text: #include <stdlib.h>
  extern void abort (void);
  
  typedef unsigned long HARD_REG_SET[2];
  HARD_REG_SET reg_class_contents[2];
  
  struct du_chain
  {
    struct du_chain *next_use;
    int cl;
  };
  
  void __attribute__((noinline))
  merge_overlapping_regs (HARD_REG_SET *p)
  {
    if ((*p)[0] != -1 || (*p)[1] != -1)
      abort ();
  }
  
  void __attribute__((noinline))
  regrename_optimize (struct du_chain *this)
  {
    HARD_REG_SET this_unavailable;
    unsigned long *scan_fp_;
    int n_uses;
    struct du_chain *last;
  
    this_unavailable[0] = 0;
    this_unavailable[1] = 0;
  
    n_uses = 0;
    for (last = this; last->next_use; last = last->next_use)
      {
        scan_fp_ = reg_class_contents[last->cl];
        n_uses++;
        this_unavailable[0] |= ~ scan_fp_[0];
        this_unavailable[1] |= ~ scan_fp_[1];
      }
    if (n_uses < 1)
      return;
  
    scan_fp_ = reg_class_contents[last->cl];
    this_unavailable[0] |= ~ scan_fp_[0];
    this_unavailable[1] |= ~ scan_fp_[1];
  
    merge_overlapping_regs (&this_unavailable);
  }
  
  int main()
  {
    struct du_chain du1 = { 0, 0 };
    struct du_chain du0 = { &du1, 1 };
    reg_class_contents[0][0] = -1;
    reg_class_contents[0][1] = -1;
    reg_class_contents[1][0] = 0;
    reg_class_contents[1][1] = 0;
    regrename_optimize (&du0);
    return 0;
  }
  