From: David Brown <david@westcontrol.com>
To: gcc@gcc.gnu.org
Subject: Re: Volatile qualification on pointer and data
Date: Thu, 22 Sep 2011 08:39:00 -0000 [thread overview]
Message-ID: <j5es6e$b1i$1@dough.gmane.org> (raw)
In-Reply-To: <j5cu04$poo$1@dough.gmane.org>
On 21/09/2011 16:57, Paulo J. Matos wrote:
> On 21/09/11 15:21, David Brown wrote:
>> And since this
>> situation would not occur in real code (at least, not code that is
>> expected to do something useful other than test the compiler's code
>> generation), there is no harm in making sub-optimal object code.
>>
>
> Actually the reason why I noticed this is because one of our engineers
> told that GCC stopped generating instructions for certain operations
> when he moved from GCC45 to GCC46. This code is real code.
>
> Cheers,
If you really have a "static const" object which you need to read as
"volatile" for some reason, then I would seriously consider changing the
code. With "static const" you are telling the compiler it knows
everything about the use of that object, and its value will never change
- with "volatile" you are telling it that it's value might change behind
the scenes. Obviously you've only posted a code snippet and not your
full code, but that sounds self-contradictory to me. Somewhere along
the line you are lying to the compiler - that's never a good idea when
you want correct and optimal code.
David
next prev parent reply other threads:[~2011-09-22 8:39 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-20 16:08 Paulo J. Matos
2011-09-20 16:36 ` Ian Lance Taylor
2011-09-21 7:07 ` David Brown
2011-09-21 8:22 ` Paulo J. Matos
2011-09-21 10:20 ` David Brown
2011-09-21 13:57 ` Ian Lance Taylor
2011-09-21 14:25 ` David Brown
2011-09-21 14:57 ` Paulo J. Matos
2011-09-22 8:39 ` David Brown [this message]
2011-09-22 21:15 ` Richard Guenther
2011-09-23 11:33 ` Paulo J. Matos
2011-09-23 11:51 ` Paulo J. Matos
2011-09-23 13:17 ` Paulo J. Matos
2011-09-21 18:51 ` Georg-Johann Lay
2011-09-22 8:53 ` David Brown
2011-09-24 15:10 ` John Regehr
2011-09-24 15:49 ` David Brown
2011-09-24 16:26 ` David Brown
2011-09-24 19:38 ` John Regehr
2011-09-25 13:03 ` David Brown
2011-09-25 15:15 ` Andreas Schwab
2011-09-25 16:33 ` David Brown
2011-09-25 16:36 ` David Brown
2011-09-25 16:06 ` Dave Korn
2011-09-25 22:05 ` David Brown
2011-09-25 22:05 ` David Brown
2011-09-26 7:14 ` Miles Bader
2011-09-26 8:53 ` David Brown
2011-09-26 8:58 ` David Brown
2011-09-21 8:14 ` Paulo J. Matos
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='j5es6e$b1i$1@dough.gmane.org' \
--to=david@westcontrol.com \
--cc=gcc@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).