fold-const.c

早期freebsd实现

     tree in;
     enum tree_code code;
     tree *varp, *conp;
     int *varsignp;
{
  register tree outtype = TREE_TYPE (in);
  *varp = 0;
  *conp = 0;

  /* Strip any conversions that don't change the machine mode.  */
  while ((TREE_CODE (in) == NOP_EXPR
	  || TREE_CODE (in) == CONVERT_EXPR)
	 && (TYPE_MODE (TREE_TYPE (in))
	     == TYPE_MODE (TREE_TYPE (TREE_OPERAND (in, 0)))))
    in = TREE_OPERAND (in, 0);

  if (TREE_CODE (in) == code
      || (TREE_CODE (TREE_TYPE (in)) != REAL_TYPE
	  /* We can associate addition and subtraction together
	     (even though the C standard doesn't say so)
	     for integers because the value is not affected.
	     For reals, the value might be affected, so we can't.  */
	  &&
	  ((code == PLUS_EXPR && TREE_CODE (in) == MINUS_EXPR)
	   || (code == MINUS_EXPR && TREE_CODE (in) == PLUS_EXPR))))
    {
      enum tree_code code = TREE_CODE (TREE_OPERAND (in, 0));
      if (code == INTEGER_CST)
	{
	  *conp = TREE_OPERAND (in, 0);
	  *varp = TREE_OPERAND (in, 1);
	  if (TYPE_MODE (TREE_TYPE (*varp)) != TYPE_MODE (outtype)
	      && TREE_TYPE (*varp) != outtype)
	    *varp = convert (outtype, *varp);
	  *varsignp = (TREE_CODE (in) == MINUS_EXPR) ? -1 : 1;
	  return 1;
	}
      if (TREE_CONSTANT (TREE_OPERAND (in, 1)))
	{
	  *conp = TREE_OPERAND (in, 1);
	  *varp = TREE_OPERAND (in, 0);
	  *varsignp = 1;
	  if (TYPE_MODE (TREE_TYPE (*varp)) != TYPE_MODE (outtype)
	      && TREE_TYPE (*varp) != outtype)
	    *varp = convert (outtype, *varp);
	  if (TREE_CODE (in) == MINUS_EXPR)
	    {
	      /* If operation is subtraction and constant is second,
		 must negate it to get an additive constant.
		 And this cannot be done unless it is a manifest constant.
		 It could also be the address of a static variable.
		 We cannot negate that, so give up.  */
	      if (TREE_CODE (*conp) == INTEGER_CST)
		/* Subtracting from integer_zero_node loses for long long.  */
		*conp = fold (build1 (NEGATE_EXPR, TREE_TYPE (*conp), *conp));
	      else
		return 0;
	    }
	  return 1;
	}
      if (TREE_CONSTANT (TREE_OPERAND (in, 0)))
	{
	  *conp = TREE_OPERAND (in, 0);
	  *varp = TREE_OPERAND (in, 1);
	  if (TYPE_MODE (TREE_TYPE (*varp)) != TYPE_MODE (outtype)
	      && TREE_TYPE (*varp) != outtype)
	    *varp = convert (outtype, *varp);
	  *varsignp = (TREE_CODE (in) == MINUS_EXPR) ? -1 : 1;
	  return 1;
	}
    }
  return 0;
}

/* Combine two constants NUM and ARG2 under operation CODE
   to produce a new constant.
   We assume ARG1 and ARG2 have the same data type,
   or at least are the same kind of constant and the same machine mode.  */

static tree
const_binop (code, arg1, arg2)
     enum tree_code code;
     register tree arg1, arg2;
{
  if (TREE_CODE (arg1) == INTEGER_CST)
    {
      register HOST_WIDE_INT int1l = TREE_INT_CST_LOW (arg1);
      register HOST_WIDE_INT int1h = TREE_INT_CST_HIGH (arg1);
      HOST_WIDE_INT int2l = TREE_INT_CST_LOW (arg2);
      HOST_WIDE_INT int2h = TREE_INT_CST_HIGH (arg2);
      HOST_WIDE_INT low, hi;
      HOST_WIDE_INT garbagel, garbageh;
      register tree t;
      int uns = TREE_UNSIGNED (TREE_TYPE (arg1));
      /* Propagate overflow flags from operands; also record new overflow.  */
      int overflow
	= TREE_CONSTANT_OVERFLOW (arg1) | TREE_CONSTANT_OVERFLOW (arg2);

      switch (code)
	{
	case BIT_IOR_EXPR:
	  t = build_int_2 (int1l | int2l, int1h | int2h);
	  break;

	case BIT_XOR_EXPR:
	  t = build_int_2 (int1l ^ int2l, int1h ^ int2h);
	  break;

	case BIT_AND_EXPR:
	  t = build_int_2 (int1l & int2l, int1h & int2h);
	  break;

	case BIT_ANDTC_EXPR:
	  t = build_int_2 (int1l & ~int2l, int1h & ~int2h);
	  break;

	case RSHIFT_EXPR:
	  int2l = - int2l;
	case LSHIFT_EXPR:
	  overflow = lshift_double (int1l, int1h, int2l,
				    TYPE_PRECISION (TREE_TYPE (arg1)),
				    &low, &hi,
				    !uns);
	  t = build_int_2 (low, hi);
	  break;

	case RROTATE_EXPR:
	  int2l = - int2l;
	case LROTATE_EXPR:
	  lrotate_double (int1l, int1h, int2l,
			  TYPE_PRECISION (TREE_TYPE (arg1)),
			  &low, &hi);
	  t = build_int_2 (low, hi);
	  break;

	case PLUS_EXPR:
	  if (int1h == 0)
	    {
	      int2l += int1l;
	      if ((unsigned HOST_WIDE_INT) int2l < int1l)
		{
		  hi = int2h++;
		  overflow = ! same_sign (hi, int2h);
		}
	      t = build_int_2 (int2l, int2h);
	      break;
	    }
	  if (int2h == 0)
	    {
	      int1l += int2l;
	      if ((unsigned HOST_WIDE_INT) int1l < int2l)
		{
		  hi = int1h++;
		  overflow = ! same_sign (hi, int1h);
		}
	      t = build_int_2 (int1l, int1h);
	      break;
	    }
	  overflow = add_double (int1l, int1h, int2l, int2h, &low, &hi);
	  t = build_int_2 (low, hi);
	  break;

	case MINUS_EXPR:
	  if (int2h == 0 && int2l == 0)
	    {
	      t = build_int_2 (int1l, int1h);
	      break;
	    }
	  neg_double (int2l, int2h, &low, &hi);
	  add_double (int1l, int1h, low, hi, &low, &hi);
	  overflow = overflow_sum_sign (hi, int2h, int1h);
	  t = build_int_2 (low, hi);
	  break;

	case MULT_EXPR:
	  /* Optimize simple cases.  */
	  if (int1h == 0)
	    {
	      unsigned HOST_WIDE_INT temp;

	      switch (int1l)
		{
		case 0:
		  t = build_int_2 (0, 0);
		  goto got_it;
		case 1:
		  t = build_int_2 (int2l, int2h);
		  goto got_it;
		case 2:
		  overflow = left_shift_overflows (int2h, 1);
		  temp = int2l + int2l;
		  int2h = (int2h << 1) + (temp < int2l);
		  t = build_int_2 (temp, int2h);
		  goto got_it;
#if 0 /* This code can lose carries.  */
		case 3:
		  temp = int2l + int2l + int2l;
		  int2h = int2h * 3 + (temp < int2l);
		  t = build_int_2 (temp, int2h);
		  goto got_it;
#endif
		case 4:
		  overflow = left_shift_overflows (int2h, 2);
		  temp = int2l + int2l;
		  int2h = (int2h << 2) + ((temp < int2l) << 1);
		  int2l = temp;
		  temp += temp;
		  int2h += (temp < int2l);
		  t = build_int_2 (temp, int2h);
		  goto got_it;
		case 8:
		  overflow = left_shift_overflows (int2h, 3);
		  temp = int2l + int2l;
		  int2h = (int2h << 3) + ((temp < int2l) << 2);
		  int2l = temp;
		  temp += temp;
		  int2h += (temp < int2l) << 1;
		  int2l = temp;
		  temp += temp;
		  int2h += (temp < int2l);
		  t = build_int_2 (temp, int2h);
		  goto got_it;
		default:
		  break;
		}
	    }

	  if (int2h == 0)
	    {
	      if (int2l == 0)
		{
		  t = build_int_2 (0, 0);
		  break;
		}
	      if (int2l == 1)
		{
		  t = build_int_2 (int1l, int1h);
		  break;
		}
	    }

	  overflow = mul_double (int1l, int1h, int2l, int2h, &low, &hi);
	  t = build_int_2 (low, hi);
	  break;

	case TRUNC_DIV_EXPR:
	case FLOOR_DIV_EXPR: case CEIL_DIV_EXPR:
	case EXACT_DIV_EXPR:
	  /* This is a shortcut for a common special case.
	     It reduces the number of tree nodes generated
	     and saves time.  */
	  if (int2h == 0 && int2l > 0
	      && TREE_TYPE (arg1) == sizetype
	      && int1h == 0 && int1l >= 0)
	    {
	      if (code == CEIL_DIV_EXPR)
		int1l += int2l-1;
	      return size_int (int1l / int2l);
	    }
	case ROUND_DIV_EXPR: 
	  if (int2h == 0 && int2l == 1)
	    {
	      t = build_int_2 (int1l, int1h);
	      break;
	    }
	  if (int1l == int2l && int1h == int2h)
	    {
	      if ((int1l | int1h) == 0)
		abort ();
	      t = build_int_2 (1, 0);
	      break;
	    }
	  overflow = div_and_round_double (code, uns,
					   int1l, int1h, int2l, int2h,
					   &low, &hi, &garbagel, &garbageh);
	  t = build_int_2 (low, hi);
	  break;

	case TRUNC_MOD_EXPR: case ROUND_MOD_EXPR: 
	case FLOOR_MOD_EXPR: case CEIL_MOD_EXPR:
	  overflow = div_and_round_double (code, uns,
					   int1l, int1h, int2l, int2h,
					   &garbagel, &garbageh, &low, &hi);
	  t = build_int_2 (low, hi);
	  break;

	case MIN_EXPR:
	case MAX_EXPR:
	  if (uns)
	    {
	      low = (((unsigned HOST_WIDE_INT) int1h
		      < (unsigned HOST_WIDE_INT) int2h)
		     || (((unsigned HOST_WIDE_INT) int1h
			  == (unsigned HOST_WIDE_INT) int2h)
			 && ((unsigned HOST_WIDE_INT) int1l
			     < (unsigned HOST_WIDE_INT) int2l)));
	    }
	  else
	    {
	      low = ((int1h < int2h)
		     || ((int1h == int2h)
			 && ((unsigned HOST_WIDE_INT) int1l
			     < (unsigned HOST_WIDE_INT) int2l)));
	    }
	  if (low == (code == MIN_EXPR))
	    t = build_int_2 (int1l, int1h);
	  else
	    t = build_int_2 (int2l, int2h);
	  break;

	default:
	  abort ();
	}
    got_it:
      TREE_TYPE (t) = TREE_TYPE (arg1);
      force_fit_type (t);
      TREE_CONSTANT_OVERFLOW (t) = overflow;
      return t;
    }
#if ! defined (REAL_IS_NOT_DOUBLE) || defined (REAL_ARITHMETIC)
  if (TREE_CODE (arg1) == REAL_CST)
    {
      register REAL_VALUE_TYPE d1;
      register REAL_VALUE_TYPE d2;
      register REAL_VALUE_TYPE value;
      tree t;

      d1 = TREE_REAL_CST (arg1);
      d2 = TREE_REAL_CST (arg2);
      if (setjmp (float_error))
	{
	  pedwarn ("floating overflow in constant expression");
	  return build (code, TREE_TYPE (arg1), arg1, arg2);
	}
      set_float_handler (float_error);

#ifdef REAL_ARITHMETIC
      REAL_ARITHMETIC (value, code, d1, d2);
#else
      switch (code)
	{
	case PLUS_EXPR:
	  value = d1 + d2;
	  break;

	case MINUS_EXPR:
	  value = d1 - d2;
	  break;

	case MULT_EXPR:
	  value = d1 * d2;
	  break;

	case RDIV_EXPR:
#ifndef REAL_INFINITY
	  if (d2 == 0)
	    abort ();
#endif

	  value = d1 / d2;
	  break;

	case MIN_EXPR:
	  value = MIN (d1, d2);
	  break;

	case MAX_EXPR:
	  value = MAX (d1, d2);
	  break;

	default:
	  abort ();
	}
#endif /* no REAL_ARITHMETIC */
      t = build_real (TREE_TYPE (arg1),
		      real_value_truncate (TYPE_MODE (TREE_TYPE (arg1)), value));
      set_float_handler (NULL_PTR);
      return t;
    }
#endif /* not REAL_IS_NOT_DOUBLE, or REAL_ARITHMETIC */
  if (TREE_CODE (arg1) == COMPLEX_CST)
    {
      register tree r1 = TREE_REALPART (arg1);
      register tree i1 = TREE_IMAGPART (arg1);
      register tree r2 = TREE_REALPART (arg2);
      register tree i2 = TREE_IMAGPART (arg2);
      register tree t;

      switch (code)
	{
	case PLUS_EXPR:
	  t = build_complex (const_binop (PLUS_EXPR, r1, r2),
			     const_binop (PLUS_EXPR, i1, i2));
	  break;

	case MINUS_EXPR:
	  t = build_complex (const_binop (MINUS_EXPR, r1, r2),
			     const_binop (MINUS_EXPR, i1, i2));
	  break;

	case MULT_EXPR:
	  t = build_complex (const_binop (MINUS_EXPR,
					  const_binop (MULT_EXPR, r1, r2),
					  const_binop (MULT_EXPR, i1, i2)),
			     const_binop (PLUS_EXPR,
					  const_binop (MULT_EXPR, r1, i2),
					  const_binop (MULT_EXPR, i1, r2)));
	  break;

	case RDIV_EXPR:
	  {
	    register tree magsquared
	      = const_binop (PLUS_EXPR,
			     const_binop (MULT_EXPR, r2, r2),
			     const_binop (MULT_EXPR, i2, i2));
	    t = build_complex (const_binop (RDIV_EXPR,
					    const_binop (PLUS_EXPR,
							 const_binop (MULT_EXPR, r1, r2),
							 const_binop (MULT_EXPR, i1, i2)),
					    magsquared),
			       const_binop (RDIV_EXPR,
					    const_binop (MINUS_EXPR,
							 const_binop (MULT_EXPR, i1, r2),
							 const_binop (MULT_EXPR, r1, i2)),
					    magsquared));
	  }
	  break;

	default:
	  abort ();
	}
      TREE_TYPE (t) = TREE_TYPE (arg1);
      return t;
    }
  return 0;
}

/* Return an INTEGER_CST with value V and type from `sizetype'.  */

tree
size_int (number)
     unsigned int number;
{
  register tree t;
  /* Type-size nodes already made for small sizes.  */
  static tree size_table[2*HOST_BITS_PER_WIDE_INT + 1];

  if (number >= 0 && number < 2*HOST_BITS_PER_WIDE_INT + 1
      && size_table[number] != 0)
    return size_table[number];
  if (number >= 0 && number < 2*HOST_BITS_PER_WIDE_INT + 1)
    {
      push_obstacks_nochange ();
      /* Make this a permanent node.  */
      end_temporary_allocation ();
      t = build_int_2 (number, 0);
      TREE_TYPE (t) = sizetype;
      size_table[number] = t;
      pop_obstacks ();
    }
  else
    {
      t = build_int_2 (number, 0);
      TREE_TYPE (t) = sizetype;
    }
  return t;
}

/* Combine operands OP1 and OP2 with arithmetic operation CODE.
   CODE is a tree code.  Data type is taken from `sizetype',
   If the operands are constant, so is the result.  */

tree
size_binop (code, arg0, arg1)
     enum tree_code code;
     tree arg0, arg1;
{
  /* Handle the special case of two integer constants faster.  */