RE: [vhdl-200x] Problems with 2008 VHDL packages.

Chuck,

If it is monolithic, then attempting to modularize it with a package usable only within that entity provides very marginal benefit!

-Steve Bailey

-----Original Message-----
From: owner-vhdl-200x@eda.org [mailto:owner-vhdl-200x@eda.org] On Behalf Of Swart, Chuck
Sent: Wednesday, April 20, 2011 7:45 PM
To: vhdl-200x@eda.org
Subject: [vhdl-200x] Problems with 2008 VHDL packages.

I have spoken with several of our Model Tech VHDL-2008 implementors
about generic packages and, especially, packages which
are declared as declarative items inside other declarations. We see
little use for this generality and we believe that the implementation
cost is not worth the marginal benefit.

Upon reflection, I can almost visualize one practical use case. Suppose
that a third party wants to supply commercial IP. He may have packages
which he would like to keep private. If his design is monolithic he
could put his package inside the entity and could therefore hide it.
However,
if his design consists of multiple entities, I don't see any reasonable
way to hide it by where it is declared (he can hide it by encrypting
it). And if
his design contains only one entity, then he might as well put the
package declarations directly in the entity.

Packages in "static" structures like entities, architectures, nested
within packages, etc. may or may not be useful, but packages declared in
subprograms, which are dynamically elaborated, are very expensive. In
general, they must be created every time a subprogram which declares it
is called and destroyed
every time that subprogram is exited. I can't think of a single use case
that can benefit from this generality.

We at Model Tech do intend to implement this feature (unless there is a
decision by the standards group to drop this generality) but it will be
a very low priority.

I would be very interested to hear of any use cases which benefit from
such packages.

Chuck Swart

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