ia64/158547: [ia64] Epilog counter (ar.ec) needs to be saved and
restored for exceptions
Marcel Moolenaar
marcel at FreeBSD.org
Thu Jun 30 23:50:05 UTC 2011
>Number: 158547
>Category: ia64
>Synopsis: [ia64] Epilog counter (ar.ec) needs to be saved and restored for exceptions
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-ia64
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Thu Jun 30 23:50:04 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator: Marcel Moolenaar
>Release: -CURRENT
>Organization:
>Environment:
FreeBSD eris.freebsd.org 9.0-CURRENT FreeBSD 9.0-CURRENT #1 r223702M: Thu Jun 30 23:04:04 UTC 2011 marcel at eris.freebsd.org:/usr/obj/tank/usr/src/sys/ERIS ia64
>Description:
The epilog counter (ar.ec) is implicitly saved and restored across function calls. The counter is saved in the previous frame register. Consequently, synchronous context switches do not need to save/restore this register.
For asynchronous context switches this is obviously not the case. Currently we do not save ar.ec in "exception_save" and we do not restore ar.ec in "exception_restore". SInce the GCC version in the source tree does not generate modulo-scheduled loops with the default options, ar.ec is typically not used. But as soon as GCC generates these loops are a different compiler is used, programs will misbehave and generally fail unless we save and restore ar.ec.
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
More information about the freebsd-ia64
mailing list