From: Ralf Baechle <ralf@linux-mips.org>
To: Indigodfw <indigodfw@yahoo.com>
Cc: linux-mips@linux-mips.org
Subject: Re: question about memory constraint in atomic_add
Date: Wed, 18 Feb 2004 14:45:01 +0100 [thread overview]
Message-ID: <20040218134501.GA24330@linux-mips.org> (raw)
In-Reply-To: <20040214151152.80368.qmail@web9502.mail.yahoo.com>
On Sat, Feb 14, 2004 at 07:11:52AM -0800, Indigodfw wrote:
> 2. Result of (C expression) should go into %xyz
> register
> So v->counter goes into %1, IOW ll from an int!
>
> Does not make sense to me.
> Why does it work, What am I missing?
> I mean in general what is the expression for a m
> constraint ptr (because I want ptr to be in regiser)
> or *ptr (because I wanna tell compiler that *ptr is
> what gets changed)
"m" gives you *something* suitable to address a memory object; that isn't
necessarily a memory address. On MIPS it can't even be just an address
in a register because "m" constraints are used with loads and stores and
those only accept the offset(reg) addressing mode. If you want an address
use something like "r" (&v->counter), then lw reg,(%xxx).
Ralf
next prev parent reply other threads:[~2004-02-18 13:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-14 15:11 question about memory constraint in atomic_add Indigodfw
2004-02-18 13:45 ` Ralf Baechle [this message]
2004-02-19 0:11 ` Indigodfw
2004-02-19 18:18 ` Daniel Jacobowitz
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