soft-fp: Add FP_DENORM_ZERO

[Joseph S. Myers]

On Wed, 8 Oct 2014, Carlos O'Donell wrote:

> > diff --git a/soft-fp/soft-fp.h b/soft-fp/soft-fp.h
> > index 86bc7fa..05fcca0 100644
> > --- a/soft-fp/soft-fp.h
> > +++ b/soft-fp/soft-fp.h
> > @@ -161,6 +161,11 @@
> >  # define FP_HANDLE_EXCEPTIONS do {} while (0)
> >  #endif
> >  
> > +/* Whether to flush subnormal inputs to zero with the same sign.  */
> > +#ifndef FP_DENORM_ZERO
> > +# define FP_DENORM_ZERO 0
> > +#endif
> 
> OK, but...
> 
> For the record this is an instance of the "centralized defaults" pattern
> which we try to avoid in glibc. What if the target accidentally defines:

I am unconvinced this can readily be avoided in the soft-fp code without a 
lot of duplication of common definitions in different sfp-machine.h files 
(of which there are a lot, when you consider those in libgcc and the Linux 
kernel as well as glibc).

-- 
Joseph S. Myers
joseph@codesourcery.com