[sv-cc] Mantis item 2226: Memory allocation schemes

John and all,

 

I can see some merit in the proposed vpiAllocScheme property.  It seems 

that we are using it to define the default allocation scheme for scopes 

and actual allocation scheme for objects.  Is that correct?

 

If so, some thoughts:

 

-- Would it be good to tie it in explicitly to the new proposed section 

"36.3.6 Lifetimes of objects"?  One could even define the new property 

here and cross reference it from the details, rather than cross 

referencing the various details to the fairly sketchy detail in the 

section on variables.

 

-- The proposed 36.9 detail 9 needs to be rewritten.  I don't think we 

really mean that vpiAllocScheme indicates how the instance itself is 

allocated in memory, do we?

 

-- I see that we've never put the vpiAutomatic property on tasks or 

functions in the first place, even though, with SystemVerilog, then can 

have an automatic or static default scope.  Should we add vpiAutomatic?

Should we add vpiAllocScheme?

 

-- Things get more ambiguous, of course, with a task or function 

(method) declared in a class.  Consider the following, for example:

 

module top;

 

  class C;

 

    static function automatic int f (int x);

      return -x;

    endfunction

 

  endclass

 

endmodule

 

Notice that the method 'f' has a static lifetime but an automatic 

default lifetime for its variables.  Should we use vpiAutomatic for the 

method's default variable lifetime, and reserve vpiAllocScheme for the 

function's own lifetime?

 

-- If an automatic variable is obtained from a function declaration 

(syntactically) it really has a lifetime that is independent of 

simulation, even though it has been declared with the keyword 

'automatic'.  But if we obtain the corresponding variable from a frame, 

then the vpiAllocScheme is unambiguously vpiAutomaticScheme.  What 

should the vpiAllocScheme be for the variable obtained from the 

syntactic context?

 

Regards,

Jim Vellenga

---------------------------------------------------------
James H. Vellenga                            978-262-6381
Software Architect                              (FAX) 978-262-6636
Cadence Design Systems, Inc.         vellenga@cadence.com
270 Billerica Rd
Chelmsford, MA 01824-4179
"We all work with partial information."
---------------------------------------------------------- 

 


________________________________

	From: owner-sv-cc@eda.org [mailto:owner-sv-cc@eda.org] On Behalf
Of Shields, John
	Sent: Wednesday, March 19, 2008 10:20 PM
	To: sv-cc@eda.org
	Subject: [sv-cc] updated mantis item 2226 with proposal
	
	

	Hi,

	 

	This is detailed proposal of the information model for dynamic
objects.  There are changes to clause 36 and 37 in 2 documents.

	 

	Regards, John Shields

	Mentor Graphics, Inc.


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