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 long double zero = 0.0;
      26  
      27  
      28  long double
      29  __remquol (long double x, long double p, int *quo)
      30  {
      31    int32_t ex,ep,hx,hp;
      32    uint32_t sx,lx,lp;
      33    int cquo,qs;
      34  
      35    GET_LDOUBLE_WORDS (ex, hx, lx, x);
      36    GET_LDOUBLE_WORDS (ep, hp, lp, p);
      37    sx = ex & 0x8000;
      38    qs = (sx ^ (ep & 0x8000)) >> 15;
      39    ep &= 0x7fff;
      40    ex &= 0x7fff;
      41  
      42    /* Purge off exception values.  */
      43    if ((ep | hp | lp) == 0)
      44      return (x * p) / (x * p); 			/* p = 0 */
      45    if ((ex == 0x7fff)				/* x not finite */
      46        || ((ep == 0x7fff)			/* p is NaN */
      47  	  && (((hp & 0x7fffffff) | lp) != 0)))
      48      return (x * p) / (x * p);
      49  
      50    if (ep <= 0x7ffb)
      51      x = __ieee754_fmodl (x, 8 * p);		/* now x < 8p */
      52  
      53    if (((ex - ep) | (hx - hp) | (lx - lp)) == 0)
      54      {
      55        *quo = qs ? -1 : 1;
      56        return zero * x;
      57      }
      58  
      59    x  = fabsl (x);
      60    p  = fabsl (p);
      61    cquo = 0;
      62  
      63    if (ep <= 0x7ffc && x >= 4 * p)
      64      {
      65        x -= 4 * p;
      66        cquo += 4;
      67      }
      68    if (ep <= 0x7ffd && x >= 2 * p)
      69      {
      70        x -= 2 * p;
      71        cquo += 2;
      72      }
      73  
      74    if (ep < 0x0002)
      75      {
      76        if (x + x > p)
      77  	{
      78  	  x -= p;
      79  	  ++cquo;
      80  	  if (x + x >= p)
      81  	    {
      82  	      x -= p;
      83  	      ++cquo;
      84  	    }
      85  	}
      86      }
      87    else
      88      {
      89        long double p_half = 0.5 * p;
      90        if (x > p_half)
      91  	{
      92  	  x -= p;
      93  	  ++cquo;
      94  	  if (x >= p_half)
      95  	    {
      96  	      x -= p;
      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 == 0.0L)
     106      x = 0.0L;
     107    if (sx)
     108      x = -x;
     109    return x;
     110  }
     111  libm_alias_ldouble (__remquo, remquo)