RE: [sv-ec] New Mantis item on Coverage: bins rhs non-constant expressions

Doug,

> class myclass;
>      int id;
>      int ign_id;
>      covergroup cg;
>          coverpoint id {
>              ignore_bins ign = {ign_id};
>          }
>      endgroup
> endclass
>
> The need for requiring constant expressions isn't clear. It would be
> possible to accept non-constant expressions, and take a "snapshot" of
> the expression value at covergroup construction time.

I suggest it would be preferable, and easier to understand, if this were
expressed as an input argument to the covergroup:

  class myclass;
    int id;
    int ign_id;
    covergroup cg(input int IGN_ID);
      coverpoint id {
        ignore_bins ign = {IGN_ID};
      }
    endgroup
    initial begin
      // set up a value on ign_id, and then...
      cg = new(ign_id);
    end
  endclass

And I certainly don't see why an input argument to a 
covergroup shouldn't be treated as if it were a constant.

Without using the input argument, I think it would be very
hard for users to remember that this expression (unlike most others
in the context of a covergroup) is sampled at construction time.
Input arguments, though, are already clearly understood to be
a way to provide "lifetime constant" values that configure a
covergroup instance's behaviour.
-- 
Jonathan Bromley, Consultant

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