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#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
pub fn scalbn(x: f64, mut n: i32) -> f64 {
let x1p1023 = f64::from_bits(0x7fe0000000000000); // 0x1p1023 === 2 ^ 1023
let x1p53 = f64::from_bits(0x4340000000000000); // 0x1p53 === 2 ^ 53
let x1p_1022 = f64::from_bits(0x0010000000000000); // 0x1p-1022 === 2 ^ (-1022)
let mut y = x;
if n > 1023 {
y *= x1p1023;
n -= 1023;
if n > 1023 {
y *= x1p1023;
n -= 1023;
if n > 1023 {
n = 1023;
}
}
} else if n < -1022 {
/* make sure final n < -53 to avoid double
rounding in the subnormal range */
y *= x1p_1022 * x1p53;
n += 1022 - 53;
if n < -1022 {
y *= x1p_1022 * x1p53;
n += 1022 - 53;
if n < -1022 {
n = -1022;
}
}
}
y * f64::from_bits(((0x3ff + n) as u64) << 52)
}