gcc/testsuite/g++.dg/gomp/flush-1.C

/* { dg-do compile } */
/* { dg-options "-fopenmp -fdump-tree-gimple" } */

void f1(void)
{
  #pragma omp flush
}

int x;

void f2(bool p)
{
  int z;
  if (p)
    {
      #pragma omp flush (x)
    }
  else
    {
      #pragma omp flush (x, z, p)
    }
}

/* { dg-final { scan-tree-dump-times "__sync_synchronize" 3 "gimple" } } */