1  /* Round to integer type.  ldbl-128 version.
       2     Copyright (C) 2016-2023 Free Software Foundation, Inc.
       3     This file is part of the GNU C Library.
       4  
       5     The GNU C Library is free software; you can redistribute it and/or
       6     modify it under the terms of the GNU Lesser General Public
       7     License as published by the Free Software Foundation; either
       8     version 2.1 of the License, or (at your option) any later version.
       9  
      10     The GNU C Library is distributed in the hope that it will be useful,
      11     but WITHOUT ANY WARRANTY; without even the implied warranty of
      12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      13     Lesser General Public License for more details.
      14  
      15     You should have received a copy of the GNU Lesser General Public
      16     License along with the GNU C Library; if not, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <errno.h>
      20  #include <fenv.h>
      21  #include <math.h>
      22  #include <math_private.h>
      23  #include <libm-alias-ldouble.h>
      24  #include <stdbool.h>
      25  #include <stdint.h>
      26  
      27  #define BIAS 0x3fff
      28  #define MANT_DIG 113
      29  
      30  #if UNSIGNED
      31  # define RET_TYPE uintmax_t
      32  #else
      33  # define RET_TYPE intmax_t
      34  #endif
      35  
      36  #include <fromfp.h>
      37  
      38  RET_TYPE
      39  FUNC (_Float128 x, int round, unsigned int width)
      40  {
      41    if (width > INTMAX_WIDTH)
      42      width = INTMAX_WIDTH;
      43    uint64_t hx, lx;
      44    GET_LDOUBLE_WORDS64 (hx, lx, x);
      45    bool negative = (hx & 0x8000000000000000ULL) != 0;
      46    if (width == 0)
      47      return fromfp_domain_error (negative, width);
      48    hx &= 0x7fffffffffffffffULL;
      49    if ((hx | lx) == 0)
      50      return 0;
      51    int exponent = hx >> (MANT_DIG - 1 - 64);
      52    exponent -= BIAS;
      53    int max_exponent = fromfp_max_exponent (negative, width);
      54    if (exponent > max_exponent)
      55      return fromfp_domain_error (negative, width);
      56  
      57    hx &= ((1ULL << (MANT_DIG - 1 - 64)) - 1);
      58    hx |= 1ULL << (MANT_DIG - 1 - 64);
      59    uintmax_t uret;
      60    bool half_bit, more_bits;
      61    /* The exponent is at most 63, so we are shifting right by at least
      62       49 bits.  */
      63    if (exponent >= -1)
      64      {
      65        int shift = MANT_DIG - 1 - exponent;
      66        if (shift <= 64)
      67  	{
      68  	  uint64_t h = 1ULL << (shift - 1);
      69  	  half_bit = (lx & h) != 0;
      70  	  more_bits = (lx & (h - 1)) != 0;
      71  	  uret = hx << (64 - shift);
      72  	  if (shift != 64)
      73  	    uret |= lx >> shift;
      74  	}
      75        else
      76  	{
      77  	  uint64_t h = 1ULL << (shift - 1 - 64);
      78  	  half_bit = (hx & h) != 0;
      79  	  more_bits = ((hx & (h - 1)) | lx) != 0;
      80  	  uret = hx >> (shift - 64);
      81  	}
      82      }
      83    else
      84      {
      85        uret = 0;
      86        half_bit = false;
      87        more_bits = true;
      88      }
      89    return fromfp_round_and_return (negative, uret, half_bit, more_bits, round,
      90  				  exponent, max_exponent, width);
      91  }