sysdeps/libm-ieee754/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
  23 #ifdef __STDC__
  24         float __nexttowardf(float x, long double y)
  25 #else
  26         float __nexttowardf(x,y)
  27         float x;
  28         long double y;
  29 #endif
  30 {
  31         int32_t hx,ix,iy;
  32         u_int32_t hy,ly,esy;
  33
  34         GET_FLOAT_WORD(hx,x);
  35         GET_LDOUBLE_WORDS(esy,hy,ly,y);
  36         ix = hx&0x7fffffff;             /* |x| */
  37         iy = esy&0x7fff;                /* |y| */
  38
  39         if((ix>0x7f800000) ||   /* x is nan */
  40            (iy>=0x7fff&&((hy|ly)|-(hy|ly))!=0))     /* y is nan */
  41            return x+y;
  42         if((long double) x==y) return y;        /* x=y, return y */
  43         if(ix==0) {                             /* x == 0 */
  44             float x2;
  45             SET_FLOAT_WORD(x,(esy&0x8000?0x80000000:0)|1);/* return +-minsub*/
  46             x2 = x*x;
  47             if(x2==x) return x2; else return x; /* raise underflow flag */
  48         }
  49         if(hx>=0) {                             /* x > 0 */
  50             if(esy>=0x8000||((ix>>23)&0xff)>iy
  51                || (((ix>>23)&0xff)==iy
  52                    && ((ix&0x7fffff)<<8)>(hy&0x7fffffff))) {/* x > y, x -= ulp */
  53                 hx -= 1;
  54             } else {                            /* x < y, x += ulp */
  55                 hx += 1;
  56             }
  57         } else {                                /* x < 0 */
  58             if(esy<0x8000||((ix>>23)&0xff)>iy
  59                || (((ix>>23)&0xff)==iy
  60                    && ((ix&0x7fffff)<<8)>(hy&0x7fffffff))) {/* x < y, x -= ulp */
  61                 hx -= 1;
  62             } else {                            /* x > y, x += ulp */
  63                 hx += 1;
  64             }
  65         }
  66         hy = hx&0x7f800000;
  67         if(hy>=0x7f800000) return x+x;  /* overflow  */
  68         if(hy<0x00800000) {             /* underflow */
  69             float x2 = x*x;
  70             if(x2!=x) {         /* raise underflow flag */
  71                 SET_FLOAT_WORD(x2,hx);
  72                 return x2;
  73             }
  74         }
  75         SET_FLOAT_WORD(x,hx);
  76         return x;
  77 }
  78 weak_alias (__nexttowardf, nexttowardf)