> > > assume hard-float by default?  We made that change for 32-bit arm
> recently.
> > >
> > > The simplest approach would be to add 'mipsn32hf' and then remove all
> the
> > > non '*hf' targets from Makefile.inc1 (if we only wanted to support
> HF).  A
> > > more drastic approach would be to change the existing 'mips*' targets
> to
> > > assume hard-float, remove all the '*hf' targets (which are only in 12
> > > anyway
> > > I think?) and add in explicit '*sf' targets if anyone has a need for
> them.
> > > Given that none of the *hf targets have been MFC'd are only present in
> 12
> > > anyway, maybe the more drastic route is actually better?  If we do go
> that
> > > route, does anyone have a use case for a '*sf' target?  That is, is
> anyone
> > > running FreeBSD/mips on a processor that does not include an FPA?
> > >
> >
> > I think that I retired the last set of SoCs that only had soft float.
> >
> > I think this is a good idea.
> >
> > The only use case I can think of is if I'm wrong and some of the early
> > Atheros SoCs can do soft float. But then we'd just have one supported
> > soft-float platform to worry about rather than the full generality we
> have
> > now.
> >
> > Warner
>
> Are you sure?  I'm pretty sure a lot of the 32 bit SoCs don't have FPUs
> standard.  I'm currently poking at a MediaTek 7621 board (EdgeRouter X)
> and it doesn't have an FPU.  Looking through the MediaTek documents it
> looks
> like FPUs are an optional accessory on many of their SoCs.
>

You may be right about that...

I think there's a good case to be made for going the <foo>sf route here for
those that need it. I can think of other alternatives, but this is the
least bad one.

Warner