math/s_nextafter.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 #if defined(LIBM_SCCS) && !defined(lint)
  14 static char rcsid[] = "$NetBSD: s_nextafter.c,v 1.8 1995/05/10 20:47:58 jtc 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 /* Ugly hack so that the aliasing works.  */
  25 #define __nexttoward __internal___nexttoward
  26 #define nexttoward __internal_nexttoward
  27
  28 #include <math.h>
  29 #include <math_private.h>
  30 #include <float.h>
  31
  32 #ifdef __STDC__
  33         double __nextafter(double x, double y)
  34 #else
  35         double __nextafter(x,y)
  36         double x,y;
  37 #endif
  38 {
  39         int32_t hx,hy,ix,iy;
  40         u_int32_t lx,ly;
  41
  42         EXTRACT_WORDS(hx,lx,x);
  43         EXTRACT_WORDS(hy,ly,y);
  44         ix = hx&0x7fffffff;             /* |x| */
  45         iy = hy&0x7fffffff;             /* |y| */
  46
  47         if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
  48            ((iy>=0x7ff00000)&&((iy-0x7ff00000)|ly)!=0))     /* y is nan */
  49            return x+y;
  50         if(x==y) return y;              /* x=y, return y */
  51         if((ix|lx)==0) {                        /* x == 0 */
  52             double u;
  53             INSERT_WORDS(x,hy&0x80000000,1);    /* return +-minsubnormal */
  54             u = math_opt_barrier (x);
  55             u = u*u;
  56             math_force_eval (u);                /* raise underflow flag */
  57             return x;
  58         }
  59         if(hx>=0) {                             /* x > 0 */
  60             if(hx>hy||((hx==hy)&&(lx>ly))) {    /* x > y, x -= ulp */
  61                 if(lx==0) hx -= 1;
  62                 lx -= 1;
  63             } else {                            /* x < y, x += ulp */
  64                 lx += 1;
  65                 if(lx==0) hx += 1;
  66             }
  67         } else {                                /* x < 0 */
  68             if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* 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         }
  76         hy = hx&0x7ff00000;
  77         if(hy>=0x7ff00000) {
  78           x = x+x;      /* overflow  */
  79           if (FLT_EVAL_METHOD != 0 && FLT_EVAL_METHOD != 1)
  80             asm ("" : "+m"(x));
  81           return x;     /* overflow  */
  82         }
  83         if(hy<0x00100000) {
  84             double u = x*x;                     /* underflow */
  85             math_force_eval (u);                /* raise underflow flag */
  86         }
  87         INSERT_WORDS(x,hx,lx);
  88         return x;
  89 }
  90 weak_alias (__nextafter, nextafter)
  91 #ifdef NO_LONG_DOUBLE
  92 strong_alias (__nextafter, __nextafterl)
  93 weak_alias (__nextafter, nextafterl)
  94 strong_alias (__nextafter, __nexttowardl)
  95 weak_alias (__nexttowardl, nexttowardl)
  96 #undef __nexttoward
  97 strong_alias (__nextafter, __nexttoward)
  98 #undef nexttoward
  99 weak_alias (__nextafter, nexttoward)
 100 #endif