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Rolko

Function do_compare override in uvm_sequence_item derived class - compare always returns '1'

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Hi,

I have created new transaction by extending uvm_sequence_item, where I have implemented do_compare function. Once implemented, compare calls seems to return '1', even if do_compare returns '0' (comparison failed).

I have traced comparison to uvm_object compare function calling uvm_comparer compare_object method. There, do_compare seems to be used in following code:

      if (field_op.user_hook_enabled()) begin
        ret_val = lhs.do_compare(rhs,this);
      end
      field_op.m_recycle();
      // If do_compare() returned 1, check for a change
      // in the result count.
      if (ret_val && (get_result() > old_result))
        ret_val = 0;
      else
        ret_val = 1;

It seems that any time do_compare returns '0', the condition below it always change ret_val (compare_object return value) to '1'.  This behaviour exists only in 1800.2-2017-0.9 reference implementation of UVM library. If I use UVM-1.2, compare calls returns '0',  if do_compare returns '0' on comparison failure (as I would expect).

I would like to ask whether this behaviour is intentional. In such case, is there any recommended way to implement do_compare task?

Thank you.

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Thanks for posting this issue Rolko.  The "else ret_val = 1" is a bug in 1800.2-2017-0.9.  It is removed in 1800.2-2017-1.0, a release which was approved last week by the committee and should be available for download very soon.

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