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
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