sysdeps/ieee754/ldbl-96/s_nexttoward.c

   1 /* s_nexttoward.c
   2  * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
   3  * drepper@cygnus.com.
   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,iy;
  41         u_int32_t lx,hy,ly,esy;
  42
  43         EXTRACT_WORDS(hx,lx,x);
  44         GET_LDOUBLE_WORDS(esy,hy,ly,y);
  45         ix = hx&0x7fffffff;             /* |x| */
  46         iy = esy&0x7fff;                /* |y| */
  47
  48         if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
  49            ((iy>=0x7fff)&&(hy|ly)!=0))        /* y is nan */
  50            return x+y;
  51         if((long double) x==y) return y;        /* x=y, return y */
  52         if((ix|lx)==0) {                        /* x == 0 */
  53             double u;
  54             INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
  55             u = math_opt_barrier (x);
  56             u = u * u;
  57             math_force_eval (u);                /* raise underflow flag */
  58             return x;
  59         }
  60         if(hx>=0) {                             /* x > 0 */
  61             if (esy>=0x8000||((ix>>20)&0x7ff)>iy-0x3c00
  62                 || (((ix>>20)&0x7ff)==iy-0x3c00
  63                     && (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
  64                         || (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
  65                             && (lx<<11)>ly)))) {        /* x > y, x -= ulp */
  66                 if(lx==0) hx -= 1;
  67                 lx -= 1;
  68             } else {                            /* x < y, x += ulp */
  69                 lx += 1;
  70                 if(lx==0) hx += 1;
  71             }
  72         } else {                                /* x < 0 */
  73             if (esy<0x8000||((ix>>20)&0x7ff)>iy-0x3c00
  74                 || (((ix>>20)&0x7ff)==iy-0x3c00
  75                     && (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
  76                         || (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
  77                             && (lx<<11)>ly))))  {/* x < y, x -= ulp */
  78                 if(lx==0) hx -= 1;
  79                 lx -= 1;
  80             } else {                            /* x > y, x += ulp */
  81                 lx += 1;
  82                 if(lx==0) hx += 1;
  83             }
  84         }
  85         hy = hx&0x7ff00000;
  86         if(hy>=0x7ff00000) {
  87           x = x+x;      /* overflow  */
  88           if (FLT_EVAL_METHOD != 0 && FLT_EVAL_METHOD != 1)
  89             /* Force conversion to double.  */
  90             asm ("" : "+m"(x));
  91           return x;
  92         }
  93         if(hy<0x00100000) {
  94             double u = x*x;                     /* underflow */
  95             math_force_eval (u);                /* raise underflow flag */
  96         }
  97         INSERT_WORDS(x,hx,lx);
  98         return x;
  99 }
 100 weak_alias (__nexttoward, nexttoward)