Function get_fix_mask

dnn/test/common/dct_ref.cpp:10–17

using Param = DctChannelSelectForward::Param;

static inline FixCase get_fix_mask(Param::FastImpl impl) {
    std::vector<int> fix_32_mask_offset{0, 16, 24, 32};
    std::vector<int> fix_32_mask_val{0,  1,  8,  16, 9, 2,  3, 10, 17, 24, 32,
                                     25, 18, 11, 4,  5, 0,  1, 8,  16, 9,  2,
                                     3,  10, 0,  1,  8, 16, 9, 2,  3,  10};
    megdnn_assert(impl == Param::FastImpl::FIX_32_MASK, "only support gen FIX_32_MASK");
    return {fix_32_mask_offset, fix_32_mask_val};
}

CheckerHelper::TensorsConstriant gen_dct_constriant(
        const size_t /* n */, const size_t ic, const size_t ih, const size_t iw,