compiler/mlib/s_nextafterl.c

   1 /* @(#)s_nextafter.c 5.1 93/09/24 */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 #ifndef lint
  14 static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_nextafterl.c,v 1.1 2005/03/07 04:56:46 das Exp $";
  15 #endif
  16
  17 /* IEEE functions
  18  *      nextafter(x,y)
  19  *      return the next machine floating-point number of x in the
  20  *      direction toward y.
  21  *   Special cases:
  22  */
  23
  24 #include <sys/cdefs.h>
  25 #include <float.h>
  26
  27 #include "fpmath.h"
  28 #include "math.h"
  29 #include "math_private.h"
  30
  31 #if LDBL_MAX_EXP != 0x4000
  32 #error "Unsupported long double format"
  33 #endif
  34
  35 long double
  36 nextafterl(long double x, long double y)
  37 {
  38         volatile long double t;
  39         union IEEEl2bits ux, uy;
  40
  41         ux.e = x;
  42         uy.e = y;
  43
  44         if ((ux.bits.exp == 0x7fff &&
  45              ((ux.bits.manh&~LDBL_NBIT)|ux.bits.manl) != 0) ||
  46             (uy.bits.exp == 0x7fff &&
  47              ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
  48            return x+y;  /* x or y is nan */
  49         if(x==y) return y;              /* x=y, return y */
  50         if(x==0.0) {
  51             ux.bits.manh = 0;                   /* return +-minsubnormal */
  52             ux.bits.manl = 1;
  53             ux.bits.sign = uy.bits.sign;
  54             t = ux.e*ux.e;
  55             if(t==ux.e) return t; else return ux.e; /* raise underflow flag */
  56         }
  57         if(x>0.0 ^ x<y) {                       /* x -= ulp */
  58             if(ux.bits.manl==0) {
  59                 if ((ux.bits.manh&~LDBL_NBIT)==0)
  60                     ux.bits.exp -= 1;
  61                 ux.bits.manh = (ux.bits.manh - 1) | (ux.bits.manh & LDBL_NBIT);
  62             }
  63             ux.bits.manl -= 1;
  64         } else {                                /* x += ulp */
  65             ux.bits.manl += 1;
  66             if(ux.bits.manl==0) {
  67                 ux.bits.manh = (ux.bits.manh + 1) | (ux.bits.manh & LDBL_NBIT);
  68                 if ((ux.bits.manh&~LDBL_NBIT)==0)
  69                     ux.bits.exp += 1;
  70             }
  71         }
  72         if(ux.bits.exp==0x7fff) return x+x;     /* overflow  */
  73         if(ux.bits.exp==0) {                    /* underflow */
  74             mask_nbit_l(ux);
  75             t = ux.e * ux.e;
  76             if(t!=ux.e)                 /* raise underflow flag */
  77                 return ux.e;
  78         }
  79         return ux.e;
  80 }
  81
  82 __strong_reference(nextafterl, nexttowardl);