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 #ifdef __STDC__
  26         float __nexttowardf(float x, long double y)
  27 #else
  28         float __nexttowardf(x,y)
  29         float x;
  30         long double y;
  31 #endif
  32 {
  33         int32_t hx,ix,iy;
  34         u_int32_t hy,ly,esy;
  35
  36         GET_FLOAT_WORD(hx,x);
  37         GET_LDOUBLE_WORDS(esy,hy,ly,y);
  38         ix = hx&0x7fffffff;             /* |x| */
  39         iy = esy&0x7fff;                /* |y| */
  40
  41         /* Intel's extended format has the normally implicit 1 explicit
  42            present.  Sigh!  */
  43         if((ix>0x7f800000) ||                   /* x is nan */
  44            (iy>=0x7fff&&(((hy&0x7fffffff)|ly)!=0))) /* y is nan */
  45            return x+y;
  46         if((long double) x==y) return y;        /* x=y, return y */
  47         if(ix==0) {                             /* x == 0 */
  48             float u;
  49             SET_FLOAT_WORD(x,((esy&0x8000)<<16)|1);/* return +-minsub*/
  50             u = math_opt_barrier (x);
  51             u = u * u;
  52             math_force_eval (u);                /* raise underflow flag */
  53             return x;
  54         }
  55         if(hx>=0) {                             /* x > 0 */
  56             if(esy>=0x8000||((ix>>23)&0xff)>iy-0x3f80
  57                || (((ix>>23)&0xff)==iy-0x3f80
  58                    && ((ix&0x7fffff)<<8)>(hy&0x7fffffff))) {/* x > y, x -= ulp */
  59                 hx -= 1;
  60             } else {                            /* x < y, x += ulp */
  61                 hx += 1;
  62             }
  63         } else {                                /* x < 0 */
  64             if(esy<0x8000||((ix>>23)&0xff)>iy-0x3f80
  65                || (((ix>>23)&0xff)==iy-0x3f80
  66                    && ((ix&0x7fffff)<<8)>(hy&0x7fffffff))) {/* x < y, x -= ulp */
  67                 hx -= 1;
  68             } else {                            /* x > y, x += ulp */
  69                 hx += 1;
  70             }
  71         }
  72         hy = hx&0x7f800000;
  73         if(hy>=0x7f800000) {
  74           x = x+x;      /* overflow  */
  75           if (FLT_EVAL_METHOD != 0)
  76             /* Force conversion to float.  */
  77             asm ("" : "+m"(x));
  78           return x;
  79         }
  80         if(hy<0x00800000) {
  81             float u = x*x;                      /* underflow */
  82             math_force_eval (u);                /* raise underflow flag */
  83         }
  84         SET_FLOAT_WORD(x,hx);
  85         return x;
  86 }
  87 weak_alias (__nexttowardf, nexttowardf)