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

   1 /* s_frexpl.c -- long double version of s_frexp.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 /*
  21  * for non-zero x
  22  *      x = frexpl(arg,&exp);
  23  * return a long double fp quantity x such that 0.5 <= |x| <1.0
  24  * and the corresponding binary exponent "exp". That is
  25  *      arg = x*2^exp.
  26  * If arg is inf, 0.0, or NaN, then frexpl(arg,&exp) returns arg
  27  * with *exp=0.
  28  */
  29
  30 #include <math.h>
  31 #include <math_private.h>
  32 #include <math_ldbl_opt.h>
  33
  34 static const long double
  35 two107 = 162259276829213363391578010288128.0; /* 0x4670000000000000, 0 */
  36
  37 long double __frexpl(long double x, int *eptr)
  38 {
  39         u_int64_t hx, lx, ix, ixl;
  40         int64_t explo;
  41         GET_LDOUBLE_WORDS64(hx,lx,x);
  42         ixl = 0x7fffffffffffffffULL&lx;
  43         ix =  0x7fffffffffffffffULL&hx;
  44         *eptr = 0;
  45         if(ix>=0x7ff0000000000000ULL||((ix|ixl)==0)) return x;  /* 0,inf,nan */
  46         if (ix<0x0010000000000000ULL) {         /* subnormal */
  47             x *= two107;
  48             GET_LDOUBLE_MSW64(hx,x);
  49             ix = hx&0x7fffffffffffffffULL;
  50             *eptr = -107;
  51         }
  52         *eptr += (ix>>52)-1022;
  53
  54         if (ixl != 0ULL) {
  55           explo = (ixl>>52) - (ix>>52) + 0x3fe;
  56           if ((ixl&0x7ff0000000000000ULL) == 0LL) {
  57             /* the lower double is a denomal so we need to correct its
  58                mantissa and perhaps its exponent.  */
  59             int cnt;
  60
  61             if (sizeof (ixl) == sizeof (long))
  62               cnt = __builtin_clzl (ixl);
  63             else if ((ixl >> 32) != 0)
  64               cnt = __builtin_clzl ((long) (ixl >> 32));
  65             else
  66               cnt = __builtin_clzl ((long) ixl) + 32;
  67             cnt = cnt - 12;
  68             lx = (lx&0x8000000000000000ULL) | ((explo-cnt)<<52)
  69                | ((ixl<<(cnt+1))&0x000fffffffffffffULL);
  70           } else
  71             lx = (lx&0x800fffffffffffffULL) | (explo<<52);
  72         } else
  73           lx = 0ULL;
  74
  75         hx = (hx&0x800fffffffffffffULL) | 0x3fe0000000000000ULL;
  76         SET_LDOUBLE_WORDS64(x,hx,lx);
  77         return x;
  78 }
  79 #ifdef IS_IN_libm
  80 long_double_symbol (libm, __frexpl, frexpl);
  81 #else
  82 long_double_symbol (libc, __frexpl, frexpl);
  83 #endif