cmpxchg8b help

cmpxchg8b help

[Scott Moonen]

List,

I have the following function in /usr/include/asm/system.h on my system.
I would like to modify it to take long long parameters and support an
8-byte cmpxchg8b as well.  My expertise these days is in S/390 assembler
rather than Intel, much less GCC's syntax to allow it, so I have little
idea where to even start.

Would anyone on the list be able to help me?  Thanks in advance!  -- Scott


static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old,
                                      unsigned long new, int size)
{
        unsigned long prev;
        switch (size) {
        case 1:
                __asm__ __volatile__(LOCK_PREFIX "cmpxchgb %b1,%2"
                                     : "=a"(prev)
                                     : "q"(new), "m"(*__xg(ptr)), "0"(old)
                                     : "memory");
                return prev;
        case 2:
                __asm__ __volatile__(LOCK_PREFIX "cmpxchgw %w1,%2"
                                     : "=a"(prev)
                                     : "q"(new), "m"(*__xg(ptr)), "0"(old)
                                     : "memory");
                return prev;
        case 4:
                __asm__ __volatile__(LOCK_PREFIX "cmpxchgl %1,%2"
                                     : "=a"(prev)
                                     : "q"(new), "m"(*__xg(ptr)), "0"(old)
                                     : "memory");
                return prev;
        }
        return old;
}


-- 
This is not a sentence.