Re: [PATCH] PowerPC Fix ibm128 defaults for pr70117.c test.

["Paul A. Clarke" <pc@us.ibm.com>]

On Wed, Nov 18, 2020 at 04:29:09PM -0600, Segher Boessenkool wrote:
> On Wed, Nov 18, 2020 at 10:53:49PM +0100, Jakub Jelinek wrote:
> > On Wed, Nov 18, 2020 at 03:43:20PM -0600, Segher Boessenkool wrote:
> > > On Sun, Nov 15, 2020 at 12:17:47PM -0500, Michael Meissner wrote:
> > > > --- a/gcc/testsuite/gcc.target/powerpc/pr70117.c
> > > > +++ b/gcc/testsuite/gcc.target/powerpc/pr70117.c
> > > > @@ -9,9 +9,11 @@
> > > >     128-bit floating point, because the type is not enabled on those
> > > >     systems.  */
> > > >  #define LDOUBLE __ibm128
> > > > +#define IBM128_MAX ((__ibm128) 1.79769313486231580793728971405301199e+308L)
> > > 
> > > This is the IEEE QP float number 43fefffffffffffff7ffffffffffff80 which
> > > I very much doubt is the maximum finite double-double?  See the 0 in the
> > 
> > Numbers without the 0 in the middle-end aren't valid, see
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95450#c6
> > for more details.  Without the 0 in the middle the double double number
> > rounded to double would require increasing the higher double, and as it is
> > the largest representable finite number, that is not possible.
> 
> Ah, in that way.  Tricky.
> 
> Mike, please add a comment, what number it represents?  Okay for trunk
> with that, thanks.
> 
> (Should those not be define in some header though?)

Would it be better to represent the number in hex, like with printf's '%a'
formatting (e.g. "0x1.921fb54442d18p+0"...this is NOT the same value)?

(I always get nervous when I see a long float hardcoded in decimal.)

PC