sysdeps/ieee754/ldbl-96/s_nexttowardf.c

   1 /* s_nexttowardf.c -- float version of s_nextafter.c.
   2  */
   3
   4 /*
   5  * ====================================================
   6  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   7  *
   8  * Developed at SunPro, a Sun Microsystems, Inc. business.
   9  * Permission to use, copy, modify, and distribute this
  10  * software is freely granted, provided that this notice
  11  * is preserved.
  12  * ====================================================
  13  */
  14
  15 #if defined(LIBM_SCCS) && !defined(lint)
  16 static char rcsid[] = "$NetBSD: $";
  17 #endif
  18
  19 #include <errno.h>
  20 #include <math.h>
  21 #include <math-barriers.h>
  22 #include <math_private.h>
  23 #include <float.h>
  24
  25 float __nexttowardf(float x, long double y)
  26 {
  27         int32_t hx,ix,iy;
  28         uint32_t hy,ly,esy;
  29
  30         GET_FLOAT_WORD(hx,x);
  31         GET_LDOUBLE_WORDS(esy,hy,ly,y);
  32         ix = hx&0x7fffffff;             /* |x| */
  33         iy = esy&0x7fff;                /* |y| */
  34
  35         if((ix>0x7f800000) ||                   /* x is nan */
  36            (iy>=0x7fff&&((hy|ly)!=0)))          /* y is nan */
  37            return x+y;
  38         if((long double) x==y) return y;        /* x=y, return y */
  39         if(ix==0) {                             /* x == 0 */
  40             float u;
  41             SET_FLOAT_WORD(x,((esy&0x8000)<<16)|1);/* return +-minsub*/
  42             u = math_opt_barrier (x);
  43             u = u * u;
  44             math_force_eval (u);                /* raise underflow flag */
  45             return x;
  46         }
  47         if(hx>=0) {                             /* x > 0 */
  48             if(x > y) {                         /* x -= ulp */
  49                 hx -= 1;
  50             } else {                            /* x < y, x += ulp */
  51                 hx += 1;
  52             }
  53         } else {                                /* x < 0 */
  54             if(x < y) {                         /* x -= ulp */
  55                 hx -= 1;
  56             } else {                            /* x > y, x += ulp */
  57                 hx += 1;
  58             }
  59         }
  60         hy = hx&0x7f800000;
  61         if(hy>=0x7f800000) {
  62           float u = x+x;                        /* overflow  */
  63           math_force_eval (u);
  64           __set_errno (ERANGE);
  65         }
  66         if(hy<0x00800000) {
  67             float u = x*x;                      /* underflow */
  68             math_force_eval (u);                /* raise underflow flag */
  69             __set_errno (ERANGE);
  70         }
  71         SET_FLOAT_WORD(x,hx);
  72         return x;
  73 }
  74 weak_alias (__nexttowardf, nexttowardf)