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[Bug math/15491] New: x86 nearbyint implementations wrongly clear all exceptions
- From: "jsm28 at gcc dot gnu.org" <sourceware-bugzilla at sourceware dot org>
- To: glibc-bugs at sourceware dot org
- Date: Sun, 19 May 2013 18:38:36 +0000
- Subject: [Bug math/15491] New: x86 nearbyint implementations wrongly clear all exceptions
- Auto-submitted: auto-generated
http://sourceware.org/bugzilla/show_bug.cgi?id=15491
Bug #: 15491
Summary: x86 nearbyint implementations wrongly clear all
exceptions
Product: glibc
Version: 2.17
Status: NEW
Severity: normal
Priority: P2
Component: math
AssignedTo: unassigned@sourceware.org
ReportedBy: jsm28@gcc.gnu.org
Classification: Unclassified
The implementations of nearbyint functions using x87 floating point (x86 all
versions, x86_64 long double only) use the fclex instruction, which clears any
exceptions that were raised before the function was called. These functions
must not clear exceptions that were raised before they were called.
I think fixing this will require saving and restoring the whole floating-point
environment as the way of avoiding raising "inexact" (which is what fesetenv
does, so use of frndint should still be faster than the C versions) - except
that if frndint raises an "invalid" exception for a sNaN operand, that *should*
be added into the restored environment.
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