[sv-ec] RE: Updated version of 2506 (covergroup filtering)

Hi Scott,

The major change in this version seems to be the following item:
-Added a restriction that the cross types are only accessible from within the cross scope.

Please consider the following points in this regard.

- Firstly, in this approach, user will have to define the functions within cross declaration.
  Now if suppose, the function needs to be modified, it has to be done by modifying the cross declaration.
  Typically, if the coverage model is part of an IP, user will be reluctant to change the IP.
  What alternative do we suggest to user in such scenarios? Basically, your actual goal is to
  provide user flexibility and this approach will probably put some kind of restriction.
  I understand that if you declare it within cross scope, you can use covergroup argument etc
  in the function, but think about a user who doesn't want to use arguments and just rewrites
  a function to create a new coverage space.

- Secondly, as I mentioned in one of my earlier mails, by opting for such syntax, we are allowing
  function calls within cross scope. This is something which is radical in the sense that so far
  we were allowing only bins/options. Now you bring function definition also and make this more
  like a class. That way we should possibly try to make covergroup look like a class and not the
  cross. So, have we thought about shifting the definition of function to covergroup level?
  In fact, why can't we move even the cross typedefs also to covergroup level? I understand that
  it will require naming the cross types differently instead of just naming them as CrossValType etc.
  for all crosses. In fact, we can append the cross names with the typedefinitions.
  Anyway, for both the cases (function within covergroup, cross), the BNF will require changes
  to show function call being allowed in appropriate scope. If we stick to your earlier proposal i.e.
  function declaration outside covergroup, we don't need any BNF change though.

I believe we were planning to explore the function scope with users. Did you receive specific f/b regarding such use model which
made you switch to this one? Please let me know if I am missing something here.

Regds,
Swapnajit

-----Original Message-----
From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf Of Little Scott-B11206
Sent: Wednesday, April 20, 2011 7:16 AM
To: sv-ec@eda.org
Cc: Fais Yaniv-RM96496; Michael Burns; Mehdi Mohtashemi
Subject: [sv-ec] Updated version of 2506 (covergroup filtering)

Hi all:

I have uploaded a revised version of the proposal for mantis 2506. The major changes are described below. I don't want to be too presumptive, but if it is okay with Mehdi I would like to suggest that we discuss this proposal first in the SV-EC meeting on 04-25. I hope that will give interested parties enough time to review the proposal and arrange their schedules to attend the meeting. Mehdi, are you okay with that?

Thanks,
Scott

mantis link: http://www.eda.org/svdb/view.php?id=2506
.docx link: http://www.eda.org/svdb/file_download.php?file_id=4928&type=bug

Major changes for v3
-Removal of <> syntax to enclose set_expression to syntax 9-2 and removed from affected examples.
-Added restriction that identifiers in the with expressions, set expressions, and cross functions are limited to constant expressions, instance constants (for classes only), or non-ref arguments to the covergroup. This is consistent with previous restrictions to variables in the open_range_list.
QUESTION: I don't like repeating the restriction several times. I wouldn't mind referencing the restriction, but it seems silly to create a subsection for a sentence just because it is used often. Does someone else have an idea to enable me to write the restriction once and use it many times?
-Added a restriction in Section 19.5.1.1 that disallows non-pure user-defined systfs -Specified with_expression application prior to bin distribution as the default behavior -Added distribute_first covergroup option to cause bin distribution to happen prior to with_expression application -Removed text describing how to access the cross types from outside the cross scope.
-Added a restriction that the cross types are only accessible from within the cross scope.

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