[sv-ac] Email ballot result (September 26)

Below are the results of the email ballot:

3564

Ashok Bhatt

Yes Eduard Cerny

Yes Ben Cohen

Dana Fisman

Tapan Kapoor

No Jacob Katz

Yes Scott Little

Yes Manisha Kulshrestha

Yes Anupam Prabhakar

No Erik Seligman

Yes Samik Sengupta

Yes Tom Thatcher

The issue failed: 7y/2n/0a.

Comments

Erik:

I assume we're really voting on 3564, not 2093?

I vote NO on 3564. Reasoning: The current proposal explicitly states that expressions in concurrent assertions do not wake up the always_comb, but I don't believe this is a correct solution. As an RTL author, I would want the always_comb to wake up at some point soon after any changes to the sampled expression, as well as any time a const' expression changes.

Since we agreed that more time is needed for a clean definition of behavior under concurrent assertions, we should just talk about immediate assertions in this proposal, and leave the concurrent case undefined (which we will fix in the next PAR). So I would rewrite the proposal as:

Expressions used in immediate assertions (see 16.3), within the block or within any function called within the block, also contribute to the implicit sensitivity list of an always_comb. In the example below, the always_comb shall trigger whenever b,c or e change.

always_comb
begin
    a = b & c;
    assert (a != e);
end

Jacob:
I suggest to remove the following statement, until the general issue of starting evaluation attempts of concurrent assertions in procedural code is clarified:
Expressions used in concurrent assertions (see 16.5) do not contribute to the implicit sensitivity list of an always_comb

Ed:
I vote yes because I agree with the statement about procedural concurrent assertions. However, I think that for immediate asserts (and deferred) it should state that variables appearing in the action blocks do not contribute to the sensitivity list.

Manisha:
It should be made clear that only the expression in the condition of immediate assertions contribute to sensitivity list.

Samik:
Friendly amendments:
1. Only the condition checked in the immediate assertion should be added to the sensitivity list, i.e., nothing from action block should wake up the always_comb.
2. I think we should be more specific and say "Expressions used in immediate, final, and deferred assertions" - not only immediate.

I agree to Ed, Anupam, and Manisha that no expression from concurrent assertion, including the clock, should go into the sensitivity list.
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