From: Albert ARIBAUD <albert.aribaud@free.fr>
To: u-boot@lists.denx.de
Subject: [U-Boot] [RFC PATCH v2] ARM: Avoid compiler optimization for usages of readb, writeb and friends.
Date: Tue, 21 Dec 2010 13:51:51 +0100 [thread overview]
Message-ID: <4D10A2E7.6050302@free.fr> (raw)
In-Reply-To: <4D109F06.1040109@ahsoftware.de>
Le 21/12/2010 13:35, Alexander Holler a ?crit :
> Hmm, is there actual somethinbg which should forbid the compiler to
> generate such code which rereads something? It might not be nice, but I
> don't think that it is forbidden for a compiler to do so. So the proper
> way to handle such, might be to use asm to avoid that the compiler
> touches that register.
Yes there is something that should prevent a compiler from inserting
reads: these accesses are to hardware, not memory, and may cause side
effects even on read (these could be acknowledges, for instance; I've
seen instances of that myself on some HW).
Another way to look at it is that the semantics of " *ptr = value " is a
pure write and should not result in a write-then-read.
> Regards,
>
> Alexander
Amicalement,
--
Albert.
next prev parent reply other threads:[~2010-12-21 12:51 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-18 22:27 [U-Boot] [RFC PATCH v2] ARM: Avoid compiler optimization for usages of readb, writeb and friends Alexander Holler
2010-12-19 7:51 ` Dirk Behme
2010-12-19 10:22 ` Alexander Holler
2010-12-19 11:28 ` Albert ARIBAUD
2010-12-19 16:34 ` Alexander Holler
2010-12-19 18:45 ` John Rigby
2010-12-19 19:59 ` Alexander Holler
2010-12-20 0:39 ` John Rigby
2010-12-20 0:56 ` Alexander Holler
2010-12-20 4:18 ` John Rigby
2010-12-20 6:07 ` John Rigby
2010-12-20 6:49 ` Dirk Behme
2010-12-20 7:37 ` John Rigby
2010-12-20 16:08 ` John Rigby
2010-12-20 16:12 ` John Rigby
2011-01-17 4:35 ` Alexander Holler
2010-12-20 17:12 ` Alexander Holler
2010-12-21 0:25 ` John Rigby
2010-12-21 0:46 ` John Rigby
2010-12-21 7:11 ` Dirk Behme
2010-12-21 7:21 ` Albert ARIBAUD
2010-12-21 8:05 ` Dirk Behme
2010-12-21 8:17 ` Wolfgang Denk
2010-12-21 8:37 ` Dirk Behme
2010-12-21 8:35 ` Dirk Behme
2010-12-21 8:46 ` John Rigby
2010-12-21 10:38 ` Albert ARIBAUD
2010-12-21 10:53 ` Wolfgang Denk
2010-12-21 12:35 ` Alexander Holler
2010-12-21 12:51 ` Albert ARIBAUD [this message]
2010-12-21 13:30 ` Alexander Holler
2010-12-21 14:33 ` Albert ARIBAUD
2010-12-21 19:52 ` Wolfgang Denk
2010-12-21 20:04 ` Dirk Behme
2010-12-21 21:49 ` Albert ARIBAUD
2010-12-22 0:11 ` Alexander Holler
2010-12-22 7:02 ` Albert ARIBAUD
2010-12-22 7:18 ` Dirk Behme
2010-12-22 7:52 ` Wolfgang Denk
2010-12-23 16:40 ` Dirk Behme
2010-12-22 9:56 ` Alexander Holler
2010-12-21 13:38 ` Alexander Holler
2010-12-22 8:02 ` Wolfgang Denk
2010-12-22 11:23 ` Alexander Holler
2010-12-29 9:40 ` Dirk Behme
2010-12-29 23:10 ` Alessandro Rubini
2010-12-30 10:39 ` Dirk Behme
2011-01-09 22:03 ` Wolfgang Denk
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=4D10A2E7.6050302@free.fr \
--to=albert.aribaud@free.fr \
--cc=u-boot@lists.denx.de \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.