sysdeps/ieee754/ldbl-128ibm/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  * and Jakub Jelinek, jj@ultra.linux.cz.
   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 <math_ldbl_opt.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;
  34         int64_t hy,iy;
  35         u_int64_t ly, uly;
  36
  37         GET_FLOAT_WORD(hx,x);
  38         GET_LDOUBLE_WORDS64(hy,ly,y);
  39         ix = hx&0x7fffffff;             /* |x| */
  40         iy = hy&0x7fffffffffffffffLL;   /* |y| */
  41         uly = ly&0x7fffffffffffffffLL;  /* |y| */
  42
  43         if((ix>0x7f800000) ||   /* x is nan */
  44            ((iy>=0x7ff0000000000000LL)&&((iy-0x7ff0000000000000LL)|uly)!=0))
  45                                 /* y is nan */
  46            return x+y;
  47         if((long double) x==y) return y;        /* x=y, return y */
  48         if(ix==0) {                             /* x == 0 */
  49             float x2;
  50             SET_FLOAT_WORD(x,(u_int32_t)((hy>>32)&0x80000000)|1);/* return +-minsub*/
  51             x2 = x*x;
  52             if(x2==x) return x2; else return x; /* raise underflow flag */
  53         }
  54         if(hx>=0) {                             /* x > 0 */
  55             if(hy<0||(ix>>23)>(iy>>52)-0x380
  56                || ((ix>>23)==(iy>>52)-0x380
  57                    && (ix&0x7fffff)>((hy>>29)&0x7fffff))) {/* x > y, x -= ulp */
  58                 hx -= 1;
  59             } else {                            /* x < y, x += ulp */
  60                 hx += 1;
  61             }
  62         } else {                                /* x < 0 */
  63             if(hy>=0||(ix>>23)>(iy>>52)-0x380
  64                || ((ix>>23)==(iy>>52)-0x380
  65                    && (ix&0x7fffff)>((hy>>29)&0x7fffff))) {/* x < y, x -= ulp */
  66                 hx -= 1;
  67             } else {                            /* x > y, x += ulp */
  68                 hx += 1;
  69             }
  70         }
  71         hy = hx&0x7f800000;
  72         if(hy>=0x7f800000) return x+x;  /* overflow  */
  73         if(hy<0x00800000) {             /* underflow */
  74             float x2 = x*x;
  75             if(x2!=x) {         /* raise underflow flag */
  76                 SET_FLOAT_WORD(x2,hx);
  77                 return x2;
  78             }
  79         }
  80         SET_FLOAT_WORD(x,hx);
  81         return x;
  82 }
  83 long_double_symbol (libm, __nexttowardf, nexttowardf);