1  #include <math.h>
       2  #include <errno.h>
       3  #include <limits.h>
       4  #include <math_private.h>
       5  #include <fenv.h>
       6  
       7  #if _GL_HAS_BUILTIN_ILOGB
       8  int
       9  M_DECL_FUNC (__ilogb) (FLOAT x)
      10  {
      11    int r;
      12    /* Check for exceptional cases.  */
      13    if (! M_SUF(__builtin_test_dc_ilogb) (x, 0x7f))
      14      r = M_SUF (__builtin_ilogb) (x);
      15    else
      16      /* Fallback to the generic ilogb if x is NaN, Inf or subnormal.  */
      17      r = M_SUF (__ieee754_ilogb) (x);
      18    if (__builtin_expect (r == FP_ILOGB0, 0)
      19        || __builtin_expect (r == FP_ILOGBNAN, 0)
      20        || __builtin_expect (r == INT_MAX, 0))
      21      {
      22        __set_errno (EDOM);
      23        __feraiseexcept (FE_INVALID);
      24      }
      25    return r;
      26  }
      27  declare_mgen_alias (__ilogb, ilogb)
      28  #else
      29  #include <math/w_ilogb_template.c>
      30  #endif