Subject: RE: DirectC C-Layer: open arrays and abstract access
From: Joao Geada (joao@synopsys.com)
Date: Tue Dec 17 2002 - 14:30:26 PST
Francoise
the problem with the VPI approach is that VPI (as described in the standard)
is a very indiscriminate interface: once you have VPI enabled you can do
*anything, anywhere*. Sure, every vendor has come up with (mutually incompatible)
approaches to reign in these capabilities but these approaches:
a- require the user to unerringly specify the access they need for each and
every instance/signal across an entire design
or
b- rely on some "learning" mechanism for the simulator to attempt to identify
what signals the user/application will access/modify
One of the conveniences of DirectC is doing away with all those complex, fragile
and vendor-specific approaches. Instead, the user just puts in the appropriate
extern declaration and can then start using the function. No fuss, no complexity.
Both the compiler and the user know straightaway what is needed/available with
no room for error.
As soon as VPI comes into the picture all that nicety goes straight out, and I
do not believe anyone has made a compelling argument as to why we should discard
the user-friendly properties that a DirectC-specific interface provides.
Please note that I am not against judicious use of VPI (eg assertion API proposal
I sent yesterday is now a VPI extension). I am just concerned that each interface
preserves all its required properties.
Joao
==============================================================================
Joao Geada, PhD Principal Engineer Verif Tech Group
Synopsys, Inc TEL: (508) 263-8083
344 Simarano Drive, Suite 300, FAX: (508) 263-8069
Marlboro, MA 01752, USA
==============================================================================
-----Original Message-----
From: owner-sv-cc@eda.org [mailto:owner-sv-cc@eda.org]On Behalf Of
Francoise Martinolle
Sent: Tuesday, December 17, 2002 4:49 PM
To: Andrzej Litwiniuk; sv-cc@eda.org
Subject: Re: DirectC C-Layer: open arrays and abstract access
I would not want to create yet another abstract interface. We already have
VPI and PLI.
VPI access to multi-dimensional arrays is already defined in Verilog 1364
2001 and with
some modifications it can be enhanced to manage open arrays.
VPI provides a nice interface to iterate over the elements of an array and
to get
the value of each element. VPI should be the abstract access interface.
DirectC should be the interface to use for direct access.
Francoise
'
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