예제 #1
0
static inline tree
chrec_fold_multiply_poly_poly (tree type,
			       tree poly0,
			       tree poly1)
{
  tree t0, t1, t2;
  int var;
  struct loop *loop0 = get_chrec_loop (poly0);
  struct loop *loop1 = get_chrec_loop (poly1);

  gcc_assert (poly0);
  gcc_assert (poly1);
  gcc_assert (TREE_CODE (poly0) == POLYNOMIAL_CHREC);
  gcc_assert (TREE_CODE (poly1) == POLYNOMIAL_CHREC);
  gcc_checking_assert (useless_type_conversion_p (type, chrec_type (poly0))
		       && useless_type_conversion_p (type, chrec_type (poly1)));

  /* {a, +, b}_1 * {c, +, d}_2  ->  {c*{a, +, b}_1, +, d}_2,
     {a, +, b}_2 * {c, +, d}_1  ->  {a*{c, +, d}_1, +, b}_2,
     {a, +, b}_x * {c, +, d}_x  ->  {a*c, +, a*d + b*c + b*d, +, 2*b*d}_x.  */
  if (flow_loop_nested_p (loop0, loop1))
    /* poly0 is a constant wrt. poly1.  */
    return build_polynomial_chrec
      (CHREC_VARIABLE (poly1),
       chrec_fold_multiply (type, CHREC_LEFT (poly1), poly0),
       CHREC_RIGHT (poly1));

  if (flow_loop_nested_p (loop1, loop0))
    /* poly1 is a constant wrt. poly0.  */
    return build_polynomial_chrec
      (CHREC_VARIABLE (poly0),
       chrec_fold_multiply (type, CHREC_LEFT (poly0), poly1),
       CHREC_RIGHT (poly0));

  gcc_assert (loop0 == loop1);

  /* poly0 and poly1 are two polynomials in the same variable,
     {a, +, b}_x * {c, +, d}_x  ->  {a*c, +, a*d + b*c + b*d, +, 2*b*d}_x.  */

  /* "a*c".  */
  t0 = chrec_fold_multiply (type, CHREC_LEFT (poly0), CHREC_LEFT (poly1));

  /* "a*d + b*c".  */
  t1 = chrec_fold_multiply (type, CHREC_LEFT (poly0), CHREC_RIGHT (poly1));
  t1 = chrec_fold_plus (type, t1, chrec_fold_multiply (type,
						       CHREC_RIGHT (poly0),
						       CHREC_LEFT (poly1)));
  /* "b*d".  */
  t2 = chrec_fold_multiply (type, CHREC_RIGHT (poly0), CHREC_RIGHT (poly1));
  /* "a*d + b*c + b*d".  */
  t1 = chrec_fold_plus (type, t1, t2);
  /* "2*b*d".  */
  t2 = chrec_fold_multiply (type, SCALAR_FLOAT_TYPE_P (type)
			    ? build_real (type, dconst2)
			    : build_int_cst (type, 2), t2);

  var = CHREC_VARIABLE (poly0);
  return build_polynomial_chrec (var, t0,
				 build_polynomial_chrec (var, t1, t2));
}
예제 #2
0
static inline tree 
chrec_fold_multiply_poly_poly (tree type, 
			       tree poly0, 
			       tree poly1)
{
  tree t0, t1, t2;
  int var;

  gcc_assert (poly0);
  gcc_assert (poly1);
  gcc_assert (TREE_CODE (poly0) == POLYNOMIAL_CHREC);
  gcc_assert (TREE_CODE (poly1) == POLYNOMIAL_CHREC);
  gcc_assert (chrec_type (poly0) == chrec_type (poly1));
  gcc_assert (type == chrec_type (poly0));
  
  /* {a, +, b}_1 * {c, +, d}_2  ->  {c*{a, +, b}_1, +, d}_2,
     {a, +, b}_2 * {c, +, d}_1  ->  {a*{c, +, d}_1, +, b}_2,
     {a, +, b}_x * {c, +, d}_x  ->  {a*c, +, a*d + b*c + b*d, +, 2*b*d}_x.  */
  if (CHREC_VARIABLE (poly0) < CHREC_VARIABLE (poly1))
    /* poly0 is a constant wrt. poly1.  */
    return build_polynomial_chrec 
      (CHREC_VARIABLE (poly1), 
       chrec_fold_multiply (type, CHREC_LEFT (poly1), poly0),
       CHREC_RIGHT (poly1));
  
  if (CHREC_VARIABLE (poly1) < CHREC_VARIABLE (poly0))
    /* poly1 is a constant wrt. poly0.  */
    return build_polynomial_chrec 
      (CHREC_VARIABLE (poly0), 
       chrec_fold_multiply (type, CHREC_LEFT (poly0), poly1),
       CHREC_RIGHT (poly0));
  
  /* poly0 and poly1 are two polynomials in the same variable,
     {a, +, b}_x * {c, +, d}_x  ->  {a*c, +, a*d + b*c + b*d, +, 2*b*d}_x.  */
      
  /* "a*c".  */
  t0 = chrec_fold_multiply (type, CHREC_LEFT (poly0), CHREC_LEFT (poly1));

  /* "a*d + b*c + b*d".  */
  t1 = chrec_fold_multiply (type, CHREC_LEFT (poly0), CHREC_RIGHT (poly1));
  t1 = chrec_fold_plus (type, t1, chrec_fold_multiply (type,
						       CHREC_RIGHT (poly0),
						       CHREC_LEFT (poly1)));
  t1 = chrec_fold_plus (type, t1, chrec_fold_multiply (type,
						       CHREC_RIGHT (poly0),
						       CHREC_RIGHT (poly1)));
  /* "2*b*d".  */
  t2 = chrec_fold_multiply (type, CHREC_RIGHT (poly0), CHREC_RIGHT (poly1));
  t2 = chrec_fold_multiply (type, SCALAR_FLOAT_TYPE_P (type)
			    ? build_real (type, dconst2)
			    : build_int_cst (type, 2), t2);

  var = CHREC_VARIABLE (poly0);
  return build_polynomial_chrec (var, t0,
				 build_polynomial_chrec (var, t1, t2));
}
예제 #3
0
static tree
chrec_evaluate (unsigned var, tree chrec, tree n, unsigned int k)
{
  tree arg0, arg1, binomial_n_k;
  tree type = TREE_TYPE (chrec);
  struct loop *var_loop = get_loop (cfun, var);

  while (TREE_CODE (chrec) == POLYNOMIAL_CHREC
	 && flow_loop_nested_p (var_loop, get_chrec_loop (chrec)))
    chrec = CHREC_LEFT (chrec);

  if (TREE_CODE (chrec) == POLYNOMIAL_CHREC
      && CHREC_VARIABLE (chrec) == var)
    {
      arg1 = chrec_evaluate (var, CHREC_RIGHT (chrec), n, k + 1);
      if (arg1 == chrec_dont_know)
	return chrec_dont_know;
      binomial_n_k = tree_fold_binomial (type, n, k);
      if (!binomial_n_k)
	return chrec_dont_know;
      arg0 = fold_build2 (MULT_EXPR, type,
			  CHREC_LEFT (chrec), binomial_n_k);
      return chrec_fold_plus (type, arg0, arg1);
    }

  binomial_n_k = tree_fold_binomial (type, n, k);
  if (!binomial_n_k)
    return chrec_dont_know;

  return fold_build2 (MULT_EXPR, type, chrec, binomial_n_k);
}
예제 #4
0
static inline tree 
chrec_fold_poly_cst (enum tree_code code, 
		     tree type, 
		     tree poly, 
		     tree cst)
{
  gcc_assert (poly);
  gcc_assert (cst);
  gcc_assert (TREE_CODE (poly) == POLYNOMIAL_CHREC);
  gcc_assert (!is_not_constant_evolution (cst));
  
  switch (code)
    {
    case PLUS_EXPR:
      return build_polynomial_chrec 
	(CHREC_VARIABLE (poly), 
	 chrec_fold_plus (type, CHREC_LEFT (poly), cst),
	 CHREC_RIGHT (poly));
      
    case MINUS_EXPR:
      return build_polynomial_chrec 
	(CHREC_VARIABLE (poly), 
	 chrec_fold_minus (type, CHREC_LEFT (poly), cst),
	 CHREC_RIGHT (poly));
      
    case MULT_EXPR:
      return build_polynomial_chrec 
	(CHREC_VARIABLE (poly), 
	 chrec_fold_multiply (type, CHREC_LEFT (poly), cst),
	 chrec_fold_multiply (type, CHREC_RIGHT (poly), cst));
      
    default:
      return chrec_dont_know;
    }
}
예제 #5
0
static tree 
chrec_evaluate (unsigned var, tree chrec, tree n, unsigned int k)
{
  tree arg0, arg1, binomial_n_k;
  tree type = TREE_TYPE (chrec);

  while (TREE_CODE (chrec) == POLYNOMIAL_CHREC
	 && CHREC_VARIABLE (chrec) > var)
    chrec = CHREC_LEFT (chrec);

  if (TREE_CODE (chrec) == POLYNOMIAL_CHREC
      && CHREC_VARIABLE (chrec) == var)
    {
      arg0 = chrec_evaluate (var, CHREC_RIGHT (chrec), n, k + 1);
      if (arg0 == chrec_dont_know)
	return chrec_dont_know;
      binomial_n_k = tree_fold_binomial (type, n, k);
      if (!binomial_n_k)
	return chrec_dont_know;
      arg1 = fold (build2 (MULT_EXPR, type,
			   CHREC_LEFT (chrec), binomial_n_k));
      return chrec_fold_plus (type, arg0, arg1);
    }

  binomial_n_k = tree_fold_binomial (type, n, k);
  if (!binomial_n_k)
    return chrec_dont_know;
  
  return fold (build2 (MULT_EXPR, type, chrec, binomial_n_k));
}
예제 #6
0
tree 
chrec_apply (unsigned var,
	     tree chrec, 
	     tree x)
{
  tree type = chrec_type (chrec);
  tree res = chrec_dont_know;

  if (automatically_generated_chrec_p (chrec)
      || automatically_generated_chrec_p (x)

      /* When the symbols are defined in an outer loop, it is possible
	 to symbolically compute the apply, since the symbols are
	 constants with respect to the varying loop.  */
      || chrec_contains_symbols_defined_in_loop (chrec, var)
      || chrec_contains_symbols (x))
    return chrec_dont_know;
  
  if (dump_file && (dump_flags & TDF_DETAILS))
    fprintf (dump_file, "(chrec_apply \n");

  if (evolution_function_is_affine_p (chrec))
    {
      /* "{a, +, b} (x)"  ->  "a + b*x".  */
      if (TREE_CODE (CHREC_LEFT (chrec)) == INTEGER_CST
	  && integer_zerop (CHREC_LEFT (chrec)))
	res = chrec_fold_multiply (type, CHREC_RIGHT (chrec), x);
      
      else
	res = chrec_fold_plus (type, CHREC_LEFT (chrec), 
			       chrec_fold_multiply (type, 
						    CHREC_RIGHT (chrec), x));
    }
  
  else if (TREE_CODE (chrec) != POLYNOMIAL_CHREC)
    res = chrec;
  
  else if (TREE_CODE (x) == INTEGER_CST
	   && tree_int_cst_sgn (x) == 1)
    /* testsuite/.../ssa-chrec-38.c.  */
    res = chrec_evaluate (var, chrec, x, 0);

  else
    res = chrec_dont_know;
  
  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "  (varying_loop = %d\n", var);
      fprintf (dump_file, ")\n  (chrec = ");
      print_generic_expr (dump_file, chrec, 0);
      fprintf (dump_file, ")\n  (x = ");
      print_generic_expr (dump_file, x, 0);
      fprintf (dump_file, ")\n  (res = ");
      print_generic_expr (dump_file, res, 0);
      fprintf (dump_file, "))\n");
    }
  
  return res;
}
예제 #7
0
static inline tree
chrec_fold_plus_poly_poly (enum tree_code code,
			   tree type,
			   tree poly0,
			   tree poly1)
{
  tree left, right;
  struct loop *loop0 = get_chrec_loop (poly0);
  struct loop *loop1 = get_chrec_loop (poly1);
  tree rtype = code == POINTER_PLUS_EXPR ? chrec_type (poly1) : type;

  gcc_assert (poly0);
  gcc_assert (poly1);
  gcc_assert (TREE_CODE (poly0) == POLYNOMIAL_CHREC);
  gcc_assert (TREE_CODE (poly1) == POLYNOMIAL_CHREC);
  if (POINTER_TYPE_P (chrec_type (poly0)))
    gcc_checking_assert (ptrofftype_p (chrec_type (poly1))
			 && useless_type_conversion_p (type, chrec_type (poly0)));
  else
    gcc_checking_assert (useless_type_conversion_p (type, chrec_type (poly0))
			 && useless_type_conversion_p (type, chrec_type (poly1)));

  /*
    {a, +, b}_1 + {c, +, d}_2  ->  {{a, +, b}_1 + c, +, d}_2,
    {a, +, b}_2 + {c, +, d}_1  ->  {{c, +, d}_1 + a, +, b}_2,
    {a, +, b}_x + {c, +, d}_x  ->  {a+c, +, b+d}_x.  */
  if (flow_loop_nested_p (loop0, loop1))
    {
      if (code == PLUS_EXPR || code == POINTER_PLUS_EXPR)
	return build_polynomial_chrec
	  (CHREC_VARIABLE (poly1),
	   chrec_fold_plus (type, poly0, CHREC_LEFT (poly1)),
	   CHREC_RIGHT (poly1));
      else
	return build_polynomial_chrec
	  (CHREC_VARIABLE (poly1),
	   chrec_fold_minus (type, poly0, CHREC_LEFT (poly1)),
	   chrec_fold_multiply (type, CHREC_RIGHT (poly1),
				SCALAR_FLOAT_TYPE_P (type)
				? build_real (type, dconstm1)
				: build_int_cst_type (type, -1)));
    }

  if (flow_loop_nested_p (loop1, loop0))
    {
      if (code == PLUS_EXPR || code == POINTER_PLUS_EXPR)
	return build_polynomial_chrec
	  (CHREC_VARIABLE (poly0),
	   chrec_fold_plus (type, CHREC_LEFT (poly0), poly1),
	   CHREC_RIGHT (poly0));
      else
	return build_polynomial_chrec
	  (CHREC_VARIABLE (poly0),
	   chrec_fold_minus (type, CHREC_LEFT (poly0), poly1),
	   CHREC_RIGHT (poly0));
    }

  /* This function should never be called for chrecs of loops that
     do not belong to the same loop nest.  */
  gcc_assert (loop0 == loop1);

  if (code == PLUS_EXPR || code == POINTER_PLUS_EXPR)
    {
      left = chrec_fold_plus
	(type, CHREC_LEFT (poly0), CHREC_LEFT (poly1));
      right = chrec_fold_plus
	(rtype, CHREC_RIGHT (poly0), CHREC_RIGHT (poly1));
    }
  else
    {
      left = chrec_fold_minus
	(type, CHREC_LEFT (poly0), CHREC_LEFT (poly1));
      right = chrec_fold_minus
	(type, CHREC_RIGHT (poly0), CHREC_RIGHT (poly1));
    }

  if (chrec_zerop (right))
    return left;
  else
    return build_polynomial_chrec
      (CHREC_VARIABLE (poly0), left, right);
}
예제 #8
0
tree
chrec_apply (unsigned var,
	     tree chrec,
	     tree x)
{
  tree type = chrec_type (chrec);
  tree res = chrec_dont_know;

  if (automatically_generated_chrec_p (chrec)
      || automatically_generated_chrec_p (x)

      /* When the symbols are defined in an outer loop, it is possible
	 to symbolically compute the apply, since the symbols are
	 constants with respect to the varying loop.  */
      || chrec_contains_symbols_defined_in_loop (chrec, var))
    return chrec_dont_know;

  if (dump_file && (dump_flags & TDF_SCEV))
    fprintf (dump_file, "(chrec_apply \n");

  if (TREE_CODE (x) == INTEGER_CST && SCALAR_FLOAT_TYPE_P (type))
    x = build_real_from_int_cst (type, x);

  switch (TREE_CODE (chrec))
    {
    case POLYNOMIAL_CHREC:
      if (evolution_function_is_affine_p (chrec))
	{
	  if (CHREC_VARIABLE (chrec) != var)
	    return build_polynomial_chrec
	      (CHREC_VARIABLE (chrec),
	       chrec_apply (var, CHREC_LEFT (chrec), x),
	       chrec_apply (var, CHREC_RIGHT (chrec), x));

	  /* "{a, +, b} (x)"  ->  "a + b*x".  */
	  x = chrec_convert_rhs (type, x, NULL);
	  res = chrec_fold_multiply (TREE_TYPE (x), CHREC_RIGHT (chrec), x);
	  res = chrec_fold_plus (type, CHREC_LEFT (chrec), res);
	}
      else if (TREE_CODE (x) == INTEGER_CST
	       && tree_int_cst_sgn (x) == 1)
	/* testsuite/.../ssa-chrec-38.c.  */
	res = chrec_evaluate (var, chrec, x, 0);
      else
	res = chrec_dont_know;
      break;

    CASE_CONVERT:
      res = chrec_convert (TREE_TYPE (chrec),
			   chrec_apply (var, TREE_OPERAND (chrec, 0), x),
			   NULL);
      break;

    default:
      res = chrec;
      break;
    }

  if (dump_file && (dump_flags & TDF_SCEV))
    {
      fprintf (dump_file, "  (varying_loop = %d\n", var);
      fprintf (dump_file, ")\n  (chrec = ");
      print_generic_expr (dump_file, chrec, 0);
      fprintf (dump_file, ")\n  (x = ");
      print_generic_expr (dump_file, x, 0);
      fprintf (dump_file, ")\n  (res = ");
      print_generic_expr (dump_file, res, 0);
      fprintf (dump_file, "))\n");
    }

  return res;
}
예제 #9
0
static tree
chrec_fold_plus_1 (enum tree_code code, tree type,
		   tree op0, tree op1)
{
  if (automatically_generated_chrec_p (op0)
      || automatically_generated_chrec_p (op1))
    return chrec_fold_automatically_generated_operands (op0, op1);

  switch (TREE_CODE (op0))
    {
    case POLYNOMIAL_CHREC:
      gcc_checking_assert
	(!chrec_contains_symbols_defined_in_loop (op0, CHREC_VARIABLE (op0)));
      switch (TREE_CODE (op1))
	{
	case POLYNOMIAL_CHREC:
	  gcc_checking_assert
	    (!chrec_contains_symbols_defined_in_loop (op1,
						      CHREC_VARIABLE (op1)));
	  return chrec_fold_plus_poly_poly (code, type, op0, op1);

	CASE_CONVERT:
	  if (tree_contains_chrecs (op1, NULL))
	    return chrec_dont_know;

	default:
	  if (code == PLUS_EXPR || code == POINTER_PLUS_EXPR)
	    return build_polynomial_chrec
	      (CHREC_VARIABLE (op0),
	       chrec_fold_plus (type, CHREC_LEFT (op0), op1),
	       CHREC_RIGHT (op0));
	  else
	    return build_polynomial_chrec
	      (CHREC_VARIABLE (op0),
	       chrec_fold_minus (type, CHREC_LEFT (op0), op1),
	       CHREC_RIGHT (op0));
	}

    CASE_CONVERT:
      if (tree_contains_chrecs (op0, NULL))
	return chrec_dont_know;

    default:
      switch (TREE_CODE (op1))
	{
	case POLYNOMIAL_CHREC:
	  gcc_checking_assert
	    (!chrec_contains_symbols_defined_in_loop (op1,
						      CHREC_VARIABLE (op1)));
	  if (code == PLUS_EXPR || code == POINTER_PLUS_EXPR)
	    return build_polynomial_chrec
	      (CHREC_VARIABLE (op1),
	       chrec_fold_plus (type, op0, CHREC_LEFT (op1)),
	       CHREC_RIGHT (op1));
	  else
	    return build_polynomial_chrec
	      (CHREC_VARIABLE (op1),
	       chrec_fold_minus (type, op0, CHREC_LEFT (op1)),
	       chrec_fold_multiply (type, CHREC_RIGHT (op1),
				    SCALAR_FLOAT_TYPE_P (type)
				    ? build_real (type, dconstm1)
				    : build_int_cst_type (type, -1)));

	CASE_CONVERT:
	  if (tree_contains_chrecs (op1, NULL))
	    return chrec_dont_know;

	default:
	  {
	    int size = 0;
	    if ((tree_contains_chrecs (op0, &size)
		 || tree_contains_chrecs (op1, &size))
		&& size < PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
	      return build2 (code, type, op0, op1);
	    else if (size < PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
	      {
		if (code == POINTER_PLUS_EXPR)
		  return fold_build_pointer_plus (fold_convert (type, op0),
						  op1);
		else
		  return fold_build2 (code, type,
				      fold_convert (type, op0),
				      fold_convert (type, op1));
	      }
	    else
	      return chrec_dont_know;
	  }
	}
    }
}
예제 #10
0
static inline tree 
chrec_fold_plus_poly_poly (enum tree_code code, 
			   tree type, 
			   tree poly0, 
			   tree poly1)
{
  tree left, right;

  gcc_assert (poly0);
  gcc_assert (poly1);
  gcc_assert (TREE_CODE (poly0) == POLYNOMIAL_CHREC);
  gcc_assert (TREE_CODE (poly1) == POLYNOMIAL_CHREC);
  gcc_assert (chrec_type (poly0) == chrec_type (poly1));
  gcc_assert (type == chrec_type (poly0));
  
  /*
    {a, +, b}_1 + {c, +, d}_2  ->  {{a, +, b}_1 + c, +, d}_2,
    {a, +, b}_2 + {c, +, d}_1  ->  {{c, +, d}_1 + a, +, b}_2,
    {a, +, b}_x + {c, +, d}_x  ->  {a+c, +, b+d}_x.  */
  if (CHREC_VARIABLE (poly0) < CHREC_VARIABLE (poly1))
    {
      if (code == PLUS_EXPR)
	return build_polynomial_chrec 
	  (CHREC_VARIABLE (poly1), 
	   chrec_fold_plus (type, poly0, CHREC_LEFT (poly1)),
	   CHREC_RIGHT (poly1));
      else
	return build_polynomial_chrec 
	  (CHREC_VARIABLE (poly1), 
	   chrec_fold_minus (type, poly0, CHREC_LEFT (poly1)),
	   chrec_fold_multiply (type, CHREC_RIGHT (poly1), 
				SCALAR_FLOAT_TYPE_P (type)
				? build_real (type, dconstm1)
				: build_int_cst_type (type, -1)));
    }
  
  if (CHREC_VARIABLE (poly0) > CHREC_VARIABLE (poly1))
    {
      if (code == PLUS_EXPR)
	return build_polynomial_chrec 
	  (CHREC_VARIABLE (poly0), 
	   chrec_fold_plus (type, CHREC_LEFT (poly0), poly1),
	   CHREC_RIGHT (poly0));
      else
	return build_polynomial_chrec 
	  (CHREC_VARIABLE (poly0), 
	   chrec_fold_minus (type, CHREC_LEFT (poly0), poly1),
	   CHREC_RIGHT (poly0));
    }
  
  if (code == PLUS_EXPR)
    {
      left = chrec_fold_plus 
	(type, CHREC_LEFT (poly0), CHREC_LEFT (poly1));
      right = chrec_fold_plus 
	(type, CHREC_RIGHT (poly0), CHREC_RIGHT (poly1));
    }
  else
    {
      left = chrec_fold_minus 
	(type, CHREC_LEFT (poly0), CHREC_LEFT (poly1));
      right = chrec_fold_minus 
	(type, CHREC_RIGHT (poly0), CHREC_RIGHT (poly1));
    }

  if (chrec_zerop (right))
    return left;
  else
    return build_polynomial_chrec 
      (CHREC_VARIABLE (poly0), left, right); 
}
예제 #11
0
static tree
chrec_fold_plus_1 (enum tree_code code, 
		   tree type, 
		   tree op0,
		   tree op1)
{
  if (automatically_generated_chrec_p (op0)
      || automatically_generated_chrec_p (op1))
    return chrec_fold_automatically_generated_operands (op0, op1);
  
  switch (TREE_CODE (op0))
    {
    case POLYNOMIAL_CHREC:
      switch (TREE_CODE (op1))
	{
	case POLYNOMIAL_CHREC:
	  return chrec_fold_plus_poly_poly (code, type, op0, op1);

	default:
	  if (code == PLUS_EXPR)
	    return build_polynomial_chrec 
	      (CHREC_VARIABLE (op0), 
	       chrec_fold_plus (type, CHREC_LEFT (op0), op1),
	       CHREC_RIGHT (op0));
	  else
	    return build_polynomial_chrec 
	      (CHREC_VARIABLE (op0), 
	       chrec_fold_minus (type, CHREC_LEFT (op0), op1),
	       CHREC_RIGHT (op0));
	}

    default:
      switch (TREE_CODE (op1))
	{
	case POLYNOMIAL_CHREC:
	  if (code == PLUS_EXPR)
	    return build_polynomial_chrec 
	      (CHREC_VARIABLE (op1), 
	       chrec_fold_plus (type, op0, CHREC_LEFT (op1)),
	       CHREC_RIGHT (op1));
	  else
	    return build_polynomial_chrec 
	      (CHREC_VARIABLE (op1), 
	       chrec_fold_minus (type, op0, CHREC_LEFT (op1)),
	       chrec_fold_multiply (type, CHREC_RIGHT (op1),
				    build_int_cst_type (type, -1)));

	default:
	  {
	    int size = 0;
	    if ((tree_contains_chrecs (op0, &size)
		 || tree_contains_chrecs (op1, &size))
		&& size < PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
	      return build2 (code, type, op0, op1);
	    else if (size < PARAM_VALUE (PARAM_SCEV_MAX_EXPR_SIZE))
	      return fold (build2 (code, type, op0, op1));
	    else
	      return chrec_dont_know;
	  }
	}
    }
}