From: "David S. Miller" <davem@davemloft.net>
To: rmk+lkml@arm.linux.org.uk
Cc: zippel@linux-m68k.org, nickpiggin@yahoo.com.au,
Linux-Kernel@vger.kernel.org, dipankar@in.ibm.com
Subject: Re: [PATCH 2/5] atomic: introduce atomic_inc_not_zero
Date: Sat, 17 Sep 2005 23:03:46 -0700 (PDT) [thread overview]
Message-ID: <20050917.230346.117470427.davem@davemloft.net> (raw)
In-Reply-To: <20050917072736.GA16523@flint.arm.linux.org.uk>
From: Russell King <rmk+lkml@arm.linux.org.uk>
Date: Sat, 17 Sep 2005 08:27:36 +0100
> gcc did have some support to pass condition codes into assembly.
> On ARM, you used to be able to do things like:
>
> if (foo)
> asm("blah%? whatever");
>
> and gcc would replace %? with whatever condition was appropriate
> for the current block of code. You can still write it as the
> above.
>
> However, this optimisation was disabled on ARM apparantly because
> it was very hard to for people to get correct - if you forgot the
> %?, you need to add a "cc" clobber, and if you forget that as well
> you might get unconditional behaviour.
Yes, that is an error prone syntax to use, that's for sure.
That is, incidentally, why I said the condition test should
be an explicit input arg to the asm.
next prev parent reply other threads:[~2005-09-18 6:05 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-14 14:48 [PATCH 1/5] atomic: introduce atomic_cmpxchg Nick Piggin
2005-09-14 14:49 ` [PATCH 2/5] atomic: introduce atomic_inc_not_zero Nick Piggin
2005-09-14 14:51 ` [PATCH 3/5] rcu file: use atomic primitives Nick Piggin
2005-09-14 14:55 ` [PATCH 4/5] atomic: dec_and_lock use cmpxchg Nick Piggin
2005-09-14 15:01 ` [PATCH 5/5] remove HAVE_ARCH_CMPXCHG Nick Piggin
2005-09-14 16:31 ` Roman Zippel
2005-09-14 16:49 ` Nick Piggin
2005-09-14 17:59 ` David S. Miller
2005-09-14 22:03 ` Russell King
2005-09-14 22:26 ` David S. Miller
2005-09-15 7:10 ` Russell King
2005-09-15 13:08 ` Alan Cox
2005-09-14 15:20 ` [PATCH 4/5] atomic: dec_and_lock use cmpxchg Nick Piggin
2005-09-14 16:24 ` David S. Miller
2005-09-14 16:52 ` Nick Piggin
2005-09-17 0:05 ` David S. Miller
2005-09-14 16:16 ` [PATCH 2/5] atomic: introduce atomic_inc_not_zero Roman Zippel
2005-09-14 16:44 ` Nick Piggin
2005-09-14 17:04 ` Nick Piggin
2005-09-14 17:18 ` Roman Zippel
2005-09-14 22:00 ` Russell King
2005-09-14 22:10 ` Roman Zippel
2005-09-14 22:21 ` Russell King
2005-09-15 1:51 ` Nick Piggin
2005-09-17 1:15 ` Roman Zippel
2005-09-17 6:36 ` Andrew Morton
2005-09-17 10:01 ` Roman Zippel
2005-09-17 7:19 ` David S. Miller
2005-09-17 7:34 ` Dipankar Sarma
2005-09-18 8:08 ` Nick Piggin
2005-09-17 0:59 ` Roman Zippel
2005-09-17 7:18 ` David S. Miller
2005-09-17 7:27 ` Russell King
2005-09-18 6:03 ` David S. Miller [this message]
2005-09-14 15:17 ` [PATCH 1/5] atomic: introduce atomic_cmpxchg Russell King
2005-09-14 15:22 ` Nick Piggin
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