math: add fma TODO comments about the underflow issue
[oweals/musl.git] / src / math / ilogbf.c
1 #include <limits.h>
2 #include "libm.h"
3
4 int ilogbf(float x)
5 {
6         union fshape u = {x};
7         int e = u.bits>>23 & 0xff;
8
9         if (!e) {
10                 u.bits <<= 9;
11                 if (u.bits == 0) {
12                         FORCE_EVAL(0/0.0f);
13                         return FP_ILOGB0;
14                 }
15                 /* subnormal x */
16                 for (e = -0x7f; u.bits < (uint32_t)1<<31; e--, u.bits<<=1);
17                 return e;
18         }
19         if (e == 0xff) {
20                 FORCE_EVAL(0/0.0f);
21                 return u.bits<<9 ? FP_ILOGBNAN : INT_MAX;
22         }
23         return e - 0x7f;
24 }