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Use widening_mul instead of a separate function #136409

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Merged
merged 1 commit into from
Feb 6, 2025
+1 −20
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Use widening_mul instead of a separate function #136409

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21 changes: 1 addition & 20 deletions library/core/src/fmt/num.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -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
}
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