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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libgomp/59194] tsan detects race for real variables in an OMP reduction clause
Date: Wed, 20 Nov 2013 13:51:00 -0000	[thread overview]
Message-ID: <bug-59194-4-vREsqlkRdY@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-59194-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59194

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Because CPUs obviously don't have floating point atomic instructions, what the
compiler does is just load it as an integer, view convert to floating point,
perform arithmetics, view convert result back to integer, and compare and swap
(if unsuccessful loop).  I bet tsan complains because the load is not atomic,
but does it really matter?  If we read garbage there, compare and swap will
fail and next time we'll have hopefully correct value already from what compare
and swap said was the previous value.


  parent reply	other threads:[~2013-11-20 13:51 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-11-19 17:51 [Bug libgomp/59194] New: " Joost.VandeVondele at mat dot ethz.ch
2013-11-19 18:25 ` [Bug libgomp/59194] " pinskia at gcc dot gnu.org
2013-11-19 18:46 ` Joost.VandeVondele at mat dot ethz.ch
2013-11-20 13:43 ` Joost.VandeVondele at mat dot ethz.ch
2013-11-20 13:51 ` jakub at gcc dot gnu.org [this message]
2013-11-20 17:26 ` Joost.VandeVondele at mat dot ethz.ch
2013-11-20 17:54 ` Joost.VandeVondele at mat dot ethz.ch
2013-11-20 17:59 ` jakub at gcc dot gnu.org
2013-11-20 18:12 ` Joost.VandeVondele at mat dot ethz.ch
2013-11-21 12:34 ` dvyukov at google dot com
2014-01-09 16:12 ` Joost.VandeVondele at mat dot ethz.ch
2014-01-13  7:57 ` jakub at gcc dot gnu.org
2014-01-13 10:54 ` Joost.VandeVondele at mat dot ethz.ch

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