RE: [sv-ec] Can a function contain a fork/join/any/none?

Dave, 

 

I think I understand the rationale here, especially about rooted threads.
One more question. Given that we do not want functions to interact with the
scheduler, we are in effect forbidding functions to trigger events as well,
correct? 

 

Just saying that we disallow time-consuming statements in functions leaves a
lot of room for misinterpretation, IMHO.

 

Regards,

-Ambar

 

  _____  

From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf Of Rich,
Dave
Sent: Thursday, February 16, 2006 9:12 AM
To: Ambar Sarkar; sv-ec@eda.org; sv-bc@eda.org
Subject: RE: [sv-ec] Can a function contain a fork/join/any/none?

 

"time consuming"  would mean anything that could block a thread(process).
But there are really two separate issues here. One is the fact that
functions are not supposed to interact with the scheduler. Events get
created outside the function as outputs are assigned, but the function does
no scheduling. We also don't have to worry about active region functions
versus inactive-region(program block) functions either.

 

But the other major issue is that time consuming threads roots can start
from more places than just always or initial blocks if you allow a function
to call a fork_join_none. They can start form continuous assignments or in
variable declarations. And those variable declarations could be in a
package, which in turn are not supposed to contain any rooted threads.

 

Dave

 

 

  _____  

From: Ambar Sarkar [mailto:ambar.sarkar@paradigm-works.com] 
Sent: Thursday, February 16, 2006 4:14 AM
To: Rich, Dave; sv-ec@eda.org; sv-bc@eda.org
Subject: RE: [sv-ec] Can a function contain a fork/join/any/none?

 

Dave,

 

Is there a definition of the term "time consuming"? A fork/join none(not the
others) is non time consuming as far as I understand. Or is it being seen as
the conceptual  equivalent of a task call and thus recommended against in
function calls?

 

Regards,

-Ambar

 

  _____  

From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf Of Rich,
Dave
Sent: Thursday, February 16, 2006 12:33 AM
To: sv-ec@eda.org; sv-bc@eda.org
Subject: [sv-ec] Can a function contain a fork/join/any/none?

 

A number of people have asked me the above question, and my immediate answer
has been no. However, it looks like a number of things that were ruled out
by the BNF in 1364 by having separate function_statement and statement
productions, have been let back in by the 1800 BNF.  Also, there are a
number of new constructs in SystemVerilog that may need restrictions for use
by a function. The fork/join_none was added to SystemVerilog, but since
there are restrictions on any time controlling statements, or task enables,
it doesn't seem to make much sense to allow it.

 

I'm not sure which committee should have this issue, but I think the sv-bc
should create some guarantees about what a function is and is not allowed to
do. The sv-ec may have to review which added constructs make or break those
guarantees.

 

This is mantis 1336.

 

Dave

 

 

David Rich
Verification Technologist
Design Verification & Test Division
Mentor Graphics Corporation
dave_rich@mentor.com
Office:   408 487-7206
Cell:     510 589-2625