src/math/ilogbf.c

   1 #include <limits.h>
   2 #include "libm.h"
   3
   4 int ilogbf(float x)
   5 {
   6         #pragma STDC FENV_ACCESS ON
   7         union {float f; uint32_t i;} u = {x};
   8         uint32_t i = u.i;
   9         int e = i>>23 & 0xff;
  10
  11         if (!e) {
  12                 i <<= 9;
  13                 if (i == 0) {
  14                         FORCE_EVAL(0/0.0f);
  15                         return FP_ILOGB0;
  16                 }
  17                 /* subnormal x */
  18                 for (e = -0x7f; i>>31 == 0; e--, i<<=1);
  19                 return e;
  20         }
  21         if (e == 0xff) {
  22                 FORCE_EVAL(0/0.0f);
  23                 return i<<9 ? FP_ILOGBNAN : INT_MAX;
  24         }
  25         return e - 0x7f;
  26 }