// -----------------------------------------------------------------------------------------------------
// Copyright (c) 2006-2020, Knut Reinert & Freie Universität Berlin
// Copyright (c) 2016-2020, Knut Reinert & MPI für molekulare Genetik
// This file may be used, modified and/or redistributed under the terms of the 3-clause BSD-License
// shipped with this file and also available at: https://github.com/seqan/seqan3/blob/master/LICENSE.md
// -----------------------------------------------------------------------------------------------------

/*!\file
 * \brief Provides specific algorithm implementations for AVX2 instruction set.
 * \author Rene Rahn <rene.rahn AT fu-berlin.de>
 */

#pragma once

#include <array>

#include <seqan3/core/simd/concept.hpp>
#include <seqan3/core/simd/detail/builtin_simd_intrinsics.hpp>
#include <seqan3/core/simd/simd_traits.hpp>

//-----------------------------------------------------------------------------
// forward declare avx2 simd algorithms that use avx2 intrinsics
//-----------------------------------------------------------------------------

namespace seqan3::detail
{
/*!\copydoc seqan3::simd::load
 * \attention This is the implementation for AVX2 intrinsics.
 */
template <simd::simd_concept simd_t>
constexpr simd_t load_avx2(void const * mem_addr);

/*!\copydoc seqan3::simd::transpose
 * \attention This is the implementation for AVX2 intrinsics.
 */
template <simd::simd_concept simd_t>
inline void transpose_matrix_avx2(std::array<simd_t, simd_traits<simd_t>::length> & matrix);

/*!\copydoc seqan3::detail::upcast_signed
 * \attention This is the implementation for AVX2 intrinsics.
 */
template <simd::simd_concept target_simd_t, simd::simd_concept source_simd_t>
constexpr target_simd_t upcast_signed_avx2(source_simd_t const & src);

/*!\copydoc seqan3::detail::upcast_unsigned
 * \attention This is the implementation for AVX2 intrinsics.
 */
template <simd::simd_concept target_simd_t, simd::simd_concept source_simd_t>
constexpr target_simd_t upcast_unsigned_avx2(source_simd_t const & src);

/*!\copydoc seqan3::detail::extract_half
 * \attention This is the implementation for AVX2 intrinsics.
 */
template <uint8_t index, simd::simd_concept simd_t>
constexpr simd_t extract_half_avx2(simd_t const & src);

/*!\copydoc seqan3::detail::extract_quarter
 * \attention This is the implementation for AVX2 intrinsics.
 */
template <uint8_t index, simd::simd_concept simd_t>
constexpr simd_t extract_quarter_avx2(simd_t const & src);

/*!\copydoc seqan3::detail::extract_eighth
 * \attention This is the implementation for AVX2 intrinsics.
 */
template <uint8_t index, simd::simd_concept simd_t>
constexpr simd_t extract_eighth_avx2(simd_t const & src);

}

//-----------------------------------------------------------------------------
// implementation
//-----------------------------------------------------------------------------

#ifdef __AVX2__

namespace seqan3::detail
{

template <simd::simd_concept simd_t>
constexpr simd_t load_avx2(void const * mem_addr)
{
    return reinterpret_cast<simd_t>(_mm256_loadu_si256(reinterpret_cast<__m256i const *>(mem_addr)));
}

template <simd::simd_concept simd_t>
inline void transpose_matrix_avx2(std::array<simd_t, simd_traits<simd_t>::length> & matrix)
{
    // emulate missing _mm256_unpacklo_epi128/_mm256_unpackhi_epi128 instructions
    auto _mm256_unpacklo_epi128 = [] (__m256i const & a, __m256i const & b)
    {
        return _mm256_permute2x128_si256(a, b, 0x20);
    };

    auto _mm256_unpackhi_epi128 = [] (__m256i const & a, __m256i const & b)
    {
        return _mm256_permute2x128_si256(a, b, 0x31);
    };

    // A look-up table to reverse the lowest 4 bits in order to permute the transposed rows.
    static const uint8_t bit_rev[] = { 0, 8, 4,12, 2,10, 6,14, 1, 9, 5,13, 3,11, 7,15,
                                      16,24,20,28,18,26,22,30,17,25,21,29,19,27,23,31};

    // transpose a 32x32 byte matrix
    __m256i tmp1[32];
    for (int i = 0; i < 16; ++i)
    {
        tmp1[i]    = _mm256_unpacklo_epi8(
            reinterpret_cast<const __m256i &>(matrix[2*i]),
            reinterpret_cast<const __m256i &>(matrix[2*i+1])
        );
        tmp1[i+16] = _mm256_unpackhi_epi8(
            reinterpret_cast<const __m256i &>(matrix[2*i]),
            reinterpret_cast<const __m256i &>(matrix[2*i+1])
        );
    }
    __m256i  tmp2[32];
    for (int i = 0; i < 16; ++i)
    {
        tmp2[i]    = _mm256_unpacklo_epi16(tmp1[2*i], tmp1[2*i+1]);
        tmp2[i+16] = _mm256_unpackhi_epi16(tmp1[2*i], tmp1[2*i+1]);
    }
    for (int i = 0; i < 16; ++i)
    {
        tmp1[i]    = _mm256_unpacklo_epi32(tmp2[2*i], tmp2[2*i+1]);
        tmp1[i+16] = _mm256_unpackhi_epi32(tmp2[2*i], tmp2[2*i+1]);
    }
    for (int i = 0; i < 16; ++i)
    {
        tmp2[i]    = _mm256_unpacklo_epi64(tmp1[2*i], tmp1[2*i+1]);
        tmp2[i+16] = _mm256_unpackhi_epi64(tmp1[2*i], tmp1[2*i+1]);
    }
    for (int i = 0; i < 16; ++i)
    {
        matrix[bit_rev[i]]    = reinterpret_cast<simd_t>(_mm256_unpacklo_epi128(tmp2[2*i],tmp2[2*i+1]));
        matrix[bit_rev[i+16]] = reinterpret_cast<simd_t>(_mm256_unpackhi_epi128(tmp2[2*i],tmp2[2*i+1]));
    }
}

template <simd::simd_concept target_simd_t, simd::simd_concept source_simd_t>
constexpr target_simd_t upcast_signed_avx2(source_simd_t const & src)
{
    __m128i const & tmp = _mm256_castsi256_si128(reinterpret_cast<__m256i const &>(src));
    if constexpr (simd_traits<source_simd_t>::length == 32) // cast from epi8 ...
    {
        if constexpr (simd_traits<target_simd_t>::length == 16) // to epi16
            return reinterpret_cast<target_simd_t>(_mm256_cvtepi8_epi16(tmp));
        if constexpr (simd_traits<target_simd_t>::length == 8) // to epi32
            return reinterpret_cast<target_simd_t>(_mm256_cvtepi8_epi32(tmp));
        if constexpr (simd_traits<target_simd_t>::length == 4) // to epi64
            return reinterpret_cast<target_simd_t>(_mm256_cvtepi8_epi64(tmp));
    }
    else if constexpr (simd_traits<source_simd_t>::length == 16) // cast from epi16 ...
    {
        if constexpr (simd_traits<target_simd_t>::length == 8) // to epi32
            return reinterpret_cast<target_simd_t>(_mm256_cvtepi16_epi32(tmp));
        if constexpr (simd_traits<target_simd_t>::length == 4) // to epi64
            return reinterpret_cast<target_simd_t>(_mm256_cvtepi16_epi64(tmp));
    }
    else // cast from epi32 to epi64
    {
        static_assert(simd_traits<source_simd_t>::length == 8, "Expected 32 bit scalar type.");
        return reinterpret_cast<target_simd_t>(_mm256_cvtepi32_epi64(tmp));
    }
}

template <simd::simd_concept target_simd_t, simd::simd_concept source_simd_t>
constexpr target_simd_t upcast_unsigned_avx2(source_simd_t const & src)
{
    __m128i const & tmp = _mm256_castsi256_si128(reinterpret_cast<__m256i const &>(src));
    if constexpr (simd_traits<source_simd_t>::length == 32) // cast from epi8 ...
    {
        if constexpr (simd_traits<target_simd_t>::length == 16) // to epi16
            return reinterpret_cast<target_simd_t>(_mm256_cvtepu8_epi16(tmp));
        if constexpr (simd_traits<target_simd_t>::length == 8) // to epi32
            return reinterpret_cast<target_simd_t>(_mm256_cvtepu8_epi32(tmp));
        if constexpr (simd_traits<target_simd_t>::length == 4) // to epi64
            return reinterpret_cast<target_simd_t>(_mm256_cvtepu8_epi64(tmp));
    }
    else if constexpr (simd_traits<source_simd_t>::length == 16) // cast from epi16 ...
    {
        if constexpr (simd_traits<target_simd_t>::length == 8) // to epi32
            return reinterpret_cast<target_simd_t>(_mm256_cvtepu16_epi32(tmp));
        if constexpr (simd_traits<target_simd_t>::length == 4) // to epi64
            return reinterpret_cast<target_simd_t>(_mm256_cvtepu16_epi64(tmp));
    }
    else // cast from epi32 to epi64
    {
        static_assert(simd_traits<source_simd_t>::length == 8, "Expected 32 bit scalar type.");
        return reinterpret_cast<target_simd_t>(_mm256_cvtepu32_epi64(tmp));
    }
}

template <uint8_t index, simd::simd_concept simd_t>
constexpr simd_t extract_half_avx2(simd_t const & src)
{
    return reinterpret_cast<simd_t>(_mm256_castsi128_si256(
            _mm256_extracti128_si256(reinterpret_cast<__m256i const &>(src), index)));
}

template <uint8_t index, simd::simd_concept simd_t>
constexpr simd_t extract_quarter_avx2(simd_t const & src)
{
    return reinterpret_cast<simd_t>(_mm256_castsi128_si256(
            _mm_cvtsi64x_si128(_mm256_extract_epi64(reinterpret_cast<__m256i const &>(src), index))));
}

template <uint8_t index, simd::simd_concept simd_t>
constexpr simd_t extract_eighth_avx2(simd_t const & src)
{
    return reinterpret_cast<simd_t>(_mm256_castsi128_si256(
            _mm_cvtsi32_si128(_mm256_extract_epi32(reinterpret_cast<__m256i const &>(src), index))));
}

} // namespace seqan3::detail

#endif // __AVX2__
