8000 perf: improve conversion to primitive integers by DaniPopes · Pull Request #477 · recmo/uint · GitHub
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perf: improve conversion to primitive integers #477

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Merged
merged 2 commits into from
May 29, 2025
Merged

perf: improve conversion to primitive integers #477

merged 2 commits into from
May 29, 2025

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DaniPopes
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@DaniPopes DaniPopes commented May 29, 2025 •
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Make the overflow check faster, and branchless for smaller BITS.

These two functions have now identical codegen:

type T = <integer>;
pub fn u256_to(x: U256) -> Option<T> {
    T::try_from(x).ok()
}

pub fn u256_to_manual(x: U256) -> Option<T> {
    let x = x.as_limbs();
    if (x[1] | x[2] | x[3]) == 0 {
        x[0].try_into().ok()
    } else {
        None
    }
}

Whereas before that was only the case for u64/usize (64 bit unsigned).

@DaniPopes DaniPopes requested a review from prestwich as a code owner May 29, 2025 02:15
@codspeed-hq CodSpeed HQ
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codspeed-hq bot commented May 29, 2025 •
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CodSpeed Performance Report

Merging #477 will degrade performances by 85.47%

Comparing DaniPopes:special-from (0e26736) with main (8a0613d)

Summary

⚡ 2 improvements
❌ 2 regressions
✅ 225 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

Benchmark BASE HEAD Change
⚡ overflowing_shl 999.1 µs 565.7 µs +76.61%
❌ overflowing_shr 588.6 µs 820.1 µs -28.22%
⚡ wrapping_shl 6,730 µs 928.2 µs ×7.3
❌ wrapping_shr 140.1 µs 964.1 µs -85.47%

@DaniPopes DaniPopes force-pushed the special-from branch 2 times, most recently from 020cd2a to 64a3d13 Compare May 29, 2025 02:43
DaniPopes
DaniPopes commented May 29, 2025
View reviewed changes
src/from.rs
if Self::LIMBS == 2 && limbs[1] > Self::MASK {
limbs[1] %= Self::MASK;
if LIMBS == 2 && limbs[1] > Self::MASK {
limbs[1] &= Self::MASK;
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minor drive-by fix: & instead of %

DaniPopes
DaniPopes commented May 29, 2025
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@DaniPopes DaniPopes mentioned this pull request May 29, 2025
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@DaniPopes
perf: improve conversion to primitive integers
81cebfc 
Make the overflow check faster, and branchless for smaller BITS.
@prestwich prestwich enabled auto-merge May 29, 2025 13:42
@prestwich prestwich merged commit fe3ba54 into recmo:main May 29, 2025
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@DaniPopes DaniPopes deleted the special-from branch May 29, 2025 14:03
@DaniPopes DaniPopes mentioned this pull request May 29, 2025
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@prestwich prestwich prestwich approved these changes

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