1  /* Macros to emit "L Nxx R" for each octal number xx between 000 and 037.  */
       2  #define OP1(L, N, R, I, J) L N##I##J R
       3  #define OP2(L, N, R, I) \
       4      OP1(L, N, R, 0, I), OP1(L, N, R, 1, I), \
       5      OP1(L, N, R, 2, I), OP1(L, N, R, 3, I)
       6  #define OP(L, N, R) \
       7      OP2(L, N, R, 0), OP2(L, N, R, 1), OP2(L, N, R, 2), OP2(L, N, R, 3), \
       8      OP2(L, N, R, 4), OP2(L, N, R, 5), OP2(L, N, R, 6), OP2(L, N, R, 7)
       9  
      10  /* Declare 32 unique variables with prefix N.  */
      11  #define DECLARE(N) OP (, N,)
      12  
      13  /* Copy 32 variables with prefix N from the array at ADDR.
      14     Leave ADDR pointing to the end of the array.  */
      15  #define COPYIN(N, ADDR) OP (, N, = *(ADDR++))
      16  
      17  /* Likewise, but copy the other way.  */
      18  #define COPYOUT(N, ADDR) OP (*(ADDR++) =, N,)
      19  
      20  /* Add the contents of the array at ADDR to 32 variables with prefix N.
      21     Leave ADDR pointing to the end of the array.  */
      22  #define ADD(N, ADDR) OP (, N, += *(ADDR++))
      23  
      24  volatile double gd[32];
      25  volatile float gf[32];
      26  
      27  void foo (int n)
      28  {
      29    double DECLARE(d);
      30    float DECLARE(f);
      31    volatile double *pd;
      32    volatile float *pf;
      33    int i;
      34  
      35    pd = gd; COPYIN (d, pd);
      36    for (i = 0; i < n; i++)
      37      {
      38        pf = gf; COPYIN (f, pf);
      39        pd = gd; ADD (d, pd);
      40        pd = gd; ADD (d, pd);
      41        pd = gd; ADD (d, pd);
      42        pf = gf; COPYOUT (f, pf);
      43      }
      44    pd = gd; COPYOUT (d, pd);
      45  }
      46  
      47  int main ()
      48  {
      49    int i;
      50  
      51    for (i = 0; i < 32; i++)
      52      gd[i] = i, gf[i] = i;
      53    foo (1);
      54    for (i = 0; i < 32; i++)
      55      if (gd[i] != i * 4 || gf[i] != i)
      56        abort ();
      57    exit (0);
      58  }