1#include "libm.h"
2#include <limits.h>
3
4int ilogbf(float x) {
5    PRAGMA_STDC_FENV_ACCESS_ON
6    union {
7        float f;
8        uint32_t i;
9    } u = {x};
10    uint32_t i = u.i;
11    int e = i >> 23 & 0xff;
12
13    if (!e) {
14        i <<= 9;
15        if (i == 0) {
16            FORCE_EVAL(0 / 0.0f);
17            return FP_ILOGB0;
18        }
19        /* subnormal x */
20        for (e = -0x7f; i >> 31 == 0; e--, i <<= 1)
21            ;
22        return e;
23    }
24    if (e == 0xff) {
25        FORCE_EVAL(0 / 0.0f);
26        return i << 9 ? FP_ILOGBNAN : INT_MAX;
27    }
28    return e - 0x7f;
29}
30