// Copyright 2019 Google LLC
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// 256-bit vectors and AVX2 instructions, plus some AVX512-VL operations when
// compiling for that target.
// External include guard in highway.h - see comment there.

// WARNING: most operations do not cross 128-bit block boundaries. In
// particular, "Broadcast", pack and zip behavior may be surprising.

// Must come before HWY_DIAGNOSTICS and HWY_COMPILER_CLANGCL
#include "third_party/highway/hwy/base.h"

// Avoid uninitialized warnings in GCC's avx512fintrin.h - see
// https://github.com/google/highway/issues/710)
HWY_DIAGNOSTICS(push)
#if HWY_COMPILER_GCC_ACTUAL
HWY_DIAGNOSTICS_OFF(disable : 4700, ignored "-Wuninitialized")
HWY_DIAGNOSTICS_OFF(disable : 4701 4703 6001 26494,
                    ignored "-Wmaybe-uninitialized")
#endif

// Must come before HWY_COMPILER_CLANGCL
#include <immintrin.h>  // AVX2+

#if HWY_COMPILER_CLANGCL
// Including <immintrin.h> should be enough, but Clang's headers helpfully skip
// including these headers when _MSC_VER is defined, like when using clang-cl.
// Include these directly here.
#include <avxintrin.h>
// avxintrin defines __m256i and must come before avx2intrin.
#include <avx2intrin.h>
#include <bmi2intrin.h>  // _pext_u64
#include <f16cintrin.h>
#include <fmaintrin.h>
#include <smmintrin.h>

#if HWY_TARGET <= HWY_AVX10_2
#include <avx512bitalgintrin.h>
#include <avx512bwintrin.h>
#include <avx512cdintrin.h>
#include <avx512dqintrin.h>
#include <avx512fintrin.h>
#include <avx512vbmi2intrin.h>
#include <avx512vbmiintrin.h>
#include <avx512vbmivlintrin.h>
#include <avx512vlbitalgintrin.h>
#include <avx512vlbwintrin.h>
#include <avx512vlcdintrin.h>
#include <avx512vldqintrin.h>
#include <avx512vlintrin.h>
#include <avx512vlvbmi2intrin.h>
#include <avx512vlvnniintrin.h>
#include <avx512vnniintrin.h>
#include <avx512vpopcntdqintrin.h>
#include <avx512vpopcntdqvlintrin.h>
// Must come after avx512fintrin, else will not define 512-bit intrinsics.
#include <avx512fp16intrin.h>
#include <avx512vlfp16intrin.h>
#include <gfniintrin.h>
#include <vaesintrin.h>
#include <vpclmulqdqintrin.h>

#endif  // HWY_TARGET <= HWY_AVX10_2

// clang-format on
#endif  // HWY_COMPILER_CLANGCL

// For half-width vectors. Already includes base.h.
#include "third_party/highway/hwy/ops/shared-inl.h"
// Already included by shared-inl, but do it again to avoid IDE warnings.
#include "third_party/highway/hwy/ops/x86_128-inl.h"

HWY_BEFORE_NAMESPACE();
namespace hwy {
namespace HWY_NAMESPACE {
namespace detail {

template <typename T>
struct Raw256 {
  using type = __m256i;
};
#if HWY_HAVE_FLOAT16
template <>
struct Raw256<float16_t> {
  using type = __m256h;
};
#endif  // HWY_HAVE_FLOAT16
template <>
struct Raw256<float> {
  using type = __m256;
};
template <>
struct Raw256<double> {
  using type = __m256d;
};

}  // namespace detail

template <typename T>
class Vec256 {
  using Raw = typename detail::Raw256<T>::type;

 public:
  using PrivateT = T;                                  // only for DFromV
  static constexpr size_t kPrivateN = 32 / sizeof(T);  // only for DFromV

  // Compound assignment. Only usable if there is a corresponding non-member
  // binary operator overload. For example, only f32 and f64 support division.
  HWY_INLINE Vec256& operator*=(const Vec256 other) {
    return *this = (*this * other);
  }
  HWY_INLINE Vec256& operator/=(const Vec256 other) {
    return *this = (*this / other);
  }
  HWY_INLINE Vec256& operator+=(const Vec256 other) {
    return *this = (*this + other);
  }
  HWY_INLINE Vec256& operator-=(const Vec256 other) {
    return *this = (*this - other);
  }
  HWY_INLINE Vec256& operator%=(const Vec256 other) {
    return *this = (*this % other);
  }
  HWY_INLINE Vec256& operator&=(const Vec256 other) {
    return *this = (*this & other);
  }
  HWY_INLINE Vec256& operator|=(const Vec256 other) {
    return *this = (*this | other);
  }
  HWY_INLINE Vec256& operator^=(const Vec256 other) {
    return *this = (*this ^ other);
  }

  Raw raw;
};

namespace detail {

#if HWY_TARGET <= HWY_AVX3

// Template arg: sizeof(lane type)
template <size_t size>
struct RawMask256T {};
template <>
struct RawMask256T<1> {
  using type = __mmask32;
};
template <>
struct RawMask256T<2> {
  using type = __mmask16;
};
template <>
struct RawMask256T<4> {
  using type = __mmask8;
};
template <>
struct RawMask256T<8> {
  using type = __mmask8;
};

template <typename T>
using RawMask256 = typename RawMask256T<sizeof(T)>::type;

#else  // AVX2 or earlier

template <typename T>
using RawMask256 = typename Raw256<T>::type;

#endif  // HWY_TARGET <= HWY_AVX3

}  // namespace detail

template <typename T>
struct Mask256 {
  using Raw = typename detail::RawMask256<T>;

  using PrivateT = T;                                  // only for DFromM
  static constexpr size_t kPrivateN = 32 / sizeof(T);  // only for DFromM

#if HWY_TARGET <= HWY_AVX3
  static Mask256<T> FromBits(uint64_t mask_bits) {
    return Mask256<T>{static_cast<Raw>(mask_bits)};
  }
#else
// Lanes are either FF..FF or 0.
#endif  // HWY_TARGET <= HWY_AVX3

  Raw raw;
};

template <typename T>
using Full256 = Simd<T, 32 / sizeof(T), 0>;


// ------------------------------ Zero

// Cannot use VFromD here because it is defined in terms of Zero.
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT_NOR_SPECIAL_D(D)>
HWY_API Vec256<TFromD<D>> Zero(D /* tag */) {
  return Vec256<TFromD<D>>{_mm256_setzero_si256()};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_BF16_D(D)>
HWY_API Vec256<bfloat16_t> Zero(D /* tag */) {
  return Vec256<bfloat16_t>{_mm256_setzero_si256()};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API Vec256<float16_t> Zero(D /* tag */) {
#if HWY_HAVE_FLOAT16
  return Vec256<float16_t>{_mm256_setzero_ph()};
#else
  return Vec256<float16_t>{_mm256_setzero_si256()};
#endif  // HWY_HAVE_FLOAT16
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> Zero(D /* tag */) {
  return Vec256<float>{_mm256_setzero_ps()};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> Zero(D /* tag */) {
  return Vec256<double>{_mm256_setzero_pd()};
}

// ------------------------------ BitCast

namespace detail {

HWY_INLINE __m256i BitCastToInteger(__m256i v) { return v; }
#if HWY_HAVE_FLOAT16
HWY_INLINE __m256i BitCastToInteger(__m256h v) {
  return _mm256_castph_si256(v);
}
#endif  // HWY_HAVE_FLOAT16
HWY_INLINE __m256i BitCastToInteger(__m256 v) { return _mm256_castps_si256(v); }
HWY_INLINE __m256i BitCastToInteger(__m256d v) {
  return _mm256_castpd_si256(v);
}

#if HWY_AVX3_HAVE_F32_TO_BF16C
HWY_INLINE __m256i BitCastToInteger(__m256bh v) {
  // Need to use reinterpret_cast on GCC/Clang or BitCastScalar on MSVC to
  // bit cast a __m256bh to a __m256i as there is currently no intrinsic
  // available (as of GCC 13 and Clang 17) that can bit cast a __m256bh vector
  // to a __m256i vector

#if HWY_COMPILER_GCC || HWY_COMPILER_CLANG
  // On GCC or Clang, use reinterpret_cast to bit cast a __m256bh to a __m256i
  return reinterpret_cast<__m256i>(v);
#else
  // On MSVC, use BitCastScalar to bit cast a __m256bh to a __m256i as MSVC does
  // not allow reinterpret_cast, static_cast, or a C-style cast to be used to
  // bit cast from one AVX vector type to a different AVX vector type
  return BitCastScalar<__m256i>(v);
#endif  // HWY_COMPILER_GCC || HWY_COMPILER_CLANG
}
#endif  // HWY_AVX3_HAVE_F32_TO_BF16C

template <typename T>
HWY_INLINE Vec256<uint8_t> BitCastToByte(Vec256<T> v) {
  return Vec256<uint8_t>{BitCastToInteger(v.raw)};
}

// Cannot rely on function overloading because return types differ.
template <typename T>
struct BitCastFromInteger256 {
  HWY_INLINE __m256i operator()(__m256i v) { return v; }
};
#if HWY_HAVE_FLOAT16
template <>
struct BitCastFromInteger256<float16_t> {
  HWY_INLINE __m256h operator()(__m256i v) { return _mm256_castsi256_ph(v); }
};
#endif  // HWY_HAVE_FLOAT16
template <>
struct BitCastFromInteger256<float> {
  HWY_INLINE __m256 operator()(__m256i v) { return _mm256_castsi256_ps(v); }
};
template <>
struct BitCastFromInteger256<double> {
  HWY_INLINE __m256d operator()(__m256i v) { return _mm256_castsi256_pd(v); }
};

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_INLINE VFromD<D> BitCastFromByte(D /* tag */, Vec256<uint8_t> v) {
  return VFromD<D>{BitCastFromInteger256<TFromD<D>>()(v.raw)};
}

}  // namespace detail

template <class D, HWY_IF_V_SIZE_D(D, 32), typename FromT>
HWY_API VFromD<D> BitCast(D d, Vec256<FromT> v) {
  return detail::BitCastFromByte(d, detail::BitCastToByte(v));
}

// ------------------------------ Set

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> Set(D /* tag */, TFromD<D> t) {
  return VFromD<D>{_mm256_set1_epi8(static_cast<char>(t))};  // NOLINT
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI16_D(D)>
HWY_API VFromD<D> Set(D /* tag */, TFromD<D> t) {
  return VFromD<D>{_mm256_set1_epi16(static_cast<short>(t))};  // NOLINT
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> Set(D /* tag */, TFromD<D> t) {
  return VFromD<D>{_mm256_set1_epi32(static_cast<int>(t))};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API VFromD<D> Set(D /* tag */, TFromD<D> t) {
  return VFromD<D>{_mm256_set1_epi64x(static_cast<long long>(t))};  // NOLINT
}
// bfloat16_t is handled by x86_128-inl.h.
#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API Vec256<float16_t> Set(D /* tag */, float16_t t) {
  return Vec256<float16_t>{_mm256_set1_ph(t)};
}
#endif  // HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> Set(D /* tag */, float t) {
  return Vec256<float>{_mm256_set1_ps(t)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> Set(D /* tag */, double t) {
  return Vec256<double>{_mm256_set1_pd(t)};
}

HWY_DIAGNOSTICS(push)
HWY_DIAGNOSTICS_OFF(disable : 4700, ignored "-Wuninitialized")

// Returns a vector with uninitialized elements.
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT_NOR_SPECIAL_D(D)>
HWY_API VFromD<D> Undefined(D /* tag */) {
  // Available on Clang 6.0, GCC 6.2, ICC 16.03, MSVC 19.14. All but ICC
  // generate an XOR instruction.
  return VFromD<D>{_mm256_undefined_si256()};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_BF16_D(D)>
HWY_API Vec256<bfloat16_t> Undefined(D /* tag */) {
  return Vec256<bfloat16_t>{_mm256_undefined_si256()};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API Vec256<float16_t> Undefined(D /* tag */) {
#if HWY_HAVE_FLOAT16
  return Vec256<float16_t>{_mm256_undefined_ph()};
#else
  return Vec256<float16_t>{_mm256_undefined_si256()};
#endif
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> Undefined(D /* tag */) {
  return Vec256<float>{_mm256_undefined_ps()};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> Undefined(D /* tag */) {
  return Vec256<double>{_mm256_undefined_pd()};
}

HWY_DIAGNOSTICS(pop)

// ------------------------------ ResizeBitCast

// 32-byte vector to 32-byte vector (or 64-byte vector to 64-byte vector on
// AVX3)
template <class D, class FromV, HWY_IF_V_SIZE_GT_V(FromV, 16),
          HWY_IF_V_SIZE_D(D, HWY_MAX_LANES_V(FromV) * sizeof(TFromV<FromV>))>
HWY_API VFromD<D> ResizeBitCast(D d, FromV v) {
  return BitCast(d, v);
}

// 32-byte vector to 16-byte vector (or 64-byte vector to 32-byte vector on
// AVX3)
template <class D, class FromV, HWY_IF_V_SIZE_GT_V(FromV, 16),
          HWY_IF_V_SIZE_D(D,
                          (HWY_MAX_LANES_V(FromV) * sizeof(TFromV<FromV>)) / 2)>
HWY_API VFromD<D> ResizeBitCast(D d, FromV v) {
  const DFromV<decltype(v)> d_from;
  const Half<decltype(d_from)> dh_from;
  return BitCast(d, LowerHalf(dh_from, v));
}

// 32-byte vector (or 64-byte vector on AVX3) to <= 8-byte vector
template <class D, class FromV, HWY_IF_V_SIZE_GT_V(FromV, 16),
          HWY_IF_V_SIZE_LE_D(D, 8)>
HWY_API VFromD<D> ResizeBitCast(D /*d*/, FromV v) {
  return VFromD<D>{ResizeBitCast(Full128<TFromD<D>>(), v).raw};
}

// <= 16-byte vector to 32-byte vector
template <class D, class FromV, HWY_IF_V_SIZE_LE_V(FromV, 16),
          HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> ResizeBitCast(D d, FromV v) {
  return BitCast(d, Vec256<uint8_t>{_mm256_castsi128_si256(
                        ResizeBitCast(Full128<uint8_t>(), v).raw)});
}

// ------------------------------ Dup128VecFromValues

template <class D, HWY_IF_UI8_D(D), HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> Dup128VecFromValues(D /*d*/, TFromD<D> t0, TFromD<D> t1,
                                      TFromD<D> t2, TFromD<D> t3, TFromD<D> t4,
                                      TFromD<D> t5, TFromD<D> t6, TFromD<D> t7,
                                      TFromD<D> t8, TFromD<D> t9, TFromD<D> t10,
                                      TFromD<D> t11, TFromD<D> t12,
                                      TFromD<D> t13, TFromD<D> t14,
                                      TFromD<D> t15) {
  return VFromD<D>{_mm256_setr_epi8(
      static_cast<char>(t0), static_cast<char>(t1), static_cast<char>(t2),
      static_cast<char>(t3), static_cast<char>(t4), static_cast<char>(t5),
      static_cast<char>(t6), static_cast<char>(t7), static_cast<char>(t8),
      static_cast<char>(t9), static_cast<char>(t10), static_cast<char>(t11),
      static_cast<char>(t12), static_cast<char>(t13), static_cast<char>(t14),
      static_cast<char>(t15), static_cast<char>(t0), static_cast<char>(t1),
      static_cast<char>(t2), static_cast<char>(t3), static_cast<char>(t4),
      static_cast<char>(t5), static_cast<char>(t6), static_cast<char>(t7),
      static_cast<char>(t8), static_cast<char>(t9), static_cast<char>(t10),
      static_cast<char>(t11), static_cast<char>(t12), static_cast<char>(t13),
      static_cast<char>(t14), static_cast<char>(t15))};
}

template <class D, HWY_IF_UI16_D(D), HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> Dup128VecFromValues(D /*d*/, TFromD<D> t0, TFromD<D> t1,
                                      TFromD<D> t2, TFromD<D> t3, TFromD<D> t4,
                                      TFromD<D> t5, TFromD<D> t6,
                                      TFromD<D> t7) {
  return VFromD<D>{
      _mm256_setr_epi16(static_cast<int16_t>(t0), static_cast<int16_t>(t1),
                        static_cast<int16_t>(t2), static_cast<int16_t>(t3),
                        static_cast<int16_t>(t4), static_cast<int16_t>(t5),
                        static_cast<int16_t>(t6), static_cast<int16_t>(t7),
                        static_cast<int16_t>(t0), static_cast<int16_t>(t1),
                        static_cast<int16_t>(t2), static_cast<int16_t>(t3),
                        static_cast<int16_t>(t4), static_cast<int16_t>(t5),
                        static_cast<int16_t>(t6), static_cast<int16_t>(t7))};
}

#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_F16_D(D), HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> Dup128VecFromValues(D /*d*/, TFromD<D> t0, TFromD<D> t1,
                                      TFromD<D> t2, TFromD<D> t3, TFromD<D> t4,
                                      TFromD<D> t5, TFromD<D> t6,
                                      TFromD<D> t7) {
  return VFromD<D>{_mm256_setr_ph(t0, t1, t2, t3, t4, t5, t6, t7, t0, t1, t2,
                                  t3, t4, t5, t6, t7)};
}
#endif

template <class D, HWY_IF_UI32_D(D), HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> Dup128VecFromValues(D /*d*/, TFromD<D> t0, TFromD<D> t1,
                                      TFromD<D> t2, TFromD<D> t3) {
  return VFromD<D>{
      _mm256_setr_epi32(static_cast<int32_t>(t0), static_cast<int32_t>(t1),
                        static_cast<int32_t>(t2), static_cast<int32_t>(t3),
                        static_cast<int32_t>(t0), static_cast<int32_t>(t1),
                        static_cast<int32_t>(t2), static_cast<int32_t>(t3))};
}

template <class D, HWY_IF_F32_D(D), HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> Dup128VecFromValues(D /*d*/, TFromD<D> t0, TFromD<D> t1,
                                      TFromD<D> t2, TFromD<D> t3) {
  return VFromD<D>{_mm256_setr_ps(t0, t1, t2, t3, t0, t1, t2, t3)};
}

template <class D, HWY_IF_UI64_D(D), HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> Dup128VecFromValues(D /*d*/, TFromD<D> t0, TFromD<D> t1) {
  return VFromD<D>{
      _mm256_setr_epi64x(static_cast<int64_t>(t0), static_cast<int64_t>(t1),
                         static_cast<int64_t>(t0), static_cast<int64_t>(t1))};
}

template <class D, HWY_IF_F64_D(D), HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> Dup128VecFromValues(D /*d*/, TFromD<D> t0, TFromD<D> t1) {
  return VFromD<D>{_mm256_setr_pd(t0, t1, t0, t1)};
}

// ================================================== LOGICAL

// ------------------------------ And

template <typename T>
HWY_API Vec256<T> And(Vec256<T> a, Vec256<T> b) {
  const DFromV<decltype(a)> d;  // for float16_t
  const RebindToUnsigned<decltype(d)> du;
  return BitCast(d, VFromD<decltype(du)>{_mm256_and_si256(BitCast(du, a).raw,
                                                          BitCast(du, b).raw)});
}

HWY_API Vec256<float> And(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_and_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> And(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_and_pd(a.raw, b.raw)};
}

// ------------------------------ AndNot

// Returns ~not_mask & mask.
template <typename T>
HWY_API Vec256<T> AndNot(Vec256<T> not_mask, Vec256<T> mask) {
  const DFromV<decltype(mask)> d;  // for float16_t
  const RebindToUnsigned<decltype(d)> du;
  return BitCast(d, VFromD<decltype(du)>{_mm256_andnot_si256(
                        BitCast(du, not_mask).raw, BitCast(du, mask).raw)});
}
HWY_API Vec256<float> AndNot(Vec256<float> not_mask, Vec256<float> mask) {
  return Vec256<float>{_mm256_andnot_ps(not_mask.raw, mask.raw)};
}
HWY_API Vec256<double> AndNot(Vec256<double> not_mask, Vec256<double> mask) {
  return Vec256<double>{_mm256_andnot_pd(not_mask.raw, mask.raw)};
}

// ------------------------------ Or

template <typename T>
HWY_API Vec256<T> Or(Vec256<T> a, Vec256<T> b) {
  const DFromV<decltype(a)> d;  // for float16_t
  const RebindToUnsigned<decltype(d)> du;
  return BitCast(d, VFromD<decltype(du)>{_mm256_or_si256(BitCast(du, a).raw,
                                                         BitCast(du, b).raw)});
}

HWY_API Vec256<float> Or(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_or_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> Or(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_or_pd(a.raw, b.raw)};
}

// ------------------------------ Xor

template <typename T>
HWY_API Vec256<T> Xor(Vec256<T> a, Vec256<T> b) {
  const DFromV<decltype(a)> d;  // for float16_t
  const RebindToUnsigned<decltype(d)> du;
  return BitCast(d, VFromD<decltype(du)>{_mm256_xor_si256(BitCast(du, a).raw,
                                                          BitCast(du, b).raw)});
}

HWY_API Vec256<float> Xor(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_xor_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> Xor(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_xor_pd(a.raw, b.raw)};
}

// ------------------------------ Not
template <typename T>
HWY_API Vec256<T> Not(const Vec256<T> v) {
  const DFromV<decltype(v)> d;
  using TU = MakeUnsigned<T>;
#if HWY_TARGET <= HWY_AVX3 && !HWY_IS_MSAN
  const __m256i vu = BitCast(RebindToUnsigned<decltype(d)>(), v).raw;
  return BitCast(d, Vec256<TU>{_mm256_ternarylogic_epi32(vu, vu, vu, 0x55)});
#else
  return Xor(v, BitCast(d, Vec256<TU>{_mm256_set1_epi32(-1)}));
#endif
}

// ------------------------------ Xor3
template <typename T>
HWY_API Vec256<T> Xor3(Vec256<T> x1, Vec256<T> x2, Vec256<T> x3) {
#if HWY_TARGET <= HWY_AVX3 && !HWY_IS_MSAN
  const DFromV<decltype(x1)> d;
  const RebindToUnsigned<decltype(d)> du;
  using VU = VFromD<decltype(du)>;
  const __m256i ret = _mm256_ternarylogic_epi64(
      BitCast(du, x1).raw, BitCast(du, x2).raw, BitCast(du, x3).raw, 0x96);
  return BitCast(d, VU{ret});
#else
  return Xor(x1, Xor(x2, x3));
#endif
}

// ------------------------------ Or3
template <typename T>
HWY_API Vec256<T> Or3(Vec256<T> o1, Vec256<T> o2, Vec256<T> o3) {
#if HWY_TARGET <= HWY_AVX3 && !HWY_IS_MSAN
  const DFromV<decltype(o1)> d;
  const RebindToUnsigned<decltype(d)> du;
  using VU = VFromD<decltype(du)>;
  const __m256i ret = _mm256_ternarylogic_epi64(
      BitCast(du, o1).raw, BitCast(du, o2).raw, BitCast(du, o3).raw, 0xFE);
  return BitCast(d, VU{ret});
#else
  return Or(o1, Or(o2, o3));
#endif
}

// ------------------------------ OrAnd
template <typename T>
HWY_API Vec256<T> OrAnd(Vec256<T> o, Vec256<T> a1, Vec256<T> a2) {
#if HWY_TARGET <= HWY_AVX3 && !HWY_IS_MSAN
  const DFromV<decltype(o)> d;
  const RebindToUnsigned<decltype(d)> du;
  using VU = VFromD<decltype(du)>;
  const __m256i ret = _mm256_ternarylogic_epi64(
      BitCast(du, o).raw, BitCast(du, a1).raw, BitCast(du, a2).raw, 0xF8);
  return BitCast(d, VU{ret});
#else
  return Or(o, And(a1, a2));
#endif
}

// ------------------------------ IfVecThenElse
template <typename T>
HWY_API Vec256<T> IfVecThenElse(Vec256<T> mask, Vec256<T> yes, Vec256<T> no) {
#if HWY_TARGET <= HWY_AVX3 && !HWY_IS_MSAN
  const DFromV<decltype(yes)> d;
  const RebindToUnsigned<decltype(d)> du;
  using VU = VFromD<decltype(du)>;
  return BitCast(d, VU{_mm256_ternarylogic_epi64(BitCast(du, mask).raw,
                                                 BitCast(du, yes).raw,
                                                 BitCast(du, no).raw, 0xCA)});
#else
  return IfThenElse(MaskFromVec(mask), yes, no);
#endif
}

// ------------------------------ Operator overloads (internal-only if float)

template <typename T>
HWY_API Vec256<T> operator&(const Vec256<T> a, const Vec256<T> b) {
  return And(a, b);
}

template <typename T>
HWY_API Vec256<T> operator|(const Vec256<T> a, const Vec256<T> b) {
  return Or(a, b);
}

template <typename T>
HWY_API Vec256<T> operator^(const Vec256<T> a, const Vec256<T> b) {
  return Xor(a, b);
}

// ------------------------------ PopulationCount

// 8/16 require BITALG, 32/64 require VPOPCNTDQ.
#if HWY_TARGET <= HWY_AVX3_DL

#ifdef HWY_NATIVE_POPCNT
#undef HWY_NATIVE_POPCNT
#else
#define HWY_NATIVE_POPCNT
#endif

namespace detail {

template <typename T>
HWY_INLINE Vec256<T> PopulationCount(hwy::SizeTag<1> /* tag */, Vec256<T> v) {
  return Vec256<T>{_mm256_popcnt_epi8(v.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> PopulationCount(hwy::SizeTag<2> /* tag */, Vec256<T> v) {
  return Vec256<T>{_mm256_popcnt_epi16(v.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> PopulationCount(hwy::SizeTag<4> /* tag */, Vec256<T> v) {
  return Vec256<T>{_mm256_popcnt_epi32(v.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> PopulationCount(hwy::SizeTag<8> /* tag */, Vec256<T> v) {
  return Vec256<T>{_mm256_popcnt_epi64(v.raw)};
}

}  // namespace detail

template <typename T>
HWY_API Vec256<T> PopulationCount(Vec256<T> v) {
  return detail::PopulationCount(hwy::SizeTag<sizeof(T)>(), v);
}

#endif  // HWY_TARGET <= HWY_AVX3_DL

// ================================================== MASK

#if HWY_TARGET <= HWY_AVX3

// ------------------------------ IfThenElse

// Returns mask ? b : a.

namespace detail {

// Templates for signed/unsigned integer of a particular size.
template <typename T>
HWY_INLINE Vec256<T> IfThenElse(hwy::SizeTag<1> /* tag */, Mask256<T> mask,
                                Vec256<T> yes, Vec256<T> no) {
  return Vec256<T>{_mm256_mask_blend_epi8(mask.raw, no.raw, yes.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> IfThenElse(hwy::SizeTag<2> /* tag */, Mask256<T> mask,
                                Vec256<T> yes, Vec256<T> no) {
  return Vec256<T>{_mm256_mask_blend_epi16(mask.raw, no.raw, yes.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> IfThenElse(hwy::SizeTag<4> /* tag */, Mask256<T> mask,
                                Vec256<T> yes, Vec256<T> no) {
  return Vec256<T>{_mm256_mask_blend_epi32(mask.raw, no.raw, yes.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> IfThenElse(hwy::SizeTag<8> /* tag */, Mask256<T> mask,
                                Vec256<T> yes, Vec256<T> no) {
  return Vec256<T>{_mm256_mask_blend_epi64(mask.raw, no.raw, yes.raw)};
}

}  // namespace detail

template <typename T, HWY_IF_NOT_FLOAT_NOR_SPECIAL(T)>
HWY_API Vec256<T> IfThenElse(Mask256<T> mask, Vec256<T> yes, Vec256<T> no) {
  return detail::IfThenElse(hwy::SizeTag<sizeof(T)>(), mask, yes, no);
}
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> IfThenElse(Mask256<float16_t> mask,
                                     Vec256<float16_t> yes,
                                     Vec256<float16_t> no) {
  return Vec256<float16_t>{_mm256_mask_blend_ph(mask.raw, no.raw, yes.raw)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> IfThenElse(Mask256<float> mask, Vec256<float> yes,
                                 Vec256<float> no) {
  return Vec256<float>{_mm256_mask_blend_ps(mask.raw, no.raw, yes.raw)};
}
HWY_API Vec256<double> IfThenElse(Mask256<double> mask, Vec256<double> yes,
                                  Vec256<double> no) {
  return Vec256<double>{_mm256_mask_blend_pd(mask.raw, no.raw, yes.raw)};
}

namespace detail {

template <typename T>
HWY_INLINE Vec256<T> IfThenElseZero(hwy::SizeTag<1> /* tag */, Mask256<T> mask,
                                    Vec256<T> yes) {
  return Vec256<T>{_mm256_maskz_mov_epi8(mask.raw, yes.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> IfThenElseZero(hwy::SizeTag<2> /* tag */, Mask256<T> mask,
                                    Vec256<T> yes) {
  return Vec256<T>{_mm256_maskz_mov_epi16(mask.raw, yes.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> IfThenElseZero(hwy::SizeTag<4> /* tag */, Mask256<T> mask,
                                    Vec256<T> yes) {
  return Vec256<T>{_mm256_maskz_mov_epi32(mask.raw, yes.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> IfThenElseZero(hwy::SizeTag<8> /* tag */, Mask256<T> mask,
                                    Vec256<T> yes) {
  return Vec256<T>{_mm256_maskz_mov_epi64(mask.raw, yes.raw)};
}

}  // namespace detail

template <typename T, HWY_IF_NOT_FLOAT_NOR_SPECIAL(T)>
HWY_API Vec256<T> IfThenElseZero(Mask256<T> mask, Vec256<T> yes) {
  return detail::IfThenElseZero(hwy::SizeTag<sizeof(T)>(), mask, yes);
}
HWY_API Vec256<float> IfThenElseZero(Mask256<float> mask, Vec256<float> yes) {
  return Vec256<float>{_mm256_maskz_mov_ps(mask.raw, yes.raw)};
}
HWY_API Vec256<double> IfThenElseZero(Mask256<double> mask,
                                      Vec256<double> yes) {
  return Vec256<double>{_mm256_maskz_mov_pd(mask.raw, yes.raw)};
}

namespace detail {

template <typename T>
HWY_INLINE Vec256<T> IfThenZeroElse(hwy::SizeTag<1> /* tag */, Mask256<T> mask,
                                    Vec256<T> no) {
  // xor_epi8/16 are missing, but we have sub, which is just as fast for u8/16.
  return Vec256<T>{_mm256_mask_sub_epi8(no.raw, mask.raw, no.raw, no.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> IfThenZeroElse(hwy::SizeTag<2> /* tag */, Mask256<T> mask,
                                    Vec256<T> no) {
  return Vec256<T>{_mm256_mask_sub_epi16(no.raw, mask.raw, no.raw, no.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> IfThenZeroElse(hwy::SizeTag<4> /* tag */, Mask256<T> mask,
                                    Vec256<T> no) {
  return Vec256<T>{_mm256_mask_xor_epi32(no.raw, mask.raw, no.raw, no.raw)};
}
template <typename T>
HWY_INLINE Vec256<T> IfThenZeroElse(hwy::SizeTag<8> /* tag */, Mask256<T> mask,
                                    Vec256<T> no) {
  return Vec256<T>{_mm256_mask_xor_epi64(no.raw, mask.raw, no.raw, no.raw)};
}

}  // namespace detail

template <typename T, HWY_IF_NOT_FLOAT_NOR_SPECIAL(T)>
HWY_API Vec256<T> IfThenZeroElse(Mask256<T> mask, Vec256<T> no) {
  return detail::IfThenZeroElse(hwy::SizeTag<sizeof(T)>(), mask, no);
}
HWY_API Vec256<float> IfThenZeroElse(Mask256<float> mask, Vec256<float> no) {
  return Vec256<float>{_mm256_mask_xor_ps(no.raw, mask.raw, no.raw, no.raw)};
}
HWY_API Vec256<double> IfThenZeroElse(Mask256<double> mask, Vec256<double> no) {
  return Vec256<double>{_mm256_mask_xor_pd(no.raw, mask.raw, no.raw, no.raw)};
}

// ------------------------------ Mask logical

namespace detail {

template <typename T>
HWY_INLINE Mask256<T> And(hwy::SizeTag<1> /*tag*/, const Mask256<T> a,
                          const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kand_mask32(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask32>(a.raw & b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> And(hwy::SizeTag<2> /*tag*/, const Mask256<T> a,
                          const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kand_mask16(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask16>(a.raw & b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> And(hwy::SizeTag<4> /*tag*/, const Mask256<T> a,
                          const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kand_mask8(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask8>(a.raw & b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> And(hwy::SizeTag<8> /*tag*/, const Mask256<T> a,
                          const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kand_mask8(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask8>(a.raw & b.raw)};
#endif
}

template <typename T>
HWY_INLINE Mask256<T> AndNot(hwy::SizeTag<1> /*tag*/, const Mask256<T> a,
                             const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kandn_mask32(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask32>(~a.raw & b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> AndNot(hwy::SizeTag<2> /*tag*/, const Mask256<T> a,
                             const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kandn_mask16(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask16>(~a.raw & b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> AndNot(hwy::SizeTag<4> /*tag*/, const Mask256<T> a,
                             const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kandn_mask8(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask8>(~a.raw & b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> AndNot(hwy::SizeTag<8> /*tag*/, const Mask256<T> a,
                             const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kandn_mask8(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask8>(~a.raw & b.raw)};
#endif
}

template <typename T>
HWY_INLINE Mask256<T> Or(hwy::SizeTag<1> /*tag*/, const Mask256<T> a,
                         const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kor_mask32(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask32>(a.raw | b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> Or(hwy::SizeTag<2> /*tag*/, const Mask256<T> a,
                         const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kor_mask16(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask16>(a.raw | b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> Or(hwy::SizeTag<4> /*tag*/, const Mask256<T> a,
                         const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kor_mask8(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask8>(a.raw | b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> Or(hwy::SizeTag<8> /*tag*/, const Mask256<T> a,
                         const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kor_mask8(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask8>(a.raw | b.raw)};
#endif
}

template <typename T>
HWY_INLINE Mask256<T> Xor(hwy::SizeTag<1> /*tag*/, const Mask256<T> a,
                          const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kxor_mask32(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask32>(a.raw ^ b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> Xor(hwy::SizeTag<2> /*tag*/, const Mask256<T> a,
                          const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kxor_mask16(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask16>(a.raw ^ b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> Xor(hwy::SizeTag<4> /*tag*/, const Mask256<T> a,
                          const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kxor_mask8(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask8>(a.raw ^ b.raw)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> Xor(hwy::SizeTag<8> /*tag*/, const Mask256<T> a,
                          const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kxor_mask8(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask8>(a.raw ^ b.raw)};
#endif
}

template <typename T>
HWY_INLINE Mask256<T> ExclusiveNeither(hwy::SizeTag<1> /*tag*/,
                                       const Mask256<T> a, const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kxnor_mask32(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask32>(~(a.raw ^ b.raw) & 0xFFFFFFFF)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> ExclusiveNeither(hwy::SizeTag<2> /*tag*/,
                                       const Mask256<T> a, const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kxnor_mask16(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask16>(~(a.raw ^ b.raw) & 0xFFFF)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> ExclusiveNeither(hwy::SizeTag<4> /*tag*/,
                                       const Mask256<T> a, const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{_kxnor_mask8(a.raw, b.raw)};
#else
  return Mask256<T>{static_cast<__mmask8>(~(a.raw ^ b.raw) & 0xFF)};
#endif
}
template <typename T>
HWY_INLINE Mask256<T> ExclusiveNeither(hwy::SizeTag<8> /*tag*/,
                                       const Mask256<T> a, const Mask256<T> b) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{static_cast<__mmask8>(_kxnor_mask8(a.raw, b.raw) & 0xF)};
#else
  return Mask256<T>{static_cast<__mmask8>(~(a.raw ^ b.raw) & 0xF)};
#endif
}

// UnmaskedNot returns ~m.raw without zeroing out any invalid bits
template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_INLINE Mask256<T> UnmaskedNot(const Mask256<T> m) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{static_cast<__mmask32>(_knot_mask32(m.raw))};
#else
  return Mask256<T>{static_cast<__mmask32>(~m.raw)};
#endif
}

template <typename T, HWY_IF_T_SIZE(T, 2)>
HWY_INLINE Mask256<T> UnmaskedNot(const Mask256<T> m) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{static_cast<__mmask16>(_knot_mask16(m.raw))};
#else
  return Mask256<T>{static_cast<__mmask16>(~m.raw)};
#endif
}

template <typename T, HWY_IF_T_SIZE_ONE_OF(T, (1 << 4) | (1 << 8))>
HWY_INLINE Mask256<T> UnmaskedNot(const Mask256<T> m) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return Mask256<T>{static_cast<__mmask8>(_knot_mask8(m.raw))};
#else
  return Mask256<T>{static_cast<__mmask8>(~m.raw)};
#endif
}

template <typename T>
HWY_INLINE Mask256<T> Not(hwy::SizeTag<1> /*tag*/, const Mask256<T> m) {
  // sizeof(T) == 1: simply return ~m as all 32 bits of m are valid
  return UnmaskedNot(m);
}
template <typename T>
HWY_INLINE Mask256<T> Not(hwy::SizeTag<2> /*tag*/, const Mask256<T> m) {
  // sizeof(T) == 2: simply return ~m as all 16 bits of m are valid
  return UnmaskedNot(m);
}
template <typename T>
HWY_INLINE Mask256<T> Not(hwy::SizeTag<4> /*tag*/, const Mask256<T> m) {
  // sizeof(T) == 4: simply return ~m as all 8 bits of m are valid
  return UnmaskedNot(m);
}
template <typename T>
HWY_INLINE Mask256<T> Not(hwy::SizeTag<8> /*tag*/, const Mask256<T> m) {
  // sizeof(T) == 8: need to zero out the upper 4 bits of ~m as only the lower
  // 4 bits of m are valid

  // Return (~m) & 0x0F
  return AndNot(hwy::SizeTag<8>(), m, Mask256<T>::FromBits(uint64_t{0x0F}));
}

}  // namespace detail

template <typename T>
HWY_API Mask256<T> And(const Mask256<T> a, Mask256<T> b) {
  return detail::And(hwy::SizeTag<sizeof(T)>(), a, b);
}

template <typename T>
HWY_API Mask256<T> AndNot(const Mask256<T> a, Mask256<T> b) {
  return detail::AndNot(hwy::SizeTag<sizeof(T)>(), a, b);
}

template <typename T>
HWY_API Mask256<T> Or(const Mask256<T> a, Mask256<T> b) {
  return detail::Or(hwy::SizeTag<sizeof(T)>(), a, b);
}

template <typename T>
HWY_API Mask256<T> Xor(const Mask256<T> a, Mask256<T> b) {
  return detail::Xor(hwy::SizeTag<sizeof(T)>(), a, b);
}

template <typename T>
HWY_API Mask256<T> Not(const Mask256<T> m) {
  // Flip only the valid bits.
  return detail::Not(hwy::SizeTag<sizeof(T)>(), m);
}

template <typename T>
HWY_API Mask256<T> ExclusiveNeither(const Mask256<T> a, Mask256<T> b) {
  return detail::ExclusiveNeither(hwy::SizeTag<sizeof(T)>(), a, b);
}

template <class D, HWY_IF_LANES_D(D, 32)>
HWY_API MFromD<D> CombineMasks(D /*d*/, MFromD<Half<D>> hi,
                               MFromD<Half<D>> lo) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  const __mmask32 combined_mask = _mm512_kunpackw(
      static_cast<__mmask32>(hi.raw), static_cast<__mmask32>(lo.raw));
#else
  const auto combined_mask =
      ((static_cast<uint32_t>(hi.raw) << 16) | (lo.raw & 0xFFFFu));
#endif

  return MFromD<D>{static_cast<decltype(MFromD<D>().raw)>(combined_mask)};
}

template <class D, HWY_IF_LANES_D(D, 16)>
HWY_API MFromD<D> UpperHalfOfMask(D /*d*/, MFromD<Twice<D>> m) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  const auto shifted_mask = _kshiftri_mask32(static_cast<__mmask32>(m.raw), 16);
#else
  const auto shifted_mask = static_cast<uint32_t>(m.raw) >> 16;
#endif

  return MFromD<D>{static_cast<decltype(MFromD<D>().raw)>(shifted_mask)};
}

template <class D, HWY_IF_LANES_D(D, 32)>
HWY_API MFromD<D> SlideMask1Up(D /*d*/, MFromD<D> m) {
  using RawM = decltype(MFromD<D>().raw);
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return MFromD<D>{
      static_cast<RawM>(_kshiftli_mask32(static_cast<__mmask32>(m.raw), 1))};
#else
  return MFromD<D>{static_cast<RawM>(static_cast<uint32_t>(m.raw) << 1)};
#endif
}

template <class D, HWY_IF_LANES_D(D, 32)>
HWY_API MFromD<D> SlideMask1Down(D /*d*/, MFromD<D> m) {
  using RawM = decltype(MFromD<D>().raw);
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return MFromD<D>{
      static_cast<RawM>(_kshiftri_mask32(static_cast<__mmask32>(m.raw), 1))};
#else
  return MFromD<D>{static_cast<RawM>(static_cast<uint32_t>(m.raw) >> 1)};
#endif
}

#else  // AVX2

// ------------------------------ Mask

// Mask and Vec are the same (true = FF..FF).
template <typename T>
HWY_API Mask256<T> MaskFromVec(const Vec256<T> v) {
  return Mask256<T>{v.raw};
}

template <typename T>
HWY_API Vec256<T> VecFromMask(const Mask256<T> v) {
  return Vec256<T>{v.raw};
}

// ------------------------------ IfThenElse

// mask ? yes : no
template <typename T, HWY_IF_NOT_FLOAT3264(T)>
HWY_API Vec256<T> IfThenElse(Mask256<T> mask, Vec256<T> yes, Vec256<T> no) {
  return Vec256<T>{_mm256_blendv_epi8(no.raw, yes.raw, mask.raw)};
}
HWY_API Vec256<float> IfThenElse(Mask256<float> mask, Vec256<float> yes,
                                 Vec256<float> no) {
  return Vec256<float>{_mm256_blendv_ps(no.raw, yes.raw, mask.raw)};
}
HWY_API Vec256<double> IfThenElse(Mask256<double> mask, Vec256<double> yes,
                                  Vec256<double> no) {
  return Vec256<double>{_mm256_blendv_pd(no.raw, yes.raw, mask.raw)};
}

// mask ? yes : 0
template <typename T>
HWY_API Vec256<T> IfThenElseZero(Mask256<T> mask, Vec256<T> yes) {
  const DFromV<decltype(yes)> d;
  return yes & VecFromMask(d, mask);
}

// mask ? 0 : no
template <typename T>
HWY_API Vec256<T> IfThenZeroElse(Mask256<T> mask, Vec256<T> no) {
  const DFromV<decltype(no)> d;
  return AndNot(VecFromMask(d, mask), no);
}

template <typename T>
HWY_API Vec256<T> ZeroIfNegative(Vec256<T> v) {
  static_assert(IsSigned<T>(), "Only for float");
  const DFromV<decltype(v)> d;
  const auto zero = Zero(d);
  // AVX2 IfThenElse only looks at the MSB for 32/64-bit lanes
  return IfThenElse(MaskFromVec(v), zero, v);
}

// ------------------------------ Mask logical

template <typename T>
HWY_API Mask256<T> Not(const Mask256<T> m) {
  const Full256<T> d;
  return MaskFromVec(Not(VecFromMask(d, m)));
}

template <typename T>
HWY_API Mask256<T> And(const Mask256<T> a, Mask256<T> b) {
  const Full256<T> d;
  return MaskFromVec(And(VecFromMask(d, a), VecFromMask(d, b)));
}

template <typename T>
HWY_API Mask256<T> AndNot(const Mask256<T> a, Mask256<T> b) {
  const Full256<T> d;
  return MaskFromVec(AndNot(VecFromMask(d, a), VecFromMask(d, b)));
}

template <typename T>
HWY_API Mask256<T> Or(const Mask256<T> a, Mask256<T> b) {
  const Full256<T> d;
  return MaskFromVec(Or(VecFromMask(d, a), VecFromMask(d, b)));
}

template <typename T>
HWY_API Mask256<T> Xor(const Mask256<T> a, Mask256<T> b) {
  const Full256<T> d;
  return MaskFromVec(Xor(VecFromMask(d, a), VecFromMask(d, b)));
}

template <typename T>
HWY_API Mask256<T> ExclusiveNeither(const Mask256<T> a, Mask256<T> b) {
  const Full256<T> d;
  return MaskFromVec(AndNot(VecFromMask(d, a), Not(VecFromMask(d, b))));
}

#endif  // HWY_TARGET <= HWY_AVX3

// ================================================== COMPARE

#if HWY_TARGET <= HWY_AVX3

// Comparisons set a mask bit to 1 if the condition is true, else 0.

template <class DTo, HWY_IF_V_SIZE_D(DTo, 32), typename TFrom>
HWY_API MFromD<DTo> RebindMask(DTo /*tag*/, Mask256<TFrom> m) {
  static_assert(sizeof(TFrom) == sizeof(TFromD<DTo>), "Must have same size");
  return MFromD<DTo>{m.raw};
}

namespace detail {

template <typename T>
HWY_INLINE Mask256<T> TestBit(hwy::SizeTag<1> /*tag*/, const Vec256<T> v,
                              const Vec256<T> bit) {
  return Mask256<T>{_mm256_test_epi8_mask(v.raw, bit.raw)};
}
template <typename T>
HWY_INLINE Mask256<T> TestBit(hwy::SizeTag<2> /*tag*/, const Vec256<T> v,
                              const Vec256<T> bit) {
  return Mask256<T>{_mm256_test_epi16_mask(v.raw, bit.raw)};
}
template <typename T>
HWY_INLINE Mask256<T> TestBit(hwy::SizeTag<4> /*tag*/, const Vec256<T> v,
                              const Vec256<T> bit) {
  return Mask256<T>{_mm256_test_epi32_mask(v.raw, bit.raw)};
}
template <typename T>
HWY_INLINE Mask256<T> TestBit(hwy::SizeTag<8> /*tag*/, const Vec256<T> v,
                              const Vec256<T> bit) {
  return Mask256<T>{_mm256_test_epi64_mask(v.raw, bit.raw)};
}

}  // namespace detail

template <typename T>
HWY_API Mask256<T> TestBit(const Vec256<T> v, const Vec256<T> bit) {
  static_assert(!hwy::IsFloat<T>(), "Only integer vectors supported");
  return detail::TestBit(hwy::SizeTag<sizeof(T)>(), v, bit);
}

// ------------------------------ Equality

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Mask256<T> operator==(const Vec256<T> a, const Vec256<T> b) {
  return Mask256<T>{_mm256_cmpeq_epi8_mask(a.raw, b.raw)};
}
template <typename T, HWY_IF_UI16(T)>
HWY_API Mask256<T> operator==(const Vec256<T> a, const Vec256<T> b) {
  return Mask256<T>{_mm256_cmpeq_epi16_mask(a.raw, b.raw)};
}
template <typename T, HWY_IF_UI32(T)>
HWY_API Mask256<T> operator==(const Vec256<T> a, const Vec256<T> b) {
  return Mask256<T>{_mm256_cmpeq_epi32_mask(a.raw, b.raw)};
}
template <typename T, HWY_IF_UI64(T)>
HWY_API Mask256<T> operator==(const Vec256<T> a, const Vec256<T> b) {
  return Mask256<T>{_mm256_cmpeq_epi64_mask(a.raw, b.raw)};
}

#if HWY_HAVE_FLOAT16
HWY_API Mask256<float16_t> operator==(Vec256<float16_t> a,
                                      Vec256<float16_t> b) {
  // Work around warnings in the intrinsic definitions (passing -1 as a mask).
  HWY_DIAGNOSTICS(push)
  HWY_DIAGNOSTICS_OFF(disable : 4245 4365, ignored "-Wsign-conversion")
  return Mask256<float16_t>{_mm256_cmp_ph_mask(a.raw, b.raw, _CMP_EQ_OQ)};
  HWY_DIAGNOSTICS(pop)
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Mask256<float> operator==(Vec256<float> a, Vec256<float> b) {
  return Mask256<float>{_mm256_cmp_ps_mask(a.raw, b.raw, _CMP_EQ_OQ)};
}

HWY_API Mask256<double> operator==(Vec256<double> a, Vec256<double> b) {
  return Mask256<double>{_mm256_cmp_pd_mask(a.raw, b.raw, _CMP_EQ_OQ)};
}

// ------------------------------ Inequality

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Mask256<T> operator!=(const Vec256<T> a, const Vec256<T> b) {
  return Mask256<T>{_mm256_cmpneq_epi8_mask(a.raw, b.raw)};
}
template <typename T, HWY_IF_UI16(T)>
HWY_API Mask256<T> operator!=(const Vec256<T> a, const Vec256<T> b) {
  return Mask256<T>{_mm256_cmpneq_epi16_mask(a.raw, b.raw)};
}
template <typename T, HWY_IF_UI32(T)>
HWY_API Mask256<T> operator!=(const Vec256<T> a, const Vec256<T> b) {
  return Mask256<T>{_mm256_cmpneq_epi32_mask(a.raw, b.raw)};
}
template <typename T, HWY_IF_UI64(T)>
HWY_API Mask256<T> operator!=(const Vec256<T> a, const Vec256<T> b) {
  return Mask256<T>{_mm256_cmpneq_epi64_mask(a.raw, b.raw)};
}

#if HWY_HAVE_FLOAT16
HWY_API Mask256<float16_t> operator!=(Vec256<float16_t> a,
                                      Vec256<float16_t> b) {
  // Work around warnings in the intrinsic definitions (passing -1 as a mask).
  HWY_DIAGNOSTICS(push)
  HWY_DIAGNOSTICS_OFF(disable : 4245 4365, ignored "-Wsign-conversion")
  return Mask256<float16_t>{_mm256_cmp_ph_mask(a.raw, b.raw, _CMP_NEQ_OQ)};
  HWY_DIAGNOSTICS(pop)
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Mask256<float> operator!=(Vec256<float> a, Vec256<float> b) {
  return Mask256<float>{_mm256_cmp_ps_mask(a.raw, b.raw, _CMP_NEQ_OQ)};
}

HWY_API Mask256<double> operator!=(Vec256<double> a, Vec256<double> b) {
  return Mask256<double>{_mm256_cmp_pd_mask(a.raw, b.raw, _CMP_NEQ_OQ)};
}

// ------------------------------ Strict inequality

HWY_API Mask256<int8_t> operator>(Vec256<int8_t> a, Vec256<int8_t> b) {
  return Mask256<int8_t>{_mm256_cmpgt_epi8_mask(a.raw, b.raw)};
}
HWY_API Mask256<int16_t> operator>(Vec256<int16_t> a, Vec256<int16_t> b) {
  return Mask256<int16_t>{_mm256_cmpgt_epi16_mask(a.raw, b.raw)};
}
HWY_API Mask256<int32_t> operator>(Vec256<int32_t> a, Vec256<int32_t> b) {
  return Mask256<int32_t>{_mm256_cmpgt_epi32_mask(a.raw, b.raw)};
}
HWY_API Mask256<int64_t> operator>(Vec256<int64_t> a, Vec256<int64_t> b) {
  return Mask256<int64_t>{_mm256_cmpgt_epi64_mask(a.raw, b.raw)};
}

HWY_API Mask256<uint8_t> operator>(Vec256<uint8_t> a, Vec256<uint8_t> b) {
  return Mask256<uint8_t>{_mm256_cmpgt_epu8_mask(a.raw, b.raw)};
}
HWY_API Mask256<uint16_t> operator>(Vec256<uint16_t> a, Vec256<uint16_t> b) {
  return Mask256<uint16_t>{_mm256_cmpgt_epu16_mask(a.raw, b.raw)};
}
HWY_API Mask256<uint32_t> operator>(Vec256<uint32_t> a, Vec256<uint32_t> b) {
  return Mask256<uint32_t>{_mm256_cmpgt_epu32_mask(a.raw, b.raw)};
}
HWY_API Mask256<uint64_t> operator>(Vec256<uint64_t> a, Vec256<uint64_t> b) {
  return Mask256<uint64_t>{_mm256_cmpgt_epu64_mask(a.raw, b.raw)};
}

#if HWY_HAVE_FLOAT16
HWY_API Mask256<float16_t> operator>(Vec256<float16_t> a, Vec256<float16_t> b) {
  // Work around warnings in the intrinsic definitions (passing -1 as a mask).
  HWY_DIAGNOSTICS(push)
  HWY_DIAGNOSTICS_OFF(disable : 4245 4365, ignored "-Wsign-conversion")
  return Mask256<float16_t>{_mm256_cmp_ph_mask(a.raw, b.raw, _CMP_GT_OQ)};
  HWY_DIAGNOSTICS(pop)
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Mask256<float> operator>(Vec256<float> a, Vec256<float> b) {
  return Mask256<float>{_mm256_cmp_ps_mask(a.raw, b.raw, _CMP_GT_OQ)};
}
HWY_API Mask256<double> operator>(Vec256<double> a, Vec256<double> b) {
  return Mask256<double>{_mm256_cmp_pd_mask(a.raw, b.raw, _CMP_GT_OQ)};
}

// ------------------------------ Weak inequality

#if HWY_HAVE_FLOAT16
HWY_API Mask256<float16_t> operator>=(Vec256<float16_t> a,
                                      Vec256<float16_t> b) {
  // Work around warnings in the intrinsic definitions (passing -1 as a mask).
  HWY_DIAGNOSTICS(push)
  HWY_DIAGNOSTICS_OFF(disable : 4245 4365, ignored "-Wsign-conversion")
  return Mask256<float16_t>{_mm256_cmp_ph_mask(a.raw, b.raw, _CMP_GE_OQ)};
  HWY_DIAGNOSTICS(pop)
}
#endif  // HWY_HAVE_FLOAT16

HWY_API Mask256<float> operator>=(Vec256<float> a, Vec256<float> b) {
  return Mask256<float>{_mm256_cmp_ps_mask(a.raw, b.raw, _CMP_GE_OQ)};
}
HWY_API Mask256<double> operator>=(Vec256<double> a, Vec256<double> b) {
  return Mask256<double>{_mm256_cmp_pd_mask(a.raw, b.raw, _CMP_GE_OQ)};
}

HWY_API Mask256<int8_t> operator>=(Vec256<int8_t> a, Vec256<int8_t> b) {
  return Mask256<int8_t>{_mm256_cmpge_epi8_mask(a.raw, b.raw)};
}
HWY_API Mask256<int16_t> operator>=(Vec256<int16_t> a, Vec256<int16_t> b) {
  return Mask256<int16_t>{_mm256_cmpge_epi16_mask(a.raw, b.raw)};
}
HWY_API Mask256<int32_t> operator>=(Vec256<int32_t> a, Vec256<int32_t> b) {
  return Mask256<int32_t>{_mm256_cmpge_epi32_mask(a.raw, b.raw)};
}
HWY_API Mask256<int64_t> operator>=(Vec256<int64_t> a, Vec256<int64_t> b) {
  return Mask256<int64_t>{_mm256_cmpge_epi64_mask(a.raw, b.raw)};
}

HWY_API Mask256<uint8_t> operator>=(Vec256<uint8_t> a, Vec256<uint8_t> b) {
  return Mask256<uint8_t>{_mm256_cmpge_epu8_mask(a.raw, b.raw)};
}
HWY_API Mask256<uint16_t> operator>=(const Vec256<uint16_t> a,
                                     const Vec256<uint16_t> b) {
  return Mask256<uint16_t>{_mm256_cmpge_epu16_mask(a.raw, b.raw)};
}
HWY_API Mask256<uint32_t> operator>=(const Vec256<uint32_t> a,
                                     const Vec256<uint32_t> b) {
  return Mask256<uint32_t>{_mm256_cmpge_epu32_mask(a.raw, b.raw)};
}
HWY_API Mask256<uint64_t> operator>=(const Vec256<uint64_t> a,
                                     const Vec256<uint64_t> b) {
  return Mask256<uint64_t>{_mm256_cmpge_epu64_mask(a.raw, b.raw)};
}

// ------------------------------ Mask

namespace detail {

template <typename T>
HWY_INLINE Mask256<T> MaskFromVec(hwy::SizeTag<1> /*tag*/, const Vec256<T> v) {
  return Mask256<T>{_mm256_movepi8_mask(v.raw)};
}
template <typename T>
HWY_INLINE Mask256<T> MaskFromVec(hwy::SizeTag<2> /*tag*/, const Vec256<T> v) {
  return Mask256<T>{_mm256_movepi16_mask(v.raw)};
}
template <typename T>
HWY_INLINE Mask256<T> MaskFromVec(hwy::SizeTag<4> /*tag*/, const Vec256<T> v) {
  return Mask256<T>{_mm256_movepi32_mask(v.raw)};
}
template <typename T>
HWY_INLINE Mask256<T> MaskFromVec(hwy::SizeTag<8> /*tag*/, const Vec256<T> v) {
  return Mask256<T>{_mm256_movepi64_mask(v.raw)};
}

}  // namespace detail

template <typename T, HWY_IF_NOT_FLOAT(T)>
HWY_API Mask256<T> MaskFromVec(const Vec256<T> v) {
  return detail::MaskFromVec(hwy::SizeTag<sizeof(T)>(), v);
}
// There do not seem to be native floating-point versions of these instructions.
template <typename T, HWY_IF_FLOAT(T)>
HWY_API Mask256<T> MaskFromVec(const Vec256<T> v) {
  const RebindToSigned<DFromV<decltype(v)>> di;
  return Mask256<T>{MaskFromVec(BitCast(di, v)).raw};
}

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Vec256<T> VecFromMask(const Mask256<T> v) {
  return Vec256<T>{_mm256_movm_epi8(v.raw)};
}

template <typename T, HWY_IF_UI16(T)>
HWY_API Vec256<T> VecFromMask(const Mask256<T> v) {
  return Vec256<T>{_mm256_movm_epi16(v.raw)};
}

template <typename T, HWY_IF_UI32(T)>
HWY_API Vec256<T> VecFromMask(const Mask256<T> v) {
  return Vec256<T>{_mm256_movm_epi32(v.raw)};
}

template <typename T, HWY_IF_UI64(T)>
HWY_API Vec256<T> VecFromMask(const Mask256<T> v) {
  return Vec256<T>{_mm256_movm_epi64(v.raw)};
}

#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> VecFromMask(const Mask256<float16_t> v) {
  return Vec256<float16_t>{_mm256_castsi256_ph(_mm256_movm_epi16(v.raw))};
}
#endif  // HWY_HAVE_FLOAT16

HWY_API Vec256<float> VecFromMask(const Mask256<float> v) {
  return Vec256<float>{_mm256_castsi256_ps(_mm256_movm_epi32(v.raw))};
}

HWY_API Vec256<double> VecFromMask(const Mask256<double> v) {
  return Vec256<double>{_mm256_castsi256_pd(_mm256_movm_epi64(v.raw))};
}

#else  // AVX2

// Comparisons fill a lane with 1-bits if the condition is true, else 0.

template <class DTo, HWY_IF_V_SIZE_D(DTo, 32), typename TFrom>
HWY_API MFromD<DTo> RebindMask(DTo d_to, Mask256<TFrom> m) {
  static_assert(sizeof(TFrom) == sizeof(TFromD<DTo>), "Must have same size");
  const Full256<TFrom> dfrom;
  return MaskFromVec(BitCast(d_to, VecFromMask(dfrom, m)));
}

template <typename T>
HWY_API Mask256<T> TestBit(const Vec256<T> v, const Vec256<T> bit) {
  static_assert(!hwy::IsFloat<T>(), "Only integer vectors supported");
  return (v & bit) == bit;
}

// ------------------------------ Equality

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Mask256<T> operator==(Vec256<T> a, Vec256<T> b) {
  return Mask256<T>{_mm256_cmpeq_epi8(a.raw, b.raw)};
}

template <typename T, HWY_IF_UI16(T)>
HWY_API Mask256<T> operator==(Vec256<T> a, Vec256<T> b) {
  return Mask256<T>{_mm256_cmpeq_epi16(a.raw, b.raw)};
}

template <typename T, HWY_IF_UI32(T)>
HWY_API Mask256<T> operator==(Vec256<T> a, Vec256<T> b) {
  return Mask256<T>{_mm256_cmpeq_epi32(a.raw, b.raw)};
}

template <typename T, HWY_IF_UI64(T)>
HWY_API Mask256<T> operator==(Vec256<T> a, Vec256<T> b) {
  return Mask256<T>{_mm256_cmpeq_epi64(a.raw, b.raw)};
}

HWY_API Mask256<float> operator==(Vec256<float> a, Vec256<float> b) {
  return Mask256<float>{_mm256_cmp_ps(a.raw, b.raw, _CMP_EQ_OQ)};
}

HWY_API Mask256<double> operator==(Vec256<double> a, Vec256<double> b) {
  return Mask256<double>{_mm256_cmp_pd(a.raw, b.raw, _CMP_EQ_OQ)};
}

// ------------------------------ Inequality

template <typename T, HWY_IF_NOT_FLOAT3264(T)>
HWY_API Mask256<T> operator!=(Vec256<T> a, Vec256<T> b) {
  return Not(a == b);
}
HWY_API Mask256<float> operator!=(Vec256<float> a, Vec256<float> b) {
  return Mask256<float>{_mm256_cmp_ps(a.raw, b.raw, _CMP_NEQ_OQ)};
}
HWY_API Mask256<double> operator!=(Vec256<double> a, Vec256<double> b) {
  return Mask256<double>{_mm256_cmp_pd(a.raw, b.raw, _CMP_NEQ_OQ)};
}

// ------------------------------ Strict inequality

// Tag dispatch instead of SFINAE for MSVC 2017 compatibility
namespace detail {

// Pre-9.3 GCC immintrin.h uses char, which may be unsigned, causing cmpgt_epi8
// to perform an unsigned comparison instead of the intended signed. Workaround
// is to cast to an explicitly signed type. See https://godbolt.org/z/PL7Ujy
#if HWY_COMPILER_GCC_ACTUAL != 0 && HWY_COMPILER_GCC_ACTUAL < 903
#define HWY_AVX2_GCC_CMPGT8_WORKAROUND 1
#else
#define HWY_AVX2_GCC_CMPGT8_WORKAROUND 0
#endif

HWY_API Mask256<int8_t> Gt(hwy::SignedTag /*tag*/, Vec256<int8_t> a,
                           Vec256<int8_t> b) {
#if HWY_AVX2_GCC_CMPGT8_WORKAROUND
  using i8x32 = signed char __attribute__((__vector_size__(32)));
  return Mask256<int8_t>{static_cast<__m256i>(reinterpret_cast<i8x32>(a.raw) >
                                              reinterpret_cast<i8x32>(b.raw))};
#else
  return Mask256<int8_t>{_mm256_cmpgt_epi8(a.raw, b.raw)};
#endif
}
HWY_API Mask256<int16_t> Gt(hwy::SignedTag /*tag*/, Vec256<int16_t> a,
                            Vec256<int16_t> b) {
  return Mask256<int16_t>{_mm256_cmpgt_epi16(a.raw, b.raw)};
}
HWY_API Mask256<int32_t> Gt(hwy::SignedTag /*tag*/, Vec256<int32_t> a,
                            Vec256<int32_t> b) {
  return Mask256<int32_t>{_mm256_cmpgt_epi32(a.raw, b.raw)};
}
HWY_API Mask256<int64_t> Gt(hwy::SignedTag /*tag*/, Vec256<int64_t> a,
                            Vec256<int64_t> b) {
  return Mask256<int64_t>{_mm256_cmpgt_epi64(a.raw, b.raw)};
}

template <typename T>
HWY_INLINE Mask256<T> Gt(hwy::UnsignedTag /*tag*/, Vec256<T> a, Vec256<T> b) {
  const Full256<T> du;
  const RebindToSigned<decltype(du)> di;
  const Vec256<T> msb = Set(du, (LimitsMax<T>() >> 1) + 1);
  return RebindMask(du, BitCast(di, Xor(a, msb)) > BitCast(di, Xor(b, msb)));
}

HWY_API Mask256<float> Gt(hwy::FloatTag /*tag*/, Vec256<float> a,
                          Vec256<float> b) {
  return Mask256<float>{_mm256_cmp_ps(a.raw, b.raw, _CMP_GT_OQ)};
}
HWY_API Mask256<double> Gt(hwy::FloatTag /*tag*/, Vec256<double> a,
                           Vec256<double> b) {
  return Mask256<double>{_mm256_cmp_pd(a.raw, b.raw, _CMP_GT_OQ)};
}

}  // namespace detail

template <typename T>
HWY_API Mask256<T> operator>(Vec256<T> a, Vec256<T> b) {
  return detail::Gt(hwy::TypeTag<T>(), a, b);
}

// ------------------------------ Weak inequality

namespace detail {

template <typename T>
HWY_INLINE Mask256<T> Ge(hwy::SignedTag tag, Vec256<T> a, Vec256<T> b) {
  return Not(Gt(tag, b, a));
}

template <typename T>
HWY_INLINE Mask256<T> Ge(hwy::UnsignedTag tag, Vec256<T> a, Vec256<T> b) {
  return Not(Gt(tag, b, a));
}

HWY_INLINE Mask256<float> Ge(hwy::FloatTag /*tag*/, Vec256<float> a,
                             Vec256<float> b) {
  return Mask256<float>{_mm256_cmp_ps(a.raw, b.raw, _CMP_GE_OQ)};
}
HWY_INLINE Mask256<double> Ge(hwy::FloatTag /*tag*/, Vec256<double> a,
                              Vec256<double> b) {
  return Mask256<double>{_mm256_cmp_pd(a.raw, b.raw, _CMP_GE_OQ)};
}

}  // namespace detail

template <typename T>
HWY_API Mask256<T> operator>=(Vec256<T> a, Vec256<T> b) {
  return detail::Ge(hwy::TypeTag<T>(), a, b);
}

#endif  // HWY_TARGET <= HWY_AVX3

// ------------------------------ Reversed comparisons

template <typename T>
HWY_API Mask256<T> operator<(const Vec256<T> a, const Vec256<T> b) {
  return b > a;
}

template <typename T>
HWY_API Mask256<T> operator<=(const Vec256<T> a, const Vec256<T> b) {
  return b >= a;
}

// ------------------------------ Min (Gt, IfThenElse)

// Unsigned
HWY_API Vec256<uint8_t> Min(const Vec256<uint8_t> a, const Vec256<uint8_t> b) {
  return Vec256<uint8_t>{_mm256_min_epu8(a.raw, b.raw)};
}
HWY_API Vec256<uint16_t> Min(const Vec256<uint16_t> a,
                             const Vec256<uint16_t> b) {
  return Vec256<uint16_t>{_mm256_min_epu16(a.raw, b.raw)};
}
HWY_API Vec256<uint32_t> Min(const Vec256<uint32_t> a,
                             const Vec256<uint32_t> b) {
  return Vec256<uint32_t>{_mm256_min_epu32(a.raw, b.raw)};
}
HWY_API Vec256<uint64_t> Min(const Vec256<uint64_t> a,
                             const Vec256<uint64_t> b) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<uint64_t>{_mm256_min_epu64(a.raw, b.raw)};
#else
  const Full256<uint64_t> du;
  const Full256<int64_t> di;
  const auto msb = Set(du, 1ull << 63);
  const auto gt = RebindMask(du, BitCast(di, a ^ msb) > BitCast(di, b ^ msb));
  return IfThenElse(gt, b, a);
#endif
}

// Signed
HWY_API Vec256<int8_t> Min(const Vec256<int8_t> a, const Vec256<int8_t> b) {
  return Vec256<int8_t>{_mm256_min_epi8(a.raw, b.raw)};
}
HWY_API Vec256<int16_t> Min(const Vec256<int16_t> a, const Vec256<int16_t> b) {
  return Vec256<int16_t>{_mm256_min_epi16(a.raw, b.raw)};
}
HWY_API Vec256<int32_t> Min(const Vec256<int32_t> a, const Vec256<int32_t> b) {
  return Vec256<int32_t>{_mm256_min_epi32(a.raw, b.raw)};
}
HWY_API Vec256<int64_t> Min(const Vec256<int64_t> a, const Vec256<int64_t> b) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<int64_t>{_mm256_min_epi64(a.raw, b.raw)};
#else
  return IfThenElse(a < b, a, b);
#endif
}

// Float
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> Min(Vec256<float16_t> a, Vec256<float16_t> b) {
  return Vec256<float16_t>{_mm256_min_ph(a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> Min(const Vec256<float> a, const Vec256<float> b) {
  return Vec256<float>{_mm256_min_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> Min(const Vec256<double> a, const Vec256<double> b) {
  return Vec256<double>{_mm256_min_pd(a.raw, b.raw)};
}

// ------------------------------ Max (Gt, IfThenElse)

// Unsigned
HWY_API Vec256<uint8_t> Max(const Vec256<uint8_t> a, const Vec256<uint8_t> b) {
  return Vec256<uint8_t>{_mm256_max_epu8(a.raw, b.raw)};
}
HWY_API Vec256<uint16_t> Max(const Vec256<uint16_t> a,
                             const Vec256<uint16_t> b) {
  return Vec256<uint16_t>{_mm256_max_epu16(a.raw, b.raw)};
}
HWY_API Vec256<uint32_t> Max(const Vec256<uint32_t> a,
                             const Vec256<uint32_t> b) {
  return Vec256<uint32_t>{_mm256_max_epu32(a.raw, b.raw)};
}
HWY_API Vec256<uint64_t> Max(const Vec256<uint64_t> a,
                             const Vec256<uint64_t> b) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<uint64_t>{_mm256_max_epu64(a.raw, b.raw)};
#else
  const Full256<uint64_t> du;
  const Full256<int64_t> di;
  const auto msb = Set(du, 1ull << 63);
  const auto gt = RebindMask(du, BitCast(di, a ^ msb) > BitCast(di, b ^ msb));
  return IfThenElse(gt, a, b);
#endif
}

// Signed
HWY_API Vec256<int8_t> Max(const Vec256<int8_t> a, const Vec256<int8_t> b) {
  return Vec256<int8_t>{_mm256_max_epi8(a.raw, b.raw)};
}
HWY_API Vec256<int16_t> Max(const Vec256<int16_t> a, const Vec256<int16_t> b) {
  return Vec256<int16_t>{_mm256_max_epi16(a.raw, b.raw)};
}
HWY_API Vec256<int32_t> Max(const Vec256<int32_t> a, const Vec256<int32_t> b) {
  return Vec256<int32_t>{_mm256_max_epi32(a.raw, b.raw)};
}
HWY_API Vec256<int64_t> Max(const Vec256<int64_t> a, const Vec256<int64_t> b) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<int64_t>{_mm256_max_epi64(a.raw, b.raw)};
#else
  return IfThenElse(a < b, b, a);
#endif
}

// Float
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> Max(Vec256<float16_t> a, Vec256<float16_t> b) {
  return Vec256<float16_t>{_mm256_max_ph(a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> Max(const Vec256<float> a, const Vec256<float> b) {
  return Vec256<float>{_mm256_max_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> Max(const Vec256<double> a, const Vec256<double> b) {
  return Vec256<double>{_mm256_max_pd(a.raw, b.raw)};
}

// ------------------------------ Iota

namespace detail {

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_INLINE VFromD<D> Iota0(D /*d*/) {
  return VFromD<D>{_mm256_set_epi8(
      static_cast<char>(31), static_cast<char>(30), static_cast<char>(29),
      static_cast<char>(28), static_cast<char>(27), static_cast<char>(26),
      static_cast<char>(25), static_cast<char>(24), static_cast<char>(23),
      static_cast<char>(22), static_cast<char>(21), static_cast<char>(20),
      static_cast<char>(19), static_cast<char>(18), static_cast<char>(17),
      static_cast<char>(16), static_cast<char>(15), static_cast<char>(14),
      static_cast<char>(13), static_cast<char>(12), static_cast<char>(11),
      static_cast<char>(10), static_cast<char>(9), static_cast<char>(8),
      static_cast<char>(7), static_cast<char>(6), static_cast<char>(5),
      static_cast<char>(4), static_cast<char>(3), static_cast<char>(2),
      static_cast<char>(1), static_cast<char>(0))};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI16_D(D)>
HWY_INLINE VFromD<D> Iota0(D /*d*/) {
  return VFromD<D>{_mm256_set_epi16(
      int16_t{15}, int16_t{14}, int16_t{13}, int16_t{12}, int16_t{11},
      int16_t{10}, int16_t{9}, int16_t{8}, int16_t{7}, int16_t{6}, int16_t{5},
      int16_t{4}, int16_t{3}, int16_t{2}, int16_t{1}, int16_t{0})};
}

#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_INLINE VFromD<D> Iota0(D /*d*/) {
  return VFromD<D>{
      _mm256_set_ph(float16_t{15}, float16_t{14}, float16_t{13}, float16_t{12},
                    float16_t{11}, float16_t{10}, float16_t{9}, float16_t{8},
                    float16_t{7}, float16_t{6}, float16_t{5}, float16_t{4},
                    float16_t{3}, float16_t{2}, float16_t{1}, float16_t{0})};
}
#endif  // HWY_HAVE_FLOAT16

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_INLINE VFromD<D> Iota0(D /*d*/) {
  return VFromD<D>{_mm256_set_epi32(int32_t{7}, int32_t{6}, int32_t{5},
                                    int32_t{4}, int32_t{3}, int32_t{2},
                                    int32_t{1}, int32_t{0})};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_INLINE VFromD<D> Iota0(D /*d*/) {
  return VFromD<D>{
      _mm256_set_epi64x(int64_t{3}, int64_t{2}, int64_t{1}, int64_t{0})};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_INLINE VFromD<D> Iota0(D /*d*/) {
  return VFromD<D>{
      _mm256_set_ps(7.0f, 6.0f, 5.0f, 4.0f, 3.0f, 2.0f, 1.0f, 0.0f)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_INLINE VFromD<D> Iota0(D /*d*/) {
  return VFromD<D>{_mm256_set_pd(3.0, 2.0, 1.0, 0.0)};
}

}  // namespace detail

template <class D, HWY_IF_V_SIZE_D(D, 32), typename T2>
HWY_API VFromD<D> Iota(D d, const T2 first) {
  return detail::Iota0(d) + Set(d, ConvertScalarTo<TFromD<D>>(first));
}

// ------------------------------ FirstN (Iota, Lt)

template <class D, HWY_IF_V_SIZE_D(D, 32), class M = MFromD<D>>
HWY_API M FirstN(const D d, size_t n) {
  constexpr size_t kN = MaxLanes(d);
  // For AVX3, this ensures `num` <= 255 as required by bzhi, which only looks
  // at the lower 8 bits; for AVX2 and below, this ensures `num` fits in TI.
  n = HWY_MIN(n, kN);

#if HWY_TARGET <= HWY_AVX3
#if HWY_ARCH_X86_64
  const uint64_t all = (1ull << kN) - 1;
  return M::FromBits(_bzhi_u64(all, n));
#else
  const uint32_t all = static_cast<uint32_t>((1ull << kN) - 1);
  return M::FromBits(_bzhi_u32(all, static_cast<uint32_t>(n)));
#endif  // HWY_ARCH_X86_64
#else
  const RebindToSigned<decltype(d)> di;  // Signed comparisons are cheaper.
  using TI = TFromD<decltype(di)>;
  return RebindMask(d, detail::Iota0(di) < Set(di, static_cast<TI>(n)));
#endif
}

// ================================================== ARITHMETIC

// ------------------------------ Addition

// Unsigned
HWY_API Vec256<uint8_t> operator+(Vec256<uint8_t> a, Vec256<uint8_t> b) {
  return Vec256<uint8_t>{_mm256_add_epi8(a.raw, b.raw)};
}
HWY_API Vec256<uint16_t> operator+(Vec256<uint16_t> a, Vec256<uint16_t> b) {
  return Vec256<uint16_t>{_mm256_add_epi16(a.raw, b.raw)};
}
HWY_API Vec256<uint32_t> operator+(Vec256<uint32_t> a, Vec256<uint32_t> b) {
  return Vec256<uint32_t>{_mm256_add_epi32(a.raw, b.raw)};
}
HWY_API Vec256<uint64_t> operator+(Vec256<uint64_t> a, Vec256<uint64_t> b) {
  return Vec256<uint64_t>{_mm256_add_epi64(a.raw, b.raw)};
}

// Signed
HWY_API Vec256<int8_t> operator+(Vec256<int8_t> a, Vec256<int8_t> b) {
  return Vec256<int8_t>{_mm256_add_epi8(a.raw, b.raw)};
}
HWY_API Vec256<int16_t> operator+(Vec256<int16_t> a, Vec256<int16_t> b) {
  return Vec256<int16_t>{_mm256_add_epi16(a.raw, b.raw)};
}
HWY_API Vec256<int32_t> operator+(Vec256<int32_t> a, Vec256<int32_t> b) {
  return Vec256<int32_t>{_mm256_add_epi32(a.raw, b.raw)};
}
HWY_API Vec256<int64_t> operator+(Vec256<int64_t> a, Vec256<int64_t> b) {
  return Vec256<int64_t>{_mm256_add_epi64(a.raw, b.raw)};
}

// Float
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> operator+(Vec256<float16_t> a, Vec256<float16_t> b) {
  return Vec256<float16_t>{_mm256_add_ph(a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> operator+(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_add_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> operator+(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_add_pd(a.raw, b.raw)};
}

// ------------------------------ Subtraction

// Unsigned
HWY_API Vec256<uint8_t> operator-(Vec256<uint8_t> a, Vec256<uint8_t> b) {
  return Vec256<uint8_t>{_mm256_sub_epi8(a.raw, b.raw)};
}
HWY_API Vec256<uint16_t> operator-(Vec256<uint16_t> a, Vec256<uint16_t> b) {
  return Vec256<uint16_t>{_mm256_sub_epi16(a.raw, b.raw)};
}
HWY_API Vec256<uint32_t> operator-(Vec256<uint32_t> a, Vec256<uint32_t> b) {
  return Vec256<uint32_t>{_mm256_sub_epi32(a.raw, b.raw)};
}
HWY_API Vec256<uint64_t> operator-(Vec256<uint64_t> a, Vec256<uint64_t> b) {
  return Vec256<uint64_t>{_mm256_sub_epi64(a.raw, b.raw)};
}

// Signed
HWY_API Vec256<int8_t> operator-(Vec256<int8_t> a, Vec256<int8_t> b) {
  return Vec256<int8_t>{_mm256_sub_epi8(a.raw, b.raw)};
}
HWY_API Vec256<int16_t> operator-(Vec256<int16_t> a, Vec256<int16_t> b) {
  return Vec256<int16_t>{_mm256_sub_epi16(a.raw, b.raw)};
}
HWY_API Vec256<int32_t> operator-(Vec256<int32_t> a, Vec256<int32_t> b) {
  return Vec256<int32_t>{_mm256_sub_epi32(a.raw, b.raw)};
}
HWY_API Vec256<int64_t> operator-(Vec256<int64_t> a, Vec256<int64_t> b) {
  return Vec256<int64_t>{_mm256_sub_epi64(a.raw, b.raw)};
}

// Float
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> operator-(Vec256<float16_t> a, Vec256<float16_t> b) {
  return Vec256<float16_t>{_mm256_sub_ph(a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> operator-(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_sub_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> operator-(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_sub_pd(a.raw, b.raw)};
}

// ------------------------------ AddSub

HWY_API Vec256<float> AddSub(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_addsub_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> AddSub(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_addsub_pd(a.raw, b.raw)};
}

// ------------------------------ PairwiseAdd128/PairwiseSub128

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI16_D(D)>
HWY_API VFromD<D> PairwiseAdd128(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_hadd_epi16(a.raw, b.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI16_D(D)>
HWY_API VFromD<D> PairwiseSub128(D /*d*/, VFromD<D> a, VFromD<D> b) {
  const DFromV<decltype(a)> d;
  const RebindToSigned<decltype(d)> di;
  return BitCast(d,
                 Neg(BitCast(di, VFromD<D>{_mm256_hsub_epi16(a.raw, b.raw)})));
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> PairwiseAdd128(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_hadd_epi32(a.raw, b.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> PairwiseSub128(D /*d*/, VFromD<D> a, VFromD<D> b) {
  const DFromV<decltype(a)> d;
  const RebindToSigned<decltype(d)> di;
  return BitCast(d,
                 Neg(BitCast(di, VFromD<D>{_mm256_hsub_epi32(a.raw, b.raw)})));
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> PairwiseAdd128(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_hadd_ps(a.raw, b.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> PairwiseSub128(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return Neg(VFromD<D>{_mm256_hsub_ps(a.raw, b.raw)});
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API VFromD<D> PairwiseAdd128(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_hadd_pd(a.raw, b.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API VFromD<D> PairwiseSub128(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return Neg(VFromD<D>{_mm256_hsub_pd(a.raw, b.raw)});
}

// ------------------------------ SumsOf8
HWY_API Vec256<uint64_t> SumsOf8(Vec256<uint8_t> v) {
  return Vec256<uint64_t>{_mm256_sad_epu8(v.raw, _mm256_setzero_si256())};
}

HWY_API Vec256<uint64_t> SumsOf8AbsDiff(Vec256<uint8_t> a, Vec256<uint8_t> b) {
  return Vec256<uint64_t>{_mm256_sad_epu8(a.raw, b.raw)};
}

// ------------------------------ SumsOf4
#if HWY_TARGET <= HWY_AVX3
namespace detail {

HWY_INLINE Vec256<uint32_t> SumsOf4(hwy::UnsignedTag /*type_tag*/,
                                    hwy::SizeTag<1> /*lane_size_tag*/,
                                    Vec256<uint8_t> v) {
  const DFromV<decltype(v)> d;

  // _mm256_maskz_dbsad_epu8 is used below as the odd uint16_t lanes need to be
  // zeroed out and the sums of the 4 consecutive lanes are already in the
  // even uint16_t lanes of the _mm256_maskz_dbsad_epu8 result.
  return Vec256<uint32_t>{_mm256_maskz_dbsad_epu8(
      static_cast<__mmask16>(0x5555), v.raw, Zero(d).raw, 0)};
}

// detail::SumsOf4 for Vec256<int8_t> on AVX3 is implemented in x86_512-inl.h

}  // namespace detail
#endif  // HWY_TARGET <= HWY_AVX3

// ------------------------------ SumsOfAdjQuadAbsDiff

template <int kAOffset, int kBOffset>
static Vec256<uint16_t> SumsOfAdjQuadAbsDiff(Vec256<uint8_t> a,
                                             Vec256<uint8_t> b) {
  static_assert(0 <= kAOffset && kAOffset <= 1,
                "kAOffset must be between 0 and 1");
  static_assert(0 <= kBOffset && kBOffset <= 3,
                "kBOffset must be between 0 and 3");
  return Vec256<uint16_t>{_mm256_mpsadbw_epu8(
      a.raw, b.raw,
      (kAOffset << 5) | (kBOffset << 3) | (kAOffset << 2) | kBOffset)};
}

// ------------------------------ SumsOfShuffledQuadAbsDiff

#if HWY_TARGET <= HWY_AVX3
template <int kIdx3, int kIdx2, int kIdx1, int kIdx0>
static Vec256<uint16_t> SumsOfShuffledQuadAbsDiff(Vec256<uint8_t> a,
                                                  Vec256<uint8_t> b) {
  static_assert(0 <= kIdx0 && kIdx0 <= 3, "kIdx0 must be between 0 and 3");
  static_assert(0 <= kIdx1 && kIdx1 <= 3, "kIdx1 must be between 0 and 3");
  static_assert(0 <= kIdx2 && kIdx2 <= 3, "kIdx2 must be between 0 and 3");
  static_assert(0 <= kIdx3 && kIdx3 <= 3, "kIdx3 must be between 0 and 3");
  return Vec256<uint16_t>{
      _mm256_dbsad_epu8(b.raw, a.raw, _MM_SHUFFLE(kIdx3, kIdx2, kIdx1, kIdx0))};
}
#endif

// ------------------------------ SaturatedAdd

// Returns a + b clamped to the destination range.

// Unsigned
HWY_API Vec256<uint8_t> SaturatedAdd(Vec256<uint8_t> a, Vec256<uint8_t> b) {
  return Vec256<uint8_t>{_mm256_adds_epu8(a.raw, b.raw)};
}
HWY_API Vec256<uint16_t> SaturatedAdd(Vec256<uint16_t> a, Vec256<uint16_t> b) {
  return Vec256<uint16_t>{_mm256_adds_epu16(a.raw, b.raw)};
}

// Signed
HWY_API Vec256<int8_t> SaturatedAdd(Vec256<int8_t> a, Vec256<int8_t> b) {
  return Vec256<int8_t>{_mm256_adds_epi8(a.raw, b.raw)};
}
HWY_API Vec256<int16_t> SaturatedAdd(Vec256<int16_t> a, Vec256<int16_t> b) {
  return Vec256<int16_t>{_mm256_adds_epi16(a.raw, b.raw)};
}

#if HWY_TARGET <= HWY_AVX3 && !HWY_IS_MSAN
HWY_API Vec256<int32_t> SaturatedAdd(Vec256<int32_t> a, Vec256<int32_t> b) {
  const DFromV<decltype(a)> d;
  const auto sum = a + b;
  const auto overflow_mask = MaskFromVec(
      Vec256<int32_t>{_mm256_ternarylogic_epi32(a.raw, b.raw, sum.raw, 0x42)});
  const auto i32_max = Set(d, LimitsMax<int32_t>());
  const Vec256<int32_t> overflow_result{_mm256_mask_ternarylogic_epi32(
      i32_max.raw, MaskFromVec(a).raw, i32_max.raw, i32_max.raw, 0x55)};
  return IfThenElse(overflow_mask, overflow_result, sum);
}

HWY_API Vec256<int64_t> SaturatedAdd(Vec256<int64_t> a, Vec256<int64_t> b) {
  const DFromV<decltype(a)> d;
  const auto sum = a + b;
  const auto overflow_mask = MaskFromVec(
      Vec256<int64_t>{_mm256_ternarylogic_epi64(a.raw, b.raw, sum.raw, 0x42)});
  const auto i64_max = Set(d, LimitsMax<int64_t>());
  const Vec256<int64_t> overflow_result{_mm256_mask_ternarylogic_epi64(
      i64_max.raw, MaskFromVec(a).raw, i64_max.raw, i64_max.raw, 0x55)};
  return IfThenElse(overflow_mask, overflow_result, sum);
}
#endif  // HWY_TARGET <= HWY_AVX3 && !HWY_IS_MSAN

// ------------------------------ SaturatedSub

// Returns a - b clamped to the destination range.

// Unsigned
HWY_API Vec256<uint8_t> SaturatedSub(Vec256<uint8_t> a, Vec256<uint8_t> b) {
  return Vec256<uint8_t>{_mm256_subs_epu8(a.raw, b.raw)};
}
HWY_API Vec256<uint16_t> SaturatedSub(Vec256<uint16_t> a, Vec256<uint16_t> b) {
  return Vec256<uint16_t>{_mm256_subs_epu16(a.raw, b.raw)};
}

// Signed
HWY_API Vec256<int8_t> SaturatedSub(Vec256<int8_t> a, Vec256<int8_t> b) {
  return Vec256<int8_t>{_mm256_subs_epi8(a.raw, b.raw)};
}
HWY_API Vec256<int16_t> SaturatedSub(Vec256<int16_t> a, Vec256<int16_t> b) {
  return Vec256<int16_t>{_mm256_subs_epi16(a.raw, b.raw)};
}

#if HWY_TARGET <= HWY_AVX3 && !HWY_IS_MSAN
HWY_API Vec256<int32_t> SaturatedSub(Vec256<int32_t> a, Vec256<int32_t> b) {
  const DFromV<decltype(a)> d;
  const auto diff = a - b;
  const auto overflow_mask = MaskFromVec(
      Vec256<int32_t>{_mm256_ternarylogic_epi32(a.raw, b.raw, diff.raw, 0x18)});
  const auto i32_max = Set(d, LimitsMax<int32_t>());
  const Vec256<int32_t> overflow_result{_mm256_mask_ternarylogic_epi32(
      i32_max.raw, MaskFromVec(a).raw, i32_max.raw, i32_max.raw, 0x55)};
  return IfThenElse(overflow_mask, overflow_result, diff);
}

HWY_API Vec256<int64_t> SaturatedSub(Vec256<int64_t> a, Vec256<int64_t> b) {
  const DFromV<decltype(a)> d;
  const auto diff = a - b;
  const auto overflow_mask = MaskFromVec(
      Vec256<int64_t>{_mm256_ternarylogic_epi64(a.raw, b.raw, diff.raw, 0x18)});
  const auto i64_max = Set(d, LimitsMax<int64_t>());
  const Vec256<int64_t> overflow_result{_mm256_mask_ternarylogic_epi64(
      i64_max.raw, MaskFromVec(a).raw, i64_max.raw, i64_max.raw, 0x55)};
  return IfThenElse(overflow_mask, overflow_result, diff);
}
#endif  // HWY_TARGET <= HWY_AVX3 && !HWY_IS_MSAN

// ------------------------------ Average

// Returns (a + b + 1) / 2

// Unsigned
HWY_API Vec256<uint8_t> AverageRound(Vec256<uint8_t> a, Vec256<uint8_t> b) {
  return Vec256<uint8_t>{_mm256_avg_epu8(a.raw, b.raw)};
}
HWY_API Vec256<uint16_t> AverageRound(Vec256<uint16_t> a, Vec256<uint16_t> b) {
  return Vec256<uint16_t>{_mm256_avg_epu16(a.raw, b.raw)};
}

// ------------------------------ Abs (Sub)

// Returns absolute value, except that LimitsMin() maps to LimitsMax() + 1.
HWY_API Vec256<int8_t> Abs(Vec256<int8_t> v) {
#if HWY_COMPILER_MSVC
  // Workaround for incorrect codegen? (wrong result)
  const DFromV<decltype(v)> d;
  const auto zero = Zero(d);
  return Vec256<int8_t>{_mm256_max_epi8(v.raw, (zero - v).raw)};
#else
  return Vec256<int8_t>{_mm256_abs_epi8(v.raw)};
#endif
}
HWY_API Vec256<int16_t> Abs(const Vec256<int16_t> v) {
  return Vec256<int16_t>{_mm256_abs_epi16(v.raw)};
}
HWY_API Vec256<int32_t> Abs(const Vec256<int32_t> v) {
  return Vec256<int32_t>{_mm256_abs_epi32(v.raw)};
}

#if HWY_TARGET <= HWY_AVX3
HWY_API Vec256<int64_t> Abs(const Vec256<int64_t> v) {
  return Vec256<int64_t>{_mm256_abs_epi64(v.raw)};
}
#endif

// ------------------------------ Integer multiplication

// Unsigned
HWY_API Vec256<uint16_t> operator*(Vec256<uint16_t> a, Vec256<uint16_t> b) {
  return Vec256<uint16_t>{_mm256_mullo_epi16(a.raw, b.raw)};
}
HWY_API Vec256<uint32_t> operator*(Vec256<uint32_t> a, Vec256<uint32_t> b) {
  return Vec256<uint32_t>{_mm256_mullo_epi32(a.raw, b.raw)};
}
#if HWY_TARGET <= HWY_AVX3
HWY_API Vec256<uint64_t> operator*(Vec256<uint64_t> a, Vec256<uint64_t> b) {
  return Vec256<uint64_t>{_mm256_mullo_epi64(a.raw, b.raw)};
}
#endif

// Signed
HWY_API Vec256<int16_t> operator*(Vec256<int16_t> a, Vec256<int16_t> b) {
  return Vec256<int16_t>{_mm256_mullo_epi16(a.raw, b.raw)};
}
HWY_API Vec256<int32_t> operator*(Vec256<int32_t> a, Vec256<int32_t> b) {
  return Vec256<int32_t>{_mm256_mullo_epi32(a.raw, b.raw)};
}
#if HWY_TARGET <= HWY_AVX3
HWY_API Vec256<int64_t> operator*(Vec256<int64_t> a, Vec256<int64_t> b) {
  return Vec256<int64_t>{_mm256_mullo_epi64(a.raw, b.raw)};
}
#endif

// Returns the upper 16 bits of a * b in each lane.
HWY_API Vec256<uint16_t> MulHigh(Vec256<uint16_t> a, Vec256<uint16_t> b) {
  return Vec256<uint16_t>{_mm256_mulhi_epu16(a.raw, b.raw)};
}
HWY_API Vec256<int16_t> MulHigh(Vec256<int16_t> a, Vec256<int16_t> b) {
  return Vec256<int16_t>{_mm256_mulhi_epi16(a.raw, b.raw)};
}

HWY_API Vec256<int16_t> MulFixedPoint15(Vec256<int16_t> a, Vec256<int16_t> b) {
  return Vec256<int16_t>{_mm256_mulhrs_epi16(a.raw, b.raw)};
}

// Multiplies even lanes (0, 2 ..) and places the double-wide result into
// even and the upper half into its odd neighbor lane.
HWY_API Vec256<int64_t> MulEven(Vec256<int32_t> a, Vec256<int32_t> b) {
  return Vec256<int64_t>{_mm256_mul_epi32(a.raw, b.raw)};
}
HWY_API Vec256<uint64_t> MulEven(Vec256<uint32_t> a, Vec256<uint32_t> b) {
  return Vec256<uint64_t>{_mm256_mul_epu32(a.raw, b.raw)};
}

// ------------------------------ ShiftLeft

#if HWY_TARGET <= HWY_AVX3_DL
namespace detail {
template <typename T>
HWY_API Vec256<T> GaloisAffine(Vec256<T> v, Vec256<uint64_t> matrix) {
  return Vec256<T>{_mm256_gf2p8affine_epi64_epi8(v.raw, matrix.raw, 0)};
}
}  // namespace detail
#endif  // HWY_TARGET <= HWY_AVX3_DL

template <int kBits>
HWY_API Vec256<uint16_t> ShiftLeft(Vec256<uint16_t> v) {
  return Vec256<uint16_t>{_mm256_slli_epi16(v.raw, kBits)};
}

template <int kBits>
HWY_API Vec256<uint32_t> ShiftLeft(Vec256<uint32_t> v) {
  return Vec256<uint32_t>{_mm256_slli_epi32(v.raw, kBits)};
}

template <int kBits>
HWY_API Vec256<uint64_t> ShiftLeft(Vec256<uint64_t> v) {
  return Vec256<uint64_t>{_mm256_slli_epi64(v.raw, kBits)};
}

template <int kBits>
HWY_API Vec256<int16_t> ShiftLeft(Vec256<int16_t> v) {
  return Vec256<int16_t>{_mm256_slli_epi16(v.raw, kBits)};
}

template <int kBits>
HWY_API Vec256<int32_t> ShiftLeft(Vec256<int32_t> v) {
  return Vec256<int32_t>{_mm256_slli_epi32(v.raw, kBits)};
}

template <int kBits>
HWY_API Vec256<int64_t> ShiftLeft(Vec256<int64_t> v) {
  return Vec256<int64_t>{_mm256_slli_epi64(v.raw, kBits)};
}

#if HWY_TARGET > HWY_AVX3_DL

template <int kBits, typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Vec256<T> ShiftLeft(const Vec256<T> v) {
  const Full256<T> d8;
  const RepartitionToWide<decltype(d8)> d16;
  const auto shifted = BitCast(d8, ShiftLeft<kBits>(BitCast(d16, v)));
  return kBits == 1
             ? (v + v)
             : (shifted & Set(d8, static_cast<T>((0xFF << kBits) & 0xFF)));
}

#endif  // HWY_TARGET > HWY_AVX3_DL

// ------------------------------ ShiftRight

template <int kBits>
HWY_API Vec256<uint16_t> ShiftRight(Vec256<uint16_t> v) {
  return Vec256<uint16_t>{_mm256_srli_epi16(v.raw, kBits)};
}

template <int kBits>
HWY_API Vec256<uint32_t> ShiftRight(Vec256<uint32_t> v) {
  return Vec256<uint32_t>{_mm256_srli_epi32(v.raw, kBits)};
}

template <int kBits>
HWY_API Vec256<uint64_t> ShiftRight(Vec256<uint64_t> v) {
  return Vec256<uint64_t>{_mm256_srli_epi64(v.raw, kBits)};
}

template <int kBits>
HWY_API Vec256<int16_t> ShiftRight(Vec256<int16_t> v) {
  return Vec256<int16_t>{_mm256_srai_epi16(v.raw, kBits)};
}

template <int kBits>
HWY_API Vec256<int32_t> ShiftRight(Vec256<int32_t> v) {
  return Vec256<int32_t>{_mm256_srai_epi32(v.raw, kBits)};
}

#if HWY_TARGET > HWY_AVX3_DL

template <int kBits>
HWY_API Vec256<uint8_t> ShiftRight(Vec256<uint8_t> v) {
  const Full256<uint8_t> d8;
  // Use raw instead of BitCast to support N=1.
  const Vec256<uint8_t> shifted{ShiftRight<kBits>(Vec256<uint16_t>{v.raw}).raw};
  return shifted & Set(d8, 0xFF >> kBits);
}

template <int kBits>
HWY_API Vec256<int8_t> ShiftRight(Vec256<int8_t> v) {
  const Full256<int8_t> di;
  const Full256<uint8_t> du;
  const auto shifted = BitCast(di, ShiftRight<kBits>(BitCast(du, v)));
  const auto shifted_sign = BitCast(di, Set(du, 0x80 >> kBits));
  return (shifted ^ shifted_sign) - shifted_sign;
}

#endif  // HWY_TARGET > HWY_AVX3_DL

// i64 is implemented after BroadcastSignBit.

// ------------------------------ RotateRight

// U8 RotateRight implementation on AVX3_DL is now in x86_512-inl.h as U8
// RotateRight uses detail::GaloisAffine on AVX3_DL

#if HWY_TARGET > HWY_AVX3_DL
template <int kBits>
HWY_API Vec256<uint8_t> RotateRight(const Vec256<uint8_t> v) {
  static_assert(0 <= kBits && kBits < 8, "Invalid shift count");
  if (kBits == 0) return v;
  // AVX3 does not support 8-bit.
  return Or(ShiftRight<kBits>(v), ShiftLeft<HWY_MIN(7, 8 - kBits)>(v));
}
#endif

template <int kBits>
HWY_API Vec256<uint16_t> RotateRight(const Vec256<uint16_t> v) {
  static_assert(0 <= kBits && kBits < 16, "Invalid shift count");
  if (kBits == 0) return v;
#if HWY_TARGET <= HWY_AVX3_DL
  return Vec256<uint16_t>{_mm256_shrdi_epi16(v.raw, v.raw, kBits)};
#else
  // AVX3 does not support 16-bit.
  return Or(ShiftRight<kBits>(v), ShiftLeft<HWY_MIN(15, 16 - kBits)>(v));
#endif
}

template <int kBits>
HWY_API Vec256<uint32_t> RotateRight(const Vec256<uint32_t> v) {
  static_assert(0 <= kBits && kBits < 32, "Invalid shift count");
#if HWY_TARGET <= HWY_AVX3
  return Vec256<uint32_t>{_mm256_ror_epi32(v.raw, kBits)};
#else
  if (kBits == 0) return v;
  return Or(ShiftRight<kBits>(v), ShiftLeft<HWY_MIN(31, 32 - kBits)>(v));
#endif
}

template <int kBits>
HWY_API Vec256<uint64_t> RotateRight(const Vec256<uint64_t> v) {
  static_assert(0 <= kBits && kBits < 64, "Invalid shift count");
#if HWY_TARGET <= HWY_AVX3
  return Vec256<uint64_t>{_mm256_ror_epi64(v.raw, kBits)};
#else
  if (kBits == 0) return v;
  return Or(ShiftRight<kBits>(v), ShiftLeft<HWY_MIN(63, 64 - kBits)>(v));
#endif
}

// ------------------------------ Rol/Ror
#if HWY_TARGET <= HWY_AVX3_DL
template <class T, HWY_IF_UI16(T)>
HWY_API Vec256<T> Ror(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_shrdv_epi16(a.raw, a.raw, b.raw)};
}
#endif  // HWY_TARGET <= HWY_AVX3_DL

#if HWY_TARGET <= HWY_AVX3

template <class T, HWY_IF_UI32(T)>
HWY_API Vec256<T> Rol(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_rolv_epi32(a.raw, b.raw)};
}

template <class T, HWY_IF_UI32(T)>
HWY_API Vec256<T> Ror(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_rorv_epi32(a.raw, b.raw)};
}

template <class T, HWY_IF_UI64(T)>
HWY_API Vec256<T> Rol(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_rolv_epi64(a.raw, b.raw)};
}

template <class T, HWY_IF_UI64(T)>
HWY_API Vec256<T> Ror(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_rorv_epi64(a.raw, b.raw)};
}

#endif

// ------------------------------ BroadcastSignBit (ShiftRight, compare, mask)

HWY_API Vec256<int8_t> BroadcastSignBit(const Vec256<int8_t> v) {
  const DFromV<decltype(v)> d;
  return VecFromMask(v < Zero(d));
}

HWY_API Vec256<int16_t> BroadcastSignBit(const Vec256<int16_t> v) {
  return ShiftRight<15>(v);
}

HWY_API Vec256<int32_t> BroadcastSignBit(const Vec256<int32_t> v) {
  return ShiftRight<31>(v);
}

#if HWY_TARGET <= HWY_AVX3

template <int kBits>
HWY_API Vec256<int64_t> ShiftRight(const Vec256<int64_t> v) {
  return Vec256<int64_t>{
      _mm256_srai_epi64(v.raw, static_cast<Shift64Count>(kBits))};
}

HWY_API Vec256<int64_t> BroadcastSignBit(const Vec256<int64_t> v) {
  return ShiftRight<63>(v);
}

#else  // AVX2

// Unlike above, this will be used to implement int64_t ShiftRight.
HWY_API Vec256<int64_t> BroadcastSignBit(const Vec256<int64_t> v) {
  const DFromV<decltype(v)> d;
  return VecFromMask(v < Zero(d));
}

template <int kBits>
HWY_API Vec256<int64_t> ShiftRight(const Vec256<int64_t> v) {
  const Full256<int64_t> di;
  const Full256<uint64_t> du;
  const auto right = BitCast(di, ShiftRight<kBits>(BitCast(du, v)));
  const auto sign = ShiftLeft<64 - kBits>(BroadcastSignBit(v));
  return right | sign;
}

#endif  // #if HWY_TARGET <= HWY_AVX3

// ------------------------------ IfNegativeThenElse (BroadcastSignBit)
HWY_API Vec256<int8_t> IfNegativeThenElse(Vec256<int8_t> v, Vec256<int8_t> yes,
                                          Vec256<int8_t> no) {
  // int8: AVX2 IfThenElse only looks at the MSB.
  return IfThenElse(MaskFromVec(v), yes, no);
}

template <typename T, HWY_IF_T_SIZE(T, 2)>
HWY_API Vec256<T> IfNegativeThenElse(Vec256<T> v, Vec256<T> yes, Vec256<T> no) {
  static_assert(IsSigned<T>(), "Only works for signed/float");

#if HWY_TARGET <= HWY_AVX3
  const auto mask = MaskFromVec(v);
#else
  // 16-bit: no native blendv on AVX2, so copy sign to lower byte's MSB.
  const DFromV<decltype(v)> d;
  const RebindToSigned<decltype(d)> di;
  const auto mask = MaskFromVec(BitCast(d, BroadcastSignBit(BitCast(di, v))));
#endif

  return IfThenElse(mask, yes, no);
}

template <typename T, HWY_IF_T_SIZE_ONE_OF(T, (1 << 4) | (1 << 8))>
HWY_API Vec256<T> IfNegativeThenElse(Vec256<T> v, Vec256<T> yes, Vec256<T> no) {
  static_assert(IsSigned<T>(), "Only works for signed/float");

#if HWY_TARGET <= HWY_AVX3
  // No need to cast to float on AVX3 as IfThenElse only looks at the MSB on
  // AVX3
  return IfThenElse(MaskFromVec(v), yes, no);
#else
  const DFromV<decltype(v)> d;
  const RebindToFloat<decltype(d)> df;
  // 32/64-bit: use float IfThenElse, which only looks at the MSB.
  const MFromD<decltype(df)> msb = MaskFromVec(BitCast(df, v));
  return BitCast(d, IfThenElse(msb, BitCast(df, yes), BitCast(df, no)));
#endif
}

// ------------------------------ IfNegativeThenNegOrUndefIfZero

HWY_API Vec256<int8_t> IfNegativeThenNegOrUndefIfZero(Vec256<int8_t> mask,
                                                      Vec256<int8_t> v) {
  return Vec256<int8_t>{_mm256_sign_epi8(v.raw, mask.raw)};
}

HWY_API Vec256<int16_t> IfNegativeThenNegOrUndefIfZero(Vec256<int16_t> mask,
                                                       Vec256<int16_t> v) {
  return Vec256<int16_t>{_mm256_sign_epi16(v.raw, mask.raw)};
}

HWY_API Vec256<int32_t> IfNegativeThenNegOrUndefIfZero(Vec256<int32_t> mask,
                                                       Vec256<int32_t> v) {
  return Vec256<int32_t>{_mm256_sign_epi32(v.raw, mask.raw)};
}

// ------------------------------ ShiftLeftSame

// Disable sign conversion warnings for GCC debug intrinsics.
HWY_DIAGNOSTICS(push)
HWY_DIAGNOSTICS_OFF(disable : 4245 4365, ignored "-Wsign-conversion")

HWY_API Vec256<uint16_t> ShiftLeftSame(const Vec256<uint16_t> v,
                                       const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<uint16_t>{_mm256_slli_epi16(v.raw, bits)};
  }
#endif
  return Vec256<uint16_t>{_mm256_sll_epi16(v.raw, _mm_cvtsi32_si128(bits))};
}
HWY_API Vec256<uint32_t> ShiftLeftSame(const Vec256<uint32_t> v,
                                       const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<uint32_t>{_mm256_slli_epi32(v.raw, bits)};
  }
#endif
  return Vec256<uint32_t>{_mm256_sll_epi32(v.raw, _mm_cvtsi32_si128(bits))};
}
HWY_API Vec256<uint64_t> ShiftLeftSame(const Vec256<uint64_t> v,
                                       const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<uint64_t>{_mm256_slli_epi64(v.raw, bits)};
  }
#endif
  return Vec256<uint64_t>{_mm256_sll_epi64(v.raw, _mm_cvtsi32_si128(bits))};
}

HWY_API Vec256<int16_t> ShiftLeftSame(const Vec256<int16_t> v, const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<int16_t>{_mm256_slli_epi16(v.raw, bits)};
  }
#endif
  return Vec256<int16_t>{_mm256_sll_epi16(v.raw, _mm_cvtsi32_si128(bits))};
}

HWY_API Vec256<int32_t> ShiftLeftSame(const Vec256<int32_t> v, const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<int32_t>{_mm256_slli_epi32(v.raw, bits)};
  }
#endif
  return Vec256<int32_t>{_mm256_sll_epi32(v.raw, _mm_cvtsi32_si128(bits))};
}

HWY_API Vec256<int64_t> ShiftLeftSame(const Vec256<int64_t> v, const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<int64_t>{_mm256_slli_epi64(v.raw, bits)};
  }
#endif
  return Vec256<int64_t>{_mm256_sll_epi64(v.raw, _mm_cvtsi32_si128(bits))};
}

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Vec256<T> ShiftLeftSame(const Vec256<T> v, const int bits) {
  const Full256<T> d8;
  const RepartitionToWide<decltype(d8)> d16;
  const auto shifted = BitCast(d8, ShiftLeftSame(BitCast(d16, v), bits));
  return shifted & Set(d8, static_cast<T>((0xFF << bits) & 0xFF));
}

// ------------------------------ ShiftRightSame (BroadcastSignBit)

HWY_API Vec256<uint16_t> ShiftRightSame(const Vec256<uint16_t> v,
                                        const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<uint16_t>{_mm256_srli_epi16(v.raw, bits)};
  }
#endif
  return Vec256<uint16_t>{_mm256_srl_epi16(v.raw, _mm_cvtsi32_si128(bits))};
}
HWY_API Vec256<uint32_t> ShiftRightSame(const Vec256<uint32_t> v,
                                        const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<uint32_t>{_mm256_srli_epi32(v.raw, bits)};
  }
#endif
  return Vec256<uint32_t>{_mm256_srl_epi32(v.raw, _mm_cvtsi32_si128(bits))};
}
HWY_API Vec256<uint64_t> ShiftRightSame(const Vec256<uint64_t> v,
                                        const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<uint64_t>{_mm256_srli_epi64(v.raw, bits)};
  }
#endif
  return Vec256<uint64_t>{_mm256_srl_epi64(v.raw, _mm_cvtsi32_si128(bits))};
}

HWY_API Vec256<uint8_t> ShiftRightSame(Vec256<uint8_t> v, const int bits) {
  const Full256<uint8_t> d8;
  const RepartitionToWide<decltype(d8)> d16;
  const auto shifted = BitCast(d8, ShiftRightSame(BitCast(d16, v), bits));
  return shifted & Set(d8, static_cast<uint8_t>(0xFF >> bits));
}

HWY_API Vec256<int16_t> ShiftRightSame(const Vec256<int16_t> v,
                                       const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<int16_t>{_mm256_srai_epi16(v.raw, bits)};
  }
#endif
  return Vec256<int16_t>{_mm256_sra_epi16(v.raw, _mm_cvtsi32_si128(bits))};
}

HWY_API Vec256<int32_t> ShiftRightSame(const Vec256<int32_t> v,
                                       const int bits) {
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<int32_t>{_mm256_srai_epi32(v.raw, bits)};
  }
#endif
  return Vec256<int32_t>{_mm256_sra_epi32(v.raw, _mm_cvtsi32_si128(bits))};
}
HWY_API Vec256<int64_t> ShiftRightSame(const Vec256<int64_t> v,
                                       const int bits) {
#if HWY_TARGET <= HWY_AVX3
#if HWY_COMPILER_GCC
  if (__builtin_constant_p(bits)) {
    return Vec256<int64_t>{
        _mm256_srai_epi64(v.raw, static_cast<Shift64Count>(bits))};
  }
#endif
  return Vec256<int64_t>{_mm256_sra_epi64(v.raw, _mm_cvtsi32_si128(bits))};
#else
  const Full256<int64_t> di;
  const Full256<uint64_t> du;
  const auto right = BitCast(di, ShiftRightSame(BitCast(du, v), bits));
  const auto sign = ShiftLeftSame(BroadcastSignBit(v), 64 - bits);
  return right | sign;
#endif
}

HWY_API Vec256<int8_t> ShiftRightSame(Vec256<int8_t> v, const int bits) {
  const Full256<int8_t> di;
  const Full256<uint8_t> du;
  const auto shifted = BitCast(di, ShiftRightSame(BitCast(du, v), bits));
  const auto shifted_sign =
      BitCast(di, Set(du, static_cast<uint8_t>(0x80 >> bits)));
  return (shifted ^ shifted_sign) - shifted_sign;
}

HWY_DIAGNOSTICS(pop)

// ------------------------------ Neg (Xor, Sub)

// Tag dispatch instead of SFINAE for MSVC 2017 compatibility
namespace detail {

template <typename T>
HWY_INLINE Vec256<T> Neg(hwy::FloatTag /*tag*/, const Vec256<T> v) {
  const DFromV<decltype(v)> d;
  return Xor(v, SignBit(d));
}

template <typename T>
HWY_INLINE Vec256<T> Neg(hwy::SpecialTag /*tag*/, const Vec256<T> v) {
  const DFromV<decltype(v)> d;
  return Xor(v, SignBit(d));
}

// Not floating-point
template <typename T>
HWY_INLINE Vec256<T> Neg(hwy::SignedTag /*tag*/, const Vec256<T> v) {
  const DFromV<decltype(v)> d;
  return Zero(d) - v;
}

}  // namespace detail

template <typename T>
HWY_API Vec256<T> Neg(const Vec256<T> v) {
  return detail::Neg(hwy::TypeTag<T>(), v);
}

// ------------------------------ Floating-point mul / div

#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> operator*(Vec256<float16_t> a, Vec256<float16_t> b) {
  return Vec256<float16_t>{_mm256_mul_ph(a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> operator*(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_mul_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> operator*(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_mul_pd(a.raw, b.raw)};
}

#if HWY_TARGET <= HWY_AVX3

#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> MulByFloorPow2(Vec256<float16_t> a,
                                         Vec256<float16_t> b) {
  return Vec256<float16_t>{_mm256_scalef_ph(a.raw, b.raw)};
}
#endif

HWY_API Vec256<float> MulByFloorPow2(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_scalef_ps(a.raw, b.raw)};
}

HWY_API Vec256<double> MulByFloorPow2(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_scalef_pd(a.raw, b.raw)};
}

#endif  // HWY_TARGET <= HWY_AVX3

#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> operator/(Vec256<float16_t> a, Vec256<float16_t> b) {
  return Vec256<float16_t>{_mm256_div_ph(a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> operator/(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_div_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> operator/(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_div_pd(a.raw, b.raw)};
}

// Approximate reciprocal
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> ApproximateReciprocal(Vec256<float16_t> v) {
  return Vec256<float16_t>{_mm256_rcp_ph(v.raw)};
}
#endif  // HWY_HAVE_FLOAT16

HWY_API Vec256<float> ApproximateReciprocal(Vec256<float> v) {
  return Vec256<float>{_mm256_rcp_ps(v.raw)};
}

#if HWY_TARGET <= HWY_AVX3
HWY_API Vec256<double> ApproximateReciprocal(Vec256<double> v) {
  return Vec256<double>{_mm256_rcp14_pd(v.raw)};
}
#endif

// ------------------------------ GetExponent

#if HWY_TARGET <= HWY_AVX3

#if HWY_HAVE_FLOAT16
template <class V, HWY_IF_F16(TFromV<V>), HWY_IF_V_SIZE_V(V, 32)>
HWY_API V GetExponent(V v) {
  return V{_mm256_getexp_ph(v.raw)};
}
#endif
template <class V, HWY_IF_F32(TFromV<V>), HWY_IF_V_SIZE_V(V, 32)>
HWY_API V GetExponent(V v) {
  return V{_mm256_getexp_ps(v.raw)};
}
template <class V, HWY_IF_F64(TFromV<V>), HWY_IF_V_SIZE_V(V, 32)>
HWY_API V GetExponent(V v) {
  return V{_mm256_getexp_pd(v.raw)};
}

#endif

// ------------------------------ MaskedMinOr

#if HWY_TARGET <= HWY_AVX3

template <typename T, HWY_IF_U8(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_epu8(no.raw, m.raw, a.raw, b.raw)};
}
template <typename T, HWY_IF_I8(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_epi8(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U16(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_epu16(no.raw, m.raw, a.raw, b.raw)};
}
template <typename T, HWY_IF_I16(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_epi16(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U32(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_epu32(no.raw, m.raw, a.raw, b.raw)};
}
template <typename T, HWY_IF_I32(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_epi32(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U64(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_epu64(no.raw, m.raw, a.raw, b.raw)};
}
template <typename T, HWY_IF_I64(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_epi64(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_F32(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_ps(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_F64(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_pd(no.raw, m.raw, a.raw, b.raw)};
}

#if HWY_HAVE_FLOAT16
template <typename T, HWY_IF_F16(T)>
HWY_API Vec256<T> MaskedMinOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_min_ph(no.raw, m.raw, a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16

// ------------------------------ MaskedMaxOr

template <typename T, HWY_IF_U8(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_epu8(no.raw, m.raw, a.raw, b.raw)};
}
template <typename T, HWY_IF_I8(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_epi8(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U16(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_epu16(no.raw, m.raw, a.raw, b.raw)};
}
template <typename T, HWY_IF_I16(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_epi16(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U32(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_epu32(no.raw, m.raw, a.raw, b.raw)};
}
template <typename T, HWY_IF_I32(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_epi32(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U64(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_epu64(no.raw, m.raw, a.raw, b.raw)};
}
template <typename T, HWY_IF_I64(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_epi64(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_F32(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_ps(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_F64(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_pd(no.raw, m.raw, a.raw, b.raw)};
}

#if HWY_HAVE_FLOAT16
template <typename T, HWY_IF_F16(T)>
HWY_API Vec256<T> MaskedMaxOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_max_ph(no.raw, m.raw, a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16

// ------------------------------ MaskedAddOr

template <typename T, HWY_IF_UI8(T)>
HWY_API Vec256<T> MaskedAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_add_epi8(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_UI16(T)>
HWY_API Vec256<T> MaskedAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_add_epi16(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_UI32(T)>
HWY_API Vec256<T> MaskedAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_add_epi32(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_UI64(T)>
HWY_API Vec256<T> MaskedAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_add_epi64(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_F32(T)>
HWY_API Vec256<T> MaskedAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_add_ps(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_F64(T)>
HWY_API Vec256<T> MaskedAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_add_pd(no.raw, m.raw, a.raw, b.raw)};
}

#if HWY_HAVE_FLOAT16
template <typename T, HWY_IF_F16(T)>
HWY_API Vec256<T> MaskedAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_add_ph(no.raw, m.raw, a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16

// ------------------------------ MaskedSubOr

template <typename T, HWY_IF_UI8(T)>
HWY_API Vec256<T> MaskedSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_sub_epi8(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_UI16(T)>
HWY_API Vec256<T> MaskedSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_sub_epi16(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_UI32(T)>
HWY_API Vec256<T> MaskedSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_sub_epi32(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_UI64(T)>
HWY_API Vec256<T> MaskedSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_sub_epi64(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_F32(T)>
HWY_API Vec256<T> MaskedSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_sub_ps(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_F64(T)>
HWY_API Vec256<T> MaskedSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_sub_pd(no.raw, m.raw, a.raw, b.raw)};
}

#if HWY_HAVE_FLOAT16
template <typename T, HWY_IF_F16(T)>
HWY_API Vec256<T> MaskedSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                              Vec256<T> b) {
  return Vec256<T>{_mm256_mask_sub_ph(no.raw, m.raw, a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16

// ------------------------------ MaskedMulOr

HWY_API Vec256<float> MaskedMulOr(Vec256<float> no, Mask256<float> m,
                                  Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_mask_mul_ps(no.raw, m.raw, a.raw, b.raw)};
}

HWY_API Vec256<double> MaskedMulOr(Vec256<double> no, Mask256<double> m,
                                   Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_mask_mul_pd(no.raw, m.raw, a.raw, b.raw)};
}

#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> MaskedMulOr(Vec256<float16_t> no,
                                      Mask256<float16_t> m, Vec256<float16_t> a,
                                      Vec256<float16_t> b) {
  return Vec256<float16_t>{_mm256_mask_mul_ph(no.raw, m.raw, a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16

// ------------------------------ MaskedDivOr

HWY_API Vec256<float> MaskedDivOr(Vec256<float> no, Mask256<float> m,
                                  Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_mask_div_ps(no.raw, m.raw, a.raw, b.raw)};
}

HWY_API Vec256<double> MaskedDivOr(Vec256<double> no, Mask256<double> m,
                                   Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_mask_div_pd(no.raw, m.raw, a.raw, b.raw)};
}

#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> MaskedDivOr(Vec256<float16_t> no,
                                      Mask256<float16_t> m, Vec256<float16_t> a,
                                      Vec256<float16_t> b) {
  return Vec256<float16_t>{_mm256_mask_div_ph(no.raw, m.raw, a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16

// ------------------------------ MaskedSatAddOr

template <typename T, HWY_IF_I8(T)>
HWY_API Vec256<T> MaskedSatAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                                 Vec256<T> b) {
  return Vec256<T>{_mm256_mask_adds_epi8(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U8(T)>
HWY_API Vec256<T> MaskedSatAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                                 Vec256<T> b) {
  return Vec256<T>{_mm256_mask_adds_epu8(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_I16(T)>
HWY_API Vec256<T> MaskedSatAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                                 Vec256<T> b) {
  return Vec256<T>{_mm256_mask_adds_epi16(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U16(T)>
HWY_API Vec256<T> MaskedSatAddOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                                 Vec256<T> b) {
  return Vec256<T>{_mm256_mask_adds_epu16(no.raw, m.raw, a.raw, b.raw)};
}

// ------------------------------ MaskedSatSubOr

template <typename T, HWY_IF_I8(T)>
HWY_API Vec256<T> MaskedSatSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                                 Vec256<T> b) {
  return Vec256<T>{_mm256_mask_subs_epi8(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U8(T)>
HWY_API Vec256<T> MaskedSatSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                                 Vec256<T> b) {
  return Vec256<T>{_mm256_mask_subs_epu8(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_I16(T)>
HWY_API Vec256<T> MaskedSatSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                                 Vec256<T> b) {
  return Vec256<T>{_mm256_mask_subs_epi16(no.raw, m.raw, a.raw, b.raw)};
}

template <typename T, HWY_IF_U16(T)>
HWY_API Vec256<T> MaskedSatSubOr(Vec256<T> no, Mask256<T> m, Vec256<T> a,
                                 Vec256<T> b) {
  return Vec256<T>{_mm256_mask_subs_epu16(no.raw, m.raw, a.raw, b.raw)};
}

#endif  // HWY_TARGET <= HWY_AVX3

// ------------------------------ Floating-point multiply-add variants

#if HWY_HAVE_FLOAT16

HWY_API Vec256<float16_t> MulAdd(Vec256<float16_t> mul, Vec256<float16_t> x,
                                 Vec256<float16_t> add) {
  return Vec256<float16_t>{_mm256_fmadd_ph(mul.raw, x.raw, add.raw)};
}

HWY_API Vec256<float16_t> NegMulAdd(Vec256<float16_t> mul, Vec256<float16_t> x,
                                    Vec256<float16_t> add) {
  return Vec256<float16_t>{_mm256_fnmadd_ph(mul.raw, x.raw, add.raw)};
}

HWY_API Vec256<float16_t> MulSub(Vec256<float16_t> mul, Vec256<float16_t> x,
                                 Vec256<float16_t> sub) {
  return Vec256<float16_t>{_mm256_fmsub_ph(mul.raw, x.raw, sub.raw)};
}

HWY_API Vec256<float16_t> NegMulSub(Vec256<float16_t> mul, Vec256<float16_t> x,
                                    Vec256<float16_t> sub) {
  return Vec256<float16_t>{_mm256_fnmsub_ph(mul.raw, x.raw, sub.raw)};
}

#endif  // HWY_HAVE_FLOAT16

HWY_API Vec256<float> MulAdd(Vec256<float> mul, Vec256<float> x,
                             Vec256<float> add) {
#ifdef HWY_DISABLE_BMI2_FMA
  return mul * x + add;
#else
  return Vec256<float>{_mm256_fmadd_ps(mul.raw, x.raw, add.raw)};
#endif
}
HWY_API Vec256<double> MulAdd(Vec256<double> mul, Vec256<double> x,
                              Vec256<double> add) {
#ifdef HWY_DISABLE_BMI2_FMA
  return mul * x + add;
#else
  return Vec256<double>{_mm256_fmadd_pd(mul.raw, x.raw, add.raw)};
#endif
}

HWY_API Vec256<float> NegMulAdd(Vec256<float> mul, Vec256<float> x,
                                Vec256<float> add) {
#ifdef HWY_DISABLE_BMI2_FMA
  return add - mul * x;
#else
  return Vec256<float>{_mm256_fnmadd_ps(mul.raw, x.raw, add.raw)};
#endif
}
HWY_API Vec256<double> NegMulAdd(Vec256<double> mul, Vec256<double> x,
                                 Vec256<double> add) {
#ifdef HWY_DISABLE_BMI2_FMA
  return add - mul * x;
#else
  return Vec256<double>{_mm256_fnmadd_pd(mul.raw, x.raw, add.raw)};
#endif
}

HWY_API Vec256<float> MulSub(Vec256<float> mul, Vec256<float> x,
                             Vec256<float> sub) {
#ifdef HWY_DISABLE_BMI2_FMA
  return mul * x - sub;
#else
  return Vec256<float>{_mm256_fmsub_ps(mul.raw, x.raw, sub.raw)};
#endif
}
HWY_API Vec256<double> MulSub(Vec256<double> mul, Vec256<double> x,
                              Vec256<double> sub) {
#ifdef HWY_DISABLE_BMI2_FMA
  return mul * x - sub;
#else
  return Vec256<double>{_mm256_fmsub_pd(mul.raw, x.raw, sub.raw)};
#endif
}

HWY_API Vec256<float> NegMulSub(Vec256<float> mul, Vec256<float> x,
                                Vec256<float> sub) {
#ifdef HWY_DISABLE_BMI2_FMA
  return Neg(mul * x) - sub;
#else
  return Vec256<float>{_mm256_fnmsub_ps(mul.raw, x.raw, sub.raw)};
#endif
}
HWY_API Vec256<double> NegMulSub(Vec256<double> mul, Vec256<double> x,
                                 Vec256<double> sub) {
#ifdef HWY_DISABLE_BMI2_FMA
  return Neg(mul * x) - sub;
#else
  return Vec256<double>{_mm256_fnmsub_pd(mul.raw, x.raw, sub.raw)};
#endif
}

#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> MulAddSub(Vec256<float16_t> mul, Vec256<float16_t> x,
                                    Vec256<float16_t> sub_or_add) {
  return Vec256<float16_t>{_mm256_fmaddsub_ph(mul.raw, x.raw, sub_or_add.raw)};
}
#endif  // HWY_HAVE_FLOAT16

HWY_API Vec256<float> MulAddSub(Vec256<float> mul, Vec256<float> x,
                                Vec256<float> sub_or_add) {
#ifdef HWY_DISABLE_BMI2_FMA
  return AddSub(mul * x, sub_or_add);
#else
  return Vec256<float>{_mm256_fmaddsub_ps(mul.raw, x.raw, sub_or_add.raw)};
#endif
}

HWY_API Vec256<double> MulAddSub(Vec256<double> mul, Vec256<double> x,
                                 Vec256<double> sub_or_add) {
#ifdef HWY_DISABLE_BMI2_FMA
  return AddSub(mul * x, sub_or_add);
#else
  return Vec256<double>{_mm256_fmaddsub_pd(mul.raw, x.raw, sub_or_add.raw)};
#endif
}

// ------------------------------ Floating-point square root

// Full precision square root
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> Sqrt(Vec256<float16_t> v) {
  return Vec256<float16_t>{_mm256_sqrt_ph(v.raw)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> Sqrt(Vec256<float> v) {
  return Vec256<float>{_mm256_sqrt_ps(v.raw)};
}
HWY_API Vec256<double> Sqrt(Vec256<double> v) {
  return Vec256<double>{_mm256_sqrt_pd(v.raw)};
}

// Approximate reciprocal square root
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> ApproximateReciprocalSqrt(Vec256<float16_t> v) {
  return Vec256<float16_t>{_mm256_rsqrt_ph(v.raw)};
}
#endif
HWY_API Vec256<float> ApproximateReciprocalSqrt(Vec256<float> v) {
  return Vec256<float>{_mm256_rsqrt_ps(v.raw)};
}

#if HWY_TARGET <= HWY_AVX3
HWY_API Vec256<double> ApproximateReciprocalSqrt(Vec256<double> v) {
#if HWY_COMPILER_MSVC
  const DFromV<decltype(v)> d;
  return Vec256<double>{_mm256_mask_rsqrt14_pd(
      Undefined(d).raw, static_cast<__mmask8>(0xFF), v.raw)};
#else
  return Vec256<double>{_mm256_rsqrt14_pd(v.raw)};
#endif
}
#endif

// ------------------------------ Floating-point rounding

// Toward nearest integer, tie to even
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> Round(Vec256<float16_t> v) {
  return Vec256<float16_t>{_mm256_roundscale_ph(
      v.raw, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> Round(Vec256<float> v) {
  return Vec256<float>{
      _mm256_round_ps(v.raw, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)};
}
HWY_API Vec256<double> Round(Vec256<double> v) {
  return Vec256<double>{
      _mm256_round_pd(v.raw, _MM_FROUND_TO_NEAREST_INT | _MM_FROUND_NO_EXC)};
}

// Toward zero, aka truncate
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> Trunc(Vec256<float16_t> v) {
  return Vec256<float16_t>{
      _mm256_roundscale_ph(v.raw, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> Trunc(Vec256<float> v) {
  return Vec256<float>{
      _mm256_round_ps(v.raw, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)};
}
HWY_API Vec256<double> Trunc(Vec256<double> v) {
  return Vec256<double>{
      _mm256_round_pd(v.raw, _MM_FROUND_TO_ZERO | _MM_FROUND_NO_EXC)};
}

// Toward +infinity, aka ceiling
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> Ceil(Vec256<float16_t> v) {
  return Vec256<float16_t>{
      _mm256_roundscale_ph(v.raw, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> Ceil(Vec256<float> v) {
  return Vec256<float>{
      _mm256_round_ps(v.raw, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)};
}
HWY_API Vec256<double> Ceil(Vec256<double> v) {
  return Vec256<double>{
      _mm256_round_pd(v.raw, _MM_FROUND_TO_POS_INF | _MM_FROUND_NO_EXC)};
}

// Toward -infinity, aka floor
#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> Floor(Vec256<float16_t> v) {
  return Vec256<float16_t>{
      _mm256_roundscale_ph(v.raw, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> Floor(Vec256<float> v) {
  return Vec256<float>{
      _mm256_round_ps(v.raw, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)};
}
HWY_API Vec256<double> Floor(Vec256<double> v) {
  return Vec256<double>{
      _mm256_round_pd(v.raw, _MM_FROUND_TO_NEG_INF | _MM_FROUND_NO_EXC)};
}

// ------------------------------ Floating-point classification

#if HWY_HAVE_FLOAT16 || HWY_IDE

HWY_API Mask256<float16_t> IsNaN(Vec256<float16_t> v) {
  return Mask256<float16_t>{_mm256_fpclass_ph_mask(
      v.raw, HWY_X86_FPCLASS_SNAN | HWY_X86_FPCLASS_QNAN)};
}

HWY_API Mask256<float16_t> IsEitherNaN(Vec256<float16_t> a,
                                       Vec256<float16_t> b) {
  // Work around warnings in the intrinsic definitions (passing -1 as a mask).
  HWY_DIAGNOSTICS(push)
  HWY_DIAGNOSTICS_OFF(disable : 4245 4365, ignored "-Wsign-conversion")
  return Mask256<float16_t>{_mm256_cmp_ph_mask(a.raw, b.raw, _CMP_UNORD_Q)};
  HWY_DIAGNOSTICS(pop)
}

HWY_API Mask256<float16_t> IsInf(Vec256<float16_t> v) {
  return Mask256<float16_t>{_mm256_fpclass_ph_mask(
      v.raw, HWY_X86_FPCLASS_NEG_INF | HWY_X86_FPCLASS_POS_INF)};
}

HWY_API Mask256<float16_t> IsFinite(Vec256<float16_t> v) {
  // fpclass doesn't have a flag for positive, so we have to check for inf/NaN
  // and negate the mask.
  return Not(Mask256<float16_t>{_mm256_fpclass_ph_mask(
      v.raw, HWY_X86_FPCLASS_SNAN | HWY_X86_FPCLASS_QNAN |
                 HWY_X86_FPCLASS_NEG_INF | HWY_X86_FPCLASS_POS_INF)});
}

#endif  // HWY_HAVE_FLOAT16

HWY_API Mask256<float> IsNaN(Vec256<float> v) {
#if HWY_TARGET <= HWY_AVX3
  return Mask256<float>{_mm256_fpclass_ps_mask(
      v.raw, HWY_X86_FPCLASS_SNAN | HWY_X86_FPCLASS_QNAN)};
#else
  return Mask256<float>{_mm256_cmp_ps(v.raw, v.raw, _CMP_UNORD_Q)};
#endif
}
HWY_API Mask256<double> IsNaN(Vec256<double> v) {
#if HWY_TARGET <= HWY_AVX3
  return Mask256<double>{_mm256_fpclass_pd_mask(
      v.raw, HWY_X86_FPCLASS_SNAN | HWY_X86_FPCLASS_QNAN)};
#else
  return Mask256<double>{_mm256_cmp_pd(v.raw, v.raw, _CMP_UNORD_Q)};
#endif
}

HWY_API Mask256<float> IsEitherNaN(Vec256<float> a, Vec256<float> b) {
#if HWY_TARGET <= HWY_AVX3
  return Mask256<float>{_mm256_cmp_ps_mask(a.raw, b.raw, _CMP_UNORD_Q)};
#else
  return Mask256<float>{_mm256_cmp_ps(a.raw, b.raw, _CMP_UNORD_Q)};
#endif
}

HWY_API Mask256<double> IsEitherNaN(Vec256<double> a, Vec256<double> b) {
#if HWY_TARGET <= HWY_AVX3
  return Mask256<double>{_mm256_cmp_pd_mask(a.raw, b.raw, _CMP_UNORD_Q)};
#else
  return Mask256<double>{_mm256_cmp_pd(a.raw, b.raw, _CMP_UNORD_Q)};
#endif
}

#if HWY_TARGET <= HWY_AVX3

HWY_API Mask256<float> IsInf(Vec256<float> v) {
  return Mask256<float>{_mm256_fpclass_ps_mask(
      v.raw, HWY_X86_FPCLASS_NEG_INF | HWY_X86_FPCLASS_POS_INF)};
}
HWY_API Mask256<double> IsInf(Vec256<double> v) {
  return Mask256<double>{_mm256_fpclass_pd_mask(
      v.raw, HWY_X86_FPCLASS_NEG_INF | HWY_X86_FPCLASS_POS_INF)};
}

HWY_API Mask256<float> IsFinite(Vec256<float> v) {
  // fpclass doesn't have a flag for positive, so we have to check for inf/NaN
  // and negate the mask.
  return Not(Mask256<float>{_mm256_fpclass_ps_mask(
      v.raw, HWY_X86_FPCLASS_SNAN | HWY_X86_FPCLASS_QNAN |
                 HWY_X86_FPCLASS_NEG_INF | HWY_X86_FPCLASS_POS_INF)});
}
HWY_API Mask256<double> IsFinite(Vec256<double> v) {
  return Not(Mask256<double>{_mm256_fpclass_pd_mask(
      v.raw, HWY_X86_FPCLASS_SNAN | HWY_X86_FPCLASS_QNAN |
                 HWY_X86_FPCLASS_NEG_INF | HWY_X86_FPCLASS_POS_INF)});
}

#endif  // HWY_TARGET <= HWY_AVX3

// ================================================== MEMORY

// ------------------------------ Load

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT_NOR_SPECIAL_D(D)>
HWY_API VFromD<D> Load(D /* tag */, const TFromD<D>* HWY_RESTRICT aligned) {
  return VFromD<D>{
      _mm256_load_si256(reinterpret_cast<const __m256i*>(aligned))};
}
// bfloat16_t is handled by x86_128-inl.h.
#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API Vec256<float16_t> Load(D /* tag */,
                               const float16_t* HWY_RESTRICT aligned) {
  return Vec256<float16_t>{_mm256_load_ph(aligned)};
}
#endif
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> Load(D /* tag */, const float* HWY_RESTRICT aligned) {
  return Vec256<float>{_mm256_load_ps(aligned)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> Load(D /* tag */, const double* HWY_RESTRICT aligned) {
  return Vec256<double>{_mm256_load_pd(aligned)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT_NOR_SPECIAL_D(D)>
HWY_API VFromD<D> LoadU(D /* tag */, const TFromD<D>* HWY_RESTRICT p) {
  return VFromD<D>{_mm256_loadu_si256(reinterpret_cast<const __m256i*>(p))};
}
// bfloat16_t is handled by x86_128-inl.h.
#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API Vec256<float16_t> LoadU(D /* tag */, const float16_t* HWY_RESTRICT p) {
  return Vec256<float16_t>{_mm256_loadu_ph(p)};
}
#endif
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> LoadU(D /* tag */, const float* HWY_RESTRICT p) {
  return Vec256<float>{_mm256_loadu_ps(p)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> LoadU(D /* tag */, const double* HWY_RESTRICT p) {
  return Vec256<double>{_mm256_loadu_pd(p)};
}

// ------------------------------ MaskedLoad

#if HWY_TARGET <= HWY_AVX3

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> MaskedLoad(MFromD<D> m, D /* tag */,
                             const TFromD<D>* HWY_RESTRICT p) {
  return VFromD<D>{_mm256_maskz_loadu_epi8(m.raw, p)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> MaskedLoad(MFromD<D> m, D d,
                             const TFromD<D>* HWY_RESTRICT p) {
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  return BitCast(d, VFromD<decltype(du)>{_mm256_maskz_loadu_epi16(m.raw, p)});
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> MaskedLoad(MFromD<D> m, D /* tag */,
                             const TFromD<D>* HWY_RESTRICT p) {
  return VFromD<D>{_mm256_maskz_loadu_epi32(m.raw, p)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API VFromD<D> MaskedLoad(MFromD<D> m, D /* tag */,
                             const TFromD<D>* HWY_RESTRICT p) {
  return VFromD<D>{_mm256_maskz_loadu_epi64(m.raw, p)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> MaskedLoad(Mask256<float> m, D /* tag */,
                                 const float* HWY_RESTRICT p) {
  return Vec256<float>{_mm256_maskz_loadu_ps(m.raw, p)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> MaskedLoad(Mask256<double> m, D /* tag */,
                                  const double* HWY_RESTRICT p) {
  return Vec256<double>{_mm256_maskz_loadu_pd(m.raw, p)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> MaskedLoadOr(VFromD<D> v, MFromD<D> m, D /* tag */,
                               const TFromD<D>* HWY_RESTRICT p) {
  return VFromD<D>{_mm256_mask_loadu_epi8(v.raw, m.raw, p)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> MaskedLoadOr(VFromD<D> v, MFromD<D> m, D d,
                               const TFromD<D>* HWY_RESTRICT p) {
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  return BitCast(d, VFromD<decltype(du)>{
                        _mm256_mask_loadu_epi16(BitCast(du, v).raw, m.raw, p)});
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> MaskedLoadOr(VFromD<D> v, MFromD<D> m, D /* tag */,
                               const TFromD<D>* HWY_RESTRICT p) {
  return VFromD<D>{_mm256_mask_loadu_epi32(v.raw, m.raw, p)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API VFromD<D> MaskedLoadOr(VFromD<D> v, MFromD<D> m, D /* tag */,
                               const TFromD<D>* HWY_RESTRICT p) {
  return VFromD<D>{_mm256_mask_loadu_epi64(v.raw, m.raw, p)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> MaskedLoadOr(VFromD<D> v, Mask256<float> m, D /* tag */,
                                   const float* HWY_RESTRICT p) {
  return Vec256<float>{_mm256_mask_loadu_ps(v.raw, m.raw, p)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> MaskedLoadOr(VFromD<D> v, Mask256<double> m, D /* tag */,
                                    const double* HWY_RESTRICT p) {
  return Vec256<double>{_mm256_mask_loadu_pd(v.raw, m.raw, p)};
}

#else  //  AVX2

// There is no maskload_epi8/16, so blend instead.
template <class D, HWY_IF_V_SIZE_D(D, 32),
          HWY_IF_T_SIZE_ONE_OF_D(D, (1 << 1) | (1 << 2))>
HWY_API VFromD<D> MaskedLoad(MFromD<D> m, D d,
                             const TFromD<D>* HWY_RESTRICT p) {
  return IfThenElseZero(m, LoadU(d, p));
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> MaskedLoad(MFromD<D> m, D /* tag */,
                             const TFromD<D>* HWY_RESTRICT p) {
  auto pi = reinterpret_cast<const int*>(p);  // NOLINT
  return VFromD<D>{_mm256_maskload_epi32(pi, m.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API VFromD<D> MaskedLoad(MFromD<D> m, D /* tag */,
                             const TFromD<D>* HWY_RESTRICT p) {
  auto pi = reinterpret_cast<const long long*>(p);  // NOLINT
  return VFromD<D>{_mm256_maskload_epi64(pi, m.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> MaskedLoad(Mask256<float> m, D d,
                                 const float* HWY_RESTRICT p) {
  const Vec256<int32_t> mi =
      BitCast(RebindToSigned<decltype(d)>(), VecFromMask(d, m));
  return Vec256<float>{_mm256_maskload_ps(p, mi.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> MaskedLoad(Mask256<double> m, D d,
                                  const double* HWY_RESTRICT p) {
  const Vec256<int64_t> mi =
      BitCast(RebindToSigned<decltype(d)>(), VecFromMask(d, m));
  return Vec256<double>{_mm256_maskload_pd(p, mi.raw)};
}

#endif

// ------------------------------ LoadDup128

// Loads 128 bit and duplicates into both 128-bit halves. This avoids the
// 3-cycle cost of moving data between 128-bit halves and avoids port 5.
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT3264_D(D)>
HWY_API VFromD<D> LoadDup128(D d, const TFromD<D>* HWY_RESTRICT p) {
  const RebindToUnsigned<decltype(d)> du;
  const Full128<TFromD<D>> d128;
  const RebindToUnsigned<decltype(d128)> du128;
  const __m128i v128 = BitCast(du128, LoadU(d128, p)).raw;
#if HWY_COMPILER_MSVC && HWY_COMPILER_MSVC < 1931
  // Workaround for incorrect results with _mm256_broadcastsi128_si256. Note
  // that MSVC also lacks _mm256_zextsi128_si256, but cast (which leaves the
  // upper half undefined) is fine because we're overwriting that anyway.
  // This workaround seems in turn to generate incorrect code in MSVC 2022
  // (19.31), so use broadcastsi128 there.
  return BitCast(d, VFromD<decltype(du)>{_mm256_inserti128_si256(
                        _mm256_castsi128_si256(v128), v128, 1)});
#else
  // The preferred path. This is perhaps surprising, because vbroadcasti128
  // with xmm input has 7 cycle latency on Intel, but Clang >= 7 is able to
  // pattern-match this to vbroadcastf128 with a memory operand as desired.
  return BitCast(d, VFromD<decltype(du)>{_mm256_broadcastsi128_si256(v128)});
#endif
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> LoadDup128(D /* tag */, const float* HWY_RESTRICT p) {
#if HWY_COMPILER_MSVC && HWY_COMPILER_MSVC < 1931
  const Full128<float> d128;
  const __m128 v128 = LoadU(d128, p).raw;
  return Vec256<float>{
      _mm256_insertf128_ps(_mm256_castps128_ps256(v128), v128, 1)};
#else
  return Vec256<float>{_mm256_broadcast_ps(reinterpret_cast<const __m128*>(p))};
#endif
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> LoadDup128(D /* tag */, const double* HWY_RESTRICT p) {
#if HWY_COMPILER_MSVC && HWY_COMPILER_MSVC < 1931
  const Full128<double> d128;
  const __m128d v128 = LoadU(d128, p).raw;
  return Vec256<double>{
      _mm256_insertf128_pd(_mm256_castpd128_pd256(v128), v128, 1)};
#else
  return Vec256<double>{
      _mm256_broadcast_pd(reinterpret_cast<const __m128d*>(p))};
#endif
}

// ------------------------------ Store

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT_NOR_SPECIAL_D(D)>
HWY_API void Store(VFromD<D> v, D /* tag */, TFromD<D>* HWY_RESTRICT aligned) {
  _mm256_store_si256(reinterpret_cast<__m256i*>(aligned), v.raw);
}
#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API void Store(Vec256<float16_t> v, D /* tag */,
                   float16_t* HWY_RESTRICT aligned) {
  _mm256_store_ph(aligned, v.raw);
}
#endif  // HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API void Store(Vec256<float> v, D /* tag */, float* HWY_RESTRICT aligned) {
  _mm256_store_ps(aligned, v.raw);
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API void Store(Vec256<double> v, D /* tag */,
                   double* HWY_RESTRICT aligned) {
  _mm256_store_pd(aligned, v.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT_NOR_SPECIAL_D(D)>
HWY_API void StoreU(VFromD<D> v, D /* tag */, TFromD<D>* HWY_RESTRICT p) {
  _mm256_storeu_si256(reinterpret_cast<__m256i*>(p), v.raw);
}
#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API void StoreU(Vec256<float16_t> v, D /* tag */,
                    float16_t* HWY_RESTRICT p) {
  _mm256_storeu_ph(p, v.raw);
}
#endif
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API void StoreU(Vec256<float> v, D /* tag */, float* HWY_RESTRICT p) {
  _mm256_storeu_ps(p, v.raw);
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API void StoreU(Vec256<double> v, D /* tag */, double* HWY_RESTRICT p) {
  _mm256_storeu_pd(p, v.raw);
}

// ------------------------------ BlendedStore

#if HWY_TARGET <= HWY_AVX3

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API void BlendedStore(VFromD<D> v, MFromD<D> m, D /* tag */,
                          TFromD<D>* HWY_RESTRICT p) {
  _mm256_mask_storeu_epi8(p, m.raw, v.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API void BlendedStore(VFromD<D> v, MFromD<D> m, D d,
                          TFromD<D>* HWY_RESTRICT p) {
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  _mm256_mask_storeu_epi16(reinterpret_cast<uint16_t*>(p),
                           RebindMask(du, m).raw, BitCast(du, v).raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API void BlendedStore(VFromD<D> v, MFromD<D> m, D /* tag */,
                          TFromD<D>* HWY_RESTRICT p) {
  _mm256_mask_storeu_epi32(p, m.raw, v.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API void BlendedStore(VFromD<D> v, MFromD<D> m, D /* tag */,
                          TFromD<D>* HWY_RESTRICT p) {
  _mm256_mask_storeu_epi64(p, m.raw, v.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API void BlendedStore(Vec256<float> v, Mask256<float> m, D /* tag */,
                          float* HWY_RESTRICT p) {
  _mm256_mask_storeu_ps(p, m.raw, v.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API void BlendedStore(Vec256<double> v, Mask256<double> m, D /* tag */,
                          double* HWY_RESTRICT p) {
  _mm256_mask_storeu_pd(p, m.raw, v.raw);
}

#else  //  AVX2

// Intel SDM says "No AC# reported for any mask bit combinations". However, AMD
// allows AC# if "Alignment checking enabled and: 256-bit memory operand not
// 32-byte aligned". Fortunately AC# is not enabled by default and requires both
// OS support (CR0) and the application to set rflags.AC. We assume these remain
// disabled because x86/x64 code and compiler output often contain misaligned
// scalar accesses, which would also fault.
//
// Caveat: these are slow on AMD Jaguar/Bulldozer.

template <class D, HWY_IF_V_SIZE_D(D, 32),
          HWY_IF_T_SIZE_ONE_OF_D(D, (1 << 1) | (1 << 2))>
HWY_API void BlendedStore(VFromD<D> v, MFromD<D> m, D d,
                          TFromD<D>* HWY_RESTRICT p) {
  // There is no maskload_epi8/16. Blending is also unsafe because loading a
  // full vector that crosses the array end causes asan faults. Resort to scalar
  // code; the caller should instead use memcpy, assuming m is FirstN(d, n).
  const RebindToUnsigned<decltype(d)> du;
  using TU = TFromD<decltype(du)>;
  alignas(32) TU buf[MaxLanes(d)];
  alignas(32) TU mask[MaxLanes(d)];
  Store(BitCast(du, v), du, buf);
  Store(BitCast(du, VecFromMask(d, m)), du, mask);
  for (size_t i = 0; i < MaxLanes(d); ++i) {
    if (mask[i]) {
      CopySameSize(buf + i, p + i);
    }
  }
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API void BlendedStore(VFromD<D> v, MFromD<D> m, D /* tag */,
                          TFromD<D>* HWY_RESTRICT p) {
  auto pi = reinterpret_cast<int*>(p);  // NOLINT
  _mm256_maskstore_epi32(pi, m.raw, v.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API void BlendedStore(VFromD<D> v, MFromD<D> m, D /* tag */,
                          TFromD<D>* HWY_RESTRICT p) {
  auto pi = reinterpret_cast<long long*>(p);  // NOLINT
  _mm256_maskstore_epi64(pi, m.raw, v.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API void BlendedStore(Vec256<float> v, Mask256<float> m, D d,
                          float* HWY_RESTRICT p) {
  const Vec256<int32_t> mi =
      BitCast(RebindToSigned<decltype(d)>(), VecFromMask(d, m));
  _mm256_maskstore_ps(p, mi.raw, v.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API void BlendedStore(Vec256<double> v, Mask256<double> m, D d,
                          double* HWY_RESTRICT p) {
  const Vec256<int64_t> mi =
      BitCast(RebindToSigned<decltype(d)>(), VecFromMask(d, m));
  _mm256_maskstore_pd(p, mi.raw, v.raw);
}

#endif

// ------------------------------ Non-temporal stores

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT3264_D(D)>
HWY_API void Stream(VFromD<D> v, D d, TFromD<D>* HWY_RESTRICT aligned) {
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  _mm256_stream_si256(reinterpret_cast<__m256i*>(aligned), BitCast(du, v).raw);
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API void Stream(Vec256<float> v, D /* tag */, float* HWY_RESTRICT aligned) {
  _mm256_stream_ps(aligned, v.raw);
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API void Stream(Vec256<double> v, D /* tag */,
                    double* HWY_RESTRICT aligned) {
  _mm256_stream_pd(aligned, v.raw);
}

// ------------------------------ ScatterOffset

// Work around warnings in the intrinsic definitions (passing -1 as a mask).
HWY_DIAGNOSTICS(push)
HWY_DIAGNOSTICS_OFF(disable : 4245 4365, ignored "-Wsign-conversion")

#if HWY_TARGET <= HWY_AVX3

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API void ScatterOffset(VFromD<D> v, D /* tag */,
                           TFromD<D>* HWY_RESTRICT base,
                           Vec256<int32_t> offset) {
  _mm256_i32scatter_epi32(base, offset.raw, v.raw, 1);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API void ScatterOffset(VFromD<D> v, D /* tag */,
                           TFromD<D>* HWY_RESTRICT base,
                           Vec256<int64_t> offset) {
  _mm256_i64scatter_epi64(base, offset.raw, v.raw, 1);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API void ScatterOffset(VFromD<D> v, D /* tag */, float* HWY_RESTRICT base,
                           const Vec256<int32_t> offset) {
  _mm256_i32scatter_ps(base, offset.raw, v.raw, 1);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API void ScatterOffset(VFromD<D> v, D /* tag */, double* HWY_RESTRICT base,
                           const Vec256<int64_t> offset) {
  _mm256_i64scatter_pd(base, offset.raw, v.raw, 1);
}

// ------------------------------ ScatterIndex

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API void ScatterIndex(VFromD<D> v, D /* tag */,
                          TFromD<D>* HWY_RESTRICT base,
                          VFromD<RebindToSigned<D>> index) {
  _mm256_i32scatter_epi32(base, index.raw, v.raw, 4);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API void ScatterIndex(VFromD<D> v, D /* tag */,
                          TFromD<D>* HWY_RESTRICT base,
                          VFromD<RebindToSigned<D>> index) {
  _mm256_i64scatter_epi64(base, index.raw, v.raw, 8);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API void ScatterIndex(VFromD<D> v, D /* tag */, float* HWY_RESTRICT base,
                          VFromD<RebindToSigned<D>> index) {
  _mm256_i32scatter_ps(base, index.raw, v.raw, 4);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API void ScatterIndex(VFromD<D> v, D /* tag */, double* HWY_RESTRICT base,
                          VFromD<RebindToSigned<D>> index) {
  _mm256_i64scatter_pd(base, index.raw, v.raw, 8);
}

// ------------------------------ MaskedScatterIndex

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API void MaskedScatterIndex(VFromD<D> v, MFromD<D> m, D /* tag */,
                                TFromD<D>* HWY_RESTRICT base,
                                VFromD<RebindToSigned<D>> index) {
  _mm256_mask_i32scatter_epi32(base, m.raw, index.raw, v.raw, 4);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API void MaskedScatterIndex(VFromD<D> v, MFromD<D> m, D /* tag */,
                                TFromD<D>* HWY_RESTRICT base,
                                VFromD<RebindToSigned<D>> index) {
  _mm256_mask_i64scatter_epi64(base, m.raw, index.raw, v.raw, 8);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API void MaskedScatterIndex(VFromD<D> v, MFromD<D> m, D /* tag */,
                                float* HWY_RESTRICT base,
                                VFromD<RebindToSigned<D>> index) {
  _mm256_mask_i32scatter_ps(base, m.raw, index.raw, v.raw, 4);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API void MaskedScatterIndex(VFromD<D> v, MFromD<D> m, D /* tag */,
                                double* HWY_RESTRICT base,
                                VFromD<RebindToSigned<D>> index) {
  _mm256_mask_i64scatter_pd(base, m.raw, index.raw, v.raw, 8);
}

#endif  // HWY_TARGET <= HWY_AVX3

// ------------------------------ Gather

namespace detail {

template <int kScale, typename T, HWY_IF_UI32(T)>
HWY_INLINE Vec256<T> NativeGather256(const T* HWY_RESTRICT base,
                                     Vec256<int32_t> indices) {
  return Vec256<T>{_mm256_i32gather_epi32(
      reinterpret_cast<const int32_t*>(base), indices.raw, kScale)};
}

template <int kScale, typename T, HWY_IF_UI64(T)>
HWY_INLINE Vec256<T> NativeGather256(const T* HWY_RESTRICT base,
                                     Vec256<int64_t> indices) {
  return Vec256<T>{_mm256_i64gather_epi64(
      reinterpret_cast<const GatherIndex64*>(base), indices.raw, kScale)};
}

template <int kScale>
HWY_API Vec256<float> NativeGather256(const float* HWY_RESTRICT base,
                                      Vec256<int32_t> indices) {
  return Vec256<float>{_mm256_i32gather_ps(base, indices.raw, kScale)};
}

template <int kScale>
HWY_API Vec256<double> NativeGather256(const double* HWY_RESTRICT base,
                                       Vec256<int64_t> indices) {
  return Vec256<double>{_mm256_i64gather_pd(base, indices.raw, kScale)};
}

}  // namespace detail

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> GatherOffset(D /*d*/, const TFromD<D>* HWY_RESTRICT base,
                               VFromD<RebindToSigned<D>> offsets) {
  return detail::NativeGather256<1>(base, offsets);
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> GatherIndex(D /*d*/, const TFromD<D>* HWY_RESTRICT base,
                              VFromD<RebindToSigned<D>> indices) {
  return detail::NativeGather256<sizeof(TFromD<D>)>(base, indices);
}

// ------------------------------ MaskedGatherIndexOr

namespace detail {

template <int kScale, typename T, HWY_IF_UI32(T)>
HWY_INLINE Vec256<T> NativeMaskedGatherOr256(Vec256<T> no, Mask256<T> m,
                                             const T* HWY_RESTRICT base,
                                             Vec256<int32_t> indices) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<T>{_mm256_mmask_i32gather_epi32(
      no.raw, m.raw, indices.raw, reinterpret_cast<const int32_t*>(base),
      kScale)};
#else
  return Vec256<T>{_mm256_mask_i32gather_epi32(
      no.raw, reinterpret_cast<const int32_t*>(base), indices.raw, m.raw,
      kScale)};
#endif
}

template <int kScale, typename T, HWY_IF_UI64(T)>
HWY_INLINE Vec256<T> NativeMaskedGatherOr256(Vec256<T> no, Mask256<T> m,
                                             const T* HWY_RESTRICT base,
                                             Vec256<int64_t> indices) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<T>{_mm256_mmask_i64gather_epi64(
      no.raw, m.raw, indices.raw, reinterpret_cast<const GatherIndex64*>(base),
      kScale)};
#else
  // For reasons unknown, _mm256_mask_i64gather_epi64 returns all-zeros.
  const Full256<T> d;
  const Full256<double> dd;
  return BitCast(d,
                 Vec256<double>{_mm256_mask_i64gather_pd(
                     BitCast(dd, no).raw, reinterpret_cast<const double*>(base),
                     indices.raw, RebindMask(dd, m).raw, kScale)});
#endif
}

template <int kScale>
HWY_API Vec256<float> NativeMaskedGatherOr256(Vec256<float> no,
                                              Mask256<float> m,
                                              const float* HWY_RESTRICT base,
                                              Vec256<int32_t> indices) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<float>{
      _mm256_mmask_i32gather_ps(no.raw, m.raw, indices.raw, base, kScale)};
#else
  return Vec256<float>{
      _mm256_mask_i32gather_ps(no.raw, base, indices.raw, m.raw, kScale)};
#endif
}

template <int kScale>
HWY_API Vec256<double> NativeMaskedGatherOr256(Vec256<double> no,
                                               Mask256<double> m,
                                               const double* HWY_RESTRICT base,
                                               Vec256<int64_t> indices) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<double>{
      _mm256_mmask_i64gather_pd(no.raw, m.raw, indices.raw, base, kScale)};
#else
  return Vec256<double>{
      _mm256_mask_i64gather_pd(no.raw, base, indices.raw, m.raw, kScale)};
#endif
}

}  // namespace detail

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> MaskedGatherIndexOr(VFromD<D> no, MFromD<D> m, D /*d*/,
                                      const TFromD<D>* HWY_RESTRICT base,
                                      VFromD<RebindToSigned<D>> indices) {
  return detail::NativeMaskedGatherOr256<sizeof(TFromD<D>)>(no, m, base,
                                                            indices);
}

HWY_DIAGNOSTICS(pop)

// ================================================== SWIZZLE

// ------------------------------ LowerHalf

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_NOT_FLOAT_NOR_SPECIAL_D(D)>
HWY_API VFromD<D> LowerHalf(D /* tag */, VFromD<Twice<D>> v) {
  return VFromD<D>{_mm256_castsi256_si128(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_BF16_D(D)>
HWY_API Vec128<bfloat16_t> LowerHalf(D /* tag */, Vec256<bfloat16_t> v) {
  return Vec128<bfloat16_t>{_mm256_castsi256_si128(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_F16_D(D)>
HWY_API Vec128<float16_t> LowerHalf(D /* tag */, Vec256<float16_t> v) {
#if HWY_HAVE_FLOAT16
  return Vec128<float16_t>{_mm256_castph256_ph128(v.raw)};
#else
  return Vec128<float16_t>{_mm256_castsi256_si128(v.raw)};
#endif  // HWY_HAVE_FLOAT16
}
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_F32_D(D)>
HWY_API Vec128<float> LowerHalf(D /* tag */, Vec256<float> v) {
  return Vec128<float>{_mm256_castps256_ps128(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_F64_D(D)>
HWY_API Vec128<double> LowerHalf(D /* tag */, Vec256<double> v) {
  return Vec128<double>{_mm256_castpd256_pd128(v.raw)};
}

template <typename T>
HWY_API Vec128<T> LowerHalf(Vec256<T> v) {
  const Full128<T> dh;
  return LowerHalf(dh, v);
}

// ------------------------------ UpperHalf

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_NOT_FLOAT3264_D(D)>
HWY_API VFromD<D> UpperHalf(D d, VFromD<Twice<D>> v) {
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  const Twice<decltype(du)> dut;
  return BitCast(d, VFromD<decltype(du)>{
                        _mm256_extracti128_si256(BitCast(dut, v).raw, 1)});
}
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_F32_D(D)>
HWY_API VFromD<D> UpperHalf(D /* tag */, Vec256<float> v) {
  return VFromD<D>{_mm256_extractf128_ps(v.raw, 1)};
}
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_F64_D(D)>
HWY_API VFromD<D> UpperHalf(D /* tag */, Vec256<double> v) {
  return VFromD<D>{_mm256_extractf128_pd(v.raw, 1)};
}

// ------------------------------ ExtractLane (Store)
template <typename T>
HWY_API T ExtractLane(const Vec256<T> v, size_t i) {
  const DFromV<decltype(v)> d;
  HWY_DASSERT(i < Lanes(d));

#if !HWY_IS_DEBUG_BUILD && HWY_COMPILER_GCC  // includes clang
  constexpr size_t kLanesPerBlock = 16 / sizeof(T);
  if (__builtin_constant_p(i < kLanesPerBlock) && (i < kLanesPerBlock)) {
    return ExtractLane(LowerHalf(Half<decltype(d)>(), v), i);
  }
#endif

  alignas(32) T lanes[32 / sizeof(T)];
  Store(v, d, lanes);
  return lanes[i];
}

// ------------------------------ InsertLane (Store)
template <typename T>
HWY_API Vec256<T> InsertLane(const Vec256<T> v, size_t i, T t) {
  return detail::InsertLaneUsingBroadcastAndBlend(v, i, t);
}

// ------------------------------ GetLane (LowerHalf)
template <typename T>
HWY_API T GetLane(const Vec256<T> v) {
  return GetLane(LowerHalf(v));
}

// ------------------------------ ExtractBlock (LowerHalf, UpperHalf)

template <int kBlockIdx, class T>
HWY_API Vec128<T> ExtractBlock(Vec256<T> v) {
  static_assert(kBlockIdx == 0 || kBlockIdx == 1, "Invalid block index");
  const Half<DFromV<decltype(v)>> dh;
  return (kBlockIdx == 0) ? LowerHalf(dh, v) : UpperHalf(dh, v);
}

// ------------------------------ ZeroExtendVector

// Unfortunately the initial _mm256_castsi128_si256 intrinsic leaves the upper
// bits undefined. Although it makes sense for them to be zero (VEX encoded
// 128-bit instructions zero the upper lanes to avoid large penalties), a
// compiler could decide to optimize out code that relies on this.
//
// The newer _mm256_zextsi128_si256 intrinsic fixes this by specifying the
// zeroing, but it is not available on MSVC until 1920 nor GCC until 10.1.
// Unfortunately as of 2023-08 it still seems to cause internal compiler errors
// on MSVC, so we consider it unavailable there.
//
// Without zext we can still possibly obtain the desired code thanks to pattern
// recognition; note that the expensive insert instruction might not actually be
// generated, see https://gcc.godbolt.org/z/1MKGaP.

#if !defined(HWY_HAVE_ZEXT)
#if (HWY_COMPILER_CLANG && HWY_COMPILER_CLANG >= 500) || \
    (HWY_COMPILER_GCC_ACTUAL && HWY_COMPILER_GCC_ACTUAL >= 1000)
#define HWY_HAVE_ZEXT 1
#else
#define HWY_HAVE_ZEXT 0
#endif
#endif  // defined(HWY_HAVE_ZEXT)

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT_NOR_SPECIAL_D(D)>
HWY_API VFromD<D> ZeroExtendVector(D /* tag */, VFromD<Half<D>> lo) {
#if HWY_HAVE_ZEXT
  return VFromD<D>{_mm256_zextsi128_si256(lo.raw)};
#elif HWY_COMPILER_MSVC
  // Workaround: _mm256_inserti128_si256 does not actually zero the hi part.
  return VFromD<D>{_mm256_set_m128i(_mm_setzero_si128(), lo.raw)};
#else
  return VFromD<D>{_mm256_inserti128_si256(_mm256_setzero_si256(), lo.raw, 0)};
#endif
}
#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API Vec256<float16_t> ZeroExtendVector(D d, Vec128<float16_t> lo) {
#if HWY_HAVE_ZEXT
  (void)d;
  return Vec256<float16_t>{_mm256_zextph128_ph256(lo.raw)};
#else
  const RebindToUnsigned<D> du;
  return BitCast(d, ZeroExtendVector(du, BitCast(du, lo)));
#endif  // HWY_HAVE_ZEXT
}
#endif  // HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> ZeroExtendVector(D /* tag */, Vec128<float> lo) {
#if HWY_HAVE_ZEXT
  return Vec256<float>{_mm256_zextps128_ps256(lo.raw)};
#else
  return Vec256<float>{_mm256_insertf128_ps(_mm256_setzero_ps(), lo.raw, 0)};
#endif
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> ZeroExtendVector(D /* tag */, Vec128<double> lo) {
#if HWY_HAVE_ZEXT
  return Vec256<double>{_mm256_zextpd128_pd256(lo.raw)};
#else
  return Vec256<double>{_mm256_insertf128_pd(_mm256_setzero_pd(), lo.raw, 0)};
#endif
}

// ------------------------------ ZeroExtendResizeBitCast

namespace detail {

template <class DTo, class DFrom>
HWY_INLINE VFromD<DTo> ZeroExtendResizeBitCast(
    hwy::SizeTag<8> /* from_size_tag */, hwy::SizeTag<32> /* to_size_tag */,
    DTo d_to, DFrom d_from, VFromD<DFrom> v) {
  const Twice<decltype(d_from)> dt_from;
  const Twice<decltype(dt_from)> dq_from;
  return BitCast(d_to, ZeroExtendVector(dq_from, ZeroExtendVector(dt_from, v)));
}

}  // namespace detail

// ------------------------------ Combine

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT3264_D(D)>
HWY_API VFromD<D> Combine(D d, VFromD<Half<D>> hi, VFromD<Half<D>> lo) {
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  const Half<decltype(du)> dh_u;
  const auto lo256 = ZeroExtendVector(du, BitCast(dh_u, lo));
  return BitCast(d, VFromD<decltype(du)>{_mm256_inserti128_si256(
                        lo256.raw, BitCast(dh_u, hi).raw, 1)});
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> Combine(D d, Vec128<float> hi, Vec128<float> lo) {
  const auto lo256 = ZeroExtendVector(d, lo);
  return Vec256<float>{_mm256_insertf128_ps(lo256.raw, hi.raw, 1)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> Combine(D d, Vec128<double> hi, Vec128<double> lo) {
  const auto lo256 = ZeroExtendVector(d, lo);
  return Vec256<double>{_mm256_insertf128_pd(lo256.raw, hi.raw, 1)};
}

// ------------------------------ ShiftLeftBytes
template <int kBytes, class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> ShiftLeftBytes(D /* tag */, VFromD<D> v) {
  static_assert(0 <= kBytes && kBytes <= 16, "Invalid kBytes");
  // This is the same operation as _mm256_bslli_epi128.
  return VFromD<D>{_mm256_slli_si256(v.raw, kBytes)};
}

// ------------------------------ ShiftRightBytes
template <int kBytes, class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> ShiftRightBytes(D /* tag */, VFromD<D> v) {
  static_assert(0 <= kBytes && kBytes <= 16, "Invalid kBytes");
  // This is the same operation as _mm256_bsrli_epi128.
  return VFromD<D>{_mm256_srli_si256(v.raw, kBytes)};
}

// ------------------------------ CombineShiftRightBytes
template <int kBytes, class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> CombineShiftRightBytes(D d, VFromD<D> hi, VFromD<D> lo) {
  const Repartition<uint8_t, decltype(d)> d8;
  return BitCast(d, Vec256<uint8_t>{_mm256_alignr_epi8(
                        BitCast(d8, hi).raw, BitCast(d8, lo).raw, kBytes)});
}

// ------------------------------ Broadcast

template <int kLane, typename T, HWY_IF_T_SIZE(T, 2)>
HWY_API Vec256<T> Broadcast(const Vec256<T> v) {
  const DFromV<decltype(v)> d;
  const RebindToUnsigned<decltype(d)> du;
  using VU = VFromD<decltype(du)>;
  const VU vu = BitCast(du, v);  // for float16_t
  static_assert(0 <= kLane && kLane < 8, "Invalid lane");
  if (kLane < 4) {
    const __m256i lo = _mm256_shufflelo_epi16(vu.raw, (0x55 * kLane) & 0xFF);
    return BitCast(d, VU{_mm256_unpacklo_epi64(lo, lo)});
  } else {
    const __m256i hi =
        _mm256_shufflehi_epi16(vu.raw, (0x55 * (kLane - 4)) & 0xFF);
    return BitCast(d, VU{_mm256_unpackhi_epi64(hi, hi)});
  }
}
template <int kLane, typename T, HWY_IF_UI32(T)>
HWY_API Vec256<T> Broadcast(const Vec256<T> v) {
  static_assert(0 <= kLane && kLane < 4, "Invalid lane");
  return Vec256<T>{_mm256_shuffle_epi32(v.raw, 0x55 * kLane)};
}

template <int kLane, typename T, HWY_IF_UI64(T)>
HWY_API Vec256<T> Broadcast(const Vec256<T> v) {
  static_assert(0 <= kLane && kLane < 2, "Invalid lane");
  return Vec256<T>{_mm256_shuffle_epi32(v.raw, kLane ? 0xEE : 0x44)};
}

template <int kLane>
HWY_API Vec256<float> Broadcast(Vec256<float> v) {
  static_assert(0 <= kLane && kLane < 4, "Invalid lane");
  return Vec256<float>{_mm256_shuffle_ps(v.raw, v.raw, 0x55 * kLane)};
}

template <int kLane>
HWY_API Vec256<double> Broadcast(const Vec256<double> v) {
  static_assert(0 <= kLane && kLane < 2, "Invalid lane");
  return Vec256<double>{_mm256_shuffle_pd(v.raw, v.raw, 15 * kLane)};
}

// ------------------------------ Concat blocks (LowerHalf, ZeroExtendVector)

// _mm256_broadcastsi128_si256 has 7 cycle latency on ICL.
// _mm256_permute2x128_si256 is slow on Zen1 (8 uops), so we avoid it (at no
// extra cost) for LowerLower and UpperLower.

// hiH,hiL loH,loL |-> hiL,loL (= lower halves)
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT3264_D(D)>
HWY_API VFromD<D> ConcatLowerLower(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  const Half<decltype(d)> d2;
  const RebindToUnsigned<decltype(d2)> du2;  // for float16_t
  return BitCast(
      d, VFromD<decltype(du)>{_mm256_inserti128_si256(
             BitCast(du, lo).raw, BitCast(du2, LowerHalf(d2, hi)).raw, 1)});
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> ConcatLowerLower(D d, Vec256<float> hi,
                                       Vec256<float> lo) {
  const Half<decltype(d)> d2;
  return Vec256<float>{_mm256_insertf128_ps(lo.raw, LowerHalf(d2, hi).raw, 1)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> ConcatLowerLower(D d, Vec256<double> hi,
                                        Vec256<double> lo) {
  const Half<decltype(d)> d2;
  return Vec256<double>{_mm256_insertf128_pd(lo.raw, LowerHalf(d2, hi).raw, 1)};
}

// hiH,hiL loH,loL |-> hiL,loH (= inner halves / swap blocks)
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT3264_D(D)>
HWY_API VFromD<D> ConcatLowerUpper(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
  return BitCast(d, VFromD<decltype(du)>{_mm256_permute2x128_si256(
                        BitCast(du, lo).raw, BitCast(du, hi).raw, 0x21)});
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> ConcatLowerUpper(D /* tag */, Vec256<float> hi,
                                       Vec256<float> lo) {
  return Vec256<float>{_mm256_permute2f128_ps(lo.raw, hi.raw, 0x21)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> ConcatLowerUpper(D /* tag */, Vec256<double> hi,
                                        Vec256<double> lo) {
  return Vec256<double>{_mm256_permute2f128_pd(lo.raw, hi.raw, 0x21)};
}

// hiH,hiL loH,loL |-> hiH,loL (= outer halves)
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT3264_D(D)>
HWY_API VFromD<D> ConcatUpperLower(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  return BitCast(d, VFromD<decltype(du)>{_mm256_blend_epi32(
                        BitCast(du, hi).raw, BitCast(du, lo).raw, 0x0F)});
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> ConcatUpperLower(D /* tag */, Vec256<float> hi,
                                       Vec256<float> lo) {
  return Vec256<float>{_mm256_blend_ps(hi.raw, lo.raw, 0x0F)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> ConcatUpperLower(D /* tag */, Vec256<double> hi,
                                        Vec256<double> lo) {
  return Vec256<double>{_mm256_blend_pd(hi.raw, lo.raw, 3)};
}

// hiH,hiL loH,loL |-> hiH,loH (= upper halves)
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT3264_D(D)>
HWY_API VFromD<D> ConcatUpperUpper(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  return BitCast(d, VFromD<decltype(du)>{_mm256_permute2x128_si256(
                        BitCast(du, lo).raw, BitCast(du, hi).raw, 0x31)});
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API Vec256<float> ConcatUpperUpper(D /* tag */, Vec256<float> hi,
                                       Vec256<float> lo) {
  return Vec256<float>{_mm256_permute2f128_ps(lo.raw, hi.raw, 0x31)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> ConcatUpperUpper(D /* tag */, Vec256<double> hi,
                                        Vec256<double> lo) {
  return Vec256<double>{_mm256_permute2f128_pd(lo.raw, hi.raw, 0x31)};
}

// ------------------------------ BroadcastBlock
template <int kBlockIdx, class T>
HWY_API Vec256<T> BroadcastBlock(Vec256<T> v) {
  static_assert(kBlockIdx == 0 || kBlockIdx == 1, "Invalid block index");
  const DFromV<decltype(v)> d;
  return (kBlockIdx == 0) ? ConcatLowerLower(d, v, v)
                          : ConcatUpperUpper(d, v, v);
}

// ------------------------------ BroadcastLane

namespace detail {

template <class T, HWY_IF_T_SIZE(T, 1)>
HWY_INLINE Vec256<T> BroadcastLane(hwy::SizeTag<0> /* lane_idx_tag */,
                                   Vec256<T> v) {
  const Half<DFromV<decltype(v)>> dh;
  return Vec256<T>{_mm256_broadcastb_epi8(LowerHalf(dh, v).raw)};
}

template <class T, HWY_IF_T_SIZE(T, 2)>
HWY_INLINE Vec256<T> BroadcastLane(hwy::SizeTag<0> /* lane_idx_tag */,
                                   Vec256<T> v) {
  const DFromV<decltype(v)> d;
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  const Half<decltype(d)> dh;
  const RebindToUnsigned<decltype(dh)> dh_u;
  return BitCast(d, VFromD<decltype(du)>{_mm256_broadcastw_epi16(
                        BitCast(dh_u, LowerHalf(dh, v)).raw)});
}

template <class T, HWY_IF_UI32(T)>
HWY_INLINE Vec256<T> BroadcastLane(hwy::SizeTag<0> /* lane_idx_tag */,
                                   Vec256<T> v) {
  const Half<DFromV<decltype(v)>> dh;
  return Vec256<T>{_mm256_broadcastd_epi32(LowerHalf(dh, v).raw)};
}

template <class T, HWY_IF_UI64(T)>
HWY_INLINE Vec256<T> BroadcastLane(hwy::SizeTag<0> /* lane_idx_tag */,
                                   Vec256<T> v) {
  const Half<DFromV<decltype(v)>> dh;
  return Vec256<T>{_mm256_broadcastq_epi64(LowerHalf(dh, v).raw)};
}

HWY_INLINE Vec256<float> BroadcastLane(hwy::SizeTag<0> /* lane_idx_tag */,
                                       Vec256<float> v) {
  const Half<DFromV<decltype(v)>> dh;
  return Vec256<float>{_mm256_broadcastss_ps(LowerHalf(dh, v).raw)};
}

HWY_INLINE Vec256<double> BroadcastLane(hwy::SizeTag<0> /* lane_idx_tag */,
                                        Vec256<double> v) {
  const Half<DFromV<decltype(v)>> dh;
  return Vec256<double>{_mm256_broadcastsd_pd(LowerHalf(dh, v).raw)};
}

template <size_t kLaneIdx, class T, hwy::EnableIf<kLaneIdx != 0>* = nullptr,
          HWY_IF_NOT_T_SIZE(T, 8)>
HWY_INLINE Vec256<T> BroadcastLane(hwy::SizeTag<kLaneIdx> /* lane_idx_tag */,
                                   Vec256<T> v) {
  constexpr size_t kLanesPerBlock = 16 / sizeof(T);
  constexpr int kBlockIdx = static_cast<int>(kLaneIdx / kLanesPerBlock);
  constexpr int kLaneInBlkIdx =
      static_cast<int>(kLaneIdx) & (kLanesPerBlock - 1);
  return Broadcast<kLaneInBlkIdx>(BroadcastBlock<kBlockIdx>(v));
}

template <size_t kLaneIdx, class T, hwy::EnableIf<kLaneIdx != 0>* = nullptr,
          HWY_IF_UI64(T)>
HWY_INLINE Vec256<T> BroadcastLane(hwy::SizeTag<kLaneIdx> /* lane_idx_tag */,
                                   Vec256<T> v) {
  static_assert(kLaneIdx <= 3, "Invalid lane");
  return Vec256<T>{
      _mm256_permute4x64_epi64(v.raw, static_cast<int>(0x55 * kLaneIdx))};
}

template <size_t kLaneIdx, hwy::EnableIf<kLaneIdx != 0>* = nullptr>
HWY_INLINE Vec256<double> BroadcastLane(
    hwy::SizeTag<kLaneIdx> /* lane_idx_tag */, Vec256<double> v) {
  static_assert(kLaneIdx <= 3, "Invalid lane");
  return Vec256<double>{
      _mm256_permute4x64_pd(v.raw, static_cast<int>(0x55 * kLaneIdx))};
}

}  // namespace detail

template <int kLaneIdx, class T>
HWY_API Vec256<T> BroadcastLane(Vec256<T> v) {
  static_assert(kLaneIdx >= 0, "Invalid lane");
  return detail::BroadcastLane(hwy::SizeTag<static_cast<size_t>(kLaneIdx)>(),
                               v);
}

// ------------------------------ Hard-coded shuffles

// Notation: let Vec256<int32_t> have lanes 7,6,5,4,3,2,1,0 (0 is
// least-significant). Shuffle0321 rotates four-lane blocks one lane to the
// right (the previous least-significant lane is now most-significant =>
// 47650321). These could also be implemented via CombineShiftRightBytes but
// the shuffle_abcd notation is more convenient.

// Swap 32-bit halves in 64-bit halves.
template <typename T, HWY_IF_UI32(T)>
HWY_API Vec256<T> Shuffle2301(const Vec256<T> v) {
  return Vec256<T>{_mm256_shuffle_epi32(v.raw, 0xB1)};
}
HWY_API Vec256<float> Shuffle2301(const Vec256<float> v) {
  return Vec256<float>{_mm256_shuffle_ps(v.raw, v.raw, 0xB1)};
}

// Used by generic_ops-inl.h
namespace detail {

template <typename T, HWY_IF_T_SIZE(T, 4)>
HWY_API Vec256<T> ShuffleTwo2301(const Vec256<T> a, const Vec256<T> b) {
  const DFromV<decltype(a)> d;
  const RebindToFloat<decltype(d)> df;
  constexpr int m = _MM_SHUFFLE(2, 3, 0, 1);
  return BitCast(d, Vec256<float>{_mm256_shuffle_ps(BitCast(df, a).raw,
                                                    BitCast(df, b).raw, m)});
}
template <typename T, HWY_IF_T_SIZE(T, 4)>
HWY_API Vec256<T> ShuffleTwo1230(const Vec256<T> a, const Vec256<T> b) {
  const DFromV<decltype(a)> d;
  const RebindToFloat<decltype(d)> df;
  constexpr int m = _MM_SHUFFLE(1, 2, 3, 0);
  return BitCast(d, Vec256<float>{_mm256_shuffle_ps(BitCast(df, a).raw,
                                                    BitCast(df, b).raw, m)});
}
template <typename T, HWY_IF_T_SIZE(T, 4)>
HWY_API Vec256<T> ShuffleTwo3012(const Vec256<T> a, const Vec256<T> b) {
  const DFromV<decltype(a)> d;
  const RebindToFloat<decltype(d)> df;
  constexpr int m = _MM_SHUFFLE(3, 0, 1, 2);
  return BitCast(d, Vec256<float>{_mm256_shuffle_ps(BitCast(df, a).raw,
                                                    BitCast(df, b).raw, m)});
}

}  // namespace detail

// Swap 64-bit halves
HWY_API Vec256<uint32_t> Shuffle1032(const Vec256<uint32_t> v) {
  return Vec256<uint32_t>{_mm256_shuffle_epi32(v.raw, 0x4E)};
}
HWY_API Vec256<int32_t> Shuffle1032(const Vec256<int32_t> v) {
  return Vec256<int32_t>{_mm256_shuffle_epi32(v.raw, 0x4E)};
}
HWY_API Vec256<float> Shuffle1032(const Vec256<float> v) {
  // Shorter encoding than _mm256_permute_ps.
  return Vec256<float>{_mm256_shuffle_ps(v.raw, v.raw, 0x4E)};
}
HWY_API Vec256<uint64_t> Shuffle01(const Vec256<uint64_t> v) {
  return Vec256<uint64_t>{_mm256_shuffle_epi32(v.raw, 0x4E)};
}
HWY_API Vec256<int64_t> Shuffle01(const Vec256<int64_t> v) {
  return Vec256<int64_t>{_mm256_shuffle_epi32(v.raw, 0x4E)};
}
HWY_API Vec256<double> Shuffle01(const Vec256<double> v) {
  // Shorter encoding than _mm256_permute_pd.
  return Vec256<double>{_mm256_shuffle_pd(v.raw, v.raw, 5)};
}

// Rotate right 32 bits
HWY_API Vec256<uint32_t> Shuffle0321(const Vec256<uint32_t> v) {
  return Vec256<uint32_t>{_mm256_shuffle_epi32(v.raw, 0x39)};
}
HWY_API Vec256<int32_t> Shuffle0321(const Vec256<int32_t> v) {
  return Vec256<int32_t>{_mm256_shuffle_epi32(v.raw, 0x39)};
}
HWY_API Vec256<float> Shuffle0321(const Vec256<float> v) {
  return Vec256<float>{_mm256_shuffle_ps(v.raw, v.raw, 0x39)};
}
// Rotate left 32 bits
HWY_API Vec256<uint32_t> Shuffle2103(const Vec256<uint32_t> v) {
  return Vec256<uint32_t>{_mm256_shuffle_epi32(v.raw, 0x93)};
}
HWY_API Vec256<int32_t> Shuffle2103(const Vec256<int32_t> v) {
  return Vec256<int32_t>{_mm256_shuffle_epi32(v.raw, 0x93)};
}
HWY_API Vec256<float> Shuffle2103(const Vec256<float> v) {
  return Vec256<float>{_mm256_shuffle_ps(v.raw, v.raw, 0x93)};
}

// Reverse
HWY_API Vec256<uint32_t> Shuffle0123(const Vec256<uint32_t> v) {
  return Vec256<uint32_t>{_mm256_shuffle_epi32(v.raw, 0x1B)};
}
HWY_API Vec256<int32_t> Shuffle0123(const Vec256<int32_t> v) {
  return Vec256<int32_t>{_mm256_shuffle_epi32(v.raw, 0x1B)};
}
HWY_API Vec256<float> Shuffle0123(const Vec256<float> v) {
  return Vec256<float>{_mm256_shuffle_ps(v.raw, v.raw, 0x1B)};
}

// ------------------------------ TableLookupLanes

// Returned by SetTableIndices/IndicesFromVec for use by TableLookupLanes.
template <typename T>
struct Indices256 {
  __m256i raw;
};

// 8-bit lanes: indices remain unchanged
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1), typename TI>
HWY_API Indices256<TFromD<D>> IndicesFromVec(D /* tag */, Vec256<TI> vec) {
  static_assert(sizeof(TFromD<D>) == sizeof(TI), "Index size must match lane");
#if HWY_IS_DEBUG_BUILD
  const Full256<TI> di;
  HWY_DASSERT(AllFalse(di, Lt(vec, Zero(di))) &&
              AllTrue(di, Lt(vec, Set(di, static_cast<TI>(2 * Lanes(di))))));
#endif
  return Indices256<TFromD<D>>{vec.raw};
}

// 16-bit lanes: convert indices to 32x8 unless AVX3 is available
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2), typename TI>
HWY_API Indices256<TFromD<D>> IndicesFromVec(D /* tag */, Vec256<TI> vec) {
  static_assert(sizeof(TFromD<D>) == sizeof(TI), "Index size must match lane");
  const Full256<TI> di;
#if HWY_IS_DEBUG_BUILD
  HWY_DASSERT(AllFalse(di, Lt(vec, Zero(di))) &&
              AllTrue(di, Lt(vec, Set(di, static_cast<TI>(2 * Lanes(di))))));
#endif

#if HWY_TARGET <= HWY_AVX3
  (void)di;
  return Indices256<TFromD<D>>{vec.raw};
#else
  const Repartition<uint8_t, decltype(di)> d8;
  using V8 = VFromD<decltype(d8)>;
  alignas(32) static constexpr uint8_t kByteOffsets[32] = {
      0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1,
      0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1};

  // Broadcast each lane index to all 2 bytes of T
  alignas(32) static constexpr uint8_t kBroadcastLaneBytes[32] = {
      0, 0, 2, 2, 4, 4, 6, 6, 8, 8, 10, 10, 12, 12, 14, 14,
      0, 0, 2, 2, 4, 4, 6, 6, 8, 8, 10, 10, 12, 12, 14, 14};
  const V8 lane_indices = TableLookupBytes(vec, Load(d8, kBroadcastLaneBytes));

  // Shift to bytes
  const Repartition<uint16_t, decltype(di)> d16;
  const V8 byte_indices = BitCast(d8, ShiftLeft<1>(BitCast(d16, lane_indices)));

  return Indices256<TFromD<D>>{Add(byte_indices, Load(d8, kByteOffsets)).raw};
#endif  // HWY_TARGET <= HWY_AVX3
}

// Native 8x32 instruction: indices remain unchanged
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 4), typename TI>
HWY_API Indices256<TFromD<D>> IndicesFromVec(D /* tag */, Vec256<TI> vec) {
  static_assert(sizeof(TFromD<D>) == sizeof(TI), "Index size must match lane");
#if HWY_IS_DEBUG_BUILD
  const Full256<TI> di;
  HWY_DASSERT(AllFalse(di, Lt(vec, Zero(di))) &&
              AllTrue(di, Lt(vec, Set(di, static_cast<TI>(2 * Lanes(di))))));
#endif
  return Indices256<TFromD<D>>{vec.raw};
}

// 64-bit lanes: convert indices to 8x32 unless AVX3 is available
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 8), typename TI>
HWY_API Indices256<TFromD<D>> IndicesFromVec(D d, Vec256<TI> idx64) {
  static_assert(sizeof(TFromD<D>) == sizeof(TI), "Index size must match lane");
  const Rebind<TI, decltype(d)> di;
  (void)di;  // potentially unused
#if HWY_IS_DEBUG_BUILD
  HWY_DASSERT(AllFalse(di, Lt(idx64, Zero(di))) &&
              AllTrue(di, Lt(idx64, Set(di, static_cast<TI>(2 * Lanes(di))))));
#endif

#if HWY_TARGET <= HWY_AVX3
  (void)d;
  return Indices256<TFromD<D>>{idx64.raw};
#else
  const Repartition<float, decltype(d)> df;  // 32-bit!
  // Replicate 64-bit index into upper 32 bits
  const Vec256<TI> dup =
      BitCast(di, Vec256<float>{_mm256_moveldup_ps(BitCast(df, idx64).raw)});
  // For each idx64 i, idx32 are 2*i and 2*i+1.
  const Vec256<TI> idx32 = dup + dup + Set(di, TI(1) << 32);
  return Indices256<TFromD<D>>{idx32.raw};
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), typename TI>
HWY_API Indices256<TFromD<D>> SetTableIndices(D d, const TI* idx) {
  const Rebind<TI, decltype(d)> di;
  return IndicesFromVec(d, LoadU(di, idx));
}

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Vec256<T> TableLookupLanes(Vec256<T> v, Indices256<T> idx) {
#if HWY_TARGET <= HWY_AVX3_DL
  return Vec256<T>{_mm256_permutexvar_epi8(idx.raw, v.raw)};
#else
  const Vec256<T> idx_vec{idx.raw};
  const DFromV<decltype(v)> d;
  const Repartition<uint16_t, decltype(d)> du16;
  const auto sel_hi_mask =
      MaskFromVec(BitCast(d, ShiftLeft<3>(BitCast(du16, idx_vec))));

  const auto a = ConcatLowerLower(d, v, v);
  const auto b = ConcatUpperUpper(d, v, v);
  const auto lo_lookup_result = TableLookupBytes(a, idx_vec);

#if HWY_TARGET <= HWY_AVX3
  return Vec256<T>{_mm256_mask_shuffle_epi8(
      lo_lookup_result.raw, sel_hi_mask.raw, b.raw, idx_vec.raw)};
#else
  const auto hi_lookup_result = TableLookupBytes(b, idx_vec);
  return IfThenElse(sel_hi_mask, hi_lookup_result, lo_lookup_result);
#endif  // HWY_TARGET <= HWY_AVX3
#endif  // HWY_TARGET <= HWY_AVX3_DL
}

template <typename T, HWY_IF_T_SIZE(T, 2), HWY_IF_NOT_SPECIAL_FLOAT(T)>
HWY_API Vec256<T> TableLookupLanes(Vec256<T> v, Indices256<T> idx) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<T>{_mm256_permutexvar_epi16(idx.raw, v.raw)};
#else
  const DFromV<decltype(v)> d;
  const Repartition<uint8_t, decltype(d)> du8;
  return BitCast(
      d, TableLookupLanes(BitCast(du8, v), Indices256<uint8_t>{idx.raw}));
#endif
}

#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> TableLookupLanes(Vec256<float16_t> v,
                                           Indices256<float16_t> idx) {
  return Vec256<float16_t>{_mm256_permutexvar_ph(idx.raw, v.raw)};
}
#endif  // HWY_HAVE_FLOAT16

template <typename T, HWY_IF_T_SIZE(T, 4)>
HWY_API Vec256<T> TableLookupLanes(Vec256<T> v, Indices256<T> idx) {
  return Vec256<T>{_mm256_permutevar8x32_epi32(v.raw, idx.raw)};
}

template <typename T, HWY_IF_T_SIZE(T, 8)>
HWY_API Vec256<T> TableLookupLanes(Vec256<T> v, Indices256<T> idx) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<T>{_mm256_permutexvar_epi64(idx.raw, v.raw)};
#else
  return Vec256<T>{_mm256_permutevar8x32_epi32(v.raw, idx.raw)};
#endif
}

HWY_API Vec256<float> TableLookupLanes(const Vec256<float> v,
                                       const Indices256<float> idx) {
  return Vec256<float>{_mm256_permutevar8x32_ps(v.raw, idx.raw)};
}

HWY_API Vec256<double> TableLookupLanes(const Vec256<double> v,
                                        const Indices256<double> idx) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<double>{_mm256_permutexvar_pd(idx.raw, v.raw)};
#else
  const Full256<double> df;
  const Full256<uint64_t> du;
  return BitCast(df, Vec256<uint64_t>{_mm256_permutevar8x32_epi32(
                         BitCast(du, v).raw, idx.raw)});
#endif
}

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Vec256<T> TwoTablesLookupLanes(Vec256<T> a, Vec256<T> b,
                                       Indices256<T> idx) {
#if HWY_TARGET <= HWY_AVX3_DL
  return Vec256<T>{_mm256_permutex2var_epi8(a.raw, idx.raw, b.raw)};
#else
  const DFromV<decltype(a)> d;
  const auto sel_hi_mask =
      MaskFromVec(BitCast(d, ShiftLeft<2>(Vec256<uint16_t>{idx.raw})));
  const auto lo_lookup_result = TableLookupLanes(a, idx);
  const auto hi_lookup_result = TableLookupLanes(b, idx);
  return IfThenElse(sel_hi_mask, hi_lookup_result, lo_lookup_result);
#endif
}

template <typename T, HWY_IF_T_SIZE(T, 2)>
HWY_API Vec256<T> TwoTablesLookupLanes(Vec256<T> a, Vec256<T> b,
                                       Indices256<T> idx) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<T>{_mm256_permutex2var_epi16(a.raw, idx.raw, b.raw)};
#else
  const DFromV<decltype(a)> d;
  const Repartition<uint8_t, decltype(d)> du8;
  return BitCast(d, TwoTablesLookupLanes(BitCast(du8, a), BitCast(du8, b),
                                         Indices256<uint8_t>{idx.raw}));
#endif
}

template <typename T, HWY_IF_UI32(T)>
HWY_API Vec256<T> TwoTablesLookupLanes(Vec256<T> a, Vec256<T> b,
                                       Indices256<T> idx) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<T>{_mm256_permutex2var_epi32(a.raw, idx.raw, b.raw)};
#else
  const DFromV<decltype(a)> d;
  const RebindToFloat<decltype(d)> df;
  const Vec256<T> idx_vec{idx.raw};

  const auto sel_hi_mask = MaskFromVec(BitCast(df, ShiftLeft<28>(idx_vec)));
  const auto lo_lookup_result = BitCast(df, TableLookupLanes(a, idx));
  const auto hi_lookup_result = BitCast(df, TableLookupLanes(b, idx));
  return BitCast(d,
                 IfThenElse(sel_hi_mask, hi_lookup_result, lo_lookup_result));
#endif
}

#if HWY_HAVE_FLOAT16
HWY_API Vec256<float16_t> TwoTablesLookupLanes(Vec256<float16_t> a,
                                               Vec256<float16_t> b,
                                               Indices256<float16_t> idx) {
  return Vec256<float16_t>{_mm256_permutex2var_ph(a.raw, idx.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16
HWY_API Vec256<float> TwoTablesLookupLanes(Vec256<float> a, Vec256<float> b,
                                           Indices256<float> idx) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<float>{_mm256_permutex2var_ps(a.raw, idx.raw, b.raw)};
#else
  const DFromV<decltype(a)> d;
  const auto sel_hi_mask =
      MaskFromVec(BitCast(d, ShiftLeft<28>(Vec256<uint32_t>{idx.raw})));
  const auto lo_lookup_result = TableLookupLanes(a, idx);
  const auto hi_lookup_result = TableLookupLanes(b, idx);
  return IfThenElse(sel_hi_mask, hi_lookup_result, lo_lookup_result);
#endif
}

template <typename T, HWY_IF_UI64(T)>
HWY_API Vec256<T> TwoTablesLookupLanes(Vec256<T> a, Vec256<T> b,
                                       Indices256<T> idx) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<T>{_mm256_permutex2var_epi64(a.raw, idx.raw, b.raw)};
#else
  const DFromV<decltype(a)> d;
  const Repartition<uint32_t, decltype(d)> du32;
  return BitCast(d, TwoTablesLookupLanes(BitCast(du32, a), BitCast(du32, b),
                                         Indices256<uint32_t>{idx.raw}));
#endif
}

HWY_API Vec256<double> TwoTablesLookupLanes(Vec256<double> a, Vec256<double> b,
                                            Indices256<double> idx) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<double>{_mm256_permutex2var_pd(a.raw, idx.raw, b.raw)};
#else
  const DFromV<decltype(a)> d;
  const Repartition<uint32_t, decltype(d)> du32;
  return BitCast(d, TwoTablesLookupLanes(BitCast(du32, a), BitCast(du32, b),
                                         Indices256<uint32_t>{idx.raw}));
#endif
}

// ------------------------------ SwapAdjacentBlocks

template <typename T>
HWY_API Vec256<T> SwapAdjacentBlocks(Vec256<T> v) {
  const DFromV<decltype(v)> d;
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  return BitCast(d, VFromD<decltype(du)>{_mm256_permute4x64_epi64(
                        BitCast(du, v).raw, _MM_SHUFFLE(1, 0, 3, 2))});
}

HWY_API Vec256<double> SwapAdjacentBlocks(Vec256<double> v) {
  return Vec256<double>{_mm256_permute4x64_pd(v.raw, _MM_SHUFFLE(1, 0, 3, 2))};
}

HWY_API Vec256<float> SwapAdjacentBlocks(Vec256<float> v) {
  // Assume no domain-crossing penalty between float/double (true on SKX).
  const DFromV<decltype(v)> d;
  const RepartitionToWide<decltype(d)> dw;
  return BitCast(d, SwapAdjacentBlocks(BitCast(dw, v)));
}

// ------------------------------ InterleaveEvenBlocks (ConcatLowerLower)
template <class D, class V = VFromD<D>, HWY_IF_V_SIZE_D(D, 32)>
HWY_API V InterleaveEvenBlocks(D d, V a, V b) {
  return ConcatLowerLower(d, b, a);
}

// ------------------------------ InterleaveOddBlocks (ConcatUpperUpper)
template <class D, class V = VFromD<D>, HWY_IF_V_SIZE_D(D, 32)>
HWY_API V InterleaveOddBlocks(D d, V a, V b) {
  return ConcatUpperUpper(d, b, a);
}

// ------------------------------ Reverse (RotateRight)

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 4)>
HWY_API VFromD<D> Reverse(D d, const VFromD<D> v) {
  alignas(32) static constexpr int32_t kReverse[8] = {7, 6, 5, 4, 3, 2, 1, 0};
  return TableLookupLanes(v, SetTableIndices(d, kReverse));
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 8)>
HWY_API VFromD<D> Reverse(D d, const VFromD<D> v) {
  alignas(32) static constexpr int64_t kReverse[4] = {3, 2, 1, 0};
  return TableLookupLanes(v, SetTableIndices(d, kReverse));
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> Reverse(D d, const VFromD<D> v) {
#if HWY_TARGET <= HWY_AVX3
  const RebindToSigned<decltype(d)> di;
  alignas(32) static constexpr int16_t kReverse[16] = {
      15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0};
  const Vec256<int16_t> idx = Load(di, kReverse);
  return BitCast(d, Vec256<int16_t>{
                        _mm256_permutexvar_epi16(idx.raw, BitCast(di, v).raw)});
#else
  const RebindToSigned<decltype(d)> di;
  const VFromD<decltype(di)> shuffle = Dup128VecFromValues(
      di, 0x0F0E, 0x0D0C, 0x0B0A, 0x0908, 0x0706, 0x0504, 0x0302, 0x0100);
  const auto rev128 = TableLookupBytes(v, shuffle);
  return VFromD<D>{
      _mm256_permute4x64_epi64(rev128.raw, _MM_SHUFFLE(1, 0, 3, 2))};
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> Reverse(D d, const VFromD<D> v) {
#if HWY_TARGET <= HWY_AVX3_DL
  alignas(32) static constexpr TFromD<D> kReverse[32] = {
      31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16,
      15, 14, 13, 12, 11, 10, 9,  8,  7,  6,  5,  4,  3,  2,  1,  0};
  return TableLookupLanes(v, SetTableIndices(d, kReverse));
#else
  // First reverse bytes within blocks via PSHUFB, then swap blocks.
  alignas(32) static constexpr TFromD<D> kReverse[32] = {
      15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0,
      15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0};
  return SwapAdjacentBlocks(TableLookupBytes(v, Load(d, kReverse)));
#endif
}

// ------------------------------ Reverse2 (in x86_128)

// ------------------------------ Reverse4 (SwapAdjacentBlocks)

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> Reverse4(D d, const VFromD<D> v) {
  const RebindToSigned<decltype(d)> di;
  const VFromD<decltype(di)> shuffle = Dup128VecFromValues(
      di, 0x0706, 0x0504, 0x0302, 0x0100, 0x0F0E, 0x0D0C, 0x0B0A, 0x0908);
  return BitCast(d, TableLookupBytes(v, shuffle));
}

// 32 bit Reverse4 defined in x86_128.

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 8)>
HWY_API VFromD<D> Reverse4(D /* tag */, const VFromD<D> v) {
  // Could also use _mm256_permute4x64_epi64.
  return SwapAdjacentBlocks(Shuffle01(v));
}

// ------------------------------ Reverse8

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> Reverse8(D d, const VFromD<D> v) {
  const RebindToSigned<decltype(d)> di;
  const VFromD<decltype(di)> shuffle = Dup128VecFromValues(
      di, 0x0F0E, 0x0D0C, 0x0B0A, 0x0908, 0x0706, 0x0504, 0x0302, 0x0100);
  return BitCast(d, TableLookupBytes(v, shuffle));
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 4)>
HWY_API VFromD<D> Reverse8(D d, const VFromD<D> v) {
  return Reverse(d, v);
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 8)>
HWY_API VFromD<D> Reverse8(D /* tag */, const VFromD<D> /* v */) {
  HWY_ASSERT(0);  // AVX2 does not have 8 64-bit lanes
}

// ------------------------------ ReverseBits in x86_512

// ------------------------------ InterleaveLower

// Interleaves lanes from halves of the 128-bit blocks of "a" (which provides
// the least-significant lane) and "b". To concatenate two half-width integers
// into one, use ZipLower/Upper instead (also works with scalar).

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Vec256<T> InterleaveLower(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_unpacklo_epi8(a.raw, b.raw)};
}
template <typename T, HWY_IF_T_SIZE(T, 2)>
HWY_API Vec256<T> InterleaveLower(Vec256<T> a, Vec256<T> b) {
  const DFromV<decltype(a)> d;
  const RebindToUnsigned<decltype(d)> du;
  using VU = VFromD<decltype(du)>;  // for float16_t
  return BitCast(
      d, VU{_mm256_unpacklo_epi16(BitCast(du, a).raw, BitCast(du, b).raw)});
}
template <typename T, HWY_IF_UI32(T)>
HWY_API Vec256<T> InterleaveLower(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_unpacklo_epi32(a.raw, b.raw)};
}
template <typename T, HWY_IF_UI64(T)>
HWY_API Vec256<T> InterleaveLower(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_unpacklo_epi64(a.raw, b.raw)};
}

HWY_API Vec256<float> InterleaveLower(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_unpacklo_ps(a.raw, b.raw)};
}
HWY_API Vec256<double> InterleaveLower(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_unpacklo_pd(a.raw, b.raw)};
}

// ------------------------------ InterleaveUpper

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> InterleaveUpper(D /* tag */, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_unpackhi_epi8(a.raw, b.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> InterleaveUpper(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  using VU = VFromD<decltype(du)>;  // for float16_t
  return BitCast(
      d, VU{_mm256_unpackhi_epi16(BitCast(du, a).raw, BitCast(du, b).raw)});
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> InterleaveUpper(D /* tag */, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_unpackhi_epi32(a.raw, b.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API VFromD<D> InterleaveUpper(D /* tag */, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_unpackhi_epi64(a.raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> InterleaveUpper(D /* tag */, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_unpackhi_ps(a.raw, b.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API VFromD<D> InterleaveUpper(D /* tag */, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_unpackhi_pd(a.raw, b.raw)};
}

// ---------------------------- InsertBlock (ConcatLowerLower, ConcatUpperLower)
template <int kBlockIdx, class T>
HWY_API Vec256<T> InsertBlock(Vec256<T> v, Vec128<T> blk_to_insert) {
  static_assert(kBlockIdx == 0 || kBlockIdx == 1, "Invalid block index");

  const DFromV<decltype(v)> d;
  const auto vec_to_insert = ResizeBitCast(d, blk_to_insert);
  return (kBlockIdx == 0) ? ConcatUpperLower(d, v, vec_to_insert)
                          : ConcatLowerLower(d, vec_to_insert, v);
}

// ------------------------------ ConcatOdd

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> ConcatOdd(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3_DL
  alignas(32) static constexpr uint8_t kIdx[32] = {
      1,  3,  5,  7,  9,  11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31,
      33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 63};
  return BitCast(
      d, Vec256<uint16_t>{_mm256_permutex2var_epi8(
             BitCast(du, lo).raw, Load(du, kIdx).raw, BitCast(du, hi).raw)});
#else
  const RepartitionToWide<decltype(du)> dw;
  // Unsigned 8-bit shift so we can pack.
  const Vec256<uint16_t> uH = ShiftRight<8>(BitCast(dw, hi));
  const Vec256<uint16_t> uL = ShiftRight<8>(BitCast(dw, lo));
  const __m256i u8 = _mm256_packus_epi16(uL.raw, uH.raw);
  return VFromD<D>{_mm256_permute4x64_epi64(u8, _MM_SHUFFLE(3, 1, 2, 0))};
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> ConcatOdd(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3
  alignas(32) static constexpr uint16_t kIdx[16] = {
      1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31};
  return BitCast(
      d, Vec256<uint16_t>{_mm256_permutex2var_epi16(
             BitCast(du, lo).raw, Load(du, kIdx).raw, BitCast(du, hi).raw)});
#else
  const RepartitionToWide<decltype(du)> dw;
  // Unsigned 16-bit shift so we can pack.
  const Vec256<uint32_t> uH = ShiftRight<16>(BitCast(dw, hi));
  const Vec256<uint32_t> uL = ShiftRight<16>(BitCast(dw, lo));
  const __m256i u16 = _mm256_packus_epi32(uL.raw, uH.raw);
  return BitCast(d, VFromD<decltype(du)>{_mm256_permute4x64_epi64(
                        u16, _MM_SHUFFLE(3, 1, 2, 0))});
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> ConcatOdd(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3
  alignas(32) static constexpr uint32_t kIdx[8] = {1, 3, 5, 7, 9, 11, 13, 15};
  return BitCast(
      d, Vec256<uint32_t>{_mm256_permutex2var_epi32(
             BitCast(du, lo).raw, Load(du, kIdx).raw, BitCast(du, hi).raw)});
#else
  const RebindToFloat<decltype(d)> df;
  const Vec256<float> v3131{_mm256_shuffle_ps(
      BitCast(df, lo).raw, BitCast(df, hi).raw, _MM_SHUFFLE(3, 1, 3, 1))};
  return VFromD<D>{_mm256_permute4x64_epi64(BitCast(du, v3131).raw,
                                            _MM_SHUFFLE(3, 1, 2, 0))};
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> ConcatOdd(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3
  alignas(32) static constexpr uint32_t kIdx[8] = {1, 3, 5, 7, 9, 11, 13, 15};
  return VFromD<D>{_mm256_permutex2var_ps(lo.raw, Load(du, kIdx).raw, hi.raw)};
#else
  const VFromD<D> v3131{
      _mm256_shuffle_ps(lo.raw, hi.raw, _MM_SHUFFLE(3, 1, 3, 1))};
  return BitCast(d, Vec256<uint32_t>{_mm256_permute4x64_epi64(
                        BitCast(du, v3131).raw, _MM_SHUFFLE(3, 1, 2, 0))});
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API VFromD<D> ConcatOdd(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3
  alignas(64) static constexpr uint64_t kIdx[4] = {1, 3, 5, 7};
  return BitCast(
      d, Vec256<uint64_t>{_mm256_permutex2var_epi64(
             BitCast(du, lo).raw, Load(du, kIdx).raw, BitCast(du, hi).raw)});
#else
  const RebindToFloat<decltype(d)> df;
  const Vec256<double> v31{
      _mm256_shuffle_pd(BitCast(df, lo).raw, BitCast(df, hi).raw, 15)};
  return VFromD<D>{
      _mm256_permute4x64_epi64(BitCast(du, v31).raw, _MM_SHUFFLE(3, 1, 2, 0))};
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> ConcatOdd(D d, Vec256<double> hi, Vec256<double> lo) {
#if HWY_TARGET <= HWY_AVX3
  const RebindToUnsigned<decltype(d)> du;
  alignas(64) static constexpr uint64_t kIdx[4] = {1, 3, 5, 7};
  return Vec256<double>{
      _mm256_permutex2var_pd(lo.raw, Load(du, kIdx).raw, hi.raw)};
#else
  (void)d;
  const Vec256<double> v31{_mm256_shuffle_pd(lo.raw, hi.raw, 15)};
  return Vec256<double>{
      _mm256_permute4x64_pd(v31.raw, _MM_SHUFFLE(3, 1, 2, 0))};
#endif
}

// ------------------------------ ConcatEven

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> ConcatEven(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3_DL
  alignas(64) static constexpr uint8_t kIdx[32] = {
      0,  2,  4,  6,  8,  10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30,
      32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62};
  return BitCast(
      d, Vec256<uint32_t>{_mm256_permutex2var_epi8(
             BitCast(du, lo).raw, Load(du, kIdx).raw, BitCast(du, hi).raw)});
#else
  const RepartitionToWide<decltype(du)> dw;
  // Isolate lower 8 bits per u16 so we can pack.
  const Vec256<uint16_t> mask = Set(dw, 0x00FF);
  const Vec256<uint16_t> uH = And(BitCast(dw, hi), mask);
  const Vec256<uint16_t> uL = And(BitCast(dw, lo), mask);
  const __m256i u8 = _mm256_packus_epi16(uL.raw, uH.raw);
  return VFromD<D>{_mm256_permute4x64_epi64(u8, _MM_SHUFFLE(3, 1, 2, 0))};
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> ConcatEven(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3
  alignas(64) static constexpr uint16_t kIdx[16] = {
      0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30};
  return BitCast(
      d, Vec256<uint32_t>{_mm256_permutex2var_epi16(
             BitCast(du, lo).raw, Load(du, kIdx).raw, BitCast(du, hi).raw)});
#else
  const RepartitionToWide<decltype(du)> dw;
  // Isolate lower 16 bits per u32 so we can pack.
  const Vec256<uint32_t> mask = Set(dw, 0x0000FFFF);
  const Vec256<uint32_t> uH = And(BitCast(dw, hi), mask);
  const Vec256<uint32_t> uL = And(BitCast(dw, lo), mask);
  const __m256i u16 = _mm256_packus_epi32(uL.raw, uH.raw);
  return BitCast(d, VFromD<decltype(du)>{_mm256_permute4x64_epi64(
                        u16, _MM_SHUFFLE(3, 1, 2, 0))});
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> ConcatEven(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3
  alignas(64) static constexpr uint32_t kIdx[8] = {0, 2, 4, 6, 8, 10, 12, 14};
  return BitCast(
      d, Vec256<uint32_t>{_mm256_permutex2var_epi32(
             BitCast(du, lo).raw, Load(du, kIdx).raw, BitCast(du, hi).raw)});
#else
  const RebindToFloat<decltype(d)> df;
  const Vec256<float> v2020{_mm256_shuffle_ps(
      BitCast(df, lo).raw, BitCast(df, hi).raw, _MM_SHUFFLE(2, 0, 2, 0))};
  return VFromD<D>{_mm256_permute4x64_epi64(BitCast(du, v2020).raw,
                                            _MM_SHUFFLE(3, 1, 2, 0))};

#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> ConcatEven(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3
  alignas(64) static constexpr uint32_t kIdx[8] = {0, 2, 4, 6, 8, 10, 12, 14};
  return VFromD<D>{_mm256_permutex2var_ps(lo.raw, Load(du, kIdx).raw, hi.raw)};
#else
  const VFromD<D> v2020{
      _mm256_shuffle_ps(lo.raw, hi.raw, _MM_SHUFFLE(2, 0, 2, 0))};
  return BitCast(d, Vec256<uint32_t>{_mm256_permute4x64_epi64(
                        BitCast(du, v2020).raw, _MM_SHUFFLE(3, 1, 2, 0))});

#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API VFromD<D> ConcatEven(D d, VFromD<D> hi, VFromD<D> lo) {
  const RebindToUnsigned<decltype(d)> du;
#if HWY_TARGET <= HWY_AVX3
  alignas(64) static constexpr uint64_t kIdx[4] = {0, 2, 4, 6};
  return BitCast(
      d, Vec256<uint64_t>{_mm256_permutex2var_epi64(
             BitCast(du, lo).raw, Load(du, kIdx).raw, BitCast(du, hi).raw)});
#else
  const RebindToFloat<decltype(d)> df;
  const Vec256<double> v20{
      _mm256_shuffle_pd(BitCast(df, lo).raw, BitCast(df, hi).raw, 0)};
  return VFromD<D>{
      _mm256_permute4x64_epi64(BitCast(du, v20).raw, _MM_SHUFFLE(3, 1, 2, 0))};

#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> ConcatEven(D d, Vec256<double> hi, Vec256<double> lo) {
#if HWY_TARGET <= HWY_AVX3
  const RebindToUnsigned<decltype(d)> du;
  alignas(64) static constexpr uint64_t kIdx[4] = {0, 2, 4, 6};
  return Vec256<double>{
      _mm256_permutex2var_pd(lo.raw, Load(du, kIdx).raw, hi.raw)};
#else
  (void)d;
  const Vec256<double> v20{_mm256_shuffle_pd(lo.raw, hi.raw, 0)};
  return Vec256<double>{
      _mm256_permute4x64_pd(v20.raw, _MM_SHUFFLE(3, 1, 2, 0))};
#endif
}

// ------------------------------ InterleaveWholeLower

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> InterleaveWholeLower(D d, VFromD<D> a, VFromD<D> b) {
#if HWY_TARGET <= HWY_AVX3_DL
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint8_t kIdx[32] = {
      0, 32, 1, 33, 2,  34, 3,  35, 4,  36, 5,  37, 6,  38, 7,  39,
      8, 40, 9, 41, 10, 42, 11, 43, 12, 44, 13, 45, 14, 46, 15, 47};
  return VFromD<D>{_mm256_permutex2var_epi8(a.raw, Load(du, kIdx).raw, b.raw)};
#else
  return ConcatLowerLower(d, InterleaveUpper(d, a, b), InterleaveLower(a, b));
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> InterleaveWholeLower(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint16_t kIdx[16] = {0, 16, 1, 17, 2, 18, 3, 19,
                                                    4, 20, 5, 21, 6, 22, 7, 23};
  return BitCast(
      d, VFromD<decltype(du)>{_mm256_permutex2var_epi16(
             BitCast(du, a).raw, Load(du, kIdx).raw, BitCast(du, b).raw)});
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> InterleaveWholeLower(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint32_t kIdx[8] = {0, 8, 1, 9, 2, 10, 3, 11};
  return VFromD<D>{_mm256_permutex2var_epi32(a.raw, Load(du, kIdx).raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> InterleaveWholeLower(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint32_t kIdx[8] = {0, 8, 1, 9, 2, 10, 3, 11};
  return VFromD<D>{_mm256_permutex2var_ps(a.raw, Load(du, kIdx).raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API VFromD<D> InterleaveWholeLower(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint64_t kIdx[4] = {0, 4, 1, 5};
  return VFromD<D>{_mm256_permutex2var_epi64(a.raw, Load(du, kIdx).raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API VFromD<D> InterleaveWholeLower(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint64_t kIdx[4] = {0, 4, 1, 5};
  return VFromD<D>{_mm256_permutex2var_pd(a.raw, Load(du, kIdx).raw, b.raw)};
}
#else  // AVX2
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> InterleaveWholeLower(D d, VFromD<D> a, VFromD<D> b) {
  return ConcatLowerLower(d, InterleaveUpper(d, a, b), InterleaveLower(a, b));
}
#endif

// ------------------------------ InterleaveWholeUpper

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> InterleaveWholeUpper(D d, VFromD<D> a, VFromD<D> b) {
#if HWY_TARGET <= HWY_AVX3_DL
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint8_t kIdx[32] = {
      16, 48, 17, 49, 18, 50, 19, 51, 20, 52, 21, 53, 22, 54, 23, 55,
      24, 56, 25, 57, 26, 58, 27, 59, 28, 60, 29, 61, 30, 62, 31, 63};
  return VFromD<D>{_mm256_permutex2var_epi8(a.raw, Load(du, kIdx).raw, b.raw)};
#else
  return ConcatUpperUpper(d, InterleaveUpper(d, a, b), InterleaveLower(a, b));
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> InterleaveWholeUpper(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint16_t kIdx[16] = {
      8, 24, 9, 25, 10, 26, 11, 27, 12, 28, 13, 29, 14, 30, 15, 31};
  return BitCast(
      d, VFromD<decltype(du)>{_mm256_permutex2var_epi16(
             BitCast(du, a).raw, Load(du, kIdx).raw, BitCast(du, b).raw)});
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> InterleaveWholeUpper(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint32_t kIdx[8] = {4, 12, 5, 13, 6, 14, 7, 15};
  return VFromD<D>{_mm256_permutex2var_epi32(a.raw, Load(du, kIdx).raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> InterleaveWholeUpper(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint32_t kIdx[8] = {4, 12, 5, 13, 6, 14, 7, 15};
  return VFromD<D>{_mm256_permutex2var_ps(a.raw, Load(du, kIdx).raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI64_D(D)>
HWY_API VFromD<D> InterleaveWholeUpper(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint64_t kIdx[4] = {2, 6, 3, 7};
  return VFromD<D>{_mm256_permutex2var_epi64(a.raw, Load(du, kIdx).raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API VFromD<D> InterleaveWholeUpper(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint64_t kIdx[4] = {2, 6, 3, 7};
  return VFromD<D>{_mm256_permutex2var_pd(a.raw, Load(du, kIdx).raw, b.raw)};
}
#else  // AVX2
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> InterleaveWholeUpper(D d, VFromD<D> a, VFromD<D> b) {
  return ConcatUpperUpper(d, InterleaveUpper(d, a, b), InterleaveLower(a, b));
}
#endif

// ------------------------------ DupEven (InterleaveLower)

template <typename T, HWY_IF_UI32(T)>
HWY_API Vec256<T> DupEven(Vec256<T> v) {
  return Vec256<T>{_mm256_shuffle_epi32(v.raw, _MM_SHUFFLE(2, 2, 0, 0))};
}
HWY_API Vec256<float> DupEven(Vec256<float> v) {
  return Vec256<float>{
      _mm256_shuffle_ps(v.raw, v.raw, _MM_SHUFFLE(2, 2, 0, 0))};
}

template <typename T, HWY_IF_T_SIZE(T, 8)>
HWY_API Vec256<T> DupEven(const Vec256<T> v) {
  const DFromV<decltype(v)> d;
  return InterleaveLower(d, v, v);
}

// ------------------------------ DupOdd (InterleaveUpper)

template <typename T, HWY_IF_UI32(T)>
HWY_API Vec256<T> DupOdd(Vec256<T> v) {
  return Vec256<T>{_mm256_shuffle_epi32(v.raw, _MM_SHUFFLE(3, 3, 1, 1))};
}
HWY_API Vec256<float> DupOdd(Vec256<float> v) {
  return Vec256<float>{
      _mm256_shuffle_ps(v.raw, v.raw, _MM_SHUFFLE(3, 3, 1, 1))};
}

template <typename T, HWY_IF_T_SIZE(T, 8)>
HWY_API Vec256<T> DupOdd(const Vec256<T> v) {
  const DFromV<decltype(v)> d;
  return InterleaveUpper(d, v, v);
}

// ------------------------------ OddEven

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_INLINE Vec256<T> OddEven(Vec256<T> a, Vec256<T> b) {
  const DFromV<decltype(a)> d;
  const Full256<uint8_t> d8;
  const VFromD<decltype(d8)> mask =
      Dup128VecFromValues(d8, 0xFF, 0, 0xFF, 0, 0xFF, 0, 0xFF, 0, 0xFF, 0, 0xFF,
                          0, 0xFF, 0, 0xFF, 0);
  return IfThenElse(MaskFromVec(BitCast(d, mask)), b, a);
}

template <typename T, HWY_IF_UI16(T)>
HWY_INLINE Vec256<T> OddEven(Vec256<T> a, Vec256<T> b) {
  const DFromV<decltype(a)> d;
  const RebindToUnsigned<decltype(d)> du;  // for float16_t
  return BitCast(d, VFromD<decltype(du)>{_mm256_blend_epi16(
                        BitCast(du, a).raw, BitCast(du, b).raw, 0x55)});
}

#if HWY_HAVE_FLOAT16
HWY_INLINE Vec256<float16_t> OddEven(Vec256<float16_t> a, Vec256<float16_t> b) {
  return Vec256<float16_t>{
      _mm256_mask_blend_ph(static_cast<__mmask16>(0x5555), a.raw, b.raw)};
}
#endif  // HWY_HAVE_FLOAT16

template <typename T, HWY_IF_UI32(T)>
HWY_INLINE Vec256<T> OddEven(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_blend_epi32(a.raw, b.raw, 0x55)};
}

template <typename T, HWY_IF_UI64(T)>
HWY_INLINE Vec256<T> OddEven(Vec256<T> a, Vec256<T> b) {
  return Vec256<T>{_mm256_blend_epi32(a.raw, b.raw, 0x33)};
}

HWY_API Vec256<float> OddEven(Vec256<float> a, Vec256<float> b) {
  return Vec256<float>{_mm256_blend_ps(a.raw, b.raw, 0x55)};
}

HWY_API Vec256<double> OddEven(Vec256<double> a, Vec256<double> b) {
  return Vec256<double>{_mm256_blend_pd(a.raw, b.raw, 5)};
}

// -------------------------- InterleaveEven

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_LANES_D(D, 8), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> InterleaveEven(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_mask_shuffle_epi32(
      a.raw, static_cast<__mmask8>(0xAA), b.raw,
      static_cast<_MM_PERM_ENUM>(_MM_SHUFFLE(2, 2, 0, 0)))};
}
template <class D, HWY_IF_LANES_D(D, 8), HWY_IF_F32_D(D)>
HWY_API VFromD<D> InterleaveEven(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_mask_shuffle_ps(a.raw, static_cast<__mmask8>(0xAA),
                                          b.raw, b.raw,
                                          _MM_SHUFFLE(2, 2, 0, 0))};
}
#else
template <class D, HWY_IF_LANES_D(D, 8), HWY_IF_T_SIZE_D(D, 4)>
HWY_API VFromD<D> InterleaveEven(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToFloat<decltype(d)> df;
  const VFromD<decltype(df)> b2_b0_a2_a0{_mm256_shuffle_ps(
      BitCast(df, a).raw, BitCast(df, b).raw, _MM_SHUFFLE(2, 0, 2, 0))};
  return BitCast(
      d, VFromD<decltype(df)>{_mm256_shuffle_ps(
             b2_b0_a2_a0.raw, b2_b0_a2_a0.raw, _MM_SHUFFLE(3, 1, 2, 0))});
}
#endif

// I64/U64/F64 InterleaveEven is generic for vector lengths >= 32 bytes
template <class D, HWY_IF_LANES_GT_D(D, 2), HWY_IF_T_SIZE_D(D, 8)>
HWY_API VFromD<D> InterleaveEven(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return InterleaveLower(a, b);
}

// -------------------------- InterleaveOdd

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_LANES_D(D, 8), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> InterleaveOdd(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_mask_shuffle_epi32(
      b.raw, static_cast<__mmask8>(0x55), a.raw,
      static_cast<_MM_PERM_ENUM>(_MM_SHUFFLE(3, 3, 1, 1)))};
}
template <class D, HWY_IF_LANES_D(D, 8), HWY_IF_F32_D(D)>
HWY_API VFromD<D> InterleaveOdd(D /*d*/, VFromD<D> a, VFromD<D> b) {
  return VFromD<D>{_mm256_mask_shuffle_ps(b.raw, static_cast<__mmask8>(0x55),
                                          a.raw, a.raw,
                                          _MM_SHUFFLE(3, 3, 1, 1))};
}
#else
template <class D, HWY_IF_LANES_D(D, 8), HWY_IF_T_SIZE_D(D, 4)>
HWY_API VFromD<D> InterleaveOdd(D d, VFromD<D> a, VFromD<D> b) {
  const RebindToFloat<decltype(d)> df;
  const VFromD<decltype(df)> b3_b1_a3_a3{_mm256_shuffle_ps(
      BitCast(df, a).raw, BitCast(df, b).raw, _MM_SHUFFLE(3, 1, 3, 1))};
  return BitCast(
      d, VFromD<decltype(df)>{_mm256_shuffle_ps(
             b3_b1_a3_a3.raw, b3_b1_a3_a3.raw, _MM_SHUFFLE(3, 1, 2, 0))});
}
#endif

// I64/U64/F64 InterleaveOdd is generic for vector lengths >= 32 bytes
template <class D, HWY_IF_LANES_GT_D(D, 2), HWY_IF_T_SIZE_D(D, 8)>
HWY_API VFromD<D> InterleaveOdd(D d, VFromD<D> a, VFromD<D> b) {
  return InterleaveUpper(d, a, b);
}

// ------------------------------ OddEvenBlocks

template <typename T, HWY_IF_NOT_FLOAT3264(T)>
Vec256<T> OddEvenBlocks(Vec256<T> odd, Vec256<T> even) {
  const DFromV<decltype(odd)> d;
  const RebindToUnsigned<decltype(d)> du;
  return BitCast(d, VFromD<decltype(du)>{_mm256_blend_epi32(
                        BitCast(du, odd).raw, BitCast(du, even).raw, 0xFu)});
}

HWY_API Vec256<float> OddEvenBlocks(Vec256<float> odd, Vec256<float> even) {
  return Vec256<float>{_mm256_blend_ps(odd.raw, even.raw, 0xFu)};
}

HWY_API Vec256<double> OddEvenBlocks(Vec256<double> odd, Vec256<double> even) {
  return Vec256<double>{_mm256_blend_pd(odd.raw, even.raw, 0x3u)};
}

// ------------------------------ ReverseBlocks (SwapAdjacentBlocks)

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> ReverseBlocks(D /*d*/, VFromD<D> v) {
  return SwapAdjacentBlocks(v);
}

// ------------------------------ TableLookupBytes (ZeroExtendVector)

// Both full
template <typename T, typename TI>
HWY_API Vec256<TI> TableLookupBytes(Vec256<T> bytes, Vec256<TI> from) {
  const DFromV<decltype(from)> d;
  return BitCast(d, Vec256<uint8_t>{_mm256_shuffle_epi8(
                        BitCast(Full256<uint8_t>(), bytes).raw,
                        BitCast(Full256<uint8_t>(), from).raw)});
}

// Partial index vector
template <typename T, typename TI, size_t NI>
HWY_API Vec128<TI, NI> TableLookupBytes(Vec256<T> bytes, Vec128<TI, NI> from) {
  const Full256<TI> di;
  const Half<decltype(di)> dih;
  // First expand to full 128, then 256.
  const auto from_256 = ZeroExtendVector(di, Vec128<TI>{from.raw});
  const auto tbl_full = TableLookupBytes(bytes, from_256);
  // Shrink to 128, then partial.
  return Vec128<TI, NI>{LowerHalf(dih, tbl_full).raw};
}

// Partial table vector
template <typename T, size_t N, typename TI>
HWY_API Vec256<TI> TableLookupBytes(Vec128<T, N> bytes, Vec256<TI> from) {
  const Full256<T> d;
  // First expand to full 128, then 256.
  const auto bytes_256 = ZeroExtendVector(d, Vec128<T>{bytes.raw});
  return TableLookupBytes(bytes_256, from);
}

// Partial both are handled by x86_128.

// ------------------------------ I8/U8 Broadcast (TableLookupBytes)

template <int kLane, class T, HWY_IF_T_SIZE(T, 1)>
HWY_API Vec256<T> Broadcast(const Vec256<T> v) {
  static_assert(0 <= kLane && kLane < 16, "Invalid lane");
  return TableLookupBytes(v, Set(Full256<T>(), static_cast<T>(kLane)));
}

// ------------------------------ Per4LaneBlockShuffle

namespace detail {

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_INLINE VFromD<D> Per4LaneBlkShufDupSet4xU32(D d, const uint32_t x3,
                                                const uint32_t x2,
                                                const uint32_t x1,
                                                const uint32_t x0) {
  return BitCast(d, Vec256<uint32_t>{_mm256_set_epi32(
                        static_cast<int32_t>(x3), static_cast<int32_t>(x2),
                        static_cast<int32_t>(x1), static_cast<int32_t>(x0),
                        static_cast<int32_t>(x3), static_cast<int32_t>(x2),
                        static_cast<int32_t>(x1), static_cast<int32_t>(x0))});
}

template <size_t kIdx3210, class V, HWY_IF_NOT_FLOAT(TFromV<V>)>
HWY_INLINE V Per4LaneBlockShuffle(hwy::SizeTag<kIdx3210> /*idx_3210_tag*/,
                                  hwy::SizeTag<4> /*lane_size_tag*/,
                                  hwy::SizeTag<32> /*vect_size_tag*/, V v) {
  return V{_mm256_shuffle_epi32(v.raw, static_cast<int>(kIdx3210 & 0xFF))};
}

template <size_t kIdx3210, class V, HWY_IF_FLOAT(TFromV<V>)>
HWY_INLINE V Per4LaneBlockShuffle(hwy::SizeTag<kIdx3210> /*idx_3210_tag*/,
                                  hwy::SizeTag<4> /*lane_size_tag*/,
                                  hwy::SizeTag<32> /*vect_size_tag*/, V v) {
  return V{_mm256_shuffle_ps(v.raw, v.raw, static_cast<int>(kIdx3210 & 0xFF))};
}

template <class V>
HWY_INLINE V Per4LaneBlockShuffle(hwy::SizeTag<0x44> /*idx_3210_tag*/,
                                  hwy::SizeTag<8> /*lane_size_tag*/,
                                  hwy::SizeTag<32> /*vect_size_tag*/, V v) {
  const DFromV<decltype(v)> d;
  return ConcatLowerLower(d, v, v);
}

template <class V>
HWY_INLINE V Per4LaneBlockShuffle(hwy::SizeTag<0xEE> /*idx_3210_tag*/,
                                  hwy::SizeTag<8> /*lane_size_tag*/,
                                  hwy::SizeTag<32> /*vect_size_tag*/, V v) {
  const DFromV<decltype(v)> d;
  return ConcatUpperUpper(d, v, v);
}

template <size_t kIdx3210, class V, HWY_IF_NOT_FLOAT(TFromV<V>)>
HWY_INLINE V Per4LaneBlockShuffle(hwy::SizeTag<kIdx3210> /*idx_3210_tag*/,
                                  hwy::SizeTag<8> /*lane_size_tag*/,
                                  hwy::SizeTag<32> /*vect_size_tag*/, V v) {
  return V{_mm256_permute4x64_epi64(v.raw, static_cast<int>(kIdx3210 & 0xFF))};
}

template <size_t kIdx3210, class V, HWY_IF_FLOAT(TFromV<V>)>
HWY_INLINE V Per4LaneBlockShuffle(hwy::SizeTag<kIdx3210> /*idx_3210_tag*/,
                                  hwy::SizeTag<8> /*lane_size_tag*/,
                                  hwy::SizeTag<32> /*vect_size_tag*/, V v) {
  return V{_mm256_permute4x64_pd(v.raw, static_cast<int>(kIdx3210 & 0xFF))};
}

}  // namespace detail

// ------------------------------ SlideUpLanes

namespace detail {

#if HWY_TARGET <= HWY_AVX3
template <int kI32Lanes, class V, HWY_IF_V_SIZE_V(V, 32)>
HWY_INLINE V CombineShiftRightI32Lanes(V hi, V lo) {
  const DFromV<decltype(hi)> d;
  const Repartition<uint32_t, decltype(d)> du32;
  return BitCast(d,
                 Vec256<uint32_t>{_mm256_alignr_epi32(
                     BitCast(du32, hi).raw, BitCast(du32, lo).raw, kI32Lanes)});
}

template <int kI64Lanes, class V, HWY_IF_V_SIZE_V(V, 32)>
HWY_INLINE V CombineShiftRightI64Lanes(V hi, V lo) {
  const DFromV<decltype(hi)> d;
  const Repartition<uint64_t, decltype(d)> du64;
  return BitCast(d,
                 Vec256<uint64_t>{_mm256_alignr_epi64(
                     BitCast(du64, hi).raw, BitCast(du64, lo).raw, kI64Lanes)});
}

template <int kI64Lanes, class V, HWY_IF_V_SIZE_V(V, 32)>
HWY_INLINE V SlideUpI64Lanes(V v) {
  static_assert(0 <= kI64Lanes && kI64Lanes <= 3,
                "kI64Lanes must be between 0 and 3");
  const DFromV<decltype(v)> d;
  return CombineShiftRightI64Lanes<4 - kI64Lanes>(v, Zero(d));
}
#else   // AVX2
template <int kI64Lanes, class V, HWY_IF_V_SIZE_V(V, 32),
          HWY_IF_NOT_FLOAT_D(DFromV<V>)>
HWY_INLINE V SlideUpI64Lanes(V v) {
  static_assert(0 <= kI64Lanes && kI64Lanes <= 3,
                "kI64Lanes must be between 0 and 3");
  constexpr int kIdx0 = (-kI64Lanes) & 3;
  constexpr int kIdx1 = (-kI64Lanes + 1) & 3;
  constexpr int kIdx2 = (-kI64Lanes + 2) & 3;
  constexpr int kIdx3 = (-kI64Lanes + 3) & 3;
  constexpr int kIdx3210 = _MM_SHUFFLE(kIdx3, kIdx2, kIdx1, kIdx0);
  constexpr int kBlendMask = (1 << (kI64Lanes * 2)) - 1;

  const DFromV<decltype(v)> d;
  return V{_mm256_blend_epi32(_mm256_permute4x64_epi64(v.raw, kIdx3210),
                              Zero(d).raw, kBlendMask)};
}

template <int kI64Lanes, class V, HWY_IF_V_SIZE_V(V, 32),
          HWY_IF_FLOAT_D(DFromV<V>)>
HWY_INLINE V SlideUpI64Lanes(V v) {
  static_assert(0 <= kI64Lanes && kI64Lanes <= 3,
                "kI64Lanes must be between 0 and 3");
  constexpr int kIdx0 = (-kI64Lanes) & 3;
  constexpr int kIdx1 = (-kI64Lanes + 1) & 3;
  constexpr int kIdx2 = (-kI64Lanes + 2) & 3;
  constexpr int kIdx3 = (-kI64Lanes + 3) & 3;
  constexpr int kIdx3210 = _MM_SHUFFLE(kIdx3, kIdx2, kIdx1, kIdx0);
  constexpr int kBlendMask = (1 << kI64Lanes) - 1;

  const DFromV<decltype(v)> d;
  const Repartition<double, decltype(d)> dd;
  return BitCast(d, Vec256<double>{_mm256_blend_pd(
                        _mm256_permute4x64_pd(BitCast(dd, v).raw, kIdx3210),
                        Zero(dd).raw, kBlendMask)});
}
#endif  // HWY_TARGET <= HWY_AVX3

template <class D, HWY_IF_V_SIZE_D(D, 32),
          HWY_IF_T_SIZE_ONE_OF_D(
              D, (1 << 1) | ((HWY_TARGET > HWY_AVX3) ? (1 << 2) : 0))>
HWY_INLINE VFromD<D> TableLookupSlideUpLanes(D d, VFromD<D> v, size_t amt) {
  const Repartition<uint8_t, decltype(d)> du8;

  const auto idx_vec =
      Iota(du8, static_cast<uint8_t>(size_t{0} - amt * sizeof(TFromD<D>)));
  const Indices256<TFromD<D>> idx{idx_vec.raw};

#if HWY_TARGET <= HWY_AVX3_DL
  return TwoTablesLookupLanes(v, Zero(d), idx);
#else
  return TableLookupLanes(v, idx);
#endif
}

template <class D, HWY_IF_V_SIZE_GT_D(D, 16),
          HWY_IF_T_SIZE_ONE_OF_D(D, (1 << 4) | ((HWY_TARGET <= HWY_AVX3)
                                                    ? ((1 << 2) | (1 << 8))
                                                    : 0))>
HWY_INLINE VFromD<D> TableLookupSlideUpLanes(D d, VFromD<D> v, size_t amt) {
  const RebindToUnsigned<decltype(d)> du;
  using TU = TFromD<decltype(du)>;

  const auto idx = Iota(du, static_cast<TU>(size_t{0} - amt));
#if HWY_TARGET <= HWY_AVX3
  const auto masked_idx =
      And(idx, Set(du, static_cast<TU>(MaxLanes(d) * 2 - 1)));
  return TwoTablesLookupLanes(v, Zero(d), IndicesFromVec(d, masked_idx));
#else
  const auto masked_idx = And(idx, Set(du, static_cast<TU>(MaxLanes(d) - 1)));
  return IfThenElseZero(RebindMask(d, idx == masked_idx),
                        TableLookupLanes(v, IndicesFromVec(d, masked_idx)));
#endif
}

#if HWY_TARGET > HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 8)>
HWY_INLINE VFromD<D> TableLookupSlideUpLanes(D d, VFromD<D> v, size_t amt) {
  const RepartitionToNarrow<D> dn;
  return BitCast(d, TableLookupSlideUpLanes(dn, BitCast(dn, v), amt * 2));
}
#endif  // HWY_TARGET > HWY_AVX3

}  // namespace detail

template <int kBlocks, class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> SlideUpBlocks(D d, VFromD<D> v) {
  static_assert(0 <= kBlocks && kBlocks <= 1,
                "kBlocks must be between 0 and 1");
  return (kBlocks == 1) ? ConcatLowerLower(d, v, Zero(d)) : v;
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> SlideUpLanes(D d, VFromD<D> v, size_t amt) {
#if !HWY_IS_DEBUG_BUILD && HWY_COMPILER_GCC  // includes clang
  constexpr size_t kLanesPerBlock = 16 / sizeof(TFromD<D>);
  if (__builtin_constant_p(amt)) {
    const auto v_lo = ConcatLowerLower(d, v, Zero(d));
    switch (amt * sizeof(TFromD<D>)) {
      case 0:
        return v;
      case 1:
        return CombineShiftRightBytes<15>(d, v, v_lo);
      case 2:
        return CombineShiftRightBytes<14>(d, v, v_lo);
      case 3:
        return CombineShiftRightBytes<13>(d, v, v_lo);
      case 4:
#if HWY_TARGET <= HWY_AVX3
        return detail::CombineShiftRightI32Lanes<7>(v, Zero(d));
#else
        return CombineShiftRightBytes<12>(d, v, v_lo);
#endif
      case 5:
        return CombineShiftRightBytes<11>(d, v, v_lo);
      case 6:
        return CombineShiftRightBytes<10>(d, v, v_lo);
      case 7:
        return CombineShiftRightBytes<9>(d, v, v_lo);
      case 8:
        return detail::SlideUpI64Lanes<1>(v);
      case 9:
        return CombineShiftRightBytes<7>(d, v, v_lo);
      case 10:
        return CombineShiftRightBytes<6>(d, v, v_lo);
      case 11:
        return CombineShiftRightBytes<5>(d, v, v_lo);
      case 12:
#if HWY_TARGET <= HWY_AVX3
        return detail::CombineShiftRightI32Lanes<5>(v, Zero(d));
#else
        return CombineShiftRightBytes<4>(d, v, v_lo);
#endif
      case 13:
        return CombineShiftRightBytes<3>(d, v, v_lo);
      case 14:
        return CombineShiftRightBytes<2>(d, v, v_lo);
      case 15:
        return CombineShiftRightBytes<1>(d, v, v_lo);
      case 16:
        return ConcatLowerLower(d, v, Zero(d));
#if HWY_TARGET <= HWY_AVX3
      case 20:
        return detail::CombineShiftRightI32Lanes<3>(v, Zero(d));
#endif
      case 24:
        return detail::SlideUpI64Lanes<3>(v);
#if HWY_TARGET <= HWY_AVX3
      case 28:
        return detail::CombineShiftRightI32Lanes<1>(v, Zero(d));
#endif
    }
  }

  if (__builtin_constant_p(amt >= kLanesPerBlock) && amt >= kLanesPerBlock) {
    const Half<decltype(d)> dh;
    return Combine(d, SlideUpLanes(dh, LowerHalf(dh, v), amt - kLanesPerBlock),
                   Zero(dh));
  }
#endif

  return detail::TableLookupSlideUpLanes(d, v, amt);
}

// ------------------------------ Slide1Up

template <typename D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> Slide1Up(D d, VFromD<D> v) {
  const auto v_lo = ConcatLowerLower(d, v, Zero(d));
  return CombineShiftRightBytes<15>(d, v, v_lo);
}

template <typename D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> Slide1Up(D d, VFromD<D> v) {
  const auto v_lo = ConcatLowerLower(d, v, Zero(d));
  return CombineShiftRightBytes<14>(d, v, v_lo);
}

template <typename D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 4)>
HWY_API VFromD<D> Slide1Up(D d, VFromD<D> v) {
#if HWY_TARGET <= HWY_AVX3
  return detail::CombineShiftRightI32Lanes<7>(v, Zero(d));
#else
  const auto v_lo = ConcatLowerLower(d, v, Zero(d));
  return CombineShiftRightBytes<12>(d, v, v_lo);
#endif
}

template <typename D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 8)>
HWY_API VFromD<D> Slide1Up(D /*d*/, VFromD<D> v) {
  return detail::SlideUpI64Lanes<1>(v);
}

// ------------------------------ SlideDownLanes

namespace detail {

#if HWY_TARGET <= HWY_AVX3
template <int kI64Lanes, class V, HWY_IF_V_SIZE_V(V, 32)>
HWY_INLINE V SlideDownI64Lanes(V v) {
  static_assert(0 <= kI64Lanes && kI64Lanes <= 3,
                "kI64Lanes must be between 0 and 3");
  const DFromV<decltype(v)> d;
  return CombineShiftRightI64Lanes<kI64Lanes>(Zero(d), v);
}
#else   // AVX2
template <int kI64Lanes, class V, HWY_IF_V_SIZE_V(V, 32),
          HWY_IF_NOT_FLOAT_D(DFromV<V>)>
HWY_INLINE V SlideDownI64Lanes(V v) {
  static_assert(0 <= kI64Lanes && kI64Lanes <= 3,
                "kI64Lanes must be between 0 and 3");
  constexpr int kIdx1 = (kI64Lanes + 1) & 3;
  constexpr int kIdx2 = (kI64Lanes + 2) & 3;
  constexpr int kIdx3 = (kI64Lanes + 3) & 3;
  constexpr int kIdx3210 = _MM_SHUFFLE(kIdx3, kIdx2, kIdx1, kI64Lanes);
  constexpr int kBlendMask =
      static_cast<int>((0xFFu << ((4 - kI64Lanes) * 2)) & 0xFFu);

  const DFromV<decltype(v)> d;
  return V{_mm256_blend_epi32(_mm256_permute4x64_epi64(v.raw, kIdx3210),
                              Zero(d).raw, kBlendMask)};
}

template <int kI64Lanes, class V, HWY_IF_V_SIZE_V(V, 32),
          HWY_IF_FLOAT_D(DFromV<V>)>
HWY_INLINE V SlideDownI64Lanes(V v) {
  static_assert(0 <= kI64Lanes && kI64Lanes <= 3,
                "kI64Lanes must be between 0 and 3");
  constexpr int kIdx1 = (kI64Lanes + 1) & 3;
  constexpr int kIdx2 = (kI64Lanes + 2) & 3;
  constexpr int kIdx3 = (kI64Lanes + 3) & 3;
  constexpr int kIdx3210 = _MM_SHUFFLE(kIdx3, kIdx2, kIdx1, kI64Lanes);
  constexpr int kBlendMask = (0x0F << (4 - kI64Lanes)) & 0x0F;

  const DFromV<decltype(v)> d;
  const Repartition<double, decltype(d)> dd;
  return BitCast(d, Vec256<double>{_mm256_blend_pd(
                        _mm256_permute4x64_pd(BitCast(dd, v).raw, kIdx3210),
                        Zero(dd).raw, kBlendMask)});
}
#endif  // HWY_TARGET <= HWY_AVX3

template <class D, HWY_IF_V_SIZE_D(D, 32),
          HWY_IF_T_SIZE_ONE_OF_D(
              D, (1 << 1) | ((HWY_TARGET > HWY_AVX3) ? (1 << 2) : 0))>
HWY_INLINE VFromD<D> TableLookupSlideDownLanes(D d, VFromD<D> v, size_t amt) {
  const Repartition<uint8_t, decltype(d)> du8;

  auto idx_vec = Iota(du8, static_cast<uint8_t>(amt * sizeof(TFromD<D>)));

#if HWY_TARGET <= HWY_AVX3_DL
  const auto result_mask = idx_vec < Set(du8, uint8_t{32});
  return VFromD<D>{
      _mm256_maskz_permutexvar_epi8(result_mask.raw, idx_vec.raw, v.raw)};
#else
  const RebindToSigned<decltype(du8)> di8;
  idx_vec =
      Or(idx_vec, BitCast(du8, VecFromMask(di8, BitCast(di8, idx_vec) >
                                                    Set(di8, int8_t{31}))));
  return TableLookupLanes(v, Indices256<TFromD<D>>{idx_vec.raw});
#endif
}

template <class D, HWY_IF_V_SIZE_GT_D(D, 16),
          HWY_IF_T_SIZE_ONE_OF_D(D, (1 << 4) | ((HWY_TARGET <= HWY_AVX3)
                                                    ? ((1 << 2) | (1 << 8))
                                                    : 0))>
HWY_INLINE VFromD<D> TableLookupSlideDownLanes(D d, VFromD<D> v, size_t amt) {
  const RebindToUnsigned<decltype(d)> du;
  using TU = TFromD<decltype(du)>;

  const auto idx = Iota(du, static_cast<TU>(amt));
  const auto masked_idx = And(idx, Set(du, static_cast<TU>(MaxLanes(d) - 1)));

  return IfThenElseZero(RebindMask(d, idx == masked_idx),
                        TableLookupLanes(v, IndicesFromVec(d, masked_idx)));
}

#if HWY_TARGET > HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 8)>
HWY_INLINE VFromD<D> TableLookupSlideDownLanes(D d, VFromD<D> v, size_t amt) {
  const RepartitionToNarrow<D> dn;
  return BitCast(d, TableLookupSlideDownLanes(dn, BitCast(dn, v), amt * 2));
}
#endif  // HWY_TARGET > HWY_AVX3

}  // namespace detail

template <int kBlocks, class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> SlideDownBlocks(D d, VFromD<D> v) {
  static_assert(0 <= kBlocks && kBlocks <= 1,
                "kBlocks must be between 0 and 1");
  const Half<decltype(d)> dh;
  return (kBlocks == 1) ? ZeroExtendVector(d, UpperHalf(dh, v)) : v;
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API VFromD<D> SlideDownLanes(D d, VFromD<D> v, size_t amt) {
#if !HWY_IS_DEBUG_BUILD && HWY_COMPILER_GCC  // includes clang
  constexpr size_t kLanesPerBlock = 16 / sizeof(TFromD<D>);
  const Half<decltype(d)> dh;
  if (__builtin_constant_p(amt)) {
    const auto v_hi = ZeroExtendVector(d, UpperHalf(dh, v));
    switch (amt * sizeof(TFromD<D>)) {
      case 0:
        return v;
      case 1:
        return CombineShiftRightBytes<1>(d, v_hi, v);
      case 2:
        return CombineShiftRightBytes<2>(d, v_hi, v);
      case 3:
        return CombineShiftRightBytes<3>(d, v_hi, v);
      case 4:
#if HWY_TARGET <= HWY_AVX3
        return detail::CombineShiftRightI32Lanes<1>(Zero(d), v);
#else
        return CombineShiftRightBytes<4>(d, v_hi, v);
#endif
      case 5:
        return CombineShiftRightBytes<5>(d, v_hi, v);
      case 6:
        return CombineShiftRightBytes<6>(d, v_hi, v);
      case 7:
        return CombineShiftRightBytes<7>(d, v_hi, v);
      case 8:
        return detail::SlideDownI64Lanes<1>(v);
      case 9:
        return CombineShiftRightBytes<9>(d, v_hi, v);
      case 10:
        return CombineShiftRightBytes<10>(d, v_hi, v);
      case 11:
        return CombineShiftRightBytes<11>(d, v_hi, v);
      case 12:
#if HWY_TARGET <= HWY_AVX3
        return detail::CombineShiftRightI32Lanes<3>(Zero(d), v);
#else
        return CombineShiftRightBytes<12>(d, v_hi, v);
#endif
      case 13:
        return CombineShiftRightBytes<13>(d, v_hi, v);
      case 14:
        return CombineShiftRightBytes<14>(d, v_hi, v);
      case 15:
        return CombineShiftRightBytes<15>(d, v_hi, v);
      case 16:
        return v_hi;
#if HWY_TARGET <= HWY_AVX3
      case 20:
        return detail::CombineShiftRightI32Lanes<5>(Zero(d), v);
#endif
      case 24:
        return detail::SlideDownI64Lanes<3>(v);
#if HWY_TARGET <= HWY_AVX3
      case 28:
        return detail::CombineShiftRightI32Lanes<7>(Zero(d), v);
#endif
    }
  }

  if (__builtin_constant_p(amt >= kLanesPerBlock) && amt >= kLanesPerBlock) {
    return ZeroExtendVector(
        d, SlideDownLanes(dh, UpperHalf(dh, v), amt - kLanesPerBlock));
  }
#endif

  return detail::TableLookupSlideDownLanes(d, v, amt);
}

// ------------------------------ Slide1Down

template <typename D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 1)>
HWY_API VFromD<D> Slide1Down(D d, VFromD<D> v) {
  const Half<decltype(d)> dh;
  const auto v_hi = ZeroExtendVector(d, UpperHalf(dh, v));
  return CombineShiftRightBytes<1>(d, v_hi, v);
}

template <typename D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API VFromD<D> Slide1Down(D d, VFromD<D> v) {
  const Half<decltype(d)> dh;
  const auto v_hi = ZeroExtendVector(d, UpperHalf(dh, v));
  return CombineShiftRightBytes<2>(d, v_hi, v);
}

template <typename D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 4)>
HWY_API VFromD<D> Slide1Down(D d, VFromD<D> v) {
#if HWY_TARGET <= HWY_AVX3
  return detail::CombineShiftRightI32Lanes<1>(Zero(d), v);
#else
  const Half<decltype(d)> dh;
  const auto v_hi = ZeroExtendVector(d, UpperHalf(dh, v));
  return CombineShiftRightBytes<4>(d, v_hi, v);
#endif
}

template <typename D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 8)>
HWY_API VFromD<D> Slide1Down(D /*d*/, VFromD<D> v) {
  return detail::SlideDownI64Lanes<1>(v);
}

// ------------------------------ Shl (Mul, ZipLower)

namespace detail {

#if HWY_TARGET > HWY_AVX3 && !HWY_IDE  // AVX2 or older
template <class V>
HWY_INLINE V AVX2ShlU16Vec256(V v, V bits) {
  const DFromV<decltype(v)> d;
  const Half<decltype(d)> dh;
  const Rebind<uint32_t, decltype(dh)> du32;

  const auto lo_shl_result = PromoteTo(du32, LowerHalf(dh, v))
                             << PromoteTo(du32, LowerHalf(dh, bits));
  const auto hi_shl_result = PromoteTo(du32, UpperHalf(dh, v))
                             << PromoteTo(du32, UpperHalf(dh, bits));
  return ConcatEven(d, BitCast(d, hi_shl_result), BitCast(d, lo_shl_result));
}
#endif

HWY_INLINE Vec256<uint16_t> Shl(hwy::UnsignedTag /*tag*/, Vec256<uint16_t> v,
                                Vec256<uint16_t> bits) {
#if HWY_TARGET <= HWY_AVX3 || HWY_IDE
  return Vec256<uint16_t>{_mm256_sllv_epi16(v.raw, bits.raw)};
#else
  return AVX2ShlU16Vec256(v, bits);
#endif
}

// 8-bit: may use the Shl overload for uint16_t.
HWY_API Vec256<uint8_t> Shl(hwy::UnsignedTag tag, Vec256<uint8_t> v,
                            Vec256<uint8_t> bits) {
  const DFromV<decltype(v)> d;
#if HWY_TARGET <= HWY_AVX3_DL
  (void)tag;
  // masks[i] = 0xFF >> i
  const VFromD<decltype(d)> masks =
      Dup128VecFromValues(d, 0xFF, 0x7F, 0x3F, 0x1F, 0x0F, 0x07, 0x03, 0x01, 0,
                          0, 0, 0, 0, 0, 0, 0);
  // kShl[i] = 1 << i
  const VFromD<decltype(d)> shl = Dup128VecFromValues(
      d, 1, 2, 4, 8, 0x10, 0x20, 0x40, 0x80, 0, 0, 0, 0, 0, 0, 0, 0);
  v = And(v, TableLookupBytes(masks, bits));
  const VFromD<decltype(d)> mul = TableLookupBytes(shl, bits);
  return VFromD<decltype(d)>{_mm256_gf2p8mul_epi8(v.raw, mul.raw)};
#else
  const Repartition<uint16_t, decltype(d)> dw;
  using VW = VFromD<decltype(dw)>;
  const VW even_mask = Set(dw, 0x00FF);
  const VW odd_mask = Set(dw, 0xFF00);
  const VW vw = BitCast(dw, v);
  const VW bits16 = BitCast(dw, bits);
  // Shift even lanes in-place
  const VW evens = Shl(tag, vw, And(bits16, even_mask));
  const VW odds = Shl(tag, And(vw, odd_mask), ShiftRight<8>(bits16));
  return OddEven(BitCast(d, odds), BitCast(d, evens));
#endif
}

HWY_INLINE Vec256<uint32_t> Shl(hwy::UnsignedTag /*tag*/, Vec256<uint32_t> v,
                                Vec256<uint32_t> bits) {
  return Vec256<uint32_t>{_mm256_sllv_epi32(v.raw, bits.raw)};
}

HWY_INLINE Vec256<uint64_t> Shl(hwy::UnsignedTag /*tag*/, Vec256<uint64_t> v,
                                Vec256<uint64_t> bits) {
  return Vec256<uint64_t>{_mm256_sllv_epi64(v.raw, bits.raw)};
}

template <typename T>
HWY_INLINE Vec256<T> Shl(hwy::SignedTag /*tag*/, Vec256<T> v, Vec256<T> bits) {
  // Signed left shifts are the same as unsigned.
  const Full256<T> di;
  const Full256<MakeUnsigned<T>> du;
  return BitCast(di,
                 Shl(hwy::UnsignedTag(), BitCast(du, v), BitCast(du, bits)));
}

}  // namespace detail

template <typename T>
HWY_API Vec256<T> operator<<(Vec256<T> v, Vec256<T> bits) {
  return detail::Shl(hwy::TypeTag<T>(), v, bits);
}

// ------------------------------ Shr (MulHigh, IfThenElse, Not)

#if HWY_TARGET > HWY_AVX3  // AVX2
namespace detail {

template <class V>
HWY_INLINE V AVX2ShrU16Vec256(V v, V bits) {
  const DFromV<decltype(v)> d;
  const Half<decltype(d)> dh;
  const Rebind<int32_t, decltype(dh)> di32;
  const Rebind<uint32_t, decltype(dh)> du32;

  const auto lo_shr_result =
      PromoteTo(du32, LowerHalf(dh, v)) >> PromoteTo(du32, LowerHalf(dh, bits));
  const auto hi_shr_result =
      PromoteTo(du32, UpperHalf(dh, v)) >> PromoteTo(du32, UpperHalf(dh, bits));
  return OrderedDemote2To(d, BitCast(di32, lo_shr_result),
                          BitCast(di32, hi_shr_result));
}

}  // namespace detail
#endif

HWY_API Vec256<uint16_t> operator>>(Vec256<uint16_t> v, Vec256<uint16_t> bits) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<uint16_t>{_mm256_srlv_epi16(v.raw, bits.raw)};
#else
  return detail::AVX2ShrU16Vec256(v, bits);
#endif
}

// 8-bit uses 16-bit shifts.
HWY_API Vec256<uint8_t> operator>>(Vec256<uint8_t> v, Vec256<uint8_t> bits) {
  const DFromV<decltype(v)> d;
  const RepartitionToWide<decltype(d)> dw;
  using VW = VFromD<decltype(dw)>;
  const VW mask = Set(dw, 0x00FF);
  const VW vw = BitCast(dw, v);
  const VW bits16 = BitCast(dw, bits);
  const VW evens = And(vw, mask) >> And(bits16, mask);
  // Shift odd lanes in-place
  const VW odds = vw >> ShiftRight<8>(bits16);
  return OddEven(BitCast(d, odds), BitCast(d, evens));
}

HWY_API Vec256<uint32_t> operator>>(Vec256<uint32_t> v, Vec256<uint32_t> bits) {
  return Vec256<uint32_t>{_mm256_srlv_epi32(v.raw, bits.raw)};
}

HWY_API Vec256<uint64_t> operator>>(Vec256<uint64_t> v, Vec256<uint64_t> bits) {
  return Vec256<uint64_t>{_mm256_srlv_epi64(v.raw, bits.raw)};
}

#if HWY_TARGET > HWY_AVX3  // AVX2
namespace detail {

template <class V>
HWY_INLINE V AVX2ShrI16Vec256(V v, V bits) {
  const DFromV<decltype(v)> d;
  const Half<decltype(d)> dh;
  const Rebind<int32_t, decltype(dh)> di32;

  const auto lo_shr_result =
      PromoteTo(di32, LowerHalf(dh, v)) >> PromoteTo(di32, LowerHalf(dh, bits));
  const auto hi_shr_result =
      PromoteTo(di32, UpperHalf(dh, v)) >> PromoteTo(di32, UpperHalf(dh, bits));
  return OrderedDemote2To(d, lo_shr_result, hi_shr_result);
}

}  // namespace detail
#endif

HWY_API Vec256<int16_t> operator>>(Vec256<int16_t> v, Vec256<int16_t> bits) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<int16_t>{_mm256_srav_epi16(v.raw, bits.raw)};
#else
  return detail::AVX2ShrI16Vec256(v, bits);
#endif
}

// 8-bit uses 16-bit shifts.
HWY_API Vec256<int8_t> operator>>(Vec256<int8_t> v, Vec256<int8_t> bits) {
  const DFromV<decltype(v)> d;
  const RepartitionToWide<decltype(d)> dw;
  const RebindToUnsigned<decltype(dw)> dw_u;
  using VW = VFromD<decltype(dw)>;
  const VW mask = Set(dw, 0x00FF);
  const VW vw = BitCast(dw, v);
  const VW bits16 = BitCast(dw, bits);
  const VW evens = ShiftRight<8>(ShiftLeft<8>(vw)) >> And(bits16, mask);
  // Shift odd lanes in-place
  const VW odds = vw >> BitCast(dw, ShiftRight<8>(BitCast(dw_u, bits16)));
  return OddEven(BitCast(d, odds), BitCast(d, evens));
}

HWY_API Vec256<int32_t> operator>>(Vec256<int32_t> v, Vec256<int32_t> bits) {
  return Vec256<int32_t>{_mm256_srav_epi32(v.raw, bits.raw)};
}

HWY_API Vec256<int64_t> operator>>(Vec256<int64_t> v, Vec256<int64_t> bits) {
#if HWY_TARGET <= HWY_AVX3
  return Vec256<int64_t>{_mm256_srav_epi64(v.raw, bits.raw)};
#else
  const DFromV<decltype(v)> d;
  return detail::SignedShr(d, v, bits);
#endif
}

// ------------------------------ WidenMulPairwiseAdd

#if HWY_NATIVE_DOT_BF16

template <class DF, HWY_IF_F32_D(DF), HWY_IF_V_SIZE_D(DF, 32),
          class VBF = VFromD<Repartition<bfloat16_t, DF>>>
HWY_API VFromD<DF> WidenMulPairwiseAdd(DF df, VBF a, VBF b) {
  return VFromD<DF>{_mm256_dpbf16_ps(Zero(df).raw,
                                     reinterpret_cast<__m256bh>(a.raw),
                                     reinterpret_cast<__m256bh>(b.raw))};
}

#endif  // HWY_NATIVE_DOT_BF16

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I32_D(D)>
HWY_API VFromD<D> WidenMulPairwiseAdd(D /*d32*/, Vec256<int16_t> a,
                                      Vec256<int16_t> b) {
  return VFromD<D>{_mm256_madd_epi16(a.raw, b.raw)};
}

// ------------------------------ SatWidenMulPairwiseAdd

template <class DI16, HWY_IF_V_SIZE_D(DI16, 32), HWY_IF_I16_D(DI16)>
HWY_API VFromD<DI16> SatWidenMulPairwiseAdd(
    DI16 /* tag */, VFromD<Repartition<uint8_t, DI16>> a,
    VFromD<Repartition<int8_t, DI16>> b) {
  return VFromD<DI16>{_mm256_maddubs_epi16(a.raw, b.raw)};
}

// ------------------------------ SatWidenMulPairwiseAccumulate

#if HWY_TARGET <= HWY_AVX3_DL
template <class DI32, HWY_IF_I32_D(DI32), HWY_IF_V_SIZE_D(DI32, 32)>
HWY_API VFromD<DI32> SatWidenMulPairwiseAccumulate(
    DI32 /* tag */, VFromD<Repartition<int16_t, DI32>> a,
    VFromD<Repartition<int16_t, DI32>> b, VFromD<DI32> sum) {
  return VFromD<DI32>{_mm256_dpwssds_epi32(sum.raw, a.raw, b.raw)};
}
#endif  // HWY_TARGET <= HWY_AVX3_DL

// ------------------------------ ReorderWidenMulAccumulate

#if HWY_NATIVE_DOT_BF16
template <class DF, HWY_IF_F32_D(DF), HWY_IF_V_SIZE_D(DF, 32),
          class VBF = VFromD<Repartition<bfloat16_t, DF>>>
HWY_API VFromD<DF> ReorderWidenMulAccumulate(DF /*df*/, VBF a, VBF b,
                                             const VFromD<DF> sum0,
                                             VFromD<DF>& /*sum1*/) {
  return VFromD<DF>{_mm256_dpbf16_ps(sum0.raw,
                                     reinterpret_cast<__m256bh>(a.raw),
                                     reinterpret_cast<__m256bh>(b.raw))};
}
#endif  // HWY_NATIVE_DOT_BF16

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I32_D(D)>
HWY_API VFromD<D> ReorderWidenMulAccumulate(D d, Vec256<int16_t> a,
                                            Vec256<int16_t> b,
                                            const VFromD<D> sum0,
                                            VFromD<D>& /*sum1*/) {
  (void)d;
#if HWY_TARGET <= HWY_AVX3_DL
  return VFromD<D>{_mm256_dpwssd_epi32(sum0.raw, a.raw, b.raw)};
#else
  return sum0 + WidenMulPairwiseAdd(d, a, b);
#endif
}

// ------------------------------ RearrangeToOddPlusEven
HWY_API Vec256<int32_t> RearrangeToOddPlusEven(const Vec256<int32_t> sum0,
                                               Vec256<int32_t> /*sum1*/) {
  return sum0;  // invariant already holds
}

HWY_API Vec256<uint32_t> RearrangeToOddPlusEven(const Vec256<uint32_t> sum0,
                                                Vec256<uint32_t> /*sum1*/) {
  return sum0;  // invariant already holds
}

// ------------------------------ SumOfMulQuadAccumulate

#if HWY_TARGET <= HWY_AVX3_DL

template <class DI32, HWY_IF_V_SIZE_D(DI32, 32)>
HWY_API VFromD<DI32> SumOfMulQuadAccumulate(
    DI32 /*di32*/, VFromD<Repartition<uint8_t, DI32>> a_u,
    VFromD<Repartition<int8_t, DI32>> b_i, VFromD<DI32> sum) {
  return VFromD<DI32>{_mm256_dpbusd_epi32(sum.raw, a_u.raw, b_i.raw)};
}

#endif

// ================================================== CONVERT

// ------------------------------ Promotions (part w/ narrow lanes -> full)

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<float> v) {
  return VFromD<D>{_mm256_cvtps_pd(v.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<int32_t> v) {
  return VFromD<D>{_mm256_cvtepi32_pd(v.raw)};
}

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API Vec256<double> PromoteTo(D /* tag */, Vec128<uint32_t> v) {
  return Vec256<double>{_mm256_cvtepu32_pd(v.raw)};
}
#endif

// Unsigned: zero-extend.
// Note: these have 3 cycle latency; if inputs are already split across the
// 128 bit blocks (in their upper/lower halves), then Zip* would be faster.
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U16_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<uint8_t> v) {
  return VFromD<D>{_mm256_cvtepu8_epi16(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U32_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<uint8_t, 8> v) {
  return VFromD<D>{_mm256_cvtepu8_epi32(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U32_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<uint16_t> v) {
  return VFromD<D>{_mm256_cvtepu16_epi32(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U64_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<uint32_t> v) {
  return VFromD<D>{_mm256_cvtepu32_epi64(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U64_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec64<uint16_t> v) {
  return VFromD<D>{_mm256_cvtepu16_epi64(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U64_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec32<uint8_t> v) {
  return VFromD<D>{_mm256_cvtepu8_epi64(v.raw)};
}

// Signed: replicate sign bit.
// Note: these have 3 cycle latency; if inputs are already split across the
// 128 bit blocks (in their upper/lower halves), then ZipUpper/lo followed by
// signed shift would be faster.
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I16_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<int8_t> v) {
  return VFromD<D>{_mm256_cvtepi8_epi16(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I32_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<int8_t, 8> v) {
  return VFromD<D>{_mm256_cvtepi8_epi32(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I32_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<int16_t> v) {
  return VFromD<D>{_mm256_cvtepi16_epi32(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I64_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec128<int32_t> v) {
  return VFromD<D>{_mm256_cvtepi32_epi64(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I64_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec64<int16_t> v) {
  return VFromD<D>{_mm256_cvtepi16_epi64(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I64_D(D)>
HWY_API VFromD<D> PromoteTo(D /* tag */, Vec32<int8_t> v) {
  return VFromD<D>{_mm256_cvtepi8_epi64(v.raw)};
}

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I64_D(D)>
HWY_API VFromD<D> PromoteInRangeTo(D /*di64*/, VFromD<Rebind<float, D>> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior with GCC if any values of v[i] are not
  // within the range of an int64_t

#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<int64_t>(v)) {
    typedef float GccF32RawVectType __attribute__((__vector_size__(16)));
    const auto raw_v = reinterpret_cast<GccF32RawVectType>(v.raw);
    return VFromD<D>{_mm256_setr_epi64x(
        detail::X86ConvertScalarFromFloat<int64_t>(raw_v[0]),
        detail::X86ConvertScalarFromFloat<int64_t>(raw_v[1]),
        detail::X86ConvertScalarFromFloat<int64_t>(raw_v[2]),
        detail::X86ConvertScalarFromFloat<int64_t>(raw_v[3]))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvttps2qq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<D>{raw_result};
#else   // !HWY_COMPILER_GCC_ACTUAL
  return VFromD<D>{_mm256_cvttps_epi64(v.raw)};
#endif  // HWY_COMPILER_GCC_ACTUAL
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U64_D(D)>
HWY_API VFromD<D> PromoteInRangeTo(D /* tag */, VFromD<Rebind<float, D>> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior with GCC if any values of v[i] are not
  // within the range of an uint64_t
#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<uint64_t>(v)) {
    typedef float GccF32RawVectType __attribute__((__vector_size__(16)));
    const auto raw_v = reinterpret_cast<GccF32RawVectType>(v.raw);
    return VFromD<D>{_mm256_setr_epi64x(
        static_cast<int64_t>(
            detail::X86ConvertScalarFromFloat<uint64_t>(raw_v[0])),
        static_cast<int64_t>(
            detail::X86ConvertScalarFromFloat<uint64_t>(raw_v[1])),
        static_cast<int64_t>(
            detail::X86ConvertScalarFromFloat<uint64_t>(raw_v[2])),
        static_cast<int64_t>(
            detail::X86ConvertScalarFromFloat<uint64_t>(raw_v[3])))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvttps2uqq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<D>{raw_result};
#else   // !HWY_COMPILER_GCC_ACTUAL
  return VFromD<D>{_mm256_cvttps_epu64(v.raw)};
#endif  // HWY_COMPILER_GCC_ACTUAL
}
#endif  // HWY_TARGET <= HWY_AVX3

// ------------------------------ PromoteEvenTo/PromoteOddTo
#if HWY_TARGET > HWY_AVX3
namespace detail {

// I32->I64 PromoteEvenTo/PromoteOddTo

template <class D, HWY_IF_LANES_D(D, 4)>
HWY_INLINE VFromD<D> PromoteEvenTo(hwy::SignedTag /*to_type_tag*/,
                                   hwy::SizeTag<8> /*to_lane_size_tag*/,
                                   hwy::SignedTag /*from_type_tag*/, D d_to,
                                   Vec256<int32_t> v) {
  return BitCast(d_to, OddEven(DupEven(BroadcastSignBit(v)), v));
}

template <class D, HWY_IF_LANES_D(D, 4)>
HWY_INLINE VFromD<D> PromoteOddTo(hwy::SignedTag /*to_type_tag*/,
                                  hwy::SizeTag<8> /*to_lane_size_tag*/,
                                  hwy::SignedTag /*from_type_tag*/, D d_to,
                                  Vec256<int32_t> v) {
  return BitCast(d_to, OddEven(BroadcastSignBit(v), DupOdd(v)));
}

}  // namespace detail
#endif

// ------------------------------ Demotions (full -> part w/ narrow lanes)

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U16_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int32_t> v) {
  const __m256i u16 = _mm256_packus_epi32(v.raw, v.raw);
  // Concatenating lower halves of both 128-bit blocks afterward is more
  // efficient than an extra input with low block = high block of v.
  return VFromD<D>{_mm256_castsi256_si128(_mm256_permute4x64_epi64(u16, 0x88))};
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U16_D(D)>
HWY_API VFromD<D> DemoteTo(D dn, Vec256<uint32_t> v) {
  const DFromV<decltype(v)> d;
  const RebindToSigned<decltype(d)> di;
  return DemoteTo(dn, BitCast(di, Min(v, Set(d, 0x7FFFFFFFu))));
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_I16_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int32_t> v) {
  const __m256i i16 = _mm256_packs_epi32(v.raw, v.raw);
  return VFromD<D>{_mm256_castsi256_si128(_mm256_permute4x64_epi64(i16, 0x88))};
}

template <class D, HWY_IF_V_SIZE_D(D, 8), HWY_IF_U8_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int32_t> v) {
  const __m256i i16_blocks = _mm256_packs_epi32(v.raw, v.raw);
  // Concatenate lower 64 bits of each 128-bit block
  const __m256i i16_concat = _mm256_permute4x64_epi64(i16_blocks, 0x88);
  const __m128i i16 = _mm256_castsi256_si128(i16_concat);
  return VFromD<D>{_mm_packus_epi16(i16, i16)};
}

template <class D, HWY_IF_V_SIZE_D(D, 8), HWY_IF_U8_D(D)>
HWY_API VFromD<D> DemoteTo(D dn, Vec256<uint32_t> v) {
#if HWY_TARGET <= HWY_AVX3
  (void)dn;
  return VFromD<D>{_mm256_cvtusepi32_epi8(v.raw)};
#else
  const DFromV<decltype(v)> d;
  const RebindToSigned<decltype(d)> di;
  return DemoteTo(dn, BitCast(di, Min(v, Set(d, 0x7FFFFFFFu))));
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U8_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int16_t> v) {
  const __m256i u8 = _mm256_packus_epi16(v.raw, v.raw);
  return VFromD<D>{_mm256_castsi256_si128(_mm256_permute4x64_epi64(u8, 0x88))};
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U8_D(D)>
HWY_API VFromD<D> DemoteTo(D dn, Vec256<uint16_t> v) {
  const DFromV<decltype(v)> d;
  const RebindToSigned<decltype(d)> di;
  return DemoteTo(dn, BitCast(di, Min(v, Set(d, 0x7FFFu))));
}

template <class D, HWY_IF_V_SIZE_D(D, 8), HWY_IF_I8_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int32_t> v) {
  const __m256i i16_blocks = _mm256_packs_epi32(v.raw, v.raw);
  // Concatenate lower 64 bits of each 128-bit block
  const __m256i i16_concat = _mm256_permute4x64_epi64(i16_blocks, 0x88);
  const __m128i i16 = _mm256_castsi256_si128(i16_concat);
  return VFromD<D>{_mm_packs_epi16(i16, i16)};
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_I8_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int16_t> v) {
  const __m256i i8 = _mm256_packs_epi16(v.raw, v.raw);
  return VFromD<D>{_mm256_castsi256_si128(_mm256_permute4x64_epi64(i8, 0x88))};
}

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_I32_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int64_t> v) {
  return VFromD<D>{_mm256_cvtsepi64_epi32(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 8), HWY_IF_I16_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int64_t> v) {
  return VFromD<D>{_mm256_cvtsepi64_epi16(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 4), HWY_IF_I8_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int64_t> v) {
  return VFromD<D>{_mm256_cvtsepi64_epi8(v.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U32_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int64_t> v) {
  const __mmask8 non_neg_mask = detail::UnmaskedNot(MaskFromVec(v)).raw;
  return VFromD<D>{_mm256_maskz_cvtusepi64_epi32(non_neg_mask, v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 8), HWY_IF_U16_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int64_t> v) {
  const __mmask8 non_neg_mask = detail::UnmaskedNot(MaskFromVec(v)).raw;
  return VFromD<D>{_mm256_maskz_cvtusepi64_epi16(non_neg_mask, v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 4), HWY_IF_U8_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<int64_t> v) {
  const __mmask8 non_neg_mask = detail::UnmaskedNot(MaskFromVec(v)).raw;
  return VFromD<D>{_mm256_maskz_cvtusepi64_epi8(non_neg_mask, v.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U32_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<uint64_t> v) {
  return VFromD<D>{_mm256_cvtusepi64_epi32(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 8), HWY_IF_U16_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<uint64_t> v) {
  return VFromD<D>{_mm256_cvtusepi64_epi16(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 4), HWY_IF_U8_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<uint64_t> v) {
  return VFromD<D>{_mm256_cvtusepi64_epi8(v.raw)};
}
#endif  // HWY_TARGET <= HWY_AVX3

#ifndef HWY_DISABLE_F16C

// Avoid "value of intrinsic immediate argument '8' is out of range '0 - 7'".
// 8 is the correct value of _MM_FROUND_NO_EXC, which is allowed here.
HWY_DIAGNOSTICS(push)
HWY_DIAGNOSTICS_OFF(disable : 4556, ignored "-Wsign-conversion")

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_F16_D(D)>
HWY_API VFromD<D> DemoteTo(D df16, Vec256<float> v) {
  const RebindToUnsigned<decltype(df16)> du16;
  return BitCast(
      df16, VFromD<decltype(du16)>{_mm256_cvtps_ph(v.raw, _MM_FROUND_NO_EXC)});
}

HWY_DIAGNOSTICS(pop)

#endif  // HWY_DISABLE_F16C

#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 8), HWY_IF_F16_D(D)>
HWY_API VFromD<D> DemoteTo(D /*df16*/, Vec256<double> v) {
  return VFromD<D>{_mm256_cvtpd_ph(v.raw)};
}
#endif  // HWY_HAVE_FLOAT16

#if HWY_AVX3_HAVE_F32_TO_BF16C
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_BF16_D(D)>
HWY_API VFromD<D> DemoteTo(D /*dbf16*/, Vec256<float> v) {
#if HWY_COMPILER_CLANG >= 1600 && HWY_COMPILER_CLANG < 2000
  // Inline assembly workaround for LLVM codegen bug
  __m128i raw_result;
  __asm__("vcvtneps2bf16 %1, %0" : "=v"(raw_result) : "v"(v.raw));
  return VFromD<D>{raw_result};
#else
  // The _mm256_cvtneps_pbh intrinsic returns a __m128bh vector that needs to be
  // bit casted to a __m128i vector
  return VFromD<D>{detail::BitCastToInteger(_mm256_cvtneps_pbh(v.raw))};
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_BF16_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D /*dbf16*/, Vec256<float> a,
                                   Vec256<float> b) {
#if HWY_COMPILER_CLANG >= 1600 && HWY_COMPILER_CLANG < 2000
  // Inline assembly workaround for LLVM codegen bug
  __m256i raw_result;
  __asm__("vcvtne2ps2bf16 %2, %1, %0"
          : "=v"(raw_result)
          : "v"(b.raw), "v"(a.raw));
  return VFromD<D>{raw_result};
#else
  // The _mm256_cvtne2ps_pbh intrinsic returns a __m256bh vector that needs to
  // be bit casted to a __m256i vector
  return VFromD<D>{detail::BitCastToInteger(_mm256_cvtne2ps_pbh(b.raw, a.raw))};
#endif
}
#endif  // HWY_AVX3_HAVE_F32_TO_BF16C

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I16_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D /*d16*/, Vec256<int32_t> a,
                                   Vec256<int32_t> b) {
  return VFromD<D>{_mm256_packs_epi32(a.raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U16_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D /*d16*/, Vec256<int32_t> a,
                                   Vec256<int32_t> b) {
  return VFromD<D>{_mm256_packus_epi32(a.raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U16_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D dn, Vec256<uint32_t> a,
                                   Vec256<uint32_t> b) {
  const DFromV<decltype(a)> d;
  const RebindToSigned<decltype(d)> di;
  const auto max_i32 = Set(d, 0x7FFFFFFFu);
  return ReorderDemote2To(dn, BitCast(di, Min(a, max_i32)),
                          BitCast(di, Min(b, max_i32)));
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I8_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D /*d16*/, Vec256<int16_t> a,
                                   Vec256<int16_t> b) {
  return VFromD<D>{_mm256_packs_epi16(a.raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U8_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D /*d16*/, Vec256<int16_t> a,
                                   Vec256<int16_t> b) {
  return VFromD<D>{_mm256_packus_epi16(a.raw, b.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U8_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D dn, Vec256<uint16_t> a,
                                   Vec256<uint16_t> b) {
  const DFromV<decltype(a)> d;
  const RebindToSigned<decltype(d)> di;
  const auto max_i16 = Set(d, 0x7FFFu);
  return ReorderDemote2To(dn, BitCast(di, Min(a, max_i16)),
                          BitCast(di, Min(b, max_i16)));
}

#if HWY_TARGET > HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I32_D(D)>
HWY_API Vec256<int32_t> ReorderDemote2To(D dn, Vec256<int64_t> a,
                                         Vec256<int64_t> b) {
  const DFromV<decltype(a)> di64;
  const RebindToUnsigned<decltype(di64)> du64;
  const Half<decltype(dn)> dnh;
  const Repartition<float, decltype(dn)> dn_f;

  // Negative values are saturated by first saturating their bitwise inverse
  // and then inverting the saturation result
  const auto invert_mask_a = BitCast(du64, BroadcastSignBit(a));
  const auto invert_mask_b = BitCast(du64, BroadcastSignBit(b));
  const auto saturated_a = Xor(
      invert_mask_a,
      detail::DemoteFromU64Saturate(dnh, Xor(invert_mask_a, BitCast(du64, a))));
  const auto saturated_b = Xor(
      invert_mask_b,
      detail::DemoteFromU64Saturate(dnh, Xor(invert_mask_b, BitCast(du64, b))));

  return BitCast(dn,
                 Vec256<float>{_mm256_shuffle_ps(BitCast(dn_f, saturated_a).raw,
                                                 BitCast(dn_f, saturated_b).raw,
                                                 _MM_SHUFFLE(2, 0, 2, 0))});
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U32_D(D)>
HWY_API Vec256<uint32_t> ReorderDemote2To(D dn, Vec256<int64_t> a,
                                          Vec256<int64_t> b) {
  const DFromV<decltype(a)> di64;
  const RebindToUnsigned<decltype(di64)> du64;
  const Half<decltype(dn)> dnh;
  const Repartition<float, decltype(dn)> dn_f;

  const auto saturated_a = detail::DemoteFromU64Saturate(
      dnh, BitCast(du64, AndNot(BroadcastSignBit(a), a)));
  const auto saturated_b = detail::DemoteFromU64Saturate(
      dnh, BitCast(du64, AndNot(BroadcastSignBit(b), b)));

  return BitCast(dn,
                 Vec256<float>{_mm256_shuffle_ps(BitCast(dn_f, saturated_a).raw,
                                                 BitCast(dn_f, saturated_b).raw,
                                                 _MM_SHUFFLE(2, 0, 2, 0))});
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D dn, Vec256<uint64_t> a,
                                   Vec256<uint64_t> b) {
  const Half<decltype(dn)> dnh;
  const Repartition<float, decltype(dn)> dn_f;

  const auto saturated_a = detail::DemoteFromU64Saturate(dnh, a);
  const auto saturated_b = detail::DemoteFromU64Saturate(dnh, b);

  return BitCast(dn,
                 Vec256<float>{_mm256_shuffle_ps(BitCast(dn_f, saturated_a).raw,
                                                 BitCast(dn_f, saturated_b).raw,
                                                 _MM_SHUFFLE(2, 0, 2, 0))});
}
#endif  // HWY_TARGET > HWY_AVX3

template <class D, class V, HWY_IF_NOT_FLOAT_NOR_SPECIAL(TFromD<D>),
          HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_FLOAT_NOR_SPECIAL_V(V),
          HWY_IF_T_SIZE_V(V, sizeof(TFromD<D>) * 2),
          HWY_IF_LANES_D(D, HWY_MAX_LANES_D(DFromV<V>) * 2),
          HWY_IF_T_SIZE_ONE_OF_V(V,
                                 (1 << 1) | (1 << 2) | (1 << 4) |
                                     ((HWY_TARGET > HWY_AVX3) ? (1 << 8) : 0))>
HWY_API VFromD<D> OrderedDemote2To(D d, V a, V b) {
  return VFromD<D>{_mm256_permute4x64_epi64(ReorderDemote2To(d, a, b).raw,
                                            _MM_SHUFFLE(3, 1, 2, 0))};
}

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, HWY_MAX_BYTES), HWY_IF_UI32_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D dn, VFromD<Repartition<int64_t, D>> a,
                                   VFromD<Repartition<int64_t, D>> b) {
  const Half<decltype(dn)> dnh;
  return Combine(dn, DemoteTo(dnh, b), DemoteTo(dnh, a));
}

template <class D, HWY_IF_V_SIZE_D(D, HWY_MAX_BYTES), HWY_IF_U32_D(D)>
HWY_API VFromD<D> ReorderDemote2To(D dn, VFromD<Repartition<uint64_t, D>> a,
                                   VFromD<Repartition<uint64_t, D>> b) {
  const Half<decltype(dn)> dnh;
  return Combine(dn, DemoteTo(dnh, b), DemoteTo(dnh, a));
}

template <class D, HWY_IF_NOT_FLOAT_NOR_SPECIAL(TFromD<D>),
          HWY_IF_V_SIZE_GT_D(D, 16), class V, HWY_IF_NOT_FLOAT_NOR_SPECIAL_V(V),
          HWY_IF_T_SIZE_V(V, sizeof(TFromD<D>) * 2),
          HWY_IF_LANES_D(D, HWY_MAX_LANES_D(DFromV<V>) * 2),
          HWY_IF_T_SIZE_V(V, 8)>
HWY_API VFromD<D> OrderedDemote2To(D d, V a, V b) {
  return ReorderDemote2To(d, a, b);
}
#endif

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_F32_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, Vec256<double> v) {
  return VFromD<D>{_mm256_cvtpd_ps(v.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_I32_D(D)>
HWY_API VFromD<D> DemoteInRangeTo(D /* tag */, Vec256<double> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvttpd_epi32 with GCC if any
  // values of v[i] are not within the range of an int32_t

#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<int32_t>(v)) {
    typedef double GccF64RawVectType __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF64RawVectType>(v.raw);
    return Dup128VecFromValues(
        D(), detail::X86ConvertScalarFromFloat<int32_t>(raw_v[0]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[1]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[2]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[3]));
  }
#endif

  __m128i raw_result;
  __asm__("vcvttpd2dq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<D>{raw_result};
#else
  return VFromD<D>{_mm256_cvttpd_epi32(v.raw)};
#endif
}

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U32_D(D)>
HWY_API VFromD<D> DemoteInRangeTo(D /* tag */, Vec256<double> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvttpd_epu32 with GCC if any
  // values of v[i] are not within the range of an uint32_t

#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<uint32_t>(v)) {
    typedef double GccF64RawVectType __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF64RawVectType>(v.raw);
    return Dup128VecFromValues(
        D(), detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[0]),
        detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[1]),
        detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[2]),
        detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[3]));
  }
#endif

  __m128i raw_result;
  __asm__("vcvttpd2udq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<D>{raw_result};
#else
  return VFromD<D>{_mm256_cvttpd_epu32(v.raw)};
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_F32_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, VFromD<Rebind<int64_t, D>> v) {
  return VFromD<D>{_mm256_cvtepi64_ps(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_F32_D(D)>
HWY_API VFromD<D> DemoteTo(D /* tag */, VFromD<Rebind<uint64_t, D>> v) {
  return VFromD<D>{_mm256_cvtepu64_ps(v.raw)};
}
#endif

// For already range-limited input [0, 255].
HWY_API Vec128<uint8_t, 8> U8FromU32(const Vec256<uint32_t> v) {
  const Full256<uint32_t> d32;
  const Full64<uint8_t> d8;
  alignas(32) static constexpr uint32_t k8From32[8] = {
      0x0C080400u, ~0u, ~0u, ~0u, ~0u, 0x0C080400u, ~0u, ~0u};
  // Place first four bytes in lo[0], remaining 4 in hi[1].
  const auto quad = TableLookupBytes(v, Load(d32, k8From32));
  // Interleave both quadruplets - OR instead of unpack reduces port5 pressure.
  const auto lo = LowerHalf(quad);
  const auto hi = UpperHalf(Half<decltype(d32)>(), quad);
  return BitCast(d8, LowerHalf(lo | hi));
}

// ------------------------------ Truncations

namespace detail {

// LO and HI each hold four indices of bytes within a 128-bit block.
template <uint32_t LO, uint32_t HI, typename T>
HWY_INLINE Vec128<uint32_t> LookupAndConcatHalves(Vec256<T> v) {
  const Full256<uint32_t> d32;

#if HWY_TARGET <= HWY_AVX3_DL
  alignas(32) static constexpr uint32_t kMap[8] = {
      LO, HI, 0x10101010 + LO, 0x10101010 + HI, 0, 0, 0, 0};
  const auto result = _mm256_permutexvar_epi8(Load(d32, kMap).raw, v.raw);
#else
  alignas(32) static constexpr uint32_t kMap[8] = {LO,  HI,  ~0u, ~0u,
                                                   ~0u, ~0u, LO,  HI};
  const auto quad = TableLookupBytes(v, Load(d32, kMap));
  const auto result = _mm256_permute4x64_epi64(quad.raw, 0xCC);
  // Possible alternative:
  // const auto lo = LowerHalf(quad);
  // const auto hi = UpperHalf(Half<decltype(d32)>(), quad);
  // const auto result = lo | hi;
#endif

  return Vec128<uint32_t>{_mm256_castsi256_si128(result)};
}

// LO and HI each hold two indices of bytes within a 128-bit block.
template <uint16_t LO, uint16_t HI, typename T>
HWY_INLINE Vec128<uint32_t, 2> LookupAndConcatQuarters(Vec256<T> v) {
  const Full256<uint16_t> d16;

#if HWY_TARGET <= HWY_AVX3_DL
  alignas(32) static constexpr uint16_t kMap[16] = {
      LO, HI, 0x1010 + LO, 0x1010 + HI, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
  const auto result = _mm256_permutexvar_epi8(Load(d16, kMap).raw, v.raw);
  return LowerHalf(Vec128<uint32_t>{_mm256_castsi256_si128(result)});
#else
  constexpr uint16_t ff = static_cast<uint16_t>(~0u);
  alignas(32) static constexpr uint16_t kMap[16] = {
      LO, ff, HI, ff, ff, ff, ff, ff, ff, ff, ff, ff, LO, ff, HI, ff};
  const auto quad = TableLookupBytes(v, Load(d16, kMap));
  const auto mixed = _mm256_permute4x64_epi64(quad.raw, 0xCC);
  const auto half = _mm256_castsi256_si128(mixed);
  return LowerHalf(Vec128<uint32_t>{_mm_packus_epi32(half, half)});
#endif
}

}  // namespace detail

template <class D, HWY_IF_V_SIZE_D(D, 4), HWY_IF_U8_D(D)>
HWY_API VFromD<D> TruncateTo(D /* tag */, Vec256<uint64_t> v) {
  const Full256<uint32_t> d32;
#if HWY_TARGET <= HWY_AVX3_DL
  alignas(32) static constexpr uint32_t kMap[8] = {0x18100800u, 0, 0, 0,
                                                   0,           0, 0, 0};
  const auto result = _mm256_permutexvar_epi8(Load(d32, kMap).raw, v.raw);
  return LowerHalf(LowerHalf(LowerHalf(Vec256<uint8_t>{result})));
#else
  alignas(32) static constexpr uint32_t kMap[8] = {0xFFFF0800u, ~0u, ~0u, ~0u,
                                                   0x0800FFFFu, ~0u, ~0u, ~0u};
  const auto quad = TableLookupBytes(v, Load(d32, kMap));
  const auto lo = LowerHalf(quad);
  const auto hi = UpperHalf(Half<decltype(d32)>(), quad);
  const auto result = lo | hi;
  return LowerHalf(LowerHalf(Vec128<uint8_t>{result.raw}));
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 8), HWY_IF_U16_D(D)>
HWY_API VFromD<D> TruncateTo(D /* tag */, Vec256<uint64_t> v) {
  const auto result = detail::LookupAndConcatQuarters<0x100, 0x908>(v);
  return VFromD<D>{result.raw};
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U32_D(D)>
HWY_API VFromD<D> TruncateTo(D /* tag */, Vec256<uint64_t> v) {
  const Full256<uint32_t> d32;
  alignas(32) static constexpr uint32_t kEven[8] = {0, 2, 4, 6, 0, 2, 4, 6};
  const auto v32 =
      TableLookupLanes(BitCast(d32, v), SetTableIndices(d32, kEven));
  return LowerHalf(Vec256<uint32_t>{v32.raw});
}

template <class D, HWY_IF_V_SIZE_D(D, 8), HWY_IF_U8_D(D)>
HWY_API VFromD<D> TruncateTo(D /* tag */, Vec256<uint32_t> v) {
  const auto full = detail::LookupAndConcatQuarters<0x400, 0xC08>(v);
  return VFromD<D>{full.raw};
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U16_D(D)>
HWY_API VFromD<D> TruncateTo(D /* tag */, Vec256<uint32_t> v) {
  const auto full = detail::LookupAndConcatHalves<0x05040100, 0x0D0C0908>(v);
  return VFromD<D>{full.raw};
}

template <class D, HWY_IF_V_SIZE_D(D, 16), HWY_IF_U8_D(D)>
HWY_API VFromD<D> TruncateTo(D /* tag */, Vec256<uint16_t> v) {
  const auto full = detail::LookupAndConcatHalves<0x06040200, 0x0E0C0A08>(v);
  return VFromD<D>{full.raw};
}

// ------------------------------ Integer <=> fp (ShiftRight, OddEven)

#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API VFromD<D> ConvertTo(D /* tag */, Vec256<uint16_t> v) {
  return VFromD<D>{_mm256_cvtepu16_ph(v.raw)};
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F16_D(D)>
HWY_API VFromD<D> ConvertTo(D /* tag */, Vec256<int16_t> v) {
  return VFromD<D>{_mm256_cvtepi16_ph(v.raw)};
}
#endif  // HWY_HAVE_FLOAT16

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> ConvertTo(D /* tag */, Vec256<int32_t> v) {
  return VFromD<D>{_mm256_cvtepi32_ps(v.raw)};
}

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> ConvertTo(D /*df*/, Vec256<uint32_t> v) {
  return VFromD<D>{_mm256_cvtepu32_ps(v.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API VFromD<D> ConvertTo(D /*dd*/, Vec256<int64_t> v) {
  return VFromD<D>{_mm256_cvtepi64_pd(v.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_API VFromD<D> ConvertTo(D /*dd*/, Vec256<uint64_t> v) {
  return VFromD<D>{_mm256_cvtepu64_pd(v.raw)};
}
#endif  // HWY_TARGET <= HWY_AVX3

// Truncates (rounds toward zero).

#if HWY_HAVE_FLOAT16
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I16_D(D)>
HWY_API VFromD<D> ConvertInRangeTo(D /*d*/, Vec256<float16_t> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvttph_epi16 with GCC if any
  // values of v[i] are not within the range of an int16_t

#if HWY_COMPILER_GCC_ACTUAL >= 1200 && !HWY_IS_DEBUG_BUILD && \
    HWY_HAVE_SCALAR_F16_TYPE
  if (detail::IsConstantX86VecForF2IConv<int16_t>(v)) {
    typedef hwy::float16_t::Native GccF16RawVectType
        __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF16RawVectType>(v.raw);
    return VFromD<D>{_mm256_setr_epi16(
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[0]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[1]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[2]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[3]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[4]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[5]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[6]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[7]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[8]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[9]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[10]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[11]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[12]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[13]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[14]),
        detail::X86ConvertScalarFromFloat<int16_t>(raw_v[15]))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvttph2w {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<D>{raw_result};
#else  // HWY_COMPILER_GCC_ACTUAL < 1200
  return VFromD<D>{_mm256_cvttph_epi16(v.raw)};
#endif
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U16_D(D)>
HWY_API VFromD<D> ConvertInRangeTo(D /* tag */, VFromD<RebindToFloat<D>> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvttph_epu16 with GCC if any
  // values of v[i] are not within the range of an uint16_t

#if HWY_COMPILER_GCC_ACTUAL >= 1200 && !HWY_IS_DEBUG_BUILD && \
    HWY_HAVE_SCALAR_F16_TYPE
  if (detail::IsConstantX86VecForF2IConv<uint16_t>(v)) {
    typedef hwy::float16_t::Native GccF16RawVectType
        __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF16RawVectType>(v.raw);
    return VFromD<D>{_mm256_setr_epi16(
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[0])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[1])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[2])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[3])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[4])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[5])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[6])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[7])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[8])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[9])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[10])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[11])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[12])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[13])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[14])),
        static_cast<int16_t>(
            detail::X86ConvertScalarFromFloat<uint16_t>(raw_v[15])))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvttph2uw {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<D>{raw_result};
#else  // HWY_COMPILER_GCC_ACTUAL < 1200
  return VFromD<D>{_mm256_cvttph_epu16(v.raw)};
#endif
}
#endif  // HWY_HAVE_FLOAT16

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I32_D(D)>
HWY_API VFromD<D> ConvertInRangeTo(D /*d*/, Vec256<float> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvttps_epi32 with GCC if any
  // values of v[i] are not within the range of an int32_t

#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<int32_t>(v)) {
    typedef float GccF32RawVectType __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF32RawVectType>(v.raw);
    return VFromD<D>{_mm256_setr_epi32(
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[0]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[1]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[2]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[3]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[4]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[5]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[6]),
        detail::X86ConvertScalarFromFloat<int32_t>(raw_v[7]))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvttps2dq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<D>{raw_result};
#else
  return VFromD<D>{_mm256_cvttps_epi32(v.raw)};
#endif
}

#if HWY_TARGET <= HWY_AVX3
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_I64_D(D)>
HWY_API VFromD<D> ConvertInRangeTo(D /*di*/, Vec256<double> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvttpd_epi64 with GCC if any
  // values of v[i] are not within the range of an int64_t

#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<int64_t>(v)) {
    typedef double GccF64RawVectType __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF64RawVectType>(v.raw);
    return VFromD<D>{_mm256_setr_epi64x(
        detail::X86ConvertScalarFromFloat<int64_t>(raw_v[0]),
        detail::X86ConvertScalarFromFloat<int64_t>(raw_v[1]),
        detail::X86ConvertScalarFromFloat<int64_t>(raw_v[2]),
        detail::X86ConvertScalarFromFloat<int64_t>(raw_v[3]))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvttpd2qq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<D>{raw_result};
#else   // !HWY_COMPILER_GCC_ACTUAL
  return VFromD<D>{_mm256_cvttpd_epi64(v.raw)};
#endif  // HWY_COMPILER_GCC_ACTUAL
}
template <class DU, HWY_IF_V_SIZE_D(DU, 32), HWY_IF_U32_D(DU)>
HWY_API VFromD<DU> ConvertInRangeTo(DU /*du*/, VFromD<RebindToFloat<DU>> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvttps_epu32 with GCC if any
  // values of v[i] are not within the range of an uint32_t

#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<uint32_t>(v)) {
    typedef float GccF32RawVectType __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF32RawVectType>(v.raw);
    return VFromD<DU>{_mm256_setr_epi32(
        static_cast<int32_t>(
            detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[0])),
        static_cast<int32_t>(
            detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[1])),
        static_cast<int32_t>(
            detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[2])),
        static_cast<int32_t>(
            detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[3])),
        static_cast<int32_t>(
            detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[4])),
        static_cast<int32_t>(
            detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[5])),
        static_cast<int32_t>(
            detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[6])),
        static_cast<int32_t>(
            detail::X86ConvertScalarFromFloat<uint32_t>(raw_v[7])))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvttps2udq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<DU>{raw_result};
#else   // !HWY_COMPILER_GCC_ACTUAL
  return VFromD<DU>{_mm256_cvttps_epu32(v.raw)};
#endif  // HWY_COMPILER_GCC_ACTUAL
}
template <class DU, HWY_IF_V_SIZE_D(DU, 32), HWY_IF_U64_D(DU)>
HWY_API VFromD<DU> ConvertInRangeTo(DU /*du*/, VFromD<RebindToFloat<DU>> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvttpd_epu64 with GCC if any
  // values of v[i] are not within the range of an uint64_t

#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<uint64_t>(v)) {
    typedef double GccF64RawVectType __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF64RawVectType>(v.raw);
    return VFromD<DU>{_mm256_setr_epi64x(
        static_cast<int64_t>(
            detail::X86ConvertScalarFromFloat<uint64_t>(raw_v[0])),
        static_cast<int64_t>(
            detail::X86ConvertScalarFromFloat<uint64_t>(raw_v[1])),
        static_cast<int64_t>(
            detail::X86ConvertScalarFromFloat<uint64_t>(raw_v[2])),
        static_cast<int64_t>(
            detail::X86ConvertScalarFromFloat<uint64_t>(raw_v[3])))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvttpd2uqq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<DU>{raw_result};
#else   // !HWY_COMPILER_GCC_ACTUAL
  return VFromD<DU>{_mm256_cvttpd_epu64(v.raw)};
#endif  // HWY_COMPILER_GCC_ACTUAL
}
#endif  // HWY_TARGET <= HWY_AVX3

template <class DI, HWY_IF_V_SIZE_D(DI, 32), HWY_IF_I32_D(DI)>
static HWY_INLINE VFromD<DI> NearestIntInRange(DI,
                                               VFromD<RebindToFloat<DI>> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvtps_epi32 if any values of
  // v[i] are not within the range of an int32_t

#if HWY_COMPILER_GCC >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<int32_t>(v)) {
    typedef float GccF32RawVectType __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF32RawVectType>(v.raw);
    return VFromD<DI>{
        _mm256_setr_epi32(detail::X86ScalarNearestInt<int32_t>(raw_v[0]),
                          detail::X86ScalarNearestInt<int32_t>(raw_v[1]),
                          detail::X86ScalarNearestInt<int32_t>(raw_v[2]),
                          detail::X86ScalarNearestInt<int32_t>(raw_v[3]),
                          detail::X86ScalarNearestInt<int32_t>(raw_v[4]),
                          detail::X86ScalarNearestInt<int32_t>(raw_v[5]),
                          detail::X86ScalarNearestInt<int32_t>(raw_v[6]),
                          detail::X86ScalarNearestInt<int32_t>(raw_v[7]))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvtps2dq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<DI>{raw_result};
#else   // !HWY_COMPILER_GCC_ACTUAL
  return VFromD<DI>{_mm256_cvtps_epi32(v.raw)};
#endif  // HWY_COMPILER_GCC_ACTUAL
}

#if HWY_HAVE_FLOAT16
template <class DI, HWY_IF_V_SIZE_D(DI, 32), HWY_IF_I16_D(DI)>
static HWY_INLINE VFromD<DI> NearestIntInRange(DI /*d*/, Vec256<float16_t> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvtph_epi16 with GCC if any
  // values of v[i] are not within the range of an int16_t

#if HWY_COMPILER_GCC_ACTUAL >= 1200 && !HWY_IS_DEBUG_BUILD && \
    HWY_HAVE_SCALAR_F16_TYPE
  if (detail::IsConstantX86VecForF2IConv<int16_t>(v)) {
    typedef hwy::float16_t::Native GccF16RawVectType
        __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF16RawVectType>(v.raw);
    return VFromD<DI>{
        _mm256_setr_epi16(detail::X86ScalarNearestInt<int16_t>(raw_v[0]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[1]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[2]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[3]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[4]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[5]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[6]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[7]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[8]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[9]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[10]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[11]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[12]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[13]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[14]),
                          detail::X86ScalarNearestInt<int16_t>(raw_v[15]))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvtph2w {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<DI>{raw_result};
#else  // HWY_COMPILER_GCC_ACTUAL
  return VFromD<DI>{_mm256_cvtph_epi16(v.raw)};
#endif
}
#endif

#if HWY_TARGET <= HWY_AVX3
template <class DI, HWY_IF_V_SIZE_D(DI, 32), HWY_IF_I64_D(DI)>
static HWY_INLINE VFromD<DI> NearestIntInRange(DI,
                                               VFromD<RebindToFloat<DI>> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvtpd_epi64 with GCC if any
  // values of v[i] are not within the range of an int64_t

#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<int64_t>(v)) {
    typedef double GccF64RawVectType __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF64RawVectType>(v.raw);
    return VFromD<DI>{
        _mm256_setr_epi64x(detail::X86ScalarNearestInt<int64_t>(raw_v[0]),
                           detail::X86ScalarNearestInt<int64_t>(raw_v[1]),
                           detail::X86ScalarNearestInt<int64_t>(raw_v[2]),
                           detail::X86ScalarNearestInt<int64_t>(raw_v[3]))};
  }
#endif

  __m256i raw_result;
  __asm__("vcvtpd2qq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<DI>{raw_result};
#else   // !HWY_COMPILER_GCC_ACTUAL
  return VFromD<DI>{_mm256_cvtpd_epi64(v.raw)};
#endif  // HWY_COMPILER_GCC_ACTUAL
}
#endif  // HWY_TARGET <= HWY_AVX3

template <class DI, HWY_IF_V_SIZE_D(DI, 16), HWY_IF_I32_D(DI)>
static HWY_INLINE VFromD<DI> DemoteToNearestIntInRange(
    DI, VFromD<Rebind<double, DI>> v) {
#if HWY_COMPILER_GCC_ACTUAL
  // Workaround for undefined behavior in _mm256_cvtpd_epi32 with GCC if any
  // values of v[i] are not within the range of an int32_t

#if HWY_COMPILER_GCC_ACTUAL >= 700 && !HWY_IS_DEBUG_BUILD
  if (detail::IsConstantX86VecForF2IConv<int32_t>(v)) {
    typedef double GccF32RawVectType __attribute__((__vector_size__(32)));
    const auto raw_v = reinterpret_cast<GccF32RawVectType>(v.raw);
    return Dup128VecFromValues(DI(),
                               detail::X86ScalarNearestInt<int32_t>(raw_v[0]),
                               detail::X86ScalarNearestInt<int32_t>(raw_v[1]),
                               detail::X86ScalarNearestInt<int32_t>(raw_v[2]),
                               detail::X86ScalarNearestInt<int32_t>(raw_v[3]));
  }
#endif

  __m128i raw_result;
  __asm__("vcvtpd2dq {%1, %0|%0, %1}"
          : "=" HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(raw_result)
          : HWY_X86_GCC_INLINE_ASM_VEC_CONSTRAINT(v.raw)
          :);
  return VFromD<DI>{raw_result};
#else  // !HWY_COMPILER_GCC_ACTUAL
  return VFromD<DI>{_mm256_cvtpd_epi32(v.raw)};
#endif
}

#ifndef HWY_DISABLE_F16C

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> PromoteTo(D df32, Vec128<float16_t> v) {
  (void)df32;
#if HWY_HAVE_FLOAT16
  const RebindToUnsigned<DFromV<decltype(v)>> du16;
  return VFromD<D>{_mm256_cvtph_ps(BitCast(du16, v).raw)};
#else
  return VFromD<D>{_mm256_cvtph_ps(v.raw)};
#endif  // HWY_HAVE_FLOAT16
}

#endif  // HWY_DISABLE_F16C

#if HWY_HAVE_FLOAT16

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F64_D(D)>
HWY_INLINE VFromD<D> PromoteTo(D /*tag*/, Vec64<float16_t> v) {
  return VFromD<D>{_mm256_cvtph_pd(v.raw)};
}

#endif  // HWY_HAVE_FLOAT16

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_F32_D(D)>
HWY_API VFromD<D> PromoteTo(D df32, Vec128<bfloat16_t> v) {
  const Rebind<uint16_t, decltype(df32)> du16;
  const RebindToSigned<decltype(df32)> di32;
  return BitCast(df32, ShiftLeft<16>(PromoteTo(di32, BitCast(du16, v))));
}

// ================================================== CRYPTO

#if !defined(HWY_DISABLE_PCLMUL_AES)

HWY_API Vec256<uint8_t> AESRound(Vec256<uint8_t> state,
                                 Vec256<uint8_t> round_key) {
#if HWY_TARGET <= HWY_AVX3_DL
  return Vec256<uint8_t>{_mm256_aesenc_epi128(state.raw, round_key.raw)};
#else
  const Full256<uint8_t> d;
  const Half<decltype(d)> d2;
  return Combine(d, AESRound(UpperHalf(d2, state), UpperHalf(d2, round_key)),
                 AESRound(LowerHalf(state), LowerHalf(round_key)));
#endif
}

HWY_API Vec256<uint8_t> AESLastRound(Vec256<uint8_t> state,
                                     Vec256<uint8_t> round_key) {
#if HWY_TARGET <= HWY_AVX3_DL
  return Vec256<uint8_t>{_mm256_aesenclast_epi128(state.raw, round_key.raw)};
#else
  const Full256<uint8_t> d;
  const Half<decltype(d)> d2;
  return Combine(d,
                 AESLastRound(UpperHalf(d2, state), UpperHalf(d2, round_key)),
                 AESLastRound(LowerHalf(state), LowerHalf(round_key)));
#endif
}

HWY_API Vec256<uint8_t> AESRoundInv(Vec256<uint8_t> state,
                                    Vec256<uint8_t> round_key) {
#if HWY_TARGET <= HWY_AVX3_DL
  return Vec256<uint8_t>{_mm256_aesdec_epi128(state.raw, round_key.raw)};
#else
  const Full256<uint8_t> d;
  const Half<decltype(d)> d2;
  return Combine(d, AESRoundInv(UpperHalf(d2, state), UpperHalf(d2, round_key)),
                 AESRoundInv(LowerHalf(state), LowerHalf(round_key)));
#endif
}

HWY_API Vec256<uint8_t> AESLastRoundInv(Vec256<uint8_t> state,
                                        Vec256<uint8_t> round_key) {
#if HWY_TARGET <= HWY_AVX3_DL
  return Vec256<uint8_t>{_mm256_aesdeclast_epi128(state.raw, round_key.raw)};
#else
  const Full256<uint8_t> d;
  const Half<decltype(d)> d2;
  return Combine(
      d, AESLastRoundInv(UpperHalf(d2, state), UpperHalf(d2, round_key)),
      AESLastRoundInv(LowerHalf(state), LowerHalf(round_key)));
#endif
}

template <class V, HWY_IF_V_SIZE_GT_V(V, 16), HWY_IF_U8_D(DFromV<V>)>
HWY_API V AESInvMixColumns(V state) {
  const DFromV<decltype(state)> d;
#if HWY_TARGET <= HWY_AVX3_DL
  // On AVX3_DL, it is more efficient to do an InvMixColumns operation for a
  // 256-bit or 512-bit vector by doing a AESLastRound operation
  // (_mm256_aesenclast_epi128/_mm512_aesenclast_epi128) followed by a
  // AESRoundInv operation (_mm256_aesdec_epi128/_mm512_aesdec_epi128) than to
  // split the vector into 128-bit vectors, carrying out multiple
  // _mm_aesimc_si128 operations, and then combining the _mm_aesimc_si128
  // results back into a 256-bit or 512-bit vector.
  const auto zero = Zero(d);
  return AESRoundInv(AESLastRound(state, zero), zero);
#else
  const Half<decltype(d)> dh;
  return Combine(d, AESInvMixColumns(UpperHalf(dh, state)),
                 AESInvMixColumns(LowerHalf(dh, state)));
#endif
}

template <uint8_t kRcon>
HWY_API Vec256<uint8_t> AESKeyGenAssist(Vec256<uint8_t> v) {
  const Full256<uint8_t> d;
#if HWY_TARGET <= HWY_AVX3_DL
  const VFromD<decltype(d)> rconXorMask = Dup128VecFromValues(
      d, 0, kRcon, 0, 0, 0, 0, 0, 0, 0, kRcon, 0, 0, 0, 0, 0, 0);
  const VFromD<decltype(d)> rotWordShuffle = Dup128VecFromValues(
      d, 0, 13, 10, 7, 1, 14, 11, 4, 8, 5, 2, 15, 9, 6, 3, 12);
  const Repartition<uint32_t, decltype(d)> du32;
  const auto w13 = BitCast(d, DupOdd(BitCast(du32, v)));
  const auto sub_word_result = AESLastRound(w13, rconXorMask);
  return TableLookupBytes(sub_word_result, rotWordShuffle);
#else
  const Half<decltype(d)> d2;
  return Combine(d, AESKeyGenAssist<kRcon>(UpperHalf(d2, v)),
                 AESKeyGenAssist<kRcon>(LowerHalf(v)));
#endif
}

HWY_API Vec256<uint64_t> CLMulLower(Vec256<uint64_t> a, Vec256<uint64_t> b) {
#if HWY_TARGET <= HWY_AVX3_DL
  return Vec256<uint64_t>{_mm256_clmulepi64_epi128(a.raw, b.raw, 0x00)};
#else
  const Full256<uint64_t> d;
  const Half<decltype(d)> d2;
  return Combine(d, CLMulLower(UpperHalf(d2, a), UpperHalf(d2, b)),
                 CLMulLower(LowerHalf(a), LowerHalf(b)));
#endif
}

HWY_API Vec256<uint64_t> CLMulUpper(Vec256<uint64_t> a, Vec256<uint64_t> b) {
#if HWY_TARGET <= HWY_AVX3_DL
  return Vec256<uint64_t>{_mm256_clmulepi64_epi128(a.raw, b.raw, 0x11)};
#else
  const Full256<uint64_t> d;
  const Half<decltype(d)> d2;
  return Combine(d, CLMulUpper(UpperHalf(d2, a), UpperHalf(d2, b)),
                 CLMulUpper(LowerHalf(a), LowerHalf(b)));
#endif
}

#endif  // HWY_DISABLE_PCLMUL_AES

// ================================================== MISC

#if HWY_TARGET <= HWY_AVX3

// ------------------------------ LoadMaskBits

// `p` points to at least 8 readable bytes, not all of which need be valid.
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API MFromD<D> LoadMaskBits(D d, const uint8_t* HWY_RESTRICT bits) {
  constexpr size_t kN = MaxLanes(d);
  constexpr size_t kNumBytes = (kN + 7) / 8;

  uint64_t mask_bits = 0;
  CopyBytes<kNumBytes>(bits, &mask_bits);

  if (kN < 8) {
    mask_bits &= (1ull << kN) - 1;
  }

  return MFromD<D>::FromBits(mask_bits);
}

// ------------------------------ StoreMaskBits

// `p` points to at least 8 writable bytes.
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API size_t StoreMaskBits(D d, MFromD<D> mask, uint8_t* bits) {
  constexpr size_t kN = MaxLanes(d);
  constexpr size_t kNumBytes = (kN + 7) / 8;

  CopyBytes<kNumBytes>(&mask.raw, bits);

  // Non-full byte, need to clear the undefined upper bits.
  if (kN < 8) {
    const int mask_bits = static_cast<int>((1ull << kN) - 1);
    bits[0] = static_cast<uint8_t>(bits[0] & mask_bits);
  }
  return kNumBytes;
}

// ------------------------------ Mask testing

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API size_t CountTrue(D /* tag */, MFromD<D> mask) {
  return PopCount(static_cast<uint64_t>(mask.raw));
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API size_t FindKnownFirstTrue(D /* tag */, MFromD<D> mask) {
  return Num0BitsBelowLS1Bit_Nonzero32(mask.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API intptr_t FindFirstTrue(D d, MFromD<D> mask) {
  return mask.raw ? static_cast<intptr_t>(FindKnownFirstTrue(d, mask))
                  : intptr_t{-1};
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API size_t FindKnownLastTrue(D /* tag */, MFromD<D> mask) {
  return 31 - Num0BitsAboveMS1Bit_Nonzero32(mask.raw);
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API intptr_t FindLastTrue(D d, MFromD<D> mask) {
  return mask.raw ? static_cast<intptr_t>(FindKnownLastTrue(d, mask))
                  : intptr_t{-1};
}

// Beware: the suffix indicates the number of mask bits, not lane size!

namespace detail {

template <typename T>
HWY_INLINE bool AllFalse(hwy::SizeTag<1> /*tag*/, const Mask256<T> mask) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return _kortestz_mask32_u8(mask.raw, mask.raw);
#else
  return mask.raw == 0;
#endif
}
template <typename T>
HWY_INLINE bool AllFalse(hwy::SizeTag<2> /*tag*/, const Mask256<T> mask) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return _kortestz_mask16_u8(mask.raw, mask.raw);
#else
  return mask.raw == 0;
#endif
}
template <typename T>
HWY_INLINE bool AllFalse(hwy::SizeTag<4> /*tag*/, const Mask256<T> mask) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return _kortestz_mask8_u8(mask.raw, mask.raw);
#else
  return mask.raw == 0;
#endif
}
template <typename T>
HWY_INLINE bool AllFalse(hwy::SizeTag<8> /*tag*/, const Mask256<T> mask) {
  return (uint64_t{mask.raw} & 0xF) == 0;
}

}  // namespace detail

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API bool AllFalse(D /* tag */, MFromD<D> mask) {
  return detail::AllFalse(hwy::SizeTag<sizeof(TFromD<D>)>(), mask);
}

namespace detail {

template <typename T>
HWY_INLINE bool AllTrue(hwy::SizeTag<1> /*tag*/, const Mask256<T> mask) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return _kortestc_mask32_u8(mask.raw, mask.raw);
#else
  return mask.raw == 0xFFFFFFFFu;
#endif
}
template <typename T>
HWY_INLINE bool AllTrue(hwy::SizeTag<2> /*tag*/, const Mask256<T> mask) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return _kortestc_mask16_u8(mask.raw, mask.raw);
#else
  return mask.raw == 0xFFFFu;
#endif
}
template <typename T>
HWY_INLINE bool AllTrue(hwy::SizeTag<4> /*tag*/, const Mask256<T> mask) {
#if HWY_COMPILER_HAS_MASK_INTRINSICS
  return _kortestc_mask8_u8(mask.raw, mask.raw);
#else
  return mask.raw == 0xFFu;
#endif
}
template <typename T>
HWY_INLINE bool AllTrue(hwy::SizeTag<8> /*tag*/, const Mask256<T> mask) {
  // Cannot use _kortestc because we have less than 8 mask bits.
  return mask.raw == 0xFu;
}

}  // namespace detail

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API bool AllTrue(D /* tag */, const MFromD<D> mask) {
  return detail::AllTrue(hwy::SizeTag<sizeof(TFromD<D>)>(), mask);
}

// ------------------------------ Compress

// 16-bit is defined in x86_512 so we can use 512-bit vectors.

template <typename T, HWY_IF_T_SIZE(T, 4)>
HWY_API Vec256<T> Compress(Vec256<T> v, Mask256<T> mask) {
  return Vec256<T>{_mm256_maskz_compress_epi32(mask.raw, v.raw)};
}

HWY_API Vec256<float> Compress(Vec256<float> v, Mask256<float> mask) {
  return Vec256<float>{_mm256_maskz_compress_ps(mask.raw, v.raw)};
}

template <typename T, HWY_IF_T_SIZE(T, 8)>
HWY_API Vec256<T> Compress(Vec256<T> v, Mask256<T> mask) {
  // See CompressIsPartition.
  alignas(16) static constexpr uint64_t packed_array[16] = {
      // PrintCompress64x4NibbleTables
      0x00003210, 0x00003210, 0x00003201, 0x00003210, 0x00003102, 0x00003120,
      0x00003021, 0x00003210, 0x00002103, 0x00002130, 0x00002031, 0x00002310,
      0x00001032, 0x00001320, 0x00000321, 0x00003210};

  // For lane i, shift the i-th 4-bit index down to bits [0, 2) -
  // _mm256_permutexvar_epi64 will ignore the upper bits.
  const DFromV<decltype(v)> d;
  const RebindToUnsigned<decltype(d)> du64;
  const auto packed = Set(du64, packed_array[mask.raw]);
  alignas(64) static constexpr uint64_t shifts[4] = {0, 4, 8, 12};
  const auto indices = Indices256<T>{(packed >> Load(du64, shifts)).raw};
  return TableLookupLanes(v, indices);
}

// ------------------------------ CompressNot (Compress)

// Implemented in x86_512 for lane size != 8.

template <typename T, HWY_IF_T_SIZE(T, 8)>
HWY_API Vec256<T> CompressNot(Vec256<T> v, Mask256<T> mask) {
  // See CompressIsPartition.
  alignas(16) static constexpr uint64_t packed_array[16] = {
      // PrintCompressNot64x4NibbleTables
      0x00003210, 0x00000321, 0x00001320, 0x00001032, 0x00002310, 0x00002031,
      0x00002130, 0x00002103, 0x00003210, 0x00003021, 0x00003120, 0x00003102,
      0x00003210, 0x00003201, 0x00003210, 0x00003210};

  // For lane i, shift the i-th 4-bit index down to bits [0, 2) -
  // _mm256_permutexvar_epi64 will ignore the upper bits.
  const DFromV<decltype(v)> d;
  const RebindToUnsigned<decltype(d)> du64;
  const auto packed = Set(du64, packed_array[mask.raw]);
  alignas(32) static constexpr uint64_t shifts[4] = {0, 4, 8, 12};
  const auto indices = Indices256<T>{(packed >> Load(du64, shifts)).raw};
  return TableLookupLanes(v, indices);
}

// ------------------------------ CompressStore (defined in x86_512)
// ------------------------------ CompressBlendedStore (defined in x86_512)
// ------------------------------ CompressBitsStore (defined in x86_512)

#else  // AVX2

// ------------------------------ LoadMaskBits (TestBit)

namespace detail {

// 256 suffix avoids ambiguity with x86_128 without needing HWY_IF_V_SIZE.
template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_INLINE Mask256<T> LoadMaskBits256(uint64_t mask_bits) {
  const Full256<T> d;
  const RebindToUnsigned<decltype(d)> du;
  const Repartition<uint32_t, decltype(d)> du32;
  const auto vbits = BitCast(du, Set(du32, static_cast<uint32_t>(mask_bits)));

  // Replicate bytes 8x such that each byte contains the bit that governs it.
  const Repartition<uint64_t, decltype(d)> du64;
  alignas(32) static constexpr uint64_t kRep8[4] = {
      0x0000000000000000ull, 0x0101010101010101ull, 0x0202020202020202ull,
      0x0303030303030303ull};
  const auto rep8 = TableLookupBytes(vbits, BitCast(du, Load(du64, kRep8)));

  const VFromD<decltype(du)> bit = Dup128VecFromValues(
      du, 1, 2, 4, 8, 16, 32, 64, 128, 1, 2, 4, 8, 16, 32, 64, 128);
  return RebindMask(d, TestBit(rep8, bit));
}

template <typename T, HWY_IF_T_SIZE(T, 2)>
HWY_INLINE Mask256<T> LoadMaskBits256(uint64_t mask_bits) {
  const Full256<T> d;
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint16_t kBit[16] = {
      1,     2,     4,     8,     16,     32,     64,     128,
      0x100, 0x200, 0x400, 0x800, 0x1000, 0x2000, 0x4000, 0x8000};
  const auto vmask_bits = Set(du, static_cast<uint16_t>(mask_bits));
  return RebindMask(d, TestBit(vmask_bits, Load(du, kBit)));
}

template <typename T, HWY_IF_T_SIZE(T, 4)>
HWY_INLINE Mask256<T> LoadMaskBits256(uint64_t mask_bits) {
  const Full256<T> d;
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint32_t kBit[8] = {1, 2, 4, 8, 16, 32, 64, 128};
  const auto vmask_bits = Set(du, static_cast<uint32_t>(mask_bits));
  return RebindMask(d, TestBit(vmask_bits, Load(du, kBit)));
}

template <typename T, HWY_IF_T_SIZE(T, 8)>
HWY_INLINE Mask256<T> LoadMaskBits256(uint64_t mask_bits) {
  const Full256<T> d;
  const RebindToUnsigned<decltype(d)> du;
  alignas(32) static constexpr uint64_t kBit[8] = {1, 2, 4, 8};
  return RebindMask(d, TestBit(Set(du, mask_bits), Load(du, kBit)));
}

}  // namespace detail

// `p` points to at least 8 readable bytes, not all of which need be valid.
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API MFromD<D> LoadMaskBits(D d, const uint8_t* HWY_RESTRICT bits) {
  constexpr size_t kN = MaxLanes(d);
  constexpr size_t kNumBytes = (kN + 7) / 8;

  uint64_t mask_bits = 0;
  CopyBytes<kNumBytes>(bits, &mask_bits);

  if (kN < 8) {
    mask_bits &= (1ull << kN) - 1;
  }

  return detail::LoadMaskBits256<TFromD<D>>(mask_bits);
}

// ------------------------------ BitsFromMask

template <class D, HWY_IF_T_SIZE_D(D, 1), HWY_IF_V_SIZE_D(D, 32)>
HWY_API uint64_t BitsFromMask(D d, MFromD<D> mask) {
  const RebindToUnsigned<D> d8;
  const auto sign_bits = BitCast(d8, VecFromMask(d, mask)).raw;
  // Prevent sign-extension of 32-bit masks because the intrinsic returns int.
  return static_cast<uint32_t>(_mm256_movemask_epi8(sign_bits));
}

template <class D, HWY_IF_T_SIZE_D(D, 2), HWY_IF_V_SIZE_D(D, 32)>
HWY_API uint64_t BitsFromMask(D d, MFromD<D> mask) {
#if !defined(HWY_DISABLE_BMI2_FMA) && !defined(HWY_DISABLE_PEXT_ON_AVX2)
  const Repartition<uint8_t, D> d8;
  const Mask256<uint8_t> mask8 = MaskFromVec(BitCast(d8, VecFromMask(d, mask)));
  const uint64_t sign_bits8 = BitsFromMask(d8, mask8);
  // Skip the bits from the lower byte of each u16 (better not to use the
  // same packs_epi16 as SSE4, because that requires an extra swizzle here).
  return _pext_u32(static_cast<uint32_t>(sign_bits8), 0xAAAAAAAAu);
#else
  // Slow workaround for when BMI2 is disabled
  // Remove useless lower half of each u16 while preserving the sign bit.
  // Bytes [0, 8) and [16, 24) have the same sign bits as the input lanes.
  const auto sign_bits = _mm256_packs_epi16(mask.raw, _mm256_setzero_si256());
  // Move odd qwords (value zero) to top so they don't affect the mask value.
  const auto compressed = _mm256_castsi256_si128(
      _mm256_permute4x64_epi64(sign_bits, _MM_SHUFFLE(3, 1, 2, 0)));
  return static_cast<unsigned>(_mm_movemask_epi8(compressed));
#endif  // HWY_ARCH_X86_64
}

template <class D, HWY_IF_T_SIZE_D(D, 4), HWY_IF_V_SIZE_D(D, 32)>
HWY_API uint64_t BitsFromMask(D d, MFromD<D> mask) {
  const RebindToFloat<D> df;
  const auto sign_bits = BitCast(df, VecFromMask(d, mask)).raw;
  return static_cast<unsigned>(_mm256_movemask_ps(sign_bits));
}

template <class D, HWY_IF_T_SIZE_D(D, 8), HWY_IF_V_SIZE_D(D, 32)>
HWY_API uint64_t BitsFromMask(D d, MFromD<D> mask) {
  const RebindToFloat<D> df;
  const auto sign_bits = BitCast(df, VecFromMask(d, mask)).raw;
  return static_cast<unsigned>(_mm256_movemask_pd(sign_bits));
}

// ------------------------------ StoreMaskBits
// `p` points to at least 8 writable bytes.
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API size_t StoreMaskBits(D d, MFromD<D> mask, uint8_t* bits) {
  HWY_LANES_CONSTEXPR size_t N = Lanes(d);
  HWY_LANES_CONSTEXPR size_t kNumBytes = (N + 7) / 8;

  const uint64_t mask_bits = BitsFromMask(d, mask);
  CopyBytes(&mask_bits, bits, kNumBytes);
  return kNumBytes;
}

// ------------------------------ Mask testing

// Specialize for 16-bit lanes to avoid unnecessary pext. This assumes each mask
// lane is 0 or ~0.
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API bool AllFalse(D d, MFromD<D> mask) {
  const Repartition<uint8_t, decltype(d)> d8;
  const Mask256<uint8_t> mask8 = MaskFromVec(BitCast(d8, VecFromMask(d, mask)));
  return BitsFromMask(d8, mask8) == 0;
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_T_SIZE_D(D, 2)>
HWY_API bool AllFalse(D d, MFromD<D> mask) {
  // Cheaper than PTEST, which is 2 uop / 3L.
  return BitsFromMask(d, mask) == 0;
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API bool AllTrue(D d, MFromD<D> mask) {
  const Repartition<uint8_t, decltype(d)> d8;
  const Mask256<uint8_t> mask8 = MaskFromVec(BitCast(d8, VecFromMask(d, mask)));
  return BitsFromMask(d8, mask8) == (1ull << 32) - 1;
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_T_SIZE_D(D, 2)>
HWY_API bool AllTrue(D d, MFromD<D> mask) {
  constexpr uint64_t kAllBits = (1ull << MaxLanes(d)) - 1;
  return BitsFromMask(d, mask) == kAllBits;
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API size_t CountTrue(D d, MFromD<D> mask) {
  const Repartition<uint8_t, decltype(d)> d8;
  const Mask256<uint8_t> mask8 = MaskFromVec(BitCast(d8, VecFromMask(d, mask)));
  return PopCount(BitsFromMask(d8, mask8)) >> 1;
}
template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_T_SIZE_D(D, 2)>
HWY_API size_t CountTrue(D d, MFromD<D> mask) {
  return PopCount(BitsFromMask(d, mask));
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API size_t FindKnownFirstTrue(D d, MFromD<D> mask) {
  const uint32_t mask_bits = static_cast<uint32_t>(BitsFromMask(d, mask));
  return Num0BitsBelowLS1Bit_Nonzero32(mask_bits);
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API intptr_t FindFirstTrue(D d, MFromD<D> mask) {
  const uint32_t mask_bits = static_cast<uint32_t>(BitsFromMask(d, mask));
  return mask_bits ? intptr_t(Num0BitsBelowLS1Bit_Nonzero32(mask_bits)) : -1;
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API size_t FindKnownLastTrue(D d, MFromD<D> mask) {
  const uint32_t mask_bits = static_cast<uint32_t>(BitsFromMask(d, mask));
  return 31 - Num0BitsAboveMS1Bit_Nonzero32(mask_bits);
}

template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API intptr_t FindLastTrue(D d, MFromD<D> mask) {
  const uint32_t mask_bits = static_cast<uint32_t>(BitsFromMask(d, mask));
  return mask_bits ? intptr_t(31 - Num0BitsAboveMS1Bit_Nonzero32(mask_bits))
                   : -1;
}

// ------------------------------ Compress, CompressBits

namespace detail {

template <typename T, HWY_IF_T_SIZE(T, 4)>
HWY_INLINE Vec256<uint32_t> IndicesFromBits256(uint64_t mask_bits) {
  const Full256<uint32_t> d32;
  // We need a masked Iota(). With 8 lanes, there are 256 combinations and a LUT
  // of SetTableIndices would require 8 KiB, a large part of L1D. The other
  // alternative is _pext_u64, but this is extremely slow on Zen2 (18 cycles)
  // and unavailable in 32-bit builds. We instead compress each index into 4
  // bits, for a total of 1 KiB.
  alignas(16) static constexpr uint32_t packed_array[256] = {
      // PrintCompress32x8Tables
      0x76543210, 0x76543218, 0x76543209, 0x76543298, 0x7654310a, 0x765431a8,
      0x765430a9, 0x76543a98, 0x7654210b, 0x765421b8, 0x765420b9, 0x76542b98,
      0x765410ba, 0x76541ba8, 0x76540ba9, 0x7654ba98, 0x7653210c, 0x765321c8,
      0x765320c9, 0x76532c98, 0x765310ca, 0x76531ca8, 0x76530ca9, 0x7653ca98,
      0x765210cb, 0x76521cb8, 0x76520cb9, 0x7652cb98, 0x76510cba, 0x7651cba8,
      0x7650cba9, 0x765cba98, 0x7643210d, 0x764321d8, 0x764320d9, 0x76432d98,
      0x764310da, 0x76431da8, 0x76430da9, 0x7643da98, 0x764210db, 0x76421db8,
      0x76420db9, 0x7642db98, 0x76410dba, 0x7641dba8, 0x7640dba9, 0x764dba98,
      0x763210dc, 0x76321dc8, 0x76320dc9, 0x7632dc98, 0x76310dca, 0x7631dca8,
      0x7630dca9, 0x763dca98, 0x76210dcb, 0x7621dcb8, 0x7620dcb9, 0x762dcb98,
      0x7610dcba, 0x761dcba8, 0x760dcba9, 0x76dcba98, 0x7543210e, 0x754321e8,
      0x754320e9, 0x75432e98, 0x754310ea, 0x75431ea8, 0x75430ea9, 0x7543ea98,
      0x754210eb, 0x75421eb8, 0x75420eb9, 0x7542eb98, 0x75410eba, 0x7541eba8,
      0x7540eba9, 0x754eba98, 0x753210ec, 0x75321ec8, 0x75320ec9, 0x7532ec98,
      0x75310eca, 0x7531eca8, 0x7530eca9, 0x753eca98, 0x75210ecb, 0x7521ecb8,
      0x7520ecb9, 0x752ecb98, 0x7510ecba, 0x751ecba8, 0x750ecba9, 0x75ecba98,
      0x743210ed, 0x74321ed8, 0x74320ed9, 0x7432ed98, 0x74310eda, 0x7431eda8,
      0x7430eda9, 0x743eda98, 0x74210edb, 0x7421edb8, 0x7420edb9, 0x742edb98,
      0x7410edba, 0x741edba8, 0x740edba9, 0x74edba98, 0x73210edc, 0x7321edc8,
      0x7320edc9, 0x732edc98, 0x7310edca, 0x731edca8, 0x730edca9, 0x73edca98,
      0x7210edcb, 0x721edcb8, 0x720edcb9, 0x72edcb98, 0x710edcba, 0x71edcba8,
      0x70edcba9, 0x7edcba98, 0x6543210f, 0x654321f8, 0x654320f9, 0x65432f98,
      0x654310fa, 0x65431fa8, 0x65430fa9, 0x6543fa98, 0x654210fb, 0x65421fb8,
      0x65420fb9, 0x6542fb98, 0x65410fba, 0x6541fba8, 0x6540fba9, 0x654fba98,
      0x653210fc, 0x65321fc8, 0x65320fc9, 0x6532fc98, 0x65310fca, 0x6531fca8,
      0x6530fca9, 0x653fca98, 0x65210fcb, 0x6521fcb8, 0x6520fcb9, 0x652fcb98,
      0x6510fcba, 0x651fcba8, 0x650fcba9, 0x65fcba98, 0x643210fd, 0x64321fd8,
      0x64320fd9, 0x6432fd98, 0x64310fda, 0x6431fda8, 0x6430fda9, 0x643fda98,
      0x64210fdb, 0x6421fdb8, 0x6420fdb9, 0x642fdb98, 0x6410fdba, 0x641fdba8,
      0x640fdba9, 0x64fdba98, 0x63210fdc, 0x6321fdc8, 0x6320fdc9, 0x632fdc98,
      0x6310fdca, 0x631fdca8, 0x630fdca9, 0x63fdca98, 0x6210fdcb, 0x621fdcb8,
      0x620fdcb9, 0x62fdcb98, 0x610fdcba, 0x61fdcba8, 0x60fdcba9, 0x6fdcba98,
      0x543210fe, 0x54321fe8, 0x54320fe9, 0x5432fe98, 0x54310fea, 0x5431fea8,
      0x5430fea9, 0x543fea98, 0x54210feb, 0x5421feb8, 0x5420feb9, 0x542feb98,
      0x5410feba, 0x541feba8, 0x540feba9, 0x54feba98, 0x53210fec, 0x5321fec8,
      0x5320fec9, 0x532fec98, 0x5310feca, 0x531feca8, 0x530feca9, 0x53feca98,
      0x5210fecb, 0x521fecb8, 0x520fecb9, 0x52fecb98, 0x510fecba, 0x51fecba8,
      0x50fecba9, 0x5fecba98, 0x43210fed, 0x4321fed8, 0x4320fed9, 0x432fed98,
      0x4310feda, 0x431feda8, 0x430feda9, 0x43feda98, 0x4210fedb, 0x421fedb8,
      0x420fedb9, 0x42fedb98, 0x410fedba, 0x41fedba8, 0x40fedba9, 0x4fedba98,
      0x3210fedc, 0x321fedc8, 0x320fedc9, 0x32fedc98, 0x310fedca, 0x31fedca8,
      0x30fedca9, 0x3fedca98, 0x210fedcb, 0x21fedcb8, 0x20fedcb9, 0x2fedcb98,
      0x10fedcba, 0x1fedcba8, 0x0fedcba9, 0xfedcba98};

  // No need to mask because _mm256_permutevar8x32_epi32 ignores bits 3..31.
  // Just shift each copy of the 32 bit LUT to extract its 4-bit fields.
  // If broadcasting 32-bit from memory incurs the 3-cycle block-crossing
  // latency, it may be faster to use LoadDup128 and PSHUFB.
  const auto packed = Set(d32, packed_array[mask_bits]);
  alignas(32) static constexpr uint32_t shifts[8] = {0,  4,  8,  12,
                                                     16, 20, 24, 28};
  return packed >> Load(d32, shifts);
}

template <typename T, HWY_IF_T_SIZE(T, 8)>
HWY_INLINE Vec256<uint32_t> IndicesFromBits256(uint64_t mask_bits) {
  const Full256<uint32_t> d32;

  // For 64-bit, we still need 32-bit indices because there is no 64-bit
  // permutevar, but there are only 4 lanes, so we can afford to skip the
  // unpacking and load the entire index vector directly.
  alignas(32) static constexpr uint32_t u32_indices[128] = {
      // PrintCompress64x4PairTables
      0,  1,  2,  3,  4,  5,  6, 7, 8, 9, 2,  3,  4,  5,  6,  7,
      10, 11, 0,  1,  4,  5,  6, 7, 8, 9, 10, 11, 4,  5,  6,  7,
      12, 13, 0,  1,  2,  3,  6, 7, 8, 9, 12, 13, 2,  3,  6,  7,
      10, 11, 12, 13, 0,  1,  6, 7, 8, 9, 10, 11, 12, 13, 6,  7,
      14, 15, 0,  1,  2,  3,  4, 5, 8, 9, 14, 15, 2,  3,  4,  5,
      10, 11, 14, 15, 0,  1,  4, 5, 8, 9, 10, 11, 14, 15, 4,  5,
      12, 13, 14, 15, 0,  1,  2, 3, 8, 9, 12, 13, 14, 15, 2,  3,
      10, 11, 12, 13, 14, 15, 0, 1, 8, 9, 10, 11, 12, 13, 14, 15};
  return Load(d32, u32_indices + 8 * mask_bits);
}

template <typename T, HWY_IF_T_SIZE(T, 4)>
HWY_INLINE Vec256<uint32_t> IndicesFromNotBits256(uint64_t mask_bits) {
  const Full256<uint32_t> d32;
  // We need a masked Iota(). With 8 lanes, there are 256 combinations and a LUT
  // of SetTableIndices would require 8 KiB, a large part of L1D. The other
  // alternative is _pext_u64, but this is extremely slow on Zen2 (18 cycles)
  // and unavailable in 32-bit builds. We instead compress each index into 4
  // bits, for a total of 1 KiB.
  alignas(16) static constexpr uint32_t packed_array[256] = {
      // PrintCompressNot32x8Tables
      0xfedcba98, 0x8fedcba9, 0x9fedcba8, 0x98fedcba, 0xafedcb98, 0xa8fedcb9,
      0xa9fedcb8, 0xa98fedcb, 0xbfedca98, 0xb8fedca9, 0xb9fedca8, 0xb98fedca,
      0xbafedc98, 0xba8fedc9, 0xba9fedc8, 0xba98fedc, 0xcfedba98, 0xc8fedba9,
      0xc9fedba8, 0xc98fedba, 0xcafedb98, 0xca8fedb9, 0xca9fedb8, 0xca98fedb,
      0xcbfeda98, 0xcb8feda9, 0xcb9feda8, 0xcb98feda, 0xcbafed98, 0xcba8fed9,
      0xcba9fed8, 0xcba98fed, 0xdfecba98, 0xd8fecba9, 0xd9fecba8, 0xd98fecba,
      0xdafecb98, 0xda8fecb9, 0xda9fecb8, 0xda98fecb, 0xdbfeca98, 0xdb8feca9,
      0xdb9feca8, 0xdb98feca, 0xdbafec98, 0xdba8fec9, 0xdba9fec8, 0xdba98fec,
      0xdcfeba98, 0xdc8feba9, 0xdc9feba8, 0xdc98feba, 0xdcafeb98, 0xdca8feb9,
      0xdca9feb8, 0xdca98feb, 0xdcbfea98, 0xdcb8fea9, 0xdcb9fea8, 0xdcb98fea,
      0xdcbafe98, 0xdcba8fe9, 0xdcba9fe8, 0xdcba98fe, 0xefdcba98, 0xe8fdcba9,
      0xe9fdcba8, 0xe98fdcba, 0xeafdcb98, 0xea8fdcb9, 0xea9fdcb8, 0xea98fdcb,
      0xebfdca98, 0xeb8fdca9, 0xeb9fdca8, 0xeb98fdca, 0xebafdc98, 0xeba8fdc9,
      0xeba9fdc8, 0xeba98fdc, 0xecfdba98, 0xec8fdba9, 0xec9fdba8, 0xec98fdba,
      0xecafdb98, 0xeca8fdb9, 0xeca9fdb8, 0xeca98fdb, 0xecbfda98, 0xecb8fda9,
      0xecb9fda8, 0xecb98fda, 0xecbafd98, 0xecba8fd9, 0xecba9fd8, 0xecba98fd,
      0xedfcba98, 0xed8fcba9, 0xed9fcba8, 0xed98fcba, 0xedafcb98, 0xeda8fcb9,
      0xeda9fcb8, 0xeda98fcb, 0xedbfca98, 0xedb8fca9, 0xedb9fca8, 0xedb98fca,
      0xedbafc98, 0xedba8fc9, 0xedba9fc8, 0xedba98fc, 0xedcfba98, 0xedc8fba9,
      0xedc9fba8, 0xedc98fba, 0xedcafb98, 0xedca8fb9, 0xedca9fb8, 0xedca98fb,
      0xedcbfa98, 0xedcb8fa9, 0xedcb9fa8, 0xedcb98fa, 0xedcbaf98, 0xedcba8f9,
      0xedcba9f8, 0xedcba98f, 0xfedcba98, 0xf8edcba9, 0xf9edcba8, 0xf98edcba,
      0xfaedcb98, 0xfa8edcb9, 0xfa9edcb8, 0xfa98edcb, 0xfbedca98, 0xfb8edca9,
      0xfb9edca8, 0xfb98edca, 0xfbaedc98, 0xfba8edc9, 0xfba9edc8, 0xfba98edc,
      0xfcedba98, 0xfc8edba9, 0xfc9edba8, 0xfc98edba, 0xfcaedb98, 0xfca8edb9,
      0xfca9edb8, 0xfca98edb, 0xfcbeda98, 0xfcb8eda9, 0xfcb9eda8, 0xfcb98eda,
      0xfcbaed98, 0xfcba8ed9, 0xfcba9ed8, 0xfcba98ed, 0xfdecba98, 0xfd8ecba9,
      0xfd9ecba8, 0xfd98ecba, 0xfdaecb98, 0xfda8ecb9, 0xfda9ecb8, 0xfda98ecb,
      0xfdbeca98, 0xfdb8eca9, 0xfdb9eca8, 0xfdb98eca, 0xfdbaec98, 0xfdba8ec9,
      0xfdba9ec8, 0xfdba98ec, 0xfdceba98, 0xfdc8eba9, 0xfdc9eba8, 0xfdc98eba,
      0xfdcaeb98, 0xfdca8eb9, 0xfdca9eb8, 0xfdca98eb, 0xfdcbea98, 0xfdcb8ea9,
      0xfdcb9ea8, 0xfdcb98ea, 0xfdcbae98, 0xfdcba8e9, 0xfdcba9e8, 0xfdcba98e,
      0xfedcba98, 0xfe8dcba9, 0xfe9dcba8, 0xfe98dcba, 0xfeadcb98, 0xfea8dcb9,
      0xfea9dcb8, 0xfea98dcb, 0xfebdca98, 0xfeb8dca9, 0xfeb9dca8, 0xfeb98dca,
      0xfebadc98, 0xfeba8dc9, 0xfeba9dc8, 0xfeba98dc, 0xfecdba98, 0xfec8dba9,
      0xfec9dba8, 0xfec98dba, 0xfecadb98, 0xfeca8db9, 0xfeca9db8, 0xfeca98db,
      0xfecbda98, 0xfecb8da9, 0xfecb9da8, 0xfecb98da, 0xfecbad98, 0xfecba8d9,
      0xfecba9d8, 0xfecba98d, 0xfedcba98, 0xfed8cba9, 0xfed9cba8, 0xfed98cba,
      0xfedacb98, 0xfeda8cb9, 0xfeda9cb8, 0xfeda98cb, 0xfedbca98, 0xfedb8ca9,
      0xfedb9ca8, 0xfedb98ca, 0xfedbac98, 0xfedba8c9, 0xfedba9c8, 0xfedba98c,
      0xfedcba98, 0xfedc8ba9, 0xfedc9ba8, 0xfedc98ba, 0xfedcab98, 0xfedca8b9,
      0xfedca9b8, 0xfedca98b, 0xfedcba98, 0xfedcb8a9, 0xfedcb9a8, 0xfedcb98a,
      0xfedcba98, 0xfedcba89, 0xfedcba98, 0xfedcba98};

  // No need to mask because <_mm256_permutevar8x32_epi32> ignores bits 3..31.
  // Just shift each copy of the 32 bit LUT to extract its 4-bit fields.
  // If broadcasting 32-bit from memory incurs the 3-cycle block-crossing
  // latency, it may be faster to use LoadDup128 and PSHUFB.
  const Vec256<uint32_t> packed = Set(d32, packed_array[mask_bits]);
  alignas(32) static constexpr uint32_t shifts[8] = {0,  4,  8,  12,
                                                     16, 20, 24, 28};
  return packed >> Load(d32, shifts);
}

template <typename T, HWY_IF_T_SIZE(T, 8)>
HWY_INLINE Vec256<uint32_t> IndicesFromNotBits256(uint64_t mask_bits) {
  const Full256<uint32_t> d32;

  // For 64-bit, we still need 32-bit indices because there is no 64-bit
  // permutevar, but there are only 4 lanes, so we can afford to skip the
  // unpacking and load the entire index vector directly.
  alignas(32) static constexpr uint32_t u32_indices[128] = {
      // PrintCompressNot64x4PairTables
      8, 9, 10, 11, 12, 13, 14, 15, 10, 11, 12, 13, 14, 15, 8,  9,
      8, 9, 12, 13, 14, 15, 10, 11, 12, 13, 14, 15, 8,  9,  10, 11,
      8, 9, 10, 11, 14, 15, 12, 13, 10, 11, 14, 15, 8,  9,  12, 13,
      8, 9, 14, 15, 10, 11, 12, 13, 14, 15, 8,  9,  10, 11, 12, 13,
      8, 9, 10, 11, 12, 13, 14, 15, 10, 11, 12, 13, 8,  9,  14, 15,
      8, 9, 12, 13, 10, 11, 14, 15, 12, 13, 8,  9,  10, 11, 14, 15,
      8, 9, 10, 11, 12, 13, 14, 15, 10, 11, 8,  9,  12, 13, 14, 15,
      8, 9, 10, 11, 12, 13, 14, 15, 8,  9,  10, 11, 12, 13, 14, 15};
  return Load(d32, u32_indices + 8 * mask_bits);
}

template <typename T, HWY_IF_NOT_T_SIZE(T, 2)>
HWY_INLINE Vec256<T> Compress(Vec256<T> v, const uint64_t mask_bits) {
  const DFromV<decltype(v)> d;
  const Repartition<uint32_t, decltype(d)> du32;

  HWY_DASSERT(mask_bits < (1ull << Lanes(d)));
  // 32-bit indices because we only have _mm256_permutevar8x32_epi32 (there is
  // no instruction for 4x64).
  const Indices256<uint32_t> indices{IndicesFromBits256<T>(mask_bits).raw};
  return BitCast(d, TableLookupLanes(BitCast(du32, v), indices));
}

// LUTs are infeasible for 2^16 possible masks, so splice together two
// half-vector Compress.
template <typename T, HWY_IF_T_SIZE(T, 2)>
HWY_INLINE Vec256<T> Compress(Vec256<T> v, const uint64_t mask_bits) {
  const DFromV<decltype(v)> d;
  const RebindToUnsigned<decltype(d)> du;
  const auto vu16 = BitCast(du, v);  // (required for float16_t inputs)
  const Half<decltype(du)> duh;
  const auto half0 = LowerHalf(duh, vu16);
  const auto half1 = UpperHalf(duh, vu16);

  const uint64_t mask_bits0 = mask_bits & 0xFF;
  const uint64_t mask_bits1 = mask_bits >> 8;
  const auto compressed0 = detail::CompressBits(half0, mask_bits0);
  const auto compressed1 = detail::CompressBits(half1, mask_bits1);

  alignas(32) uint16_t all_true[16] = {};
  // Store mask=true lanes, left to right.
  const size_t num_true0 = PopCount(mask_bits0);
  Store(compressed0, duh, all_true);
  StoreU(compressed1, duh, all_true + num_true0);

  if (hwy::HWY_NAMESPACE::CompressIsPartition<T>::value) {
    // Store mask=false lanes, right to left. The second vector fills the upper
    // half with right-aligned false lanes. The first vector is shifted
    // rightwards to overwrite the true lanes of the second.
    alignas(32) uint16_t all_false[16] = {};
    const size_t num_true1 = PopCount(mask_bits1);
    Store(compressed1, duh, all_false + 8);
    StoreU(compressed0, duh, all_false + num_true1);

    const auto mask = FirstN(du, num_true0 + num_true1);
    return BitCast(d,
                   IfThenElse(mask, Load(du, all_true), Load(du, all_false)));
  } else {
    // Only care about the mask=true lanes.
    return BitCast(d, Load(du, all_true));
  }
}

template <typename T, HWY_IF_T_SIZE_ONE_OF(T, (1 << 4) | (1 << 8))>
HWY_INLINE Vec256<T> CompressNot(Vec256<T> v, const uint64_t mask_bits) {
  const DFromV<decltype(v)> d;
  const Repartition<uint32_t, decltype(d)> du32;

  HWY_DASSERT(mask_bits < (1ull << Lanes(d)));
  // 32-bit indices because we only have _mm256_permutevar8x32_epi32 (there is
  // no instruction for 4x64).
  const Indices256<uint32_t> indices{IndicesFromNotBits256<T>(mask_bits).raw};
  return BitCast(d, TableLookupLanes(BitCast(du32, v), indices));
}

// LUTs are infeasible for 2^16 possible masks, so splice together two
// half-vector Compress.
template <typename T, HWY_IF_T_SIZE(T, 2)>
HWY_INLINE Vec256<T> CompressNot(Vec256<T> v, const uint64_t mask_bits) {
  // Compress ensures only the lower 16 bits are set, so flip those.
  return Compress(v, mask_bits ^ 0xFFFF);
}

}  // namespace detail

template <typename T, HWY_IF_NOT_T_SIZE(T, 1)>
HWY_API Vec256<T> Compress(Vec256<T> v, Mask256<T> m) {
  const DFromV<decltype(v)> d;
  return detail::Compress(v, BitsFromMask(d, m));
}

template <typename T, HWY_IF_NOT_T_SIZE(T, 1)>
HWY_API Vec256<T> CompressNot(Vec256<T> v, Mask256<T> m) {
  const DFromV<decltype(v)> d;
  return detail::CompressNot(v, BitsFromMask(d, m));
}

HWY_API Vec256<uint64_t> CompressBlocksNot(Vec256<uint64_t> v,
                                           Mask256<uint64_t> mask) {
  return CompressNot(v, mask);
}

template <typename T, HWY_IF_NOT_T_SIZE(T, 1)>
HWY_API Vec256<T> CompressBits(Vec256<T> v, const uint8_t* HWY_RESTRICT bits) {
  constexpr size_t N = 32 / sizeof(T);
  constexpr size_t kNumBytes = (N + 7) / 8;

  uint64_t mask_bits = 0;
  CopyBytes<kNumBytes>(bits, &mask_bits);

  if (N < 8) {
    mask_bits &= (1ull << N) - 1;
  }

  return detail::Compress(v, mask_bits);
}

// ------------------------------ CompressStore, CompressBitsStore

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_T_SIZE_D(D, 1)>
HWY_API size_t CompressStore(VFromD<D> v, MFromD<D> m, D d,
                             TFromD<D>* HWY_RESTRICT unaligned) {
  const uint64_t mask_bits = BitsFromMask(d, m);
  const size_t count = PopCount(mask_bits);
  StoreU(detail::Compress(v, mask_bits), d, unaligned);
  detail::MaybeUnpoison(unaligned, count);
  return count;
}

template <class D, HWY_IF_V_SIZE_D(D, 32),
          HWY_IF_T_SIZE_ONE_OF_D(D, (1 << 4) | (1 << 8))>
HWY_API size_t CompressBlendedStore(VFromD<D> v, MFromD<D> m, D d,
                                    TFromD<D>* HWY_RESTRICT unaligned) {
  const uint64_t mask_bits = BitsFromMask(d, m);
  const size_t count = PopCount(mask_bits);

  const RebindToUnsigned<decltype(d)> du;
  const Repartition<uint32_t, decltype(d)> du32;
  HWY_DASSERT(mask_bits < (1ull << Lanes(d)));
  // 32-bit indices because we only have _mm256_permutevar8x32_epi32 (there is
  // no instruction for 4x64). Nibble MSB encodes FirstN.
  const Vec256<uint32_t> idx_mask =
      detail::IndicesFromBits256<TFromD<D>>(mask_bits);
  // Shift nibble MSB into MSB
  const Mask256<uint32_t> mask32 = MaskFromVec(ShiftLeft<28>(idx_mask));
  // First cast to unsigned (RebindMask cannot change lane size)
  const MFromD<decltype(du)> mask_u{mask32.raw};
  const MFromD<D> mask = RebindMask(d, mask_u);
  const VFromD<D> compressed = BitCast(
      d,
      TableLookupLanes(BitCast(du32, v), Indices256<uint32_t>{idx_mask.raw}));

  BlendedStore(compressed, mask, d, unaligned);
  detail::MaybeUnpoison(unaligned, count);
  return count;
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_T_SIZE_D(D, 2)>
HWY_API size_t CompressBlendedStore(VFromD<D> v, MFromD<D> m, D d,
                                    TFromD<D>* HWY_RESTRICT unaligned) {
  const uint64_t mask_bits = BitsFromMask(d, m);
  const size_t count = PopCount(mask_bits);
  const VFromD<D> compressed = detail::Compress(v, mask_bits);

#if HWY_MEM_OPS_MIGHT_FAULT  // true if HWY_IS_MSAN
  // BlendedStore tests mask for each lane, but we know that the mask is
  // FirstN, so we can just copy.
  alignas(32) TFromD<D> buf[16];
  Store(compressed, d, buf);
  CopyBytes(buf, unaligned, count * sizeof(TFromD<D>));
#else
  BlendedStore(compressed, FirstN(d, count), d, unaligned);
#endif
  return count;
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_NOT_T_SIZE_D(D, 1)>
HWY_API size_t CompressBitsStore(VFromD<D> v, const uint8_t* HWY_RESTRICT bits,
                                 D d, TFromD<D>* HWY_RESTRICT unaligned) {
  HWY_LANES_CONSTEXPR size_t N = Lanes(d);
  HWY_LANES_CONSTEXPR size_t kNumBytes = (N + 7) / 8;

  uint64_t mask_bits = 0;
  CopyBytes(bits, &mask_bits, kNumBytes);

  if (N < 8) {
    mask_bits &= (1ull << N) - 1;
  }
  const size_t count = PopCount(mask_bits);

  StoreU(detail::Compress(v, mask_bits), d, unaligned);
  detail::MaybeUnpoison(unaligned, count);
  return count;
}

#endif  // HWY_TARGET <= HWY_AVX3

// ------------------------------ Dup128MaskFromMaskBits

// Generic for all vector lengths >= 32 bytes
template <class D, HWY_IF_V_SIZE_GT_D(D, 16)>
HWY_API MFromD<D> Dup128MaskFromMaskBits(D d, unsigned mask_bits) {
  const Half<decltype(d)> dh;
  const auto mh = Dup128MaskFromMaskBits(dh, mask_bits);
  return CombineMasks(d, mh, mh);
}

// ------------------------------ Expand

// Always define Expand/LoadExpand because generic_ops only does so for Vec128.

namespace detail {

#if HWY_TARGET <= HWY_AVX3_DL || HWY_IDE  // VBMI2

HWY_INLINE Vec256<uint8_t> NativeExpand(Vec256<uint8_t> v,
                                        Mask256<uint8_t> mask) {
  return Vec256<uint8_t>{_mm256_maskz_expand_epi8(mask.raw, v.raw)};
}

HWY_INLINE Vec256<uint16_t> NativeExpand(Vec256<uint16_t> v,
                                         Mask256<uint16_t> mask) {
  return Vec256<uint16_t>{_mm256_maskz_expand_epi16(mask.raw, v.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U8_D(D)>
HWY_INLINE VFromD<D> NativeLoadExpand(MFromD<D> mask, D /* d */,
                                      const uint8_t* HWY_RESTRICT unaligned) {
  return VFromD<D>{_mm256_maskz_expandloadu_epi8(mask.raw, unaligned)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U16_D(D)>
HWY_INLINE VFromD<D> NativeLoadExpand(MFromD<D> mask, D /* d */,
                                      const uint16_t* HWY_RESTRICT unaligned) {
  return VFromD<D>{_mm256_maskz_expandloadu_epi16(mask.raw, unaligned)};
}

#endif  // HWY_TARGET <= HWY_AVX3_DL
#if HWY_TARGET <= HWY_AVX3 || HWY_IDE

HWY_INLINE Vec256<uint32_t> NativeExpand(Vec256<uint32_t> v,
                                         Mask256<uint32_t> mask) {
  return Vec256<uint32_t>{_mm256_maskz_expand_epi32(mask.raw, v.raw)};
}

HWY_INLINE Vec256<uint64_t> NativeExpand(Vec256<uint64_t> v,
                                         Mask256<uint64_t> mask) {
  return Vec256<uint64_t>{_mm256_maskz_expand_epi64(mask.raw, v.raw)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U32_D(D)>
HWY_INLINE VFromD<D> NativeLoadExpand(MFromD<D> mask, D /* d */,
                                      const uint32_t* HWY_RESTRICT unaligned) {
  return VFromD<D>{_mm256_maskz_expandloadu_epi32(mask.raw, unaligned)};
}

template <class D, HWY_IF_V_SIZE_D(D, 32), HWY_IF_U64_D(D)>
HWY_INLINE VFromD<D> NativeLoadExpand(MFromD<D> mask, D /* d */,
                                      const uint64_t* HWY_RESTRICT unaligned) {
  return VFromD<D>{_mm256_maskz_expandloadu_epi64(mask.raw, unaligned)};
}

#endif  // HWY_TARGET <= HWY_AVX3

}  // namespace detail

template <typename T, HWY_IF_T_SIZE(T, 1)>
HWY_API Vec256<T> Expand(Vec256<T> v, Mask256<T> mask) {
  const DFromV<decltype(v)> d;
#if HWY_TARGET <= HWY_AVX3_DL  // VBMI2
  const RebindToUnsigned<decltype(d)> du;
  const MFromD<decltype(du)> mu = RebindMask(du, mask);
  return BitCast(d, detail::NativeExpand(BitCast(du, v), mu));
#else
  // LUTs are infeasible for so many mask combinations, so Combine two
  // half-vector Expand.
  const Half<decltype(d)> dh;
  const uint64_t mask_bits = BitsFromMask(d, mask);
  constexpr size_t N = 32 / sizeof(T);
  const size_t countL = PopCount(mask_bits & ((1 << (N / 2)) - 1));
  const Mask128<T> maskL = MaskFromVec(LowerHalf(VecFromMask(d, mask)));
  const Vec128<T> expandL = Expand(LowerHalf(v), maskL);
  // We have to shift the input by a variable number of bytes, but there isn't
  // a table-driven option for that until VBMI, and CPUs with that likely also
  // have VBMI2 and thus native Expand.
  alignas(32) T lanes[N];
  Store(v, d, lanes);
  const Mask128<T> maskH = MaskFromVec(UpperHalf(dh, VecFromMask(d, mask)));
  const Vec128<T> expandH = Expand(LoadU(dh, lanes + countL), maskH);
  return Combine(d, expandH, expandL);
#endif
}

// If AVX3, this is already implemented by x86_512.
#if HWY_TARGET != HWY_AVX3

template <typename T, HWY_IF_T_SIZE(T, 2)>
HWY_API Vec256<T> Expand(Vec256<T> v, Mask256<T> mask) {
  const Full256<T> d;
#if HWY_TARGET <= HWY_AVX3_DL  // VBMI2
  const RebindToUnsigned<decltype(d)> du;
  return BitCast(d, detail::NativeExpand(BitCast(du, v), RebindMask(du, mask)));
#else   // AVX2
  // LUTs are infeasible for 2^16 possible masks, so splice together two
  // half-vector Expand.
  const Half<decltype(d)> dh;
  const Mask128<T> maskL = MaskFromVec(LowerHalf(VecFromMask(d, mask)));
  const Vec128<T> expandL = Expand(LowerHalf(v), maskL);
  // We have to shift the input by a variable number of u16. permutevar_epi16
  // requires AVX3 and if we had that, we'd use native u32 Expand. The only
  // alternative is re-loading, which incurs a store to load forwarding stall.
  alignas(32) T lanes[32 / sizeof(T)];
  Store(v, d, lanes);
  const Vec128<T> vH = LoadU(dh, lanes + CountTrue(dh, maskL));
  const Mask128<T> maskH = MaskFromVec(UpperHalf(dh, VecFromMask(d, mask)));
  const Vec128<T> expandH = Expand(vH, maskH);
  return Combine(d, expandH, expandL);
#endif  // AVX2
}

#endif  // HWY_TARGET != HWY_AVX3

template <typename T, HWY_IF_T_SIZE(T, 4)>
HWY_API Vec256<T> Expand(Vec256<T> v, Mask256<T> mask) {
  const Full256<T> d;
#if HWY_TARGET <= HWY_AVX3
  const RebindToUnsigned<decltype(d)> du;
  const MFromD<decltype(du)> mu = RebindMask(du, mask);
  return BitCast(d, detail::NativeExpand(BitCast(du, v), mu));
#else
  const RebindToUnsigned<decltype(d)> du;
  const uint64_t mask_bits = BitsFromMask(d, mask);

  alignas(16) constexpr uint32_t packed_array[256] = {
      // PrintExpand32x8Nibble.
      0xffffffff, 0xfffffff0, 0xffffff0f, 0xffffff10, 0xfffff0ff, 0xfffff1f0,
      0xfffff10f, 0xfffff210, 0xffff0fff, 0xffff1ff0, 0xffff1f0f, 0xffff2f10,
      0xffff10ff, 0xffff21f0, 0xffff210f, 0xffff3210, 0xfff0ffff, 0xfff1fff0,
      0xfff1ff0f, 0xfff2ff10, 0xfff1f0ff, 0xfff2f1f0, 0xfff2f10f, 0xfff3f210,
      0xfff10fff, 0xfff21ff0, 0xfff21f0f, 0xfff32f10, 0xfff210ff, 0xfff321f0,
      0xfff3210f, 0xfff43210, 0xff0fffff, 0xff1ffff0, 0xff1fff0f, 0xff2fff10,
      0xff1ff0ff, 0xff2ff1f0, 0xff2ff10f, 0xff3ff210, 0xff1f0fff, 0xff2f1ff0,
      0xff2f1f0f, 0xff3f2f10, 0xff2f10ff, 0xff3f21f0, 0xff3f210f, 0xff4f3210,
      0xff10ffff, 0xff21fff0, 0xff21ff0f, 0xff32ff10, 0xff21f0ff, 0xff32f1f0,
      0xff32f10f, 0xff43f210, 0xff210fff, 0xff321ff0, 0xff321f0f, 0xff432f10,
      0xff3210ff, 0xff4321f0, 0xff43210f, 0xff543210, 0xf0ffffff, 0xf1fffff0,
      0xf1ffff0f, 0xf2ffff10, 0xf1fff0ff, 0xf2fff1f0, 0xf2fff10f, 0xf3fff210,
      0xf1ff0fff, 0xf2ff1ff0, 0xf2ff1f0f, 0xf3ff2f10, 0xf2ff10ff, 0xf3ff21f0,
      0xf3ff210f, 0xf4ff3210, 0xf1f0ffff, 0xf2f1fff0, 0xf2f1ff0f, 0xf3f2ff10,
      0xf2f1f0ff, 0xf3f2f1f0, 0xf3f2f10f, 0xf4f3f210, 0xf2f10fff, 0xf3f21ff0,
      0xf3f21f0f, 0xf4f32f10, 0xf3f210ff, 0xf4f321f0, 0xf4f3210f, 0xf5f43210,
      0xf10fffff, 0xf21ffff0, 0xf21fff0f, 0xf32fff10, 0xf21ff0ff, 0xf32ff1f0,
      0xf32ff10f, 0xf43ff210, 0xf21f0fff, 0xf32f1ff0, 0xf32f1f0f, 0xf43f2f10,
      0xf32f10ff, 0xf43f21f0, 0xf43f210f, 0xf54f3210, 0xf210ffff, 0xf321fff0,
      0xf321ff0f, 0xf432ff10, 0xf321f0ff, 0xf432f1f0, 0xf432f10f, 0xf543f210,
      0xf3210fff, 0xf4321ff0, 0xf4321f0f, 0xf5432f10, 0xf43210ff, 0xf54321f0,
      0xf543210f, 0xf6543210, 0x0fffffff, 0x1ffffff0, 0x1fffff0f, 0x2fffff10,
      0x1ffff0ff, 0x2ffff1f0, 0x2ffff10f, 0x3ffff210, 0x1fff0fff, 0x2fff1ff0,
      0x2fff1f0f, 0x3fff2f10, 0x2fff10ff, 0x3fff21f0, 0x3fff210f, 0x4fff3210,
      0x1ff0ffff, 0x2ff1fff0, 0x2ff1ff0f, 0x3ff2ff10, 0x2ff1f0ff, 0x3ff2f1f0,
      0x3ff2f10f, 0x4ff3f210, 0x2ff10fff, 0x3ff21ff0, 0x3ff21f0f, 0x4ff32f10,
      0x3ff210ff, 0x4ff321f0, 0x4ff3210f, 0x5ff43210, 0x1f0fffff, 0x2f1ffff0,
      0x2f1fff0f, 0x3f2fff10, 0x2f1ff0ff, 0x3f2ff1f0, 0x3f2ff10f, 0x4f3ff210,
      0x2f1f0fff, 0x3f2f1ff0, 0x3f2f1f0f, 0x4f3f2f10, 0x3f2f10ff, 0x4f3f21f0,
      0x4f3f210f, 0x5f4f3210, 0x2f10ffff, 0x3f21fff0, 0x3f21ff0f, 0x4f32ff10,
      0x3f21f0ff, 0x4f32f1f0, 0x4f32f10f, 0x5f43f210, 0x3f210fff, 0x4f321ff0,
      0x4f321f0f, 0x5f432f10, 0x4f3210ff, 0x5f4321f0, 0x5f43210f, 0x6f543210,
      0x10ffffff, 0x21fffff0, 0x21ffff0f, 0x32ffff10, 0x21fff0ff, 0x32fff1f0,
      0x32fff10f, 0x43fff210, 0x21ff0fff, 0x32ff1ff0, 0x32ff1f0f, 0x43ff2f10,
      0x32ff10ff, 0x43ff21f0, 0x43ff210f, 0x54ff3210, 0x21f0ffff, 0x32f1fff0,
      0x32f1ff0f, 0x43f2ff10, 0x32f1f0ff, 0x43f2f1f0, 0x43f2f10f, 0x54f3f210,
      0x32f10fff, 0x43f21ff0, 0x43f21f0f, 0x54f32f10, 0x43f210ff, 0x54f321f0,
      0x54f3210f, 0x65f43210, 0x210fffff, 0x321ffff0, 0x321fff0f, 0x432fff10,
      0x321ff0ff, 0x432ff1f0, 0x432ff10f, 0x543ff210, 0x321f0fff, 0x432f1ff0,
      0x432f1f0f, 0x543f2f10, 0x432f10ff, 0x543f21f0, 0x543f210f, 0x654f3210,
      0x3210ffff, 0x4321fff0, 0x4321ff0f, 0x5432ff10, 0x4321f0ff, 0x5432f1f0,
      0x5432f10f, 0x6543f210, 0x43210fff, 0x54321ff0, 0x54321f0f, 0x65432f10,
      0x543210ff, 0x654321f0, 0x6543210f, 0x76543210,
  };

  // For lane i, shift the i-th 4-bit index down to bits [0, 3).
  const Vec256<uint32_t> packed = Set(du, packed_array[mask_bits]);
  alignas(32) constexpr uint32_t shifts[8] = {0, 4, 8, 12, 16, 20, 24, 28};
  // TableLookupLanes ignores upper bits; avoid bounds-check in IndicesFromVec.
  const Indices256<uint32_t> indices{(packed >> Load(du, shifts)).raw};
  const Vec256<uint32_t> expand = TableLookupLanes(BitCast(du, v), indices);
  // TableLookupLanes cannot also zero masked-off lanes, so do that now.
  return IfThenElseZero(mask, BitCast(d, expand));
#endif
}

template <typename T, HWY_IF_T_SIZE(T, 8)>
HWY_API Vec256<T> Expand(Vec256<T> v, Mask256<T> mask) {
  const Full256<T> d;
#if HWY_TARGET <= HWY_AVX3
  const RebindToUnsigned<decltype(d)> du;
  const MFromD<decltype(du)> mu = RebindMask(du, mask);
  return BitCast(d, detail::NativeExpand(BitCast(du, v), mu));
#else
  const RebindToUnsigned<decltype(d)> du;
  const uint64_t mask_bits = BitsFromMask(d, mask);

  alignas(16) constexpr uint64_t packed_array[16] = {
      // PrintExpand64x4Nibble.
      0x0000ffff, 0x0000fff0, 0x0000ff0f, 0x0000ff10, 0x0000f0ff, 0x0000f1f0,
      0x0000f10f, 0x0000f210, 0x00000fff, 0x00001ff0, 0x00001f0f, 0x00002f10,
      0x000010ff, 0x000021f0, 0x0000210f, 0x00003210};

  // For lane i, shift the i-th 4-bit index down to bits [0, 2).
  const Vec256<uint64_t> packed = Set(du, packed_array[mask_bits]);
  alignas(32) constexpr uint64_t shifts[8] = {0, 4, 8, 12, 16, 20, 24, 28};
#if HWY_TARGET <= HWY_AVX3  // native 64-bit TableLookupLanes
  // TableLookupLanes ignores upper bits; avoid bounds-check in IndicesFromVec.
  const Indices256<uint64_t> indices{(packed >> Load(du, shifts)).raw};
#else
  // 64-bit TableLookupLanes on AVX2 requires IndicesFromVec, which checks
  // bounds, so clear the upper bits.
  const Vec256<uint64_t> masked = And(packed >> Load(du, shifts), Set(du, 3));
  const Indices256<uint64_t> indices = IndicesFromVec(du, masked);
#endif
  const Vec256<uint64_t> expand = TableLookupLanes(BitCast(du, v), indices);
  // TableLookupLanes cannot also zero masked-off lanes, so do that now.
  return IfThenElseZero(mask, BitCast(d, expand));
#endif
}

// ------------------------------ LoadExpand

template <class D, HWY_IF_V_SIZE_D(D, 32),
          HWY_IF_T_SIZE_ONE_OF_D(D, (1 << 1) | (1 << 2))>
HWY_API VFromD<D> LoadExpand(MFromD<D> mask, D d,
                             const TFromD<D>* HWY_RESTRICT unaligned) {
#if HWY_TARGET <= HWY_AVX3_DL  // VBMI2
  const RebindToUnsigned<decltype(d)> du;
  using TU = TFromD<decltype(du)>;
  const TU* HWY_RESTRICT pu = reinterpret_cast<const TU*>(unaligned);
  const MFromD<decltype(du)> mu = RebindMask(du, mask);
  return BitCast(d, detail::NativeLoadExpand(mu, du, pu));
#else
  return Expand(LoadU(d, unaligned), mask);
#endif
}

template <class D, HWY_IF_V_SIZE_D(D, 32),
          HWY_IF_T_SIZE_ONE_OF_D(D, (1 << 4) | (1 << 8))>
HWY_API VFromD<D> LoadExpand(MFromD<D> mask, D d,
                             const TFromD<D>* HWY_RESTRICT unaligned) {
#if HWY_TARGET <= HWY_AVX3
  const RebindToUnsigned<decltype(d)> du;
  using TU = TFromD<decltype(du)>;
  const TU* HWY_RESTRICT pu = reinterpret_cast<const TU*>(unaligned);
  const MFromD<decltype(du)> mu = RebindMask(du, mask);
  return BitCast(d, detail::NativeLoadExpand(mu, du, pu));
#else
  return Expand(LoadU(d, unaligned), mask);
#endif
}

// ------------------------------ LoadInterleaved3/4

// Implemented in generic_ops, we just overload LoadTransposedBlocks3/4.

namespace detail {
// Input:
// 1 0 (<- first block of unaligned)
// 3 2
// 5 4
// Output:
// 3 0
// 4 1
// 5 2
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API void LoadTransposedBlocks3(D d, const TFromD<D>* HWY_RESTRICT unaligned,
                                   VFromD<D>& A, VFromD<D>& B, VFromD<D>& C) {
  HWY_LANES_CONSTEXPR size_t N = Lanes(d);
  const VFromD<D> v10 = LoadU(d, unaligned + 0 * N);  // 1 0
  const VFromD<D> v32 = LoadU(d, unaligned + 1 * N);
  const VFromD<D> v54 = LoadU(d, unaligned + 2 * N);

  A = ConcatUpperLower(d, v32, v10);
  B = ConcatLowerUpper(d, v54, v10);
  C = ConcatUpperLower(d, v54, v32);
}

// Input (128-bit blocks):
// 1 0 (first block of unaligned)
// 3 2
// 5 4
// 7 6
// Output:
// 4 0 (LSB of vA)
// 5 1
// 6 2
// 7 3
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API void LoadTransposedBlocks4(D d, const TFromD<D>* HWY_RESTRICT unaligned,
                                   VFromD<D>& vA, VFromD<D>& vB, VFromD<D>& vC,
                                   VFromD<D>& vD) {
  HWY_LANES_CONSTEXPR size_t N = Lanes(d);
  const VFromD<D> v10 = LoadU(d, unaligned + 0 * N);
  const VFromD<D> v32 = LoadU(d, unaligned + 1 * N);
  const VFromD<D> v54 = LoadU(d, unaligned + 2 * N);
  const VFromD<D> v76 = LoadU(d, unaligned + 3 * N);

  vA = ConcatLowerLower(d, v54, v10);
  vB = ConcatUpperUpper(d, v54, v10);
  vC = ConcatLowerLower(d, v76, v32);
  vD = ConcatUpperUpper(d, v76, v32);
}
}  // namespace detail

// ------------------------------ StoreInterleaved2/3/4 (ConcatUpperLower)

// Implemented in generic_ops, we just overload StoreTransposedBlocks2/3/4.

namespace detail {
// Input (128-bit blocks):
// 2 0 (LSB of i)
// 3 1
// Output:
// 1 0
// 3 2
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API void StoreTransposedBlocks2(VFromD<D> i, VFromD<D> j, D d,
                                    TFromD<D>* HWY_RESTRICT unaligned) {
  HWY_LANES_CONSTEXPR size_t N = Lanes(d);
  const auto out0 = ConcatLowerLower(d, j, i);
  const auto out1 = ConcatUpperUpper(d, j, i);
  StoreU(out0, d, unaligned + 0 * N);
  StoreU(out1, d, unaligned + 1 * N);
}

// Input (128-bit blocks):
// 3 0 (LSB of i)
// 4 1
// 5 2
// Output:
// 1 0
// 3 2
// 5 4
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API void StoreTransposedBlocks3(VFromD<D> i, VFromD<D> j, VFromD<D> k, D d,
                                    TFromD<D>* HWY_RESTRICT unaligned) {
  HWY_LANES_CONSTEXPR size_t N = Lanes(d);
  const auto out0 = ConcatLowerLower(d, j, i);
  const auto out1 = ConcatUpperLower(d, i, k);
  const auto out2 = ConcatUpperUpper(d, k, j);
  StoreU(out0, d, unaligned + 0 * N);
  StoreU(out1, d, unaligned + 1 * N);
  StoreU(out2, d, unaligned + 2 * N);
}

// Input (128-bit blocks):
// 4 0 (LSB of i)
// 5 1
// 6 2
// 7 3
// Output:
// 1 0
// 3 2
// 5 4
// 7 6
template <class D, HWY_IF_V_SIZE_D(D, 32)>
HWY_API void StoreTransposedBlocks4(VFromD<D> i, VFromD<D> j, VFromD<D> k,
                                    VFromD<D> l, D d,
                                    TFromD<D>* HWY_RESTRICT unaligned) {
  HWY_LANES_CONSTEXPR size_t N = Lanes(d);
  // Write lower halves, then upper.
  const auto out0 = ConcatLowerLower(d, j, i);
  const auto out1 = ConcatLowerLower(d, l, k);
  StoreU(out0, d, unaligned + 0 * N);
  StoreU(out1, d, unaligned + 1 * N);
  const auto out2 = ConcatUpperUpper(d, j, i);
  const auto out3 = ConcatUpperUpper(d, l, k);
  StoreU(out2, d, unaligned + 2 * N);
  StoreU(out3, d, unaligned + 3 * N);
}
}  // namespace detail

// ------------------------------ Additional mask logical operations

#if HWY_TARGET <= HWY_AVX3
template <class T>
HWY_API Mask256<T> SetAtOrAfterFirst(Mask256<T> mask) {
  constexpr size_t N = MaxLanes(Full256<T>());
  constexpr uint32_t kActiveElemMask =
      static_cast<uint32_t>((uint64_t{1} << N) - 1);
  return Mask256<T>{static_cast<typename Mask256<T>::Raw>(
      (0u - detail::AVX3Blsi(mask.raw)) & kActiveElemMask)};
}
template <class T>
HWY_API Mask256<T> SetBeforeFirst(Mask256<T> mask) {
  constexpr size_t N = MaxLanes(Full256<T>());
  constexpr uint32_t kActiveElemMask =
      static_cast<uint32_t>((uint64_t{1} << N) - 1);
  return Mask256<T>{static_cast<typename Mask256<T>::Raw>(
      (detail::AVX3Blsi(mask.raw) - 1u) & kActiveElemMask)};
}
template <class T>
HWY_API Mask256<T> SetAtOrBeforeFirst(Mask256<T> mask) {
  constexpr size_t N = MaxLanes(Full256<T>());
  constexpr uint32_t kActiveElemMask =
      static_cast<uint32_t>((uint64_t{1} << N) - 1);
  return Mask256<T>{static_cast<typename Mask256<T>::Raw>(
      detail::AVX3Blsmsk(mask.raw) & kActiveElemMask)};
}
template <class T>
HWY_API Mask256<T> SetOnlyFirst(Mask256<T> mask) {
  return Mask256<T>{
      static_cast<typename Mask256<T>::Raw>(detail::AVX3Blsi(mask.raw))};
}
#else   // AVX2
template <class T>
HWY_API Mask256<T> SetAtOrAfterFirst(Mask256<T> mask) {
  const Full256<T> d;
  const Repartition<int64_t, decltype(d)> di64;
  const Repartition<float, decltype(d)> df32;
  const Repartition<int32_t, decltype(d)> di32;
  const Half<decltype(di64)> dh_i64;
  const Half<decltype(di32)> dh_i32;
  using VF32 = VFromD<decltype(df32)>;

  auto vmask = BitCast(di64, VecFromMask(d, mask));
  vmask = Or(vmask, Neg(vmask));

  // Copy the sign bit of the even int64_t lanes to the odd int64_t lanes
  const auto vmask2 = BitCast(
      di32, VF32{_mm256_shuffle_ps(Zero(df32).raw, BitCast(df32, vmask).raw,
                                   _MM_SHUFFLE(1, 1, 0, 0))});
  vmask = Or(vmask, BitCast(di64, BroadcastSignBit(vmask2)));

  // Copy the sign bit of the lower 128-bit half to the upper 128-bit half
  const auto vmask3 =
      BroadcastSignBit(Broadcast<3>(BitCast(dh_i32, LowerHalf(dh_i64, vmask))));
  vmask = Or(vmask, BitCast(di64, Combine(di32, vmask3, Zero(dh_i32))));
  return MaskFromVec(BitCast(d, vmask));
}

template <class T>
HWY_API Mask256<T> SetBeforeFirst(Mask256<T> mask) {
  return Not(SetAtOrAfterFirst(mask));
}

template <class T>
HWY_API Mask256<T> SetOnlyFirst(Mask256<T> mask) {
  const Full256<T> d;
  const RebindToSigned<decltype(d)> di;
  const Repartition<int64_t, decltype(d)> di64;
  const Half<decltype(di64)> dh_i64;

  const auto zero = Zero(di64);
  const auto vmask = BitCast(di64, VecFromMask(d, mask));

  const auto vmask_eq_0 = VecFromMask(di64, vmask == zero);
  auto vmask2_lo = LowerHalf(dh_i64, vmask_eq_0);
  auto vmask2_hi = UpperHalf(dh_i64, vmask_eq_0);

  vmask2_lo = And(vmask2_lo, InterleaveLower(vmask2_lo, vmask2_lo));
  vmask2_hi = And(ConcatLowerUpper(dh_i64, vmask2_hi, vmask2_lo),
                  InterleaveUpper(dh_i64, vmask2_lo, vmask2_lo));
  vmask2_lo = InterleaveLower(Set(dh_i64, int64_t{-1}), vmask2_lo);

  const auto vmask2 = Combine(di64, vmask2_hi, vmask2_lo);
  const auto only_first_vmask = Neg(BitCast(di, And(vmask, Neg(vmask))));
  return MaskFromVec(BitCast(d, And(only_first_vmask, BitCast(di, vmask2))));
}

template <class T>
HWY_API Mask256<T> SetAtOrBeforeFirst(Mask256<T> mask) {
  const Full256<T> d;
  constexpr size_t kLanesPerBlock = MaxLanes(d) / 2;

  const auto vmask = VecFromMask(d, mask);
  const auto vmask_lo = ConcatLowerLower(d, vmask, Zero(d));
  return SetBeforeFirst(
      MaskFromVec(CombineShiftRightBytes<(kLanesPerBlock - 1) * sizeof(T)>(
          d, vmask, vmask_lo)));
}
#endif  // HWY_TARGET <= HWY_AVX3

// ------------------------------ Reductions in generic_ops

// ------------------------------ BitShuffle
#if HWY_TARGET <= HWY_AVX3_DL
template <class V, class VI, HWY_IF_UI64(TFromV<V>), HWY_IF_UI8(TFromV<VI>),
          HWY_IF_V_SIZE_V(V, 32), HWY_IF_V_SIZE_V(VI, 32)>
HWY_API V BitShuffle(V v, VI idx) {
  const DFromV<decltype(v)> d64;
  const RebindToUnsigned<decltype(d64)> du64;
  const Rebind<uint8_t, decltype(d64)> du8;

  int32_t i32_bit_shuf_result =
      static_cast<int32_t>(_mm256_bitshuffle_epi64_mask(v.raw, idx.raw));

  return BitCast(d64, PromoteTo(du64, VFromD<decltype(du8)>{_mm_cvtsi32_si128(
                                          i32_bit_shuf_result)}));
}
#endif  // HWY_TARGET <= HWY_AVX3_DL

// ------------------------------ MultiRotateRight

#if HWY_TARGET <= HWY_AVX3_DL

#ifdef HWY_NATIVE_MULTIROTATERIGHT
#undef HWY_NATIVE_MULTIROTATERIGHT
#else
#define HWY_NATIVE_MULTIROTATERIGHT
#endif

template <class V, class VI, HWY_IF_UI64(TFromV<V>), HWY_IF_UI8(TFromV<VI>),
          HWY_IF_V_SIZE_V(V, 32), HWY_IF_V_SIZE_V(VI, HWY_MAX_LANES_V(V) * 8)>
HWY_API V MultiRotateRight(V v, VI idx) {
  return V{_mm256_multishift_epi64_epi8(idx.raw, v.raw)};
}

#endif

// ------------------------------ LeadingZeroCount

#if HWY_TARGET <= HWY_AVX3
template <class V, HWY_IF_UI32(TFromV<V>), HWY_IF_V_SIZE_V(V, 32)>
HWY_API V LeadingZeroCount(V v) {
  return V{_mm256_lzcnt_epi32(v.raw)};
}

template <class V, HWY_IF_UI64(TFromV<V>), HWY_IF_V_SIZE_V(V, 32)>
HWY_API V LeadingZeroCount(V v) {
  return V{_mm256_lzcnt_epi64(v.raw)};
}

namespace detail {

template <class V, HWY_IF_UNSIGNED_V(V),
          HWY_IF_T_SIZE_ONE_OF_V(V, (1 << 1) | (1 << 2)),
          HWY_IF_LANES_LE_D(DFromV<V>, HWY_MAX_BYTES / 4)>
static HWY_INLINE HWY_MAYBE_UNUSED V Lzcnt32ForU8OrU16OrU32(V v) {
  const DFromV<decltype(v)> d;
  const Rebind<int32_t, decltype(d)> di32;
  const Rebind<uint32_t, decltype(d)> du32;

  const auto v_lz_count = LeadingZeroCount(PromoteTo(du32, v));
  return DemoteTo(d, BitCast(di32, v_lz_count));
}

template <class V, HWY_IF_UNSIGNED_V(V), HWY_IF_T_SIZE_V(V, 4)>
static HWY_INLINE HWY_MAYBE_UNUSED V Lzcnt32ForU8OrU16OrU32(V v) {
  return LeadingZeroCount(v);
}

template <class V, HWY_IF_UNSIGNED_V(V),
          HWY_IF_T_SIZE_ONE_OF_V(V, (1 << 1) | (1 << 2)),
          HWY_IF_LANES_GT_D(DFromV<V>, HWY_MAX_BYTES / 4)>
static HWY_INLINE HWY_MAYBE_UNUSED V Lzcnt32ForU8OrU16OrU32(V v) {
  const DFromV<decltype(v)> d;
  const RepartitionToWide<decltype(d)> dw;
  const RebindToSigned<decltype(dw)> dw_i;

  const auto lo_v_lz_count = Lzcnt32ForU8OrU16OrU32(PromoteLowerTo(dw, v));
  const auto hi_v_lz_count = Lzcnt32ForU8OrU16OrU32(PromoteUpperTo(dw, v));
  return OrderedDemote2To(d, BitCast(dw_i, lo_v_lz_count),
                          BitCast(dw_i, hi_v_lz_count));
}

}  // namespace detail

template <class V, HWY_IF_NOT_FLOAT_NOR_SPECIAL_V(V),
          HWY_IF_T_SIZE_ONE_OF_V(V, (1 << 1) | (1 << 2))>
HWY_API V LeadingZeroCount(V v) {
  const DFromV<decltype(v)> d;
  const RebindToUnsigned<decltype(d)> du;
  using TU = TFromD<decltype(du)>;

  constexpr TU kNumOfBitsInT{sizeof(TU) * 8};
  const auto v_lzcnt32 = detail::Lzcnt32ForU8OrU16OrU32(BitCast(du, v));
  return BitCast(d, Min(v_lzcnt32 - Set(du, TU{32 - kNumOfBitsInT}),
                        Set(du, TU{kNumOfBitsInT})));
}

template <class V, HWY_IF_NOT_FLOAT_NOR_SPECIAL_V(V),
          HWY_IF_T_SIZE_ONE_OF_V(V, (1 << 1) | (1 << 2))>
HWY_API V HighestSetBitIndex(V v) {
  const DFromV<decltype(v)> d;
  const RebindToUnsigned<decltype(d)> du;
  using TU = TFromD<decltype(du)>;
  return BitCast(
      d, Set(du, TU{31}) - detail::Lzcnt32ForU8OrU16OrU32(BitCast(du, v)));
}

template <class V, HWY_IF_NOT_FLOAT_NOR_SPECIAL_V(V),
          HWY_IF_T_SIZE_ONE_OF_V(V, (1 << 4) | (1 << 8))>
HWY_API V HighestSetBitIndex(V v) {
  const DFromV<decltype(v)> d;
  using T = TFromD<decltype(d)>;
  return BitCast(d, Set(d, T{sizeof(T) * 8 - 1}) - LeadingZeroCount(v));
}

template <class V, HWY_IF_NOT_FLOAT_NOR_SPECIAL_V(V)>
HWY_API V TrailingZeroCount(V v) {
  const DFromV<decltype(v)> d;
  const RebindToSigned<decltype(d)> di;
  using T = TFromD<decltype(d)>;

  const auto vi = BitCast(di, v);
  const auto lowest_bit = BitCast(d, And(vi, Neg(vi)));
  constexpr T kNumOfBitsInT{sizeof(T) * 8};
  const auto bit_idx = HighestSetBitIndex(lowest_bit);
  return IfThenElse(MaskFromVec(bit_idx), Set(d, kNumOfBitsInT), bit_idx);
}
#endif  // HWY_TARGET <= HWY_AVX3

// NOLINTNEXTLINE(google-readability-namespace-comments)
}  // namespace HWY_NAMESPACE
}  // namespace hwy
HWY_AFTER_NAMESPACE();

// Note that the GCC warnings are not suppressed if we only wrap the *intrin.h -
// the warning seems to be issued at the call site of intrinsics, i.e. our code.
HWY_DIAGNOSTICS(pop)