RE: [sv-ac] Checker instantiation in always procedures

Hi Ben,

I think, your second question has been answered by Shalom. As for the first one, it depends on the vendor. From a contradictory statement it is possible to infer everything:). Usually an explicit example is a better argument than an abstract statement.

Regards,
Dmitry

From: ben cohen [mailto:hdlcohen@gmail.com]
Sent: Tuesday, July 14, 2009 6:32 PM
To: Korchemny, Dmitry
Cc: sv-ac@server.eda.org
Subject: Re: [sv-ac] Checker instantiation in always procedures

 Dmitry,
Agree that it should be revisited in the future.  The question I have though right now is:
What should a tool vendor implement?  He could implement what is in 17.3.2
"However, a checker shall be evaluated statically or procedurally depending on its placement in the parent checker".
Specifically, as shown in (a modification to what is in 17.3.2)
checker c3(event clk, logic a);  p3: assert property (@clk a); endchecker
checker c2(event clk, logic a);
  c3 c3_stat(clk, a);
  always @(clk) begin
    c3 c3_proc(clk, a); // LEGAL if c2 is instantiated as below
  end
endchecker

module m2(logic clk, logic [3:0] d);
  always @(posedge clk) begin
  c2 check_d1(posedge clk, d[1]);  // OK here ?
  end
endmodule : m2

On a separate issue, in current LRM, 17.3.2 shows the following.  Where is "in1"  declared?  Don't we mean "posedge clk" instead?
module m2(logic clk, logic [3:0] d);
  always @(posedge clk) begin
    for (int i = 0; i < 4; i++) begin
      c2 check_loop(in1, d [const'(i)]);
   end
  end
endmodule : m2
Ben Cohen

On Tue, Jul 14, 2009 at 7:45 AM, Korchemny, Dmitry <dmitry.korchemny@intel.com<mailto:dmitry.korchemny@intel.com>> wrote:

Hi all,



In 17.5 Checker procedures it is written:



An always procedure in a checker body may contain deferred and concurrent assertions, nonblocking variable

assignments (see 17.7.1) and a procedural timing control statement using an event control. All other

statements shall not appear inside an always procedure.



From here I understand that a checker cannot be instantiated in an always procedure of another checker.



Nevertheless, 17.3.2 Nested checker instantiations explicitly discusses what happens if one checker is instantiated in another checker.



It looks to be a contradiction that should be fixed (in the future).



What do you think?



Thanks,

Dmitry

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