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[Bug math/18857] [ldbl-128ibm] nearbyintl wrongly uses signaling comparisons
- From: "cvs-commit at gcc dot gnu.org" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Tue, 15 Sep 2015 20:49:08 +0000
- Subject: [Bug math/18857] [ldbl-128ibm] nearbyintl wrongly uses signaling comparisons
- Auto-submitted: auto-generated
- References: <bug-18857-131 at http dot sourceware dot org/bugzilla/>
https://sourceware.org/bugzilla/show_bug.cgi?id=18857
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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=dfa0f62011b50cc36107df5fad4130c5368b11e1
commit dfa0f62011b50cc36107df5fad4130c5368b11e1
Author: Joseph Myers <joseph@codesourcery.com>
Date: Tue Sep 15 20:48:05 2015 +0000
Fix ldbl-128ibm nearbyintl use of signaling comparisons on NaNs (bug
18857).
The ldbl-128ibm implementation of nearbyintl wrongly uses signaling
comparisons such as "if (fabs (u.d[0].d) < TWO52)" on arguments that
might be NaNs, when "invalid" exceptions should not be raised. (For
hard float, this issue may be hidden by
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58684>, powerpc GCC
wrongly only using unordered comparison instructions.) This patch
fixes this by just returning the argument if it is not finite (because
of the arbitrary value of the low part of a NaN in IBM long double,
there are quite a lot of comparisons that could end up involving a NaN
when the argument to nearbyintl is a NaN, so excluding NaN arguments
at the start is the simplest and safest fix).
Tested for powerpc-nofpu, where it removes failures for spurious
"invalid" exceptions from nearbyintl.
[BZ #18857]
* sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c (__nearbyintl): Just
return non-finite argument without doing ordered comparisons on
it.
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 5 +++++
NEWS | 4 ++--
sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c | 4 +++-
3 files changed, 10 insertions(+), 3 deletions(-)
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