From: "Rolf" <rolf.ebert_nospam_@gmx.net>
Subject: Re: volatile vs aliased
Date: 6 Oct 2005 04:36:44 -0700
Date: 2005-10-06T04:36:44-07:00 [thread overview]
Message-ID: <1128598604.142021.239190@g44g2000cwa.googlegroups.com> (raw)
In-Reply-To: <1421562.dbAHjS9XJS@linux1.krischik.com>
Martin Krischik wrote:
> Ludovic Brenta wrote:
>
> > pragma Volatile (Variable) says the compiler must not optimise away
> > any reads or writes to that variable, and that it may not add extra
> > reads or writes beyond those you explicitly request in your program
> > text. You want to use that for hardware registers, where a "read"
> > operation may have a side effect such as changing the device's state.
>
> Interesting! So with pragma Volatile (X) the following two statements are
> not the same:
>
> Y := X * X;
> Y := X ** 2;
Do we have a difference to C/C++ increment operator here? consider
pragma Volatile (x);
x := x + 1; -- (1)
vs.
x++; -- (2)
In the Ada case (1) we are forced to have "read from memory",
"increment" and "write to memory" instructions, whereas in C/C++ (2)
you can get a single "increment memory" instruction (presuming the
mentioned assembler instructions exist on a given processor)
Rolf
next prev parent reply other threads:[~2005-10-06 11:36 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-05 15:22 volatile vs aliased REH
2005-10-05 18:22 ` Ludovic Brenta
2005-10-05 18:39 ` REH
2005-10-05 19:46 ` Ludovic Brenta
2005-10-05 20:02 ` REH
2005-10-05 20:11 ` Ludovic Brenta
2005-10-05 20:20 ` REH
2005-10-06 5:21 ` Ludovic Brenta
2005-10-05 20:55 ` Simon Wright
2005-10-06 18:32 ` Jeffrey R. Carter
2005-10-05 23:38 ` Randy Brukardt
2005-10-06 0:02 ` tmoran
2005-10-06 13:40 ` REH
2005-10-06 23:52 ` Randy Brukardt
2005-10-06 18:40 ` Jeffrey R. Carter
2005-10-06 19:37 ` Robert A Duff
2005-10-06 23:56 ` Randy Brukardt
2005-10-06 19:08 ` REH
2005-10-06 19:21 ` Ed Falis
2005-10-06 19:37 ` REH
2005-10-06 19:46 ` Robert A Duff
2005-10-06 8:05 ` Martin Krischik
2005-10-06 8:52 ` Dmitry A. Kazakov
2005-10-06 11:36 ` Rolf [this message]
2005-10-06 18:43 ` Björn Persson
2005-10-06 19:03 ` Niklas Holsti
2005-10-07 6:36 ` Martin Krischik
2005-10-07 6:33 ` Martin Krischik
2005-10-07 15:56 ` Adrian Knoth
2005-10-07 18:48 ` Martin Krischik
2005-10-07 22:44 ` REH
2005-10-08 6:10 ` Simon Wright
2005-10-17 2:16 ` Dave Thompson
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