sysdeps/ieee754/ldbl-96/s_nexttowardf.c

   1 /* s_nexttowardf.c -- float version of s_nextafter.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: $";
  18 #endif
  19
  20 #include "math.h"
  21 #include <math_private.h>
  22 #include <float.h>
  23
  24 #ifdef __STDC__
  25         float __nexttowardf(float x, long double y)
  26 #else
  27         float __nexttowardf(x,y)
  28         float x;
  29         long double y;
  30 #endif
  31 {
  32         int32_t hx,ix,iy;
  33         u_int32_t hy,ly,esy;
  34
  35         GET_FLOAT_WORD(hx,x);
  36         GET_LDOUBLE_WORDS(esy,hy,ly,y);
  37         ix = hx&0x7fffffff;             /* |x| */
  38         iy = esy&0x7fff;                /* |y| */
  39
  40         if((ix>0x7f800000) ||                   /* x is nan */
  41            (iy>=0x7fff&&((hy|ly)!=0)))          /* y is nan */
  42            return x+y;
  43         if((long double) x==y) return y;        /* x=y, return y */
  44         if(ix==0) {                             /* x == 0 */
  45             float u;
  46             SET_FLOAT_WORD(x,((esy&0x8000)<<16)|1);/* return +-minsub*/
  47             u = math_opt_barrier (x);
  48             u = u * u;
  49             math_force_eval (u);                /* raise underflow flag */
  50             return x;
  51         }
  52         if(hx>=0) {                             /* x > 0 */
  53             if(esy>=0x8000||((ix>>23)&0xff)>iy-0x3f80
  54                || (((ix>>23)&0xff)==iy-0x3f80
  55                    && ((ix&0x7fffff)<<8)>(hy&0x7fffffff))) {/* x > y, x -= ulp */
  56                 hx -= 1;
  57             } else {                            /* x < y, x += ulp */
  58                 hx += 1;
  59             }
  60         } else {                                /* x < 0 */
  61             if(esy<0x8000||((ix>>23)&0xff)>iy-0x3f80
  62                || (((ix>>23)&0xff)==iy-0x3f80
  63                    && ((ix&0x7fffff)<<8)>(hy&0x7fffffff))) {/* x < y, x -= ulp */
  64                 hx -= 1;
  65             } else {                            /* x > y, x += ulp */
  66                 hx += 1;
  67             }
  68         }
  69         hy = hx&0x7f800000;
  70         if(hy>=0x7f800000) {
  71           x = x+x;      /* overflow  */
  72           if (FLT_EVAL_METHOD != 0)
  73             /* Force conversion to float.  */
  74             asm ("" : "+m"(x));
  75           return x;
  76         }
  77         if(hy<0x00800000) {
  78             float u = x*x;                      /* underflow */
  79             math_force_eval (u);                /* raise underflow flag */
  80         }
  81         SET_FLOAT_WORD(x,hx);
  82         return x;
  83 }
  84 weak_alias (__nexttowardf, nexttowardf)