sysdeps/ieee754/flt-32/s_logbf.c

   1 /* s_logbf.c -- float version of s_logb.c.
   2  */
   3
   4 /*
   5  * ====================================================
   6  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   7  *
   8  * Developed at SunPro, a Sun Microsystems, Inc. business.
   9  * Permission to use, copy, modify, and distribute this
  10  * software is freely granted, provided that this notice
  11  * is preserved.
  12  * ====================================================
  13  */
  14
  15 #include <math.h>
  16 #include <math_private.h>
  17 #include <libm-alias-float.h>
  18 #include <fix-int-fp-convert-zero.h>
  19 #include <math-use-builtins.h>
  20
  21 float
  22 __logbf (float x)
  23 {
  24 #if USE_LOGBF_BUILTIN
  25   return __builtin_logbf (x);
  26 #else
  27   int32_t ix, rix;
  28
  29   GET_FLOAT_WORD (ix, x);
  30   ix &= 0x7fffffff;             /* high |x| */
  31   if (ix == 0)
  32     return (float) -1.0 / fabsf (x);
  33   if (ix >= 0x7f800000)
  34     return x * x;
  35   if (__glibc_unlikely ((rix = ix >> 23) == 0))
  36     {
  37       /* POSIX specifies that denormal number is treated as
  38          though it were normalized.  */
  39       rix -= __builtin_clz (ix) - 9;
  40     }
  41   if (FIX_INT_FP_CONVERT_ZERO && rix == 127)
  42     return 0.0f;
  43   return (float) (rix - 127);
  44 #endif /* ! USE_LOGBF_BUILTIN */
  45 }
  46 libm_alias_float (__logb, logb)