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

   1 /* s_logbl.c -- long double version of s_logb.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 /*
  17  * long double logbl(x)
  18  * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
  19  * Use ilogb instead.
  20  */
  21
  22 #include <math.h>
  23 #include <math_private.h>
  24 #include <math_ldbl_opt.h>
  25
  26 long double
  27 __logbl (long double x)
  28 {
  29   int64_t hx, rhx;
  30   double xhi;
  31
  32   xhi = ldbl_high (x);
  33   EXTRACT_WORDS64 (hx, xhi);
  34   hx &= 0x7fffffffffffffffLL;   /* high |x| */
  35   if (hx == 0)
  36     return -1.0 / fabs (x);
  37   if (hx >= 0x7ff0000000000000LL)
  38     return x * x;
  39   if (__glibc_unlikely ((rhx = hx >> 52) == 0))
  40     {
  41       /* POSIX specifies that denormal number is treated as
  42          though it were normalized.  */
  43       rhx -= __builtin_clzll (hx) - 12;
  44     }
  45   return (long double) (rhx - 1023);
  46 }
  47 #ifndef __logbl
  48 long_double_symbol (libm, __logbl, logbl);
  49 #endif