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From: "hubicka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/53383] Allow -mpreferred-stack-boundary=3 on x86-64
Date: Fri, 18 May 2012 12:02:00 -0000 [thread overview]
Message-ID: <bug-53383-4-Z3OlnITUlQ@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-53383-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53383
Jan Hubicka <hubicka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |hubicka at gcc dot gnu.org
--- Comment #6 from Jan Hubicka <hubicka at gcc dot gnu.org> 2012-05-18 11:54:03 UTC ---
The reason why -mpreferred-stack-boundary=3 is not allowed is that the va-args
sequences generated are not safe in the case frame is misaligned and values
with higher intended alignment are passed.
In that case the caller would be required to do dynamic stack alignment.
Otherwise the value might end up misaligned on the stack and va-arg sequence
will do alignment using & operation resulting in fetching wrong value from
memory.
Since we have dynamic stack alignment now, we could allow that and explicitely
document that as ABI breaking (like we have the double alignment and other
kludges on x86)
Honza
next prev parent reply other threads:[~2012-05-18 11:54 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-17 0:19 [Bug c/53383] New: " hpa at zytor dot com
2012-05-17 14:12 ` [Bug target/53383] " hjl.tools at gmail dot com
2012-05-17 14:29 ` hpa at zytor dot com
2012-05-17 15:44 ` hjl.tools at gmail dot com
2012-05-17 16:00 ` hpa at zytor dot com
2012-05-17 16:28 ` hpa at zytor dot com
2012-05-18 11:41 ` rguenth at gcc dot gnu.org
2012-05-18 12:02 ` hubicka at gcc dot gnu.org [this message]
2012-05-18 17:29 ` hpa at zytor dot com
2012-05-19 19:22 ` hubicka at ucw dot cz
2012-05-19 21:28 ` hjl.tools at gmail dot com
2012-05-19 21:54 ` hubicka at ucw dot cz
2012-05-20 4:45 ` hjl.tools at gmail dot com
2012-05-20 11:15 ` hubicka at ucw dot cz
2012-05-20 11:35 ` Jan Hubicka
2012-05-20 13:56 ` hubicka at ucw dot cz
2012-05-20 15:36 ` hjl.tools at gmail dot com
2012-05-20 15:39 ` hjl.tools at gmail dot com
2012-06-22 17:11 ` hjl at gcc dot gnu.org
2012-06-22 17:12 ` hjl.tools at gmail dot com
2012-06-22 17:13 ` hjl at gcc dot gnu.org
2013-02-27 10:22 ` paolo.carlini at oracle dot com
2015-07-05 19:56 ` luto at mit dot edu
2015-07-05 20:36 ` hjl.tools at gmail dot com
2015-07-05 20:49 ` luto at mit dot edu
2015-07-05 21:04 ` hjl.tools at gmail dot com
2015-07-06 11:51 ` hjl at gcc dot gnu.org
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