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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/51766] [4.7 regression] sync_fetch_and_xxx atomicity
Date: Mon, 09 Jan 2012 15:45:00 -0000	[thread overview]
Message-ID: <bug-51766-4-RhcrVyrI6f@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-51766-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51766

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-01-09 15:45:06 UTC ---
(In reply to comment #1)
> The docs of __sync_* say
> 
> This builtin is not a full barrier, but rather an @dfn{acquire barrier}.
> This means that references after the builtin cannot move to (or be
> speculated to) before the builtin, but previous memory stores may not
> be globally visible yet, and previous memory loads may not yet be
> satisfied.
> 
> But it is not exactly clear to which builtins this applies.  Thus, is
> the intended behavior actually target depedent?

It refers to __sync_lock_test_and_set only (it says "this builtin" and follows
that one)

And "This builtin is not a full barrier, but rather a release barrier." refers
to __sync_lock_release.

All the others are full barriers.  It says above them "In most cases, these
builtins are considered a full barrier." and only __sync_lock_test_and_set and
__sync_lock_release specify different barrier semantics.


  parent reply	other threads:[~2012-01-09 15:45 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-05 15:01 [Bug middle-end/51766] New: " dje at gcc dot gnu.org
2012-01-05 15:02 ` [Bug middle-end/51766] " dje at gcc dot gnu.org
2012-01-09 15:40 ` rguenth at gcc dot gnu.org
2012-01-09 15:45 ` redi at gcc dot gnu.org [this message]
2012-01-09 16:51 ` dje at gcc dot gnu.org
2012-01-10  9:43 ` rguenth at gcc dot gnu.org
2012-01-10 14:40 ` dje at gcc dot gnu.org
2012-01-10 14:49 ` rguenth at gcc dot gnu.org
2012-01-10 15:31 ` redi at gcc dot gnu.org
2012-01-10 18:09 ` dje at gcc dot gnu.org
2012-01-10 18:20 ` redi at gcc dot gnu.org
2012-01-10 18:24 ` redi at gcc dot gnu.org
2012-01-10 18:34 ` dje at gcc dot gnu.org
2012-01-10 18:47 ` jakub at gcc dot gnu.org
2012-01-10 19:14 ` amacleod at redhat dot com
2012-01-10 20:26 ` dje at gcc dot gnu.org
2012-01-12 20:41 ` dje at gcc dot gnu.org

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