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

   1 /* s_scalbnl.c -- long double version of s_scalbn.c.
   2  * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
   3  */
   4
   5 /* @(#)s_scalbn.c 5.1 93/09/24 */
   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 /*
  22  * scalbnl (long double x, int n)
  23  * scalbnl(x,n) returns x* 2**n  computed by  exponent
  24  * manipulation rather than by actually performing an
  25  * exponentiation or a multiplication.
  26  */
  27
  28 #include "math.h"
  29 #include "math_private.h"
  30 #include <math_ldbl_opt.h>
  31
  32 #ifdef __STDC__
  33 static const long double
  34 #else
  35 static long double
  36 #endif
  37 twolm54 = 5.55111512312578270212e-17, /* 0x3C90000000000000, 0 */
  38 huge   = 1.0E+300L,
  39 tiny   = 1.0E-300L;
  40 #ifdef __STDC__
  41 static const double
  42 #else
  43 static double
  44 #endif
  45 two54 = 1.80143985094819840000e+16, /* 0x4350000000000000 */
  46 twom54 = 5.55111512312578270212e-17; /* 0x3C90000000000000 */
  47
  48 #ifdef __STDC__
  49         long double __scalbnl (long double x, int n)
  50 #else
  51         long double __scalbnl (x,n)
  52         long double x; int n;
  53 #endif
  54 {
  55         int64_t k,l,hx,lx;
  56         union { int64_t i; double d; } u;
  57         GET_LDOUBLE_WORDS64(hx,lx,x);
  58         k = (hx>>52)&0x7ff;             /* extract exponent */
  59         l = (lx>>52)&0x7ff;
  60         if (k==0) {                             /* 0 or subnormal x */
  61             if (((hx|lx)&0x7fffffffffffffffULL)==0) return x; /* +-0 */
  62             u.i = hx;
  63             u.d *= two54;
  64             hx = u.i;
  65             k = ((hx>>52)&0x7ff) - 54;
  66         }
  67         else if (k==0x7ff) return x+x;          /* NaN or Inf */
  68         k = k+n;
  69         if (n> 50000 || k > 0x7fe)
  70           return huge*__copysignl(huge,x); /* overflow */
  71         if (n< -50000) return tiny*__copysignl(tiny,x); /*underflow */
  72         if (k > 0) {                            /* normal result */
  73             hx = (hx&0x800fffffffffffffULL)|(k<<52);
  74             if ((lx & 0x7fffffffffffffffULL) == 0) { /* low part +-0 */
  75                 SET_LDOUBLE_WORDS64(x,hx,lx);
  76                 return x;
  77             }
  78             if (l == 0) { /* low part subnormal */
  79                 u.i = lx;
  80                 u.d *= two54;
  81                 lx = u.i;
  82                 l = ((lx>>52)&0x7ff) - 54;
  83             }
  84             l = l + n;
  85             if (l > 0)
  86                 lx = (lx&0x800fffffffffffffULL)|(l<<52);
  87             else if (l <= -54)
  88                 lx = (lx&0x8000000000000000ULL);
  89             else {
  90                 l += 54;
  91                 u.i = (lx&0x800fffffffffffffULL)|(l<<52);
  92                 u.d *= twom54;
  93                 lx = u.i;
  94             }
  95             SET_LDOUBLE_WORDS64(x,hx,lx);
  96             return x;
  97         }
  98         if (k <= -54)
  99           return tiny*__copysignl(tiny,x);      /*underflow*/
 100         k += 54;                                /* subnormal result */
 101         lx &= 0x8000000000000000ULL;
 102         SET_LDOUBLE_WORDS64(x,(hx&0x800fffffffffffffULL)|(k<<52),lx);
 103         return x*twolm54;
 104 }
 105 #ifdef IS_IN_libm
 106 long_double_symbol (libm, __scalbnl, scalbnl);
 107 #else
 108 long_double_symbol (libc, __scalbnl, scalbnl);
 109 #endif