Exemple #1
0
static rtx_expr_list *
extract_mentioned_regs (rtx x)
{
  rtx_expr_list *mentioned_regs = NULL;
  subrtx_var_iterator::array_type array;
  FOR_EACH_SUBRTX_VAR (iter, array, x, NONCONST)
    {
      rtx x = *iter;
      if (REG_P (x))
	mentioned_regs = alloc_EXPR_LIST (0, x, mentioned_regs);
    }
/* Unswitch single LOOP.  COND_CHECKED holds list of conditions we already
   unswitched on and are therefore known to be true in this LOOP.  NUM is
   number of unswitchings done; do not allow it to grow too much, it is too
   easy to create example on that the code would grow exponentially.
   Returns true LOOP was unswitched.  */
static bool 
unswitch_single_loop (struct loop *loop, rtx cond_checked, int num)
{
  basic_block *bbs;
  struct loop *nloop;
  unsigned i;
  rtx cond, rcond = NULL_RTX, conds, rconds, acond, cinsn;
  int repeat;
  edge e;
  HOST_WIDE_INT iterations;

  /* Do not unswitch too much.  */
  if (num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL))
    {
      if (dump_file)
	fprintf (dump_file, ";; Not unswitching anymore, hit max level\n");
      return false;
    }

  /* Only unswitch innermost loops.  */
  if (loop->inner)
    {
      if (dump_file)
	fprintf (dump_file, ";; Not unswitching, not innermost loop\n");
      return false;
    }

  /* We must be able to duplicate loop body.  */
  if (!can_duplicate_loop_p (loop))
    {
      if (dump_file)
	fprintf (dump_file, ";; Not unswitching, can't duplicate loop\n");
      return false;
    }

  /* The loop should not be too large, to limit code growth.  */
  if (num_loop_insns (loop) > PARAM_VALUE (PARAM_MAX_UNSWITCH_INSNS))
    {
      if (dump_file)
	fprintf (dump_file, ";; Not unswitching, loop too big\n");
      return false;
    }

  /* Do not unswitch in cold areas.  */
  if (optimize_loop_for_size_p (loop))
    {
      if (dump_file)
	fprintf (dump_file, ";; Not unswitching, not hot area\n");
      return false;
    }

  /* Nor if the loop usually does not roll.  */
  iterations = estimated_loop_iterations_int (loop);
  if (iterations >= 0 && iterations <= 1)
    {
      if (dump_file)
	fprintf (dump_file, ";; Not unswitching, loop iterations < 1\n");
      return false;
    }

  do
    {
      repeat = 0;
      cinsn = NULL_RTX;

      /* Find a bb to unswitch on.  */
      bbs = get_loop_body (loop);
      iv_analysis_loop_init (loop);
      for (i = 0; i < loop->num_nodes; i++)
	if ((cond = may_unswitch_on (bbs[i], loop, &cinsn)))
	  break;

      if (i == loop->num_nodes)
	{
	  free (bbs);
	  return false;
	}

      if (cond != const0_rtx
	  && cond != const_true_rtx)
	{
	  rcond = reversed_condition (cond);
	  if (rcond)
	    rcond = canon_condition (rcond);

	  /* Check whether the result can be predicted.  */
	  for (acond = cond_checked; acond; acond = XEXP (acond, 1))
	    simplify_using_condition (XEXP (acond, 0), &cond, NULL);
	}

      if (cond == const_true_rtx)
	{
	  /* Remove false path.  */
	  e = FALLTHRU_EDGE (bbs[i]);
	  remove_path (e);
	  free (bbs);
	  repeat = 1;
	}
      else if (cond == const0_rtx)
	{
	  /* Remove true path.  */
	  e = BRANCH_EDGE (bbs[i]);
	  remove_path (e);
	  free (bbs);
	  repeat = 1;
	}
    } while (repeat);

  /* We found the condition we can unswitch on.  */
  conds = alloc_EXPR_LIST (0, cond, cond_checked);
  if (rcond)
    rconds = alloc_EXPR_LIST (0, rcond, cond_checked);
  else
    rconds = cond_checked;

  if (dump_file)
    fprintf (dump_file, ";; Unswitching loop\n");

  /* Unswitch the loop on this condition.  */
  nloop = unswitch_loop (loop, bbs[i], copy_rtx_if_shared (cond), cinsn);
  gcc_assert (nloop);

  /* Invoke itself on modified loops.  */
  unswitch_single_loop (nloop, rconds, num + 1);
  unswitch_single_loop (loop, conds, num + 1);

  free_EXPR_LIST_node (conds);
  if (rcond)
    free_EXPR_LIST_node (rconds);

  free (bbs);

  return true;
}