Re: [PATCH] soft-fp: Add floattixf.c and floatuntixf.c

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Mon, Jan 21, 2019 at 2:39 PM Joseph Myers <joseph@codesourcery.com> wrote:
>
> On Mon, 21 Jan 2019, H.J. Lu wrote:
>
> > TI->XF conversions in libgcc2.c:
> >
> > XFtype
> > __floatdixf (DWtype u)
> > {
> >   XFtype d = (Wtype) (u >> W_TYPE_SIZE);
> >   d *= Wtype_MAXp1_F;
> >   d += (UWtype)u;
> >   return d;
> > }
> >
> > have no rounding mode support.  Add floattixf.c and floatuntixf.c to
>
> That doesn't need rounding mode support.  XFmode has 64-bit precision, so
> all 64-bit integer values can be represented exactly in XFmode, so that
> function only has a single possibly inexact operation (the addition), so
> only a single rounding, which will use the hardware rounding mode.  (The
> x87 rounding mode, not the SSE rounding mode, of course, but nothing
> should make those two rounding modes different other than a limited amount
> of code inside glibc that optimizes by knowing that certain code only ever
> uses one of the floating-point units so only needs that rounding mode
> changed.)
>
> > soft-fp to support rounding mode.
>
> I see no reasonable use for XFmode soft-fp functions in libgcc (other than
> the conversions to/from TFmode, of course); XFmode is only used in libgcc
> when it's a hardware type, which means the libgcc2.c functions that are
> based around hardware operations are preferable.
>

You are right.  I withdrew this patch.

Thanks.

-- 
H.J.