math: fix __fpclassifyl(-0.0) for IEEE binary128
[oweals/musl.git] / 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 }