#include <limits.h> | |
#include "libm.h" | |
int ilogb(double x) { | |
PRAGMA_STDC_FENV_ACCESS_ON | |
union { | |
double f; | |
uint64_t i; | |
} u = {x}; | |
uint64_t i = u.i; | |
int e = i >> 52 & 0x7ff; | |
if (!e) { | |
i <<= 12; | |
if (i == 0) { | |
FORCE_EVAL(0 / 0.0f); | |
return FP_ILOGB0; | |
} | |
/* subnormal x */ | |
for (e = -0x3ff; i >> 63 == 0; e--, i <<= 1) | |
; | |
return e; | |
} | |
if (e == 0x7ff) { | |
FORCE_EVAL(0 / 0.0f); | |
return i << 12 ? FP_ILOGBNAN : INT_MAX; | |
} | |
return e - 0x3ff; | |
} |