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From: "paulmck at linux dot vnet.ibm.com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/56028] Splitting a 64-bit volatile store
Date: Fri, 18 Jan 2013 17:40:00 -0000	[thread overview]
Message-ID: <bug-56028-4-vSONIamWWd@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-56028-4@http.gcc.gnu.org/bugzilla/>


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56028

--- Comment #6 from Paul E. McKenney <paulmck at linux dot vnet.ibm.com> 2013-01-18 17:40:13 UTC ---
The fact that a data-race-free program cannot observe the non-atomicity of a
64-bit store, though true, is beside the point.  The plain fact is that
hardware registers (for which volatile was intended) really do care about the
size of the store.  A pair of 32-bit stores does not necessarily mean the same
thing to hardware as does a single 64-bit store.  Given that C is intended to
be used for device drivers, volatile stores of reasonably-sized basic types
must be atomic, and on 64-bit systems, "reasonably-sized" very clearly includes
64-bit stores.

So this bug really does need to be fixed.


  parent reply	other threads:[~2013-01-18 17:40 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-18 11:07 [Bug target/56028] New: " amonakov at gcc dot gnu.org
2013-01-18 11:10 ` [Bug target/56028] " ubizjak at gmail dot com
2013-01-18 11:26 ` paulmck at linux dot vnet.ibm.com
2013-01-18 11:57 ` eugeni.stepanov at gmail dot com
2013-01-18 16:23 ` paulmck at linux dot vnet.ibm.com
2013-01-18 16:38 ` eugeni.stepanov at gmail dot com
2013-01-18 17:40 ` paulmck at linux dot vnet.ibm.com [this message]
2013-01-18 18:23 ` pluto at agmk dot net
2013-01-19 12:35 ` paulmck at linux dot vnet.ibm.com
2013-01-22  7:33 ` ubizjak at gmail dot com
2013-01-22  8:18 ` jakub at gcc dot gnu.org
2013-01-22  8:47 ` ubizjak at gmail dot com
2013-01-22 20:58 ` ubizjak at gmail dot com
2013-01-22 20:59 ` uros at gcc dot gnu.org
2013-01-27 14:28 ` uros at gcc dot gnu.org
2013-01-27 14:30 ` ubizjak at gmail dot com

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