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const FP_ILOGBNAN: i32 = -1 - 0x7fffffff;
const FP_ILOGB0: i32 = FP_ILOGBNAN;
#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn ilogb(x: f64) -> i32 {
let mut i: u64 = x.to_bits();
let e = ((i >> 52) & 0x7ff) as i32;
if e == 0 {
i <<= 12;
if i == 0 {
force_eval!(0.0 / 0.0);
return FP_ILOGB0;
}
/* subnormal x */
let mut e = -0x3ff;
while (i >> 63) == 0 {
e -= 1;
i <<= 1;
}
e
} else if e == 0x7ff {
force_eval!(0.0 / 0.0);
if (i << 12) != 0 {
FP_ILOGBNAN
} else {
i32::max_value()
}
} else {
e - 0x3ff
}
}