Phil Endecott writes:
> Dear Experts,
>
> I believe that ARM's swap instruction can be used to implement the
> __sync_lock_test_and_set builtin, yet as far as I can see it is not
> implemented. Can anyone please confirm if (a) it is implemented but
> I'm doing something wrong, or (b) there's some reason why it can't be
> done? FWIW here is some asm that I am currently using for this:
>
> asm volatile ("swp\t%0, %1, [%2]"
> :"=r" (oldval)
> :"r" (newval),
> "r" (&mem)
> :"memory");
Looks fine to me.
Andrew.
