sysdeps/i386/fpu/s_nexttowardf.c

   1 /* s_nexttowardf.c -- float version of s_nextafter.c.
   2  * Special i387 version.
   3  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@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 #include <math.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         u_int32_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         /* Intel's extended format has the normally implicit 1 explicit
  36            present.  Sigh!  */
  37         if((ix>0x7f800000) ||                   /* x is nan */
  38            (iy>=0x7fff&&(((hy&0x7fffffff)|ly)!=0))) /* y is nan */
  39            return x+y;
  40         if((long double) x==y) return y;        /* x=y, return y */
  41         if(ix==0) {                             /* x == 0 */
  42             float u;
  43             SET_FLOAT_WORD(x,((esy&0x8000)<<16)|1);/* return +-minsub*/
  44             u = math_opt_barrier (x);
  45             u = u * u;
  46             math_force_eval (u);                /* raise underflow flag */
  47             return x;
  48         }
  49         if(hx>=0) {                             /* x > 0 */
  50             if(x > y) {                         /* x -= ulp */
  51                 hx -= 1;
  52             } else {                            /* x < y, x += ulp */
  53                 hx += 1;
  54             }
  55         } else {                                /* x < 0 */
  56             if(x < y) {                         /* x -= ulp */
  57                 hx -= 1;
  58             } else {                            /* x > y, x += ulp */
  59                 hx += 1;
  60             }
  61         }
  62         hy = hx&0x7f800000;
  63         if(hy>=0x7f800000) {
  64           x = x+x;      /* overflow  */
  65           if (FLT_EVAL_METHOD != 0)
  66             /* Force conversion to float.  */
  67             asm ("" : "+m"(x));
  68           return x;
  69         }
  70         if(hy<0x00800000) {
  71             float u = x*x;                      /* underflow */
  72             math_force_eval (u);                /* raise underflow flag */
  73         }
  74         SET_FLOAT_WORD(x,hx);
  75         return x;
  76 }
  77 weak_alias (__nexttowardf, nexttowardf)