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Optimize f32 horizontal_add #87

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Optimize f32 horizontal_add #87

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24 changes: 13 additions & 11 deletions src/ops/f32.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -675,19 +675,21 @@ impl_op! {
impl_op! {
fn horizontal_add<f32> {
for Avx2(a: __m256) -> f32 {
let a = _mm256_hadd_ps(a, a);
let b = _mm256_hadd_ps(a, a);

let first = _mm_cvtss_f32(_mm256_extractf128_ps(b, 0));
let second = _mm_cvtss_f32(_mm256_extractf128_ps(b, 1));

first + second
// benches show shuffle + add is ~20% faster than hadd for 4-wide vectors
let hi128 = _mm256_extractf128_ps(a, 1);
let lo128 = _mm256_castps256_ps128(a);
let sum128 = _mm_add_ps(lo128, hi128);
let shuf = _mm_movehdup_ps(sum128);
let sums = _mm_add_ps(sum128, shuf);
let shuf = _mm_movehl_ps(sums, sums);
_mm_cvtss_f32(_mm_add_ss(sums, shuf))
}
for Sse41(a: __m128) -> f32 {
let a = _mm_hadd_ps(a, a);
let b = _mm_hadd_ps(a, a);

_mm_cvtss_f32(b)
// benches show shuffle + add is ~24% faster than hadd for 4-wide vectors
let shuf = _mm_movehdup_ps(a);
let sums = _mm_add_ps(a, shuf);
let shuf = _mm_movehl_ps(sums, sums);
_mm_cvtss_f32(_mm_add_ss(sums, shuf))
}
for Sse2(a: __m128) -> f32 {
let t1 = _mm_movehl_ps(a, a);
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2 changes: 2 additions & 0 deletions src/ops/f64.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -653,12 +653,14 @@ impl_op! {
impl_op! {
fn horizontal_add<f64> {
for Avx2(a: __m256d) -> f64 {
// benches show no benefit to shuffle + add for 2-wide vectors.
let a = _mm256_hadd_pd(a, a);
let first = _mm_cvtsd_f64(_mm256_extractf128_pd(a, 0));
let second = _mm_cvtsd_f64(_mm256_extractf128_pd(a, 1));
first + second
}
for Sse41(a: __m128d) -> f64 {
// benches show no benefit to shuffle + add for 2-wide vectors.
_mm_cvtsd_f64(_mm_hadd_pd(a, a))
}
for Sse2(a: __m128d) -> f64 {
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