1  /* Compute remainder and a congruent to the quotient.
       2     Copyright (C) 1997-2023 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 <math.h>
      20  
      21  #include <math_private.h>
      22  #include <libm-alias-ldouble.h>
      23  
      24  
      25  static const _Float128 zero = 0.0;
      26  
      27  
      28  _Float128
      29  __remquol (_Float128 x, _Float128 y, int *quo)
      30  {
      31    int64_t hx,hy;
      32    uint64_t sx,lx,ly,qs;
      33    int cquo;
      34  
      35    GET_LDOUBLE_WORDS64 (hx, lx, x);
      36    GET_LDOUBLE_WORDS64 (hy, ly, y);
      37    sx = hx & 0x8000000000000000ULL;
      38    qs = sx ^ (hy & 0x8000000000000000ULL);
      39    hy &= 0x7fffffffffffffffLL;
      40    hx &= 0x7fffffffffffffffLL;
      41  
      42    /* Purge off exception values.  */
      43    if ((hy | ly) == 0)
      44      return (x * y) / (x * y); 			/* y = 0 */
      45    if ((hx >= 0x7fff000000000000LL)		/* x not finite */
      46        || ((hy >= 0x7fff000000000000LL)		/* y is NaN */
      47  	  && (((hy - 0x7fff000000000000LL) | ly) != 0)))
      48      return (x * y) / (x * y);
      49  
      50    if (hy <= 0x7ffbffffffffffffLL)
      51      x = __ieee754_fmodl (x, 8 * y);              /* now x < 8y */
      52  
      53    if (((hx - hy) | (lx - ly)) == 0)
      54      {
      55        *quo = qs ? -1 : 1;
      56        return zero * x;
      57      }
      58  
      59    x  = fabsl (x);
      60    y  = fabsl (y);
      61    cquo = 0;
      62  
      63    if (hy <= 0x7ffcffffffffffffLL && x >= 4 * y)
      64      {
      65        x -= 4 * y;
      66        cquo += 4;
      67      }
      68    if (hy <= 0x7ffdffffffffffffLL && x >= 2 * y)
      69      {
      70        x -= 2 * y;
      71        cquo += 2;
      72      }
      73  
      74    if (hy < 0x0002000000000000LL)
      75      {
      76        if (x + x > y)
      77  	{
      78  	  x -= y;
      79  	  ++cquo;
      80  	  if (x + x >= y)
      81  	    {
      82  	      x -= y;
      83  	      ++cquo;
      84  	    }
      85  	}
      86      }
      87    else
      88      {
      89        _Float128 y_half = L(0.5) * y;
      90        if (x > y_half)
      91  	{
      92  	  x -= y;
      93  	  ++cquo;
      94  	  if (x >= y_half)
      95  	    {
      96  	      x -= y;
      97  	      ++cquo;
      98  	    }
      99  	}
     100      }
     101  
     102    *quo = qs ? -cquo : cquo;
     103  
     104    /* Ensure correct sign of zero result in round-downward mode.  */
     105    if (x == 0)
     106      x = 0;
     107    if (sx)
     108      x = -x;
     109    return x;
     110  }
     111  libm_alias_ldouble (__remquo, remquo)