linux-kernel - RE: Memory corruption due to word sharing

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Date:	Thu, 02 Feb 2012 10:28:42 +0100
From:	Bernd Petrovitsch <bernd@...rovitsch.priv.at>
To:	"Boehm, Hans" <hans.boehm@...com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Torvald Riegel <triegel@...hat.com>, Jan Kara <jack@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	"dsterba@...e.cz" <dsterba@...e.cz>,
	"ptesarik@...e.cz" <ptesarik@...e.cz>,
	"rguenther@...e.de" <rguenther@...e.de>,
	"gcc@....gnu.org" <gcc@....gnu.org>
Subject: RE: Memory corruption due to word sharing

On Mit, 2012-02-01 at 21:04 +0000, Boehm, Hans wrote:
[...]
> The C11 memory model potentially adds overhead in only two cases:
> 
> 1. When current code involves touching a field that wouldn't otherwise
> be touched.  There are odd cases in which this measurably slows down
> code, but I think all agree that we need it.  In addition to
> bitfields, it can affect speculatively promoting a value to a register
> in a loop, which at least older versions of gcc also do.

Just adding an -f option for this and/or activating it only for -O5 (or
whatever the highest level is) and - in case that feature is activated -
emit warnings if bitfields (and/or any other data types that might be
affected)?

Kind regards,
	Bernd
-- 
Bernd Petrovitsch                  Email : bernd@...rovitsch.priv.at
                     LUGA : http://www.luga.at

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