libquadmath/math/nextafterq.c

   1 /* s_nextafterl.c -- long double version of s_nextafter.c.
   2  * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #if defined(LIBM_SCCS) && !defined(lint)
  17 static char rcsid[] = "$NetBSD: $";
  18 #endif
  19
  20 /* IEEE functions
  21  *      nextafterq(x,y)
  22  *      return the next machine floating-point number of x in the
  23  *      direction toward y.
  24  *   Special cases:
  25  */
  26
  27 #include "quadmath-imp.h"
  28
  29 __float128 nextafterq(__float128 x, __float128 y)
  30 {
  31         int64_t hx,hy,ix,iy;
  32         uint64_t lx,ly;
  33
  34         GET_FLT128_WORDS64(hx,lx,x);
  35         GET_FLT128_WORDS64(hy,ly,y);
  36         ix = hx&0x7fffffffffffffffLL;           /* |x| */
  37         iy = hy&0x7fffffffffffffffLL;           /* |y| */
  38
  39         if(((ix>=0x7fff000000000000LL)&&((ix-0x7fff000000000000LL)|lx)!=0) ||   /* x is nan */
  40            ((iy>=0x7fff000000000000LL)&&((iy-0x7fff000000000000LL)|ly)!=0))     /* y is nan */
  41            return x+y;
  42         if(x==y) return y;              /* x=y, return y */
  43         if((ix|lx)==0) {                        /* x == 0 */
  44             __float128 u;
  45             SET_FLT128_WORDS64(x,hy&0x8000000000000000ULL,1);/* return +-minsubnormal */
  46             u = math_opt_barrier (x);
  47             u = u * u;
  48             math_force_eval (u);                /* raise underflow flag */
  49             return x;
  50         }
  51         if(hx>=0) {                     /* x > 0 */
  52             if(hx>hy||((hx==hy)&&(lx>ly))) {    /* x > y, x -= ulp */
  53                 if(lx==0) hx--;
  54                 lx--;
  55             } else {                            /* x < y, x += ulp */
  56                 lx++;
  57                 if(lx==0) hx++;
  58             }
  59         } else {                                /* x < 0 */
  60             if(hy>=0||hx>hy||((hx==hy)&&(lx>ly))){/* x < y, x -= ulp */
  61                 if(lx==0) hx--;
  62                 lx--;
  63             } else {                            /* x > y, x += ulp */
  64                 lx++;
  65                 if(lx==0) hx++;
  66             }
  67         }
  68         hy = hx&0x7fff000000000000LL;
  69         if(hy==0x7fff000000000000LL) {
  70             __float128 u = x + x;               /* overflow  */
  71             math_force_eval (u);
  72             errno = ERANGE;
  73         }
  74         if(hy==0) {
  75             __float128 u = x*x;         /* underflow */
  76             math_force_eval (u);                /* raise underflow flag */
  77             errno = ERANGE;
  78         }
  79         SET_FLT128_WORDS64(x,hx,lx);
  80         return x;
  81 }