sysdeps/ieee754/ldbl-128ibm/s_nexttoward.c

   1 /* s_nexttoward.c
   2  * Conversion from s_nextafter.c by Ulrich Drepper, Cygnus Support,
   3  * drepper@cygnus.com 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 /* IEEE functions
  22  *      nexttoward(x,y)
  23  *      return the next machine floating-point number of x in the
  24  *      direction toward y.
  25  *   Special cases:
  26  */
  27
  28 #include "math.h"
  29 #include <math_private.h>
  30 #include <math_ldbl_opt.h>
  31 #include <float.h>
  32
  33 double __nexttoward(double x, long double y)
  34 {
  35         int32_t hx,ix;
  36         int64_t hy,iy;
  37         u_int32_t lx;
  38         u_int64_t ly,uly;
  39
  40         EXTRACT_WORDS(hx,lx,x);
  41         GET_LDOUBLE_WORDS64(hy,ly,y);
  42         ix = hx&0x7fffffff;             /* |x| */
  43         iy = hy&0x7fffffffffffffffLL;   /* |y| */
  44         uly = ly&0x7fffffffffffffffLL;  /* |y| */
  45
  46         if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
  47            ((iy>=0x7ff0000000000000LL)&&((iy-0x7ff0000000000000LL)|uly)!=0))
  48                                                             /* y is nan */
  49            return x+y;
  50         if((long double) x==y) return y;        /* x=y, return y */
  51         if((ix|lx)==0) {                        /* x == 0 */
  52             double u;
  53             INSERT_WORDS(x,(u_int32_t)((hy>>32)&0x80000000),1);/* return +-minsub */
  54             u = math_opt_barrier (x);
  55             u = u * u;
  56             math_force_eval (u);                /* raise underflow flag */
  57             return x;
  58         }
  59         if(hx>=0) {                             /* x > 0 */
  60             if (hy<0||(ix>>20)>(iy>>52)
  61                 || ((ix>>20)==(iy>>52)
  62                     && (((((int64_t)hx)<<32)|(lx))>(hy&0x000fffffffffffffLL)
  63                         || (((((int64_t)hx)<<32)|(lx))==(hy&0x000fffffffffffffLL)
  64                             )))) {      /* x > y, x -= ulp */
  65                 if(lx==0) hx -= 1;
  66                 lx -= 1;
  67             } else {                            /* x < y, x += ulp */
  68                 lx += 1;
  69                 if(lx==0) hx += 1;
  70             }
  71         } else {                                /* x < 0 */
  72             if (hy>=0||(ix>>20)>(iy>>52)
  73                 || ((ix>>20)==(iy>>52)
  74                     && (((((int64_t)hx)<<32)|(lx))>(hy&0x000fffffffffffffLL)
  75                         || (((((int64_t)hx)<<32)|(lx))==(hy&0x000fffffffffffffLL)
  76                            )))) {       /* x < y, x -= ulp */
  77                 if(lx==0) hx -= 1;
  78                 lx -= 1;
  79             } else {                            /* x > y, x += ulp */
  80                 lx += 1;
  81                 if(lx==0) hx += 1;
  82             }
  83         }
  84         hy = hx&0x7ff00000;
  85         if(hy>=0x7ff00000) {
  86           x = x+x;      /* overflow  */
  87           if (FLT_EVAL_METHOD != 0 && FLT_EVAL_METHOD != 1)
  88             /* Force conversion to double.  */
  89             asm ("" : "+m"(x));
  90           return x;
  91         }
  92         if(hy<0x00100000) {
  93             double u = x*x;                     /* underflow */
  94             math_force_eval (u);                /* raise underflow flag */
  95         }
  96         INSERT_WORDS(x,hx,lx);
  97         return x;
  98 }
  99 long_double_symbol (libm, __nexttoward, nexttoward);