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Re: [PATCH][RFC] Remove volatile from data members in libstdc++

From: Mark Mitchell <mark at codesourcery dot com>
To: Hans Boehm <Hans dot Boehm at hp dot com>
Cc: Richard Guenther <rguenther at suse dot de>, Ian Lance Taylor <iant at google dot com>, Paolo Carlini <pcarlini at suse dot de>, gcc-patches at gcc dot gnu dot org, libstdc++ at gcc dot gnu dot org
Date: Mon, 17 Jul 2006 20:43:22 -0700
Subject: Re: [PATCH][RFC] Remove volatile from data members in libstdc++
References: <65953E8166311641A685BDF71D865826C1E2AA@cacexc12.americas.cpqcorp.net> <44BC30F8.9080705@codesourcery.com> <Pine.GHP.4.58.0607171937530.18586@tomil.hpl.hp.com>

Hans Boehm wrote:
> I'm really more interested in the volatility of "global".
> 
> You are saying that neither the current, nor a future version of gcc, will
> ever spill the variable "local" by reloading it from "global"?  It is
> certainly allowed to do so by current standards if "global" is not
> volatile.

I'm not promising that local will never be reloaded from global, if
global is non-volatile.  However, that promise is good if global *is*
volatile.  In that case, the compiler must read it exactly once, in your
example.

-- 
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713

References:
- RE: [PATCH][RFC] Remove volatile from data members in libstdc++
  - From: Boehm, Hans
- Re: [PATCH][RFC] Remove volatile from data members in libstdc++
  - From: Mark Mitchell
- Re: [PATCH][RFC] Remove volatile from data members in libstdc++
  - From: Hans Boehm

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