sysdeps/ieee754/ldbl-128/s_nexttoward.c

   1 /* s_nexttoward.c
   2  * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
   3  * drepper@cygnus.com and Jakub Jelinek, jj@ultra.linux.cz.
   4  */
   5
   6 /*
   7  * ====================================================
   8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   9  *
  10  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11  * Permission to use, copy, modify, and distribute this
  12  * software is freely granted, provided that this notice
  13  * is preserved.
  14  * ====================================================
  15  */
  16
  17 #if defined(LIBM_SCCS) && !defined(lint)
  18 static char rcsid[] = "$NetBSD: $";
  19 #endif
  20
  21 /* IEEE functions
  22  *      nexttoward(x,y)
  23  *      return the next machine floating-point number of x in the
  24  *      direction toward y.
  25  *   Special cases:
  26  */
  27
  28 #include "math.h"
  29 #include <math_private.h>
  30 #include <float.h>
  31
  32 #ifdef __STDC__
  33         double __nexttoward(double x, long double y)
  34 #else
  35         double __nexttoward(x,y)
  36         double x;
  37         long double y;
  38 #endif
  39 {
  40         int32_t hx,ix;
  41         int64_t hy,iy;
  42         u_int32_t lx;
  43         u_int64_t ly;
  44
  45         EXTRACT_WORDS(hx,lx,x);
  46         GET_LDOUBLE_WORDS64(hy,ly,y);
  47         ix = hx&0x7fffffff;             /* |x| */
  48         iy = hy&0x7fffffffffffffffLL;   /* |y| */
  49
  50         if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
  51            ((iy>=0x7fff000000000000LL)&&((iy-0x7fff000000000000LL)|ly)!=0))
  52                                                             /* y is nan */
  53            return x+y;
  54         if((long double) x==y) return y;        /* x=y, return y */
  55         if((ix|lx)==0) {                        /* x == 0 */
  56             double u;
  57             INSERT_WORDS(x,(u_int32_t)((hy>>32)&0x80000000),1);/* return +-minsub */
  58             u = math_opt_barrier (x);
  59             u = u * u;
  60             math_force_eval (u);                /* raise underflow flag */
  61             return x;
  62         }
  63         if(hx>=0) {                             /* x > 0 */
  64             if (hy<0||(ix>>20)>(iy>>48)-0x3c00
  65                 || ((ix>>20)==(iy>>48)-0x3c00
  66                     && (((((int64_t)hx)<<28)|(lx>>4))>(hy&0x0000ffffffffffffLL)
  67                         || (((((int64_t)hx)<<28)|(lx>>4))==(hy&0x0000ffffffffffffLL)
  68                             && (lx&0xf)>(ly>>60))))) {  /* x > y, x -= ulp */
  69                 if(lx==0) hx -= 1;
  70                 lx -= 1;
  71             } else {                            /* x < y, x += ulp */
  72                 lx += 1;
  73                 if(lx==0) hx += 1;
  74             }
  75         } else {                                /* x < 0 */
  76             if (hy>=0||(ix>>20)>(iy>>48)-0x3c00
  77                 || ((ix>>20)==(iy>>48)-0x3c00
  78                     && (((((int64_t)hx)<<28)|(lx>>4))>(hy&0x0000ffffffffffffLL)
  79                         || (((((int64_t)hx)<<28)|(lx>>4))==(hy&0x0000ffffffffffffLL)
  80                             && (lx&0xf)>(ly>>60))))) {  /* x < y, x -= ulp */
  81                 if(lx==0) hx -= 1;
  82                 lx -= 1;
  83             } else {                            /* x > y, x += ulp */
  84                 lx += 1;
  85                 if(lx==0) hx += 1;
  86             }
  87         }
  88         hy = hx&0x7ff00000;
  89         if(hy>=0x7ff00000) {
  90           x = x+x;      /* overflow  */
  91           if (FLT_EVAL_METHOD != 0 && FLT_EVAL_METHOD != 1)
  92             /* Force conversion to double.  */
  93             asm ("" : "+m"(x));
  94           return x;
  95         }
  96         if(hy<0x00100000) {
  97             double u = x*x;                     /* underflow */
  98             math_force_eval (u);                /* raise underflow flag */
  99         }
 100         INSERT_WORDS(x,hx,lx);
 101         return x;
 102 }
 103 weak_alias (__nexttoward, nexttoward)