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Use widening_mul

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Tobias Decking 2025-02-01 23:44:52 +01:00 • committed by GitHub
parent e08cd3cf05
commit 4f5116e236
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21
library/core/src/fmt/num.rs
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@ -726,28 +726,9 @@ fn udiv_1e19(n: u128) -> (u128, u64) {
let quot = if n < 1 << 83 {
((n >> 19) as u64 / (DIV >> 19)) as u128
} else {
u128_mulhi(n, FACTOR) >> 62
n.widening_mul(FACTOR).1 >> 62
};
let rem = (n - quot * DIV as u128) as u64;
(quot, rem)
}
/// Multiply unsigned 128 bit integers, return upper 128 bits of the result
#[inline]
fn u128_mulhi(x: u128, y: u128) -> u128 {
let x_lo = x as u64;
let x_hi = (x >> 64) as u64;
let y_lo = y as u64;
let y_hi = (y >> 64) as u64;
// handle possibility of overflow
let carry = (x_lo as u128 * y_lo as u128) >> 64;
let m = x_lo as u128 * y_hi as u128 + carry;
let high1 = m >> 64;
let m_lo = m as u64;
let high2 = (x_hi as u128 * y_lo as u128 + m_lo as u128) >> 64;
x_hi as u128 * y_hi as u128 + high1 + high2
}