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Optimize swizzle_dyn on ssse3 #543

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Merged
programmerjake merged 1 commit into from
Jul 26, 2026
+5 −4
Merged

Optimize swizzle_dyn on ssse3 #543

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7 changes: 4 additions & 3 deletions crates/core_simd/src/swizzle_dyn.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -338,7 +338,8 @@ unsafe fn transize<T, const N: usize>(
#[allow(unused)]
#[inline(always)]
fn zeroing_idxs<const N: usize>(idxs: Simd<u8, N>) -> Simd<u8, N> {
use crate::simd::{Select, cmp::SimdPartialOrd};
idxs.simd_lt(Simd::splat(N as u8))
.select(idxs, Simd::splat(u8::MAX))
// Adding this sets the high bit for indices N..=127, while PSHUFB ignores
// the other changed bits. The OR preserves the high bit for indices 128..=255.
let zeroing_bits = idxs + Simd::splat((127 - N + 1) as u8);
idxs | zeroing_bits
}
2 changes: 1 addition & 1 deletion crates/core_simd/tests/swizzle_dyn.rs
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Expand Up @@ -61,7 +61,7 @@ pub trait SwizzleStrategy {
impl SwizzleStrategy for u8 {
type Strategy = RangeInclusive<u8>;
fn swizzled_strategy() -> Self::Strategy {
0..=64
0..=u8::MAX
}
}

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