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polyval: const generic pmull wrapper #288

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Merged
tarcieri merged 1 commit into from
Feb 3, 2026
Merged

polyval: const generic pmull wrapper #288

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26 changes: 8 additions & 18 deletions polyval/src/field_element/armv8.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -109,12 +109,12 @@ unsafe fn karatsuba1(x: Simd128, y: Simd128) -> (Simd128, Simd128, Simd128) {
// M H L
//
// m = x.hi^x.lo * y.hi^y.lo
let m = pmull(
let m = pmull::<0>(
veorq_u8(x, vextq_u8(x, x, 8)), // x.hi^x.lo
veorq_u8(y, vextq_u8(y, y, 8)), // y.hi^y.lo
);
let h = pmull2(x, y); // h = x.hi * y.hi
let l = pmull(x, y); // l = x.lo * y.lo
let h = pmull::<1>(x, y); // h = x.hi * y.hi
let l = pmull::<0>(x, y); // l = x.lo * y.lo
(h, m, l)
}

Expand Down Expand Up @@ -175,28 +175,18 @@ unsafe fn mont_reduce(x23: Simd128, x01: Simd128) -> Simd128 {
// [D1:D0] = [B0 ⊕ C1 : B1 ⊕ C0]
// Output: [D1 ⊕ X3 : D0 ⊕ X2]
let poly = vreinterpretq_u8_p128(POLY);
let a = pmull(x01, poly);
let a = pmull::<0>(x01, poly);
let b = veorq_u8(x01, vextq_u8(a, a, 8));
let c = pmull2(b, poly);
let c = pmull::<1>(b, poly);
veorq_u8(x23, veorq_u8(c, b))
}

/// Multiplies the low bits in `a` and `b`.
#[inline]
#[target_feature(enable = "aes,neon")]
unsafe fn pmull(a: Simd128, b: Simd128) -> Simd128 {
unsafe fn pmull<const LANE: i32>(a: Simd128, b: Simd128) -> Simd128 {
vreinterpretq_u8_p128(vmull_p64(
vgetq_lane_u64(vreinterpretq_u64_u8(a), 0),
vgetq_lane_u64(vreinterpretq_u64_u8(b), 0),
))
}

/// Multiplies the high bits in `a` and `b`.
#[inline]
#[target_feature(enable = "aes,neon")]
unsafe fn pmull2(a: Simd128, b: Simd128) -> Simd128 {
vreinterpretq_u8_p128(vmull_p64(
vgetq_lane_u64(vreinterpretq_u64_u8(a), 1),
vgetq_lane_u64(vreinterpretq_u64_u8(b), 1),
vgetq_lane_u64(vreinterpretq_u64_u8(a), LANE),
vgetq_lane_u64(vreinterpretq_u64_u8(b), LANE),
))
}