/*
 * Copyright (c) 2020 Arm Limited.
 *
 * SPDX-License-Identifier: MIT
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#include <cmath>
#include <limits>

#if defined(__ARM_FEATURE_SVE)

namespace arm_compute
{
inline svfloat32_t svtaylor_poly_f32_z(svbool_t pg, svfloat32_t x, const std::array<svfloat32_t, 8> &coeffs)
{
    const auto A   = svmla_f32_z(pg, coeffs[0], coeffs[4], x);
    const auto B   = svmla_f32_z(pg, coeffs[2], coeffs[6], x);
    const auto C   = svmla_f32_z(pg, coeffs[1], coeffs[5], x);
    const auto D   = svmla_f32_z(pg, coeffs[3], coeffs[7], x);
    const auto x2  = svmul_f32_z(pg, x, x);
    const auto x4  = svmul_f32_z(pg, x2, x2);
    const auto res = svmla_f32_z(pg, svmla_f32_z(pg, A, B, x2), svmla_f32_z(pg, C, D, x2), x4);
    return res;
}

inline svfloat16_t svtaylor_poly_f16_z(svbool_t pg, svfloat16_t x, const std::array<svfloat16_t, 8> &coeffs)
{
    const auto A   = svmla_f16_z(pg, coeffs[0], coeffs[4], x);
    const auto B   = svmla_f16_z(pg, coeffs[2], coeffs[6], x);
    const auto C   = svmla_f16_z(pg, coeffs[1], coeffs[5], x);
    const auto D   = svmla_f16_z(pg, coeffs[3], coeffs[7], x);
    const auto x2  = svmul_f16_z(pg, x, x);
    const auto x4  = svmul_f16_z(pg, x2, x2);
    const auto res = svmla_f16_z(pg, svmla_f16_z(pg, A, B, x2), svmla_f16_z(pg, C, D, x2), x4);
    return res;
}

inline svfloat16_t svinv_f16_z(svbool_t pg, svfloat16_t x)
{
    auto recip = svrecpe_f16(x);
    recip      = svmul_f16_z(pg, svrecps_f16(x, recip), recip);
    recip      = svmul_f16_z(pg, svrecps_f16(x, recip), recip);
    return recip;
}

inline svfloat32_t svinv_f32_z(svbool_t pg, svfloat32_t x)
{
    auto recip = svrecpe_f32(x);
    recip      = svmul_f32_z(pg, svrecps_f32(x, recip), recip);
    recip      = svmul_f32_z(pg, svrecps_f32(x, recip), recip);
    return recip;
}

inline svfloat32_t svexp_f32_z(svbool_t pg, svfloat32_t x)
{
    const auto CONST_LN2          = svdup_n_f32(0.6931471805f); // ln(2)
    const auto CONST_INV_LN2      = svdup_n_f32(1.4426950408f); // 1/ln(2)
    const auto CONST_INF          = svdup_n_f32(std::numeric_limits<float>::infinity());
    const auto CONST_MAX_INPUT    = svdup_n_f32(88.7f);
    const auto CONST_0            = svdup_n_f32(0.f);
    const auto CONST_NEGATIVE_126 = svdup_n_s32(-126);

    /** Exponent polynomial coefficients */
    const std::array<svfloat32_t, 8> exp_tab =
    {
        {
            svdup_n_f32(1.f),
            svdup_n_f32(0.0416598916054f),
            svdup_n_f32(0.500000596046f),
            svdup_n_f32(0.0014122662833f),
            svdup_n_f32(1.00000011921f),
            svdup_n_f32(0.00833693705499f),
            svdup_n_f32(0.166665703058f),
            svdup_n_f32(0.000195780929062f),
        }
    };

    // Perform range reduction [-log(2),log(2)]
    auto m   = svcvt_s32_f32_z(pg, svmul_f32_z(pg, x, CONST_INV_LN2));
    auto val = svmls_f32_z(pg, x, svcvt_f32_s32_z(pg, m), CONST_LN2);

    // Polynomial Approximation
    auto poly = svtaylor_poly_f32_z(pg, val, exp_tab);

    // Reconstruct
    poly = svreinterpret_f32_s32(svqadd_s32(svreinterpret_s32_f32(poly), svlsl_n_s32_z(pg, m, 23)));

    // Handle underflow
    svbool_t ltpg = svcmplt_s32(pg, m, CONST_NEGATIVE_126);
    poly          = svsel_f32(ltpg, CONST_0, poly);

    // Handle overflow
    svbool_t gtpg = svcmpgt_f32(pg, x, CONST_MAX_INPUT);
    poly          = svsel_f32(gtpg, CONST_INF, poly);

    return poly;
}

inline svfloat16_t svexp_f16_z(svbool_t pg, svfloat16_t x)
{
    const auto CONST_LN2          = svdup_n_f16(0.6931471805f); // ln(2)
    const auto CONST_INV_LN2      = svdup_n_f16(1.4426950408f); // 1/ln(2)
    const auto CONST_INF          = svdup_n_f16(std::numeric_limits<float16_t>::infinity());
    const auto CONST_MAX_INPUT    = svdup_n_f16(88.7f);
    const auto CONST_0            = svdup_n_f16(0.f);
    const auto CONST_NEGATIVE_126 = svdup_n_s16(-126);

    /** Exponent polynomial coefficients */
    const std::array<svfloat16_t, 8> exp_tab =
    {
        {
            svdup_n_f16(1.f),
            svdup_n_f16(0.0416598916054f),
            svdup_n_f16(0.500000596046f),
            svdup_n_f16(0.0014122662833f),
            svdup_n_f16(1.00000011921f),
            svdup_n_f16(0.00833693705499f),
            svdup_n_f16(0.166665703058f),
            svdup_n_f16(0.000195780929062f),
        }
    };

    // Perform range reduction [-log(2),log(2)]
    auto m   = svcvt_s16_f16_z(pg, svmul_f16_z(pg, x, CONST_INV_LN2));
    auto val = svmls_f16_z(pg, x, svcvt_f16_s16_z(pg, m), CONST_LN2);

    // Polynomial Approximation
    auto poly = svtaylor_poly_f16_z(pg, val, exp_tab);

    // Reconstruct
    poly = svreinterpret_f16_s16(svqadd_s16(svreinterpret_s16_f16(poly), svlsl_n_s16_z(pg, m, 11)));

    // Handle underflow
    svbool_t ltpg = svcmplt_s16(pg, m, CONST_NEGATIVE_126);
    poly          = svsel_f16(ltpg, CONST_0, poly);

    // Handle overflow
    svbool_t gtpg = svcmpgt_f16(pg, x, CONST_MAX_INPUT);
    poly          = svsel_f16(gtpg, CONST_INF, poly);

    return poly;
}

inline svfloat32_t svtanh_f32_z(svbool_t pg, svfloat32_t val)
{
    const svfloat32_t CONST_1        = svdup_n_f32(1.f);
    const svfloat32_t CONST_2        = svdup_n_f32(2.f);
    const svfloat32_t CONST_MIN_TANH = svdup_n_f32(-10.f);
    const svfloat32_t CONST_MAX_TANH = svdup_n_f32(10.f);

    svfloat32_t x     = svmin_f32_z(pg, svmax_f32_z(pg, val, CONST_MIN_TANH), CONST_MAX_TANH);
    svfloat32_t exp2x = svexp_f32_z(pg, svmul_f32_z(pg, CONST_2, x));
    svfloat32_t num   = svsub_f32_z(pg, exp2x, CONST_1);
    svfloat32_t den   = svadd_f32_z(pg, exp2x, CONST_1);
    svfloat32_t tanh  = svdiv_f32_z(pg, num, den);
    return tanh;
}

inline svfloat16_t svtanh_f16_z(svbool_t pg, svfloat16_t val)
{
    const svfloat16_t CONST_1        = svdup_n_f16(1.f);
    const svfloat16_t CONST_2        = svdup_n_f16(2.f);
    const svfloat16_t CONST_MIN_TANH = svdup_n_f16(-10.f);
    const svfloat16_t CONST_MAX_TANH = svdup_n_f16(10.f);

    const svfloat16_t x     = svmin_f16_z(pg, svmax_f16_z(pg, val, CONST_MIN_TANH), CONST_MAX_TANH);
    const svfloat16_t exp2x = svexp_f16_z(pg, svmul_f16_z(pg, CONST_2, x));
    const svfloat16_t num   = svsub_f16_z(pg, exp2x, CONST_1);
    const svfloat16_t den   = svadd_f16_z(pg, exp2x, CONST_1);
    const svfloat16_t tanh  = svdiv_f16_z(pg, num, den);
    return tanh;
}

inline svfloat32_t svlog_f32_z(svbool_t pg, svfloat32_t x)
{
#if defined(__ARM_FEATURE_SVE2)
    return svcvt_f32_s32_z(pg, svlogb_f32_z(pg, x));
#else  /* !defined(__ARM_FEATURE_SVE2) */
    /** Logarithm polynomial coefficients */
    const std::array<svfloat32_t, 8> log_tab =
    {
        {
            svdup_n_f32(-2.29561495781f),
            svdup_n_f32(-2.47071170807f),
            svdup_n_f32(-5.68692588806f),
            svdup_n_f32(-0.165253549814f),
            svdup_n_f32(5.17591238022f),
            svdup_n_f32(0.844007015228f),
            svdup_n_f32(4.58445882797f),
            svdup_n_f32(0.0141278216615f),
        }
    };

    const auto CONST_127 = svdup_n_s32(127);           // 127
    const auto CONST_LN2 = svdup_n_f32(0.6931471805f); // ln(2)

    // Extract exponent
    auto m   = svsub_s32_z(pg, svasr_n_s32_z(pg, svreinterpret_s32_f32(x), 23), CONST_127);
    auto val = svreinterpret_f32_s32(svsub_s32_z(pg, svreinterpret_s32_f32(x), svlsl_n_s32_z(pg, m, 23)));

    // Polynomial Approximation
    auto poly = svtaylor_poly_f32_z(pg, val, log_tab);

    // Reconstruct
    poly = svmla_f32_z(pg, poly, svcvt_f32_s32_z(pg, m), CONST_LN2);

    return poly;
#endif /* defined(__ARM_FEATURE_SVE2) */
}

inline svfloat16_t svlog_f16_z(svbool_t pg, svfloat16_t x)
{
#if defined(__ARM_FEATURE_SVE2)
    return svcvt_f16_s16_z(pg, svlogb_f16_z(pg, x));
#else  /* !defined(__ARM_FEATURE_SVE2) */

    /** Logarithm polynomial coefficients */
    const std::array<svfloat16_t, 8> log_tab
    {
        {
            svdup_n_f16(-2.29561495781f),
            svdup_n_f16(-2.47071170807f),
            svdup_n_f16(-5.68692588806f),
            svdup_n_f16(-0.165253549814f),
            svdup_n_f16(5.17591238022f),
            svdup_n_f16(0.844007015228f),
            svdup_n_f16(4.58445882797f),
            svdup_n_f16(0.0141278216615f),
        }
    };

    const auto CONST_7   = svdup_n_s16(7);             // 7
    const auto CONST_LN2 = svdup_n_f16(0.6931471805f); // ln(2)

    // Extract exponent
    auto m   = svsub_s16_z(pg, svasr_n_s16_z(pg, svreinterpret_s16_f16(x), 11), CONST_7);
    auto val = svreinterpret_f16_s16(svsub_s16_z(pg, svreinterpret_s16_f16(x), svlsl_n_s16_z(pg, m, 11)));

    // Polynomial Approximation
    auto poly = svtaylor_poly_f16_z(pg, val, log_tab);

    // Reconstruct
    poly = svmla_f16_z(pg, poly, svcvt_f16_s16_z(pg, m), CONST_LN2);

    return poly;
#endif /* defined(__ARM_FEATURE_SVE2) */
}
} // namespace arm_compute
#endif /* defined(__ARM_FEATURE_SVE) */