This is the mail archive of the
glibc-bugs@sourceware.org
mailing list for the glibc project.
[Bug math/14645] New: Incorrect sign of inexact zero result from fma
- From: "jsm28 at gcc dot gnu.org" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sources dot redhat dot com
- Date: Sat, 29 Sep 2012 11:44:39 +0000
- Subject: [Bug math/14645] New: Incorrect sign of inexact zero result from fma
- Auto-submitted: auto-generated
http://sourceware.org/bugzilla/show_bug.cgi?id=14645
Bug #: 14645
Summary: Incorrect sign of inexact zero result from fma
Product: glibc
Version: 2.16
Status: NEW
Severity: normal
Priority: P2
Component: math
AssignedTo: unassigned@sourceware.org
ReportedBy: jsm28@gcc.gnu.org
Classification: Unclassified
Various fma functions produce zero results with incorrect sign in the case
where the zero is (underflowing multiplication) + 0. In such a case, IEEE
754-2008 (6.3 The sign bit) explicitly says "the zero result takes the sign of
the exact result". But for example fmal (-LDBL_MIN, LDBL_MIN, 0.0L) wrongly
returns +0.0L instead of -0.0L on x86 because the implementation adds the -0.0L
from the multiplication to the +0.0L, so changing its sign to +0.0L (in
round-to-nearest mode). This is the case even after my patch
http://sourceware.org/ml/libc-alpha/2012-09/msg00792.html for bug 14638 (signs
of *exact* zero results), which doesn't change the relevant code.
--
Configure bugmail: http://sourceware.org/bugzilla/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.