From: Joel Sherrill <joel@rtems.org>
To: Marco Atzeri <marco.atzeri@gmail.com>
Cc: Newlib <newlib@sourceware.org>
Subject: Re: incorrectly rounded square root
Date: Wed, 2 Jun 2021 14:12:09 -0500 [thread overview]
Message-ID: <CAF9ehCUPhf41dt4wCRhEfWLjBfrKYLdEHYqJdhYfCUVrYKqh1w@mail.gmail.com> (raw)
In-Reply-To: <2f8796f4-f164-5734-16ca-9a392e788beb@gmail.com>
On Wed, Jun 2, 2021, 2:08 PM Marco Atzeri <marco.atzeri@gmail.com> wrote:
> On 02.06.2021 20:43, Jeff Johnston wrote:
> > On Wed, Jun 2, 2021 at 9:08 AM Joel Sherrill <joel@rtems.org> wrote:
> >
> >>
> >>
> >> On Wed, Jun 2, 2021 at 2:51 AM Paul Zimmermann <
> Paul.Zimmermann@inria.fr>
> >> 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
>
>
next prev parent reply other threads:[~2021-06-02 19:12 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-04 8:08 Paul Zimmermann
2021-05-31 20:52 ` Jeff Johnston
2021-06-01 7:11 ` Paul Zimmermann
2021-06-01 16:28 ` Jeff Johnston
2021-06-02 7:51 ` Paul Zimmermann
2021-06-02 13:07 ` Joel Sherrill
2021-06-02 18:43 ` Jeff Johnston
2021-06-02 19:07 ` Marco Atzeri
2021-06-02 19:12 ` Joel Sherrill [this message]
2021-06-03 3:01 ` Jeff Johnston
2021-06-03 10:21 ` Paul Zimmermann
2021-06-03 15:50 ` Jeff Johnston
2021-06-04 7:14 ` Paul Zimmermann
2021-06-04 18:44 ` Jeff Johnston
2021-06-04 18:59 ` Joel Sherrill
2021-06-05 13:25 ` Brian Inglis
2021-06-07 9:51 ` Paul Zimmermann
2021-06-12 22:31 ` Maciej W. Rozycki
2021-06-03 11:25 ` Paul Zimmermann
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