openmpi/src/include/sys/amd64/atomic.h

/*
 * $HEADER$
 */

#ifndef OMPI_SYS_ARCH_ATOMIC_H
#define OMPI_SYS_ARCH_ATOMIC_H 1

/*
 * On amd64, we use cmpxchg.
 */


#ifdef HAVE_SMP
#define SMPLOCK "lock; "
#define MB() __asm__ __volatile__("": : :"memory")
#else
#define SMPLOCK
#define MB()
#endif


static inline void ompi_atomic_mb(void)
{
    MB();
}


static inline void ompi_atomic_rmb(void)
{
    MB();
}


static inline void ompi_atomic_wmb(void)
{
    MB();
}

static inline int ompi_atomic_cmpset_32(volatile uint32_t *addr,
                                        uint32_t oldval,
                                        uint32_t newval)
{
   unsigned long prev;
   __asm__ __volatile__(SMPLOCK "cmpxchgl %k1,%2"
                        : "=a"(prev)
                        : "q"(newval), "m"(*addr), "0"(oldval)
                        : "memory");
   return prev == oldval;
}

#define ompi_atomic_cmpset_acq_32 ompi_atomic_cmpset_32
#define ompi_atomic_cmpset_rel_32 ompi_atomic_cmpset_32

static inline int ompi_atomic_cmpset_64(volatile uint64_t *addr,
                                        uint64_t oldval,
                                        uint64_t newval)
{
   uint64_t ret = oldval;
    
   __asm__ __volatile (
                       SMPLOCK "cmpxchgq %1,%2   \n\t"
                               "setz     %%al    \n\t"
                               "movzbl   %%al,%0 \n\t"
                       : "+a" (ret)
                       : "r" (newval), "m" (*(addr))
                       : "memory");
    
   return (ret == oldval);
}

#define ompi_atomic_cmpset_acq_64 ompi_atomic_cmpset_64
#define ompi_atomic_cmpset_rel_64 ompi_atomic_cmpset_64

#endif /* ! OMPI_SYS_ARCH_ATOMIC_H */