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 x2;
  54             INSERT_WORDS(x,(esy&0x8000)<<16,1); /* return +-minsub */
  55             x2 = x*x;
  56             if(x2==x) return x2; else return x; /* raise underflow flag */
  57         }
  58         if(hx>=0) {                             /* x > 0 */
  59             if (esy>=0x8000||((ix>>20)&0x7ff)>iy-0x3c00
  60                 || (((ix>>20)&0x7ff)==iy-0x3c00
  61                     && (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
  62                         || (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
  63                             && (lx<<11)>ly)))) {        /* x > y, x -= ulp */
  64                 if(lx==0) hx -= 1;
  65                 lx -= 1;
  66             } else {                            /* x < y, x += ulp */
  67                 lx += 1;
  68                 if(lx==0) hx += 1;
  69             }
  70         } else {                                /* x < 0 */
  71             if (esy<0x8000||((ix>>20)&0x7ff)>iy-0x3c00
  72                 || (((ix>>20)&0x7ff)==iy-0x3c00
  73                     && (((hx<<11)|(lx>>21))>(hy&0x7fffffff)
  74                         || (((hx<<11)|(lx>>21))==(hy&0x7fffffff)
  75                             && (lx<<11)>ly))))  {/* x < y, x -= ulp */
  76                 if(lx==0) hx -= 1;
  77                 lx -= 1;
  78             } else {                            /* x > y, x += ulp */
  79                 lx += 1;
  80                 if(lx==0) hx += 1;
  81             }
  82         }
  83         hy = hx&0x7ff00000;
  84         if(hy>=0x7ff00000) {
  85           x = x+x;      /* overflow  */
  86           if (FLT_EVAL_METHOD != 0 && FLT_EVAL_METHOD != 1)
  87             /* Force conversion to float.  */
  88             asm ("" : "=m"(x) : "m"(x));
  89           return x;
  90         }
  91         if(hy<0x00100000) {             /* underflow */
  92             double x2 = x*x;
  93             if(x2!=x) {         /* raise underflow flag */
  94                 INSERT_WORDS(x2,hx,lx);
  95                 return x2;
  96             }
  97         }
  98         INSERT_WORDS(x,hx,lx);
  99         return x;
 100 }
 101 weak_alias (__nexttoward, nexttoward)