Soft Float for PC386

[Joel Sherrill]

Angelo Fraietta wrote:
> 
> If I build the pc386 with both the -mno-fp-ret-in-387 and the -msoft-float flags
> the machine re-boots if you try to create a task. Eg, if you try to run the
> ticker sample, the machine re-boots.  If you only use the -msoft-float and not
> the -mno-fp-ret-in-387 flag, the tasks run OK.
> I am mentioning this because the ts_386ex build uses both flags, and so if
> someone tests these on a ts_386ex, they may want to try running ticker on it to
> see if it crashes.
> 
> The exception is still thrown if I try to use a floating point routine.

Ralf has been trying to solve this.  It turns out that newlib is always
built with FPU instructions enabled.  The next round of tool RPMs and
patches will fix this and add appropriate multilibs.  The RPMs are
about 1/2 cooked at the moment.  Once built, we always build all
RTEMS BSPs in at least a minimal sense before putting them on the
ftp site.  So they should be on there next week if all goes well. 

> Joel Sherrill wrote:
> 
> > angelo wrote:
> > >
> > > I have successfully run  RTEMS apps on a Pentium using the pc386 build,
> > > however, when I attempt to run the apps (including the hello world ) on a
> > > 386 with no co-processor, The console just display an infinite Exception
> > > which I cannot read.
> >
> > Hmmm.. I would be surprised if the lack of an FPU is causing this.  But
> > stranger things have happened over the years.  What RTEMS version are
> > you trying?  It might also be worth it to put a "while 1" loop in the
> > exception handler temporarily so the message won't disappear.
> >
> > > I suspect that it may be that soft float is required,
> > > but I am not sure.  Is there a way of ensuring that I am not trying to use
> > > the co-processor and am in fact using the soft floating point libraries.
> >
> > The answer is simple and not so simple at the same time.  The standard
> > gcc sources do not have soft-float support turned on for the i386 targets.
> > The RTEMS gcc patches and RPMs post 4.5.0 do include support for this.
> >
> > If you look at the ts_386ex target in recent snapshots, its CPU_CFLAGS
> > should be the basis for adding a new pc386 variant (like pc[56]86 and
> > pck6).  Right now all pc386 variants assume an FPU.
> >
> > > --
> > > Angelo Fraietta
> > >
> > > PO Box 859
> > > Hamilton NSW 2303
> > >
> > > Home Page
> > >
> > > http://users.hunterlink.net.au/~maaaf/
> > >
> > > There are those who seek knowledge for the sake of knowledge - that is
> > > CURIOSITY
> > > There are those who seek knowledge to be known by others - that is VANITY
> > > There are those who seek knowledge in order to serve - that is LOVE
> > >     Bernard of Clairvaux (1090 - 1153)
> >
> > --
> > Joel Sherrill, Ph.D.             Director of Research & Development
> > joel at OARcorp.com                 On-Line Applications Research
> > Ask me about RTEMS: a free RTOS  Huntsville AL 35805
> > Support Available                (256) 722-9985
> 
> --
> Angelo Fraietta
> 
> PO Box 859
> Hamilton NSW 2303
> 
> Home Page
> 
> http://users.hunterlink.net.au/~maaaf/
> 
> There are those who seek knowledge for the sake of knowledge - that is CURIOSITY
> 
> There are those who seek knowledge to be known by others - that is VANITY
> There are those who seek knowledge in order to serve - that is LOVE
>     Bernard of Clairvaux (1090 - 1153)

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel at OARcorp.com                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
Support Available                (256) 722-9985