sysdeps/ieee754/ldbl-128/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 <float.h>
  31
  32 double __nexttoward(double x, long double y)
  33 {
  34         int32_t hx,ix;
  35         int64_t hy,iy;
  36         u_int32_t lx;
  37         u_int64_t ly;
  38
  39         EXTRACT_WORDS(hx,lx,x);
  40         GET_LDOUBLE_WORDS64(hy,ly,y);
  41         ix = hx&0x7fffffff;             /* |x| */
  42         iy = hy&0x7fffffffffffffffLL;   /* |y| */
  43
  44         if(((ix>=0x7ff00000)&&((ix-0x7ff00000)|lx)!=0) ||   /* x is nan */
  45            ((iy>=0x7fff000000000000LL)&&((iy-0x7fff000000000000LL)|ly)!=0))
  46                                                             /* y is nan */
  47            return x+y;
  48         if((long double) x==y) return y;        /* x=y, return y */
  49         if((ix|lx)==0) {                        /* x == 0 */
  50             double u;
  51             INSERT_WORDS(x,(u_int32_t)((hy>>32)&0x80000000),1);/* return +-minsub */
  52             u = math_opt_barrier (x);
  53             u = u * u;
  54             math_force_eval (u);                /* raise underflow flag */
  55             return x;
  56         }
  57         if(hx>=0) {                             /* x > 0 */
  58             if (x > y) {                        /* x -= ulp */
  59                 if(lx==0) hx -= 1;
  60                 lx -= 1;
  61             } else {                            /* x < y, x += ulp */
  62                 lx += 1;
  63                 if(lx==0) hx += 1;
  64             }
  65         } else {                                /* x < 0 */
  66             if (x < y) {                        /* x -= ulp */
  67                 if(lx==0) hx -= 1;
  68                 lx -= 1;
  69             } else {                            /* x > y, x += ulp */
  70                 lx += 1;
  71                 if(lx==0) hx += 1;
  72             }
  73         }
  74         hy = hx&0x7ff00000;
  75         if(hy>=0x7ff00000) {
  76           x = x+x;      /* overflow  */
  77           if (FLT_EVAL_METHOD != 0 && FLT_EVAL_METHOD != 1)
  78             /* Force conversion to double.  */
  79             asm ("" : "+m"(x));
  80           return x;
  81         }
  82         if(hy<0x00100000) {
  83             double u = x*x;                     /* underflow */
  84             math_force_eval (u);                /* raise underflow flag */
  85         }
  86         INSERT_WORDS(x,hx,lx);
  87         return x;
  88 }
  89 weak_alias (__nexttoward, nexttoward)