#define forget(a)	__asm__ __volatile__ ("" :"=m" (a) :"m" (a))

[ This is exactly equivalent to using "+m" in the constraints, as 
recently
  explained on a GCC list somewhere, in response to the patch in my 
bitops
  series a few weeks back where I thought "+m" was bogus. ]

[It wasn't explained on a GCC list in response to your patch, as
far as I can see -- if I missed it, please point me to an archived
version of it].

One last time: it isn't equivalent on older (but still supported
by Linux) versions of GCC.  Current versions of GCC allow it, but
it has no documented behaviour at all, so use it at your own risk.


Segher