sysdeps/ieee754/flt-32/s_logbf.c

   1 /* s_logbf.c -- float version of s_logb.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   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 #include <math.h>
  17 #include <math_private.h>
  18
  19 float
  20 __logbf (float x)
  21 {
  22   int32_t ix, rix;
  23
  24   GET_FLOAT_WORD (ix, x);
  25   ix &= 0x7fffffff;             /* high |x| */
  26   if (ix == 0)
  27     return (float) -1.0 / fabsf (x);
  28   if (ix >= 0x7f800000)
  29     return x * x;
  30   if (__glibc_unlikely ((rix = ix >> 23) == 0))
  31     {
  32       /* POSIX specifies that denormal number is treated as
  33          though it were normalized.  */
  34       rix -= __builtin_clz (ix) - 9;
  35     }
  36   return (float) (rix - 127);
  37 }
  38 weak_alias (__logbf, logbf)