Re: incorrectly rounded square root

On Wed, Jun 2, 2021, 2:08 PM Marco Atzeri <[email protected]> wrote:

> On 02.06.2021 20:43, Jeff Johnston wrote:
> > On Wed, Jun 2, 2021 at 9:08 AM Joel Sherrill <[email protected]> wrote:
> >
> >>
> >>
> >> On Wed, Jun 2, 2021 at 2:51 AM Paul Zimmermann <
> [email protected]>
> >> wrote:
> >>
>
> >>
> > I'll second Joel's comment.  The code is extremely close to the glibc
> code
> > both in sqrtf and fesetround.  The only
> > thing I can think of is that the glibc code does the x87 stuff first and
> > does the set back into FPU state before doing the
> > SSE stuff.  The newlib code sets back the FPU state at the end after the
> > SSE stuff.  Don't know if this is relevant or not.
> >
> > Any Cygwin users out there who can verify that the code is working/not
> > working for them?
> >
> > -- Jeff J.
> >
>
> current Cygwin produces for both i686 and X86_64
>
>   $ gcc -DNEWLIB -fno-builtin test_sqrt.c  -lm
>
>   $ ./a.exe
> RNDN: 0x1.ff83fp+63
> RNDZ: 0x1.ff83fp+63
> RNDU: 0x1.ff83fp+63
> RNDD: 0x1.ff83fp+63
>

Does fegetround() return different values based on what mode was set?

--joel

>
>