Function q8_prepare_lut

src/cpu/kernels/CpuElementwiseUnaryKernel.cpp:51–113

#ifdef __aarch64__

std::unique_ptr<uint8_t[]> q8_prepare_lut(ElementWiseUnary op, const ITensorInfo *src, const ITensorInfo *dst)
{
    ARM_COMPUTE_ERROR_ON(src->data_type() != dst->data_type());
    ARM_COMPUTE_ERROR_ON(!is_data_type_quantized(src->data_type()));
    ARM_COMPUTE_ERROR_ON(src->element_size() != 1);

    auto       lut       = std::unique_ptr<uint8_t[]>(new uint8_t[256]);
    const auto is_signed = src->data_type() == DataType::QASYMM8_SIGNED;
    const auto src_qi    = src->quantization_info().uniform();
    const auto dst_qi    = dst->quantization_info().uniform();

    const auto dst_min_fp = (((is_signed) ? -128 : 0) - dst_qi.offset) * dst_qi.scale;
    const auto dst_max_fp = (((is_signed) ? 127 : 255) - dst_qi.offset) * dst_qi.scale;

    for (int i = 0; i < 256; ++i)
    {
        const auto in =
            (is_signed) ? dequantize_qasymm8_signed(static_cast<int8_t>(i), src_qi) : dequantize_qasymm8(i, src_qi);
        float result = 0;

        switch (op)
        {
            case ElementWiseUnary::RSQRT:
                result = 1 / sqrt(in);
                break;

            case ElementWiseUnary::EXP:
                result = std::exp(in);
                break;

            case ElementWiseUnary::NEG:
                result = -in;
                break;

            case ElementWiseUnary::LOG:
                result = std::log(in);
                break;

            case ElementWiseUnary::ABS:
                result = std::abs(in);
                break;

            case ElementWiseUnary::ROUND:
                result = support::cpp11::nearbyint(in);
                break;

            case ElementWiseUnary::SIN:
                result = std::sin(in);
                break;

            default:
                ARM_COMPUTE_ERROR("NOT_SUPPORTED!");
        }

        result = utility::clamp(result, dst_min_fp, dst_max_fp);

        const auto out = (is_signed) ? static_cast<uint8_t>(quantize_qasymm8_signed(result, dst_qi))
                                     : quantize_qasymm8(result, dst_qi);