In coverage cross...with...question

hi, I hope to constraint the range in coverage cross again. So in coverage I write like this, but it won’t run after generate the transactions. Maybe it is too huge to constraint?

coverage cross_x_related_cg;
    x_cp: coverponit dma_tr.x{
        bins x_bin[16] = {[0:16'hffff]};
    x_len_cp: coverponit dma_tr.x_len{
        bins x_len_bin[16] = {[0:16'hffff]};
    x__offset_cp: coverponit dma_tr.x_offset{
        bins x_offset_bin[16] = {[0:16'hffff]};
    x_x_len_x_offset_cross: cross x_cp, x_len_cp, x_offset_cp{
        illegal_bins x_x_len_x_offset_illegal_bins = x_x_len_x_offset_cross with (x_offset_cp > (x_cp - x_cp));

In reply to crystalysj:

Why do you have (x_cp-x_cp)? That is always 0.

In reply to dave_59:
sorry, typo should be (x_cp-x_len_cp).In my code it is right.