lkml.org 
[lkml]   [2005]   [Sep]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
DateSat, 17 Sep 2005 23:03:46 -0700 (PDT)
SubjectRe: [PATCH 2/5] atomic: introduce atomic_inc_not_zero
From"David S. Miller" <>
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.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-09-18 08:08    [from the cache]
©2003-2010