[sv-cc] [Fwd: FW: FW: [sv-bc] Open array mixed with normal array]

Hi All,

Would anyone like to comment on this response?

   -Chas

-------- Original Message --------
Subject: FW: FW: [sv-bc] Open array mixed with normal array
Date: Wed, 4 Jan 2006 15:09:41 -0800
From: "Ghassan Khoory" <Ghassan.Khoory@synopsys.com>
To: "Charlie Dawson" <chas>


Hi Chas:

This is a response to the question that was raised through Brad.
Please, review and check if you are in agreement before sending to the
user that originally inquired.

Thanks,
/gjk
-----Original Message-----
From: Andrzej Litwiniuk

On Wed, 21 Dec 2005, Ghassan Khoory wrote:
 > Can you comment on this to Chas and myself based on SV LRM.

The subject "Open array mixed with normal array" and the question
"whether open array can be mixed up with normal array or not" need
clarification as it is a possible misunderstanding. An open array is not
a new data type, it is merely an incomplete declaration of a regular
array with missing sizes of some of dimensions, or, in other words, a
generic
declaration.
Here is the excerpt from SV LRM (draft 4):

28.4.6.1 Open arrays

"The size of the packed dimension, the unpacked dimension, or both
  dimensions can remain unspecified; such cases are referred to as open
  arrays (or unsized arrays). [...] A formal argument is an open array
when
  a range of one or more of its dimensions is unspecified (denoted by
using
  square brackets ( [] )). This is solely a relaxation of the
  argument-matching rules. An actual argument shall match the formal one
  regardless of the range(s) for its corresponding dimension(s)"

The key part is "a range of one or more of its dimensions is
unspecified".
Therefore both examples seem correct.

Unfortunately the same notation, '[]', is used also for dynamic arrays,
what may make an impression that '[]' inside a declaration of DPI
function
denotes another type of array, or even worse, that a formal argument is
a
dynamic array.

The following examples may illustrate this (based on the original ones):

module top;
typedef bit array_int[1:0][2:0];

import "DPI" function void foo(array_int yi[][]);

array_int b1[3][5];
array_int b2[4][2];
initial begin
	foo(b1);
	foo(b2);
	end
endmodule


module top;

import "DPI" function void foo(input logic yi[1:0][]);
logic b1[1:0][5];
logic b2[3:2][7];
initial begin
	foo(b1);
	foo(b2);
	end
endmodule


Regards,
Andrzej




 > -----Original Message-----
 > From: Brad Pierce
 > Sent: Wednesday, December 21, 2005 11:41 AM
 > To: Ghassan Khoory; chas@cadence.com
 > Subject: FW: [sv-bc] Open array mixed with normal array
 >
 >
 >
 > -----Original Message-----
 > From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of
 > Surya Pratik Saha
 > Sent: Wednesday, December 21, 2005 3:30 AM
 > To: sv-bc@eda.org
 > Cc: Trainee19 (Moumita Das)
 > Subject: [sv-bc] Open array mixed with normal array
 >
 > SV supports open array for DPI construct. It is not clear whether open
 > array
 > can be mixed up with normal array or not. Please can you someone
clarify
 > whether
 > the following two examples are correct or not.
 >
 > e.g. 1
 > module top;
 > typedef bit  array_int[1:0][2:0];
 >
 > import "DPI" function  int XYZ_1(array_int yi[][], bit[5:0] b);
 >
 > endmodule
 >
 > e.g. 2
 > module top;
 >
 > import "DPI" function  int XYZ_1(input logic yi[1:0][]);
 >
 > endmodule
 >
 > Regards
 > Surya.
 >
 >



-- 
Charles Dawson
Senior Engineering Manager
NC-Verilog Team
Cadence Design Systems, Inc.
270 Billerica Road
Chelmsford, MA  01824
(978) 262 - 6273
chas@cadence.com