sysdeps/ieee754/ldbl-128/s_scalblnl.c

   1 /* s_scalblnl.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  * scalblnl (long double x, long int n)
  23  * scalblnl(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
  31 #ifdef __STDC__
  32 static const long double
  33 #else
  34 static long double
  35 #endif
  36 two114 = 2.0769187434139310514121985316880384E+34L, /* 0x4071000000000000, 0 */
  37 twom114 = 4.8148248609680896326399448564623183E-35L, /* 0x3F8D000000000000, 0 */
  38 huge   = 1.0E+4900L,
  39 tiny   = 1.0E-4900L;
  40
  41 #ifdef __STDC__
  42         long double __scalblnl (long double x, long int n)
  43 #else
  44         long double __scalblnl (x,n)
  45         long double x; long int n;
  46 #endif
  47 {
  48         int64_t k,hx,lx;
  49         GET_LDOUBLE_WORDS64(hx,lx,x);
  50         k = (hx>>48)&0x7fff;            /* extract exponent */
  51         if (k==0) {                             /* 0 or subnormal x */
  52             if ((lx|(hx&0x7fffffffffffffffULL))==0) return x; /* +-0 */
  53             x *= two114;
  54             GET_LDOUBLE_MSW64(hx,x);
  55             k = ((hx>>48)&0x7fff) - 114;
  56         }
  57         if (k==0x7fff) return x+x;              /* NaN or Inf */
  58         k = k+n;
  59         if (n> 50000 || k > 0x7ffe)
  60           return huge*__copysignl(huge,x); /* overflow  */
  61         if (n< -50000) return tiny*__copysignl(tiny,x); /*underflow*/
  62         if (k > 0)                              /* normal result */
  63             {SET_LDOUBLE_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48)); return x;}
  64         if (k <= -114)
  65           return tiny*__copysignl(tiny,x);      /*underflow*/
  66         k += 114;                               /* subnormal result */
  67         SET_LDOUBLE_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48));
  68         return x*twom114;
  69 }
  70 weak_alias (__scalblnl, scalblnl)