How to add UVM_NOCOMPARE to fields of extended class

UVM
, ,
1

I have a base class, where all fields are registered as UVM_ALL_ON. In class extended from this base class,i want to remove some field from comparing (UVM_NOCOMPARE).

class a ;
rand [2:0] bit tag;
rand [7:0] bit addr;

**uvm_field_int (tag, UVM_ALL_ON)** uvm_field_int (addr, UVM_ALL_ON)

endclass

/////////////////////////////
class b extend a;
`uvm_field_init (tag, UVM_ALL_ON | UVM_NOCOMPARE)

//other functions and fields
endclass

But, still TAG is getting compare even though its been registered as NO_COMPARE in extended class.
Any clue is appreciated, about how to remove “tag” from comparing.

Thanks,
Debashis

2

In reply to debashis_paul:

You should remove all of the `uvm_field_* macros and implement the Transaction Methods individually to give you better control. This will allow you to override the required methods in your extended class as required.

3

In reply to cgales:

I don’t think you’ve answered the question. Sometimes there are legacy reasons to not follow this advice. I also have the same question as Debashis. Can it be done?

Thanks,
Ed

4

In reply to enolan:

No.

5

In reply to dave_59:

One solution that I found can work is to remove the field macro registration from the base class, and relocate the field macro registration into the extended class for the base class elements.

6

In reply to enolan:

Thze recommendation is to avoid the field macros because it puts a big overhead on the simulation and might cause additional problems.
BTW, why do you want to have UVM_NOCOMPARE? UVM_ALL_ON creates automatically the do_compare function. It is there but you do not have to use the compare function where do_compare is called.

If you are using a UVM Framework Generator like UVMF from Mentor or the EasierUVM Code Generator from Doulos(Doulos) it creates all the seq_item methods automatically for you.

7

In reply to enolan:
(Not denying others’ recommendation. Yes, we should follow the recommendation for performance reasons. But just to answer the question:)
I was trying to achieve the same thing as per my scoreboard requirements. Was able to achieve it using the same approach using UVM_1.2 and UVM_IEEE_1800.2-2017.

UVM has separate bits for UVM_COMPARE and UVM_NOCOMPARE.


parameter uvm_field_flag_t UVM_COMPARE      = (1<<2);
parameter uvm_field_flag_t UVM_NOCOMPARE    = (1<<3);

The above method essentially sets both the bits (COMPARE & NOCOMPARE).
Not sure how it was handled in the previous implementation if both bits are set.

Can you try this? (- to explicitly deassert the COMPARE bit and set the NOCOMPARE BIT, while keeping others ON)


`uvm_field_init (tag, UVM_ALL_ON - UVM_COMPARE + UVM_NOCOMPARE)

This also worked for me.