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 x2;
  57             INSERT_WORDS(x,(u_int32_t)((hy>>32)&0x80000000),1);/* return +-minsub */
  58             x2 = x*x;
  59             if(x2==x) return x2; else return x; /* raise underflow flag */
  60         }
  61         if(hx>=0) {                             /* x > 0 */
  62             if (hy<0||(ix>>20)>(iy>>48)-0x3c00
  63                 || ((ix>>20)==(iy>>48)-0x3c00
  64                     && (((((int64_t)hx)<<28)|(lx>>4))>(hy&0x0000ffffffffffffLL)
  65                         || (((((int64_t)hx)<<28)|(lx>>4))==(hy&0x0000ffffffffffffLL)
  66                             && (lx&0xf)>(ly>>60))))) {  /* x > y, x -= ulp */
  67                 if(lx==0) hx -= 1;
  68                 lx -= 1;
  69             } else {                            /* x < y, x += ulp */
  70                 lx += 1;
  71                 if(lx==0) hx += 1;
  72             }
  73         } else {                                /* x < 0 */
  74             if (hy>=0||(ix>>20)>(iy>>48)-0x3c00
  75                 || ((ix>>20)==(iy>>48)-0x3c00
  76                     && (((((int64_t)hx)<<28)|(lx>>4))>(hy&0x0000ffffffffffffLL)
  77                         || (((((int64_t)hx)<<28)|(lx>>4))==(hy&0x0000ffffffffffffLL)
  78                             && (lx&0xf)>(ly>>60))))) {  /* x < y, x -= ulp */
  79                 if(lx==0) hx -= 1;
  80                 lx -= 1;
  81             } else {                            /* x > y, x += ulp */
  82                 lx += 1;
  83                 if(lx==0) hx += 1;
  84             }
  85         }
  86         hy = hx&0x7ff00000;
  87         if(hy>=0x7ff00000) {
  88           x = x+x;      /* overflow  */
  89           if (FLT_EVAL_METHOD != 0 && FLT_EVAL_METHOD != 1)
  90             /* Force conversion to float.  */
  91             asm ("" : "=m"(x) : "m"(x));
  92           return x;
  93         }
  94         if(hy<0x00100000) {             /* underflow */
  95             double x2 = x*x;
  96             if(x2!=x) {         /* raise underflow flag */
  97                 INSERT_WORDS(x2,hx,lx);
  98                 return x2;
  99             }
 100         }
 101         INSERT_WORDS(x,hx,lx);
 102         return x;
 103 }
 104 weak_alias (__nexttoward, nexttoward)