1  /* { dg-do run } */
       2  /* { dg-options "-pthread" } */
       3  /* { dg-require-effective-target pthread } */
       4  
       5  #include <pthread.h>
       6  
       7  static volatile int sem1;
       8  static volatile int sem2;
       9  
      10  static void *f(void *va)
      11  {
      12    void **p = va;
      13    if (*p) return *p;
      14    sem1 = 1;
      15    while (!sem2)
      16      sched_yield ();
      17    __atomic_thread_fence(__ATOMIC_ACQUIRE);
      18    // GCC used to RTL-CSE this and the first load, causing 0 to be returned
      19    return *p;
      20  }
      21  
      22  int main()
      23  {
      24    void *p = 0;
      25    pthread_t thr;
      26    if (pthread_create(&thr, 0, f, &p))
      27      return 2;
      28    while (!sem1)
      29      sched_yield ();
      30    __atomic_thread_fence(__ATOMIC_ACQUIRE);
      31    p = &p;
      32    __atomic_thread_fence(__ATOMIC_RELEASE);
      33    sem2 = 1;
      34    pthread_join(thr, &p);
      35    return !p;
      36  }