/*
 * Copyright (c) 2021, 2023, Intel Corporation. All rights reserved.
 * Copyright (c) 2021 Serge Sans Paille. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

// This implementation is based on x86-simd-sort(https://github.com/intel/x86-simd-sort)

#ifndef AVX2_EMU_FUNCS
#define AVX2_EMU_FUNCS

#include <array>
#include <utility>

#include "xss-common-qsort.h"

constexpr auto avx2_mask_helper_lut32 = [] {
    std::array<std::array<int32_t, 8>, 256> lut{};
    for (int64_t i = 0; i <= 0xFF; i++) {
        std::array<int32_t, 8> entry{};
        for (int j = 0; j < 8; j++) {
            if (((i >> j) & 1) == 1)
                entry[j] = 0xFFFFFFFF;
            else
                entry[j] = 0;
        }
        lut[i] = entry;
    }
    return lut;
}();

constexpr auto avx2_compressstore_lut32_gen = [] {
    std::array<std::array<std::array<int32_t, 8>, 256>, 2> lutPair{};
    auto &permLut = lutPair[0];
    auto &leftLut = lutPair[1];
    for (int64_t i = 0; i <= 0xFF; i++) {
        std::array<int32_t, 8> indices{};
        std::array<int32_t, 8> leftEntry = {0, 0, 0, 0, 0, 0, 0, 0};
        int right = 7;
        int left = 0;
        for (int j = 0; j < 8; j++) {
            bool ge = (i >> j) & 1;
            if (ge) {
                indices[right] = j;
                right--;
            } else {
                indices[left] = j;
                leftEntry[left] = 0xFFFFFFFF;
                left++;
            }
        }
        permLut[i] = indices;
        leftLut[i] = leftEntry;
    }
    return lutPair;
}();

constexpr auto avx2_compressstore_lut32_perm = avx2_compressstore_lut32_gen[0];
constexpr auto avx2_compressstore_lut32_left = avx2_compressstore_lut32_gen[1];


X86_SIMD_SORT_INLINE
__m256i convert_int_to_avx2_mask(int32_t m) {
    return _mm256_loadu_si256(
        (const __m256i *)avx2_mask_helper_lut32[m].data());
}

X86_SIMD_SORT_INLINE
int32_t convert_avx2_mask_to_int(__m256i m) {
    return _mm256_movemask_ps(_mm256_castsi256_ps(m));
}

// Emulators for intrinsics missing from AVX2 compared to AVX512
template <typename T>
T avx2_emu_reduce_max32(typename avx2_vector<T>::reg_t x) {
    using vtype = avx2_vector<T>;
    using reg_t = typename vtype::reg_t;

    reg_t inter1 =
        vtype::max(x, vtype::template shuffle<SHUFFLE_MASK(2, 3, 0, 1)>(x));
    reg_t inter2 = vtype::max(
        inter1, vtype::template shuffle<SHUFFLE_MASK(1, 0, 3, 2)>(inter1));
    T arr[vtype::numlanes];
    vtype::storeu(arr, inter2);
    return std::max(arr[0], arr[7]);
}

template <typename T>
T avx2_emu_reduce_min32(typename avx2_vector<T>::reg_t x) {
    using vtype = avx2_vector<T>;
    using reg_t = typename vtype::reg_t;

    reg_t inter1 =
        vtype::min(x, vtype::template shuffle<SHUFFLE_MASK(2, 3, 0, 1)>(x));
    reg_t inter2 = vtype::min(
        inter1, vtype::template shuffle<SHUFFLE_MASK(1, 0, 3, 2)>(inter1));
    T arr[vtype::numlanes];
    vtype::storeu(arr, inter2);
    return std::min(arr[0], arr[7]);
}

template <typename T>
void avx2_emu_mask_compressstoreu32(void *base_addr,
                                    typename avx2_vector<T>::opmask_t k,
                                    typename avx2_vector<T>::reg_t reg) {
    using vtype = avx2_vector<T>;

    T *leftStore = (T *)base_addr;

    int32_t shortMask = convert_avx2_mask_to_int(k);
    const __m256i &perm = _mm256_loadu_si256(
        (const __m256i *)avx2_compressstore_lut32_perm[shortMask].data());
    const __m256i &left = _mm256_loadu_si256(
        (const __m256i *)avx2_compressstore_lut32_left[shortMask].data());

    typename vtype::reg_t temp = vtype::permutevar(reg, perm);

    vtype::mask_storeu(leftStore, left, temp);
}


template <typename T>
int avx2_double_compressstore32(void *left_addr, void *right_addr,
                                typename avx2_vector<T>::opmask_t k,
                                typename avx2_vector<T>::reg_t reg) {
    using vtype = avx2_vector<T>;

    T *leftStore = (T *)left_addr;
    T *rightStore = (T *)right_addr;

    int32_t shortMask = convert_avx2_mask_to_int(k);
    const __m256i &perm = _mm256_loadu_si256(
        (const __m256i *)avx2_compressstore_lut32_perm[shortMask].data());

    typename vtype::reg_t temp = vtype::permutevar(reg, perm);

    vtype::storeu(leftStore, temp);
    vtype::storeu(rightStore, temp);

    return _mm_popcnt_u32(shortMask);
}


template <typename T>
typename avx2_vector<T>::reg_t avx2_emu_max(typename avx2_vector<T>::reg_t x,
                                            typename avx2_vector<T>::reg_t y) {
    using vtype = avx2_vector<T>;
    typename vtype::opmask_t nlt = vtype::gt(x, y);
    return _mm256_castpd_si256(_mm256_blendv_pd(_mm256_castsi256_pd(y),
                                                _mm256_castsi256_pd(x),
                                                _mm256_castsi256_pd(nlt)));
}

template <typename T>
typename avx2_vector<T>::reg_t avx2_emu_min(typename avx2_vector<T>::reg_t x,
                                            typename avx2_vector<T>::reg_t y) {
    using vtype = avx2_vector<T>;
    typename vtype::opmask_t nlt = vtype::gt(x, y);
    return _mm256_castpd_si256(_mm256_blendv_pd(_mm256_castsi256_pd(x),
                                                _mm256_castsi256_pd(y),
                                                _mm256_castsi256_pd(nlt)));
}

#endif