lib/libm/src/s_nextafterl.c

   1 /*      $NetBSD: s_nextafterl.c,v 1.5 2014/01/31 19:38:47 matt Exp $    */
   2
   3 /* @(#)s_nextafter.c 5.1 93/09/24 */
   4 /*
   5  * ====================================================
   6  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   7  *
   8  * Developed at SunPro, a Sun Microsystems, Inc. business.
   9  * Permission to use, copy, modify, and distribute this
  10  * software is freely granted, provided that this notice
  11  * is preserved.
  12  * ====================================================
  13  */
  14
  15 #include <sys/cdefs.h>
  16 __RCSID("$NetBSD: s_nextafterl.c,v 1.5 2014/01/31 19:38:47 matt Exp $");
  17
  18 #include <float.h>
  19 #include <math.h>
  20 #include <machine/ieee.h>
  21
  22 #ifdef __HAVE_LONG_DOUBLE
  23
  24 #ifdef EXT_EXP_INFNAN
  25 #if LDBL_MAX_EXP != 0x4000
  26 #error "Unsupported long double format"
  27 #endif
  28
  29 #ifdef LDBL_IMPLICIT_NBIT
  30 #define LDBL_NBIT       0
  31 #endif
  32
  33 /*
  34  * IEEE functions
  35  *      nextafterl(x,y)
  36  *      return the next machine floating-point number of x in the
  37  *      direction toward y.
  38  *   Special cases:
  39  *      If x == y, y shall be returned
  40  *      If x or y is NaN, a NaN shall be returned
  41  */
  42 long double
  43 nextafterl(long double x, long double y)
  44 {
  45         volatile long double t;
  46         union ieee_ext_u ux, uy;
  47
  48         ux.extu_ld = x;
  49         uy.extu_ld = y;
  50
  51         if ((ux.extu_exp == EXT_EXP_INFNAN &&
  52                 ((ux.extu_frach &~ LDBL_NBIT)|ux.extu_fracl) != 0) ||
  53             (uy.extu_exp == EXT_EXP_INFNAN &&
  54                 ((uy.extu_frach &~ LDBL_NBIT)|uy.extu_fracl) != 0))
  55                 return x+y;                     /* x or y is nan */
  56
  57         if (x == y) return y;                   /* x=y, return y */
  58
  59         if (x == 0.0) {
  60                 ux.extu_frach = 0;              /* return +-minsubnormal */
  61                 ux.extu_fracl = 1;
  62                 ux.extu_sign = uy.extu_sign;
  63                 t = ux.extu_ld * ux.extu_ld;
  64                 if (t == ux.extu_ld)
  65                         return t;
  66                 else
  67                         return ux.extu_ld;      /* raise underflow flag */
  68         }
  69
  70         if ((x>0.0) ^ (x<y)) {                  /* x -= ulp */
  71                 if (ux.extu_fracl == 0) {
  72                         if ((ux.extu_frach & ~LDBL_NBIT) == 0)
  73                                 ux.extu_exp -= 1;
  74                         ux.extu_frach = (ux.extu_frach - 1) |
  75                                         (ux.extu_frach & LDBL_NBIT);
  76                 }
  77                 ux.extu_fracl -= 1;
  78         } else {                                /* x += ulp */
  79                 ux.extu_fracl += 1;
  80                 if (ux.extu_fracl == 0) {
  81                         ux.extu_frach = (ux.extu_frach + 1) |
  82                                         (ux.extu_frach & LDBL_NBIT);
  83                         if ((ux.extu_frach & ~LDBL_NBIT) == 0)
  84                                 ux.extu_exp += 1;
  85                 }
  86         }
  87
  88         if (ux.extu_exp == EXT_EXP_INFNAN)
  89                 return x+x;                     /* overflow  */
  90
  91         if (ux.extu_exp == 0) {                 /* underflow */
  92 #ifndef LDBL_IMPLICIT_NBIT
  93                 mask_nbit_l(ux);
  94 #endif
  95                 t = ux.extu_ld * ux.extu_ld;
  96                 if (t != ux.extu_ld)            /* raise underflow flag */
  97                         return ux.extu_ld;
  98         }
  99
 100         return ux.extu_ld;
 101 }
 102 #endif
 103
 104 #endif /* __HAVE_LONG_DOUBLE */