RE: [sv-bc] Aggregate / struct - 2 questions

Brad, Matt & Nikhil -

Question for the three of you below.

Other comments included.

At 08:44 AM 2/27/2006, Jonathan Bromley wrote:
> > Is there some way to unpack the struct (almost like aggregate
> > de-assignment) so that the display command could be written
> > something like:
> >
> > $display("dst=%h src=%h data=%h crc=%h", pkt1);
>
>I personally don't think this is a very good idea.
>
>If the struct were packed, as is likely for synthesis, then
>you couldn't reasonably do this (because the packed struct
>also has a perfectly good integer value when taken as a whole).
>This could lead to all sorts of hideous ambiguity; how about
>this... (p2 is of the same type as pkt1):
>
>$display(
>    "pkt1=%h, p2.dst=%h p2.src=%h p2.data=%h p2.crc=%h",
>        pkt1, p2);
>
>How could $display work out which %h is associated with what?

I was hoping there was some undiscovered piece of magic, perhaps 
using one of the streaming operators, that would take each field of 
the struct and parse them out in struct-order to the respective %h 
format specifiers. I did not really think it existed but sometimes I 
ask these questions and people share very clever and concise 
solutions. Oh well, no big deal!

>For simulation only, you could use a class instead, and then
>the class could provide its own to-string method - psdisplay()
>in VMM-speak.  And indeed, since we now have a full-fledged
>string data type, it's easy to provide a to-string function
>for any data type.
>
>I sometimes wonder whether there is any utility at all in
>unpacked structs.  They make little sense for synthesis, and
>for simulation it's surely better to use a class; the class can
>then have a pack method that converts the appropriate parts of
>its content into a packed struct suitable for injection into
>an RTL model.

Interesting questions. Perhaps we could get the following three 
committee members to respond:

Matt Maidment from Intel, who has been using SV for synthesis for 3-4 
years now.
Brad Pierce (and Karen if she has time) on Synopsys' take on unpacked 
structs for synthesis.
Nikhil Rishiyur from the Bluespec synthesis perspective.

Regards - Cliff

>--
>Jonathan Bromley, Consultant
>
>DOULOS - Developing Design Know-how
>VHDL * Verilog * SystemC * e * Perl * Tcl/Tk * Project Services
>
>Doulos Ltd. Church Hatch, 22 Market Place, Ringwood, Hampshire, BH24 1AW, UK
>Tel: +44 (0)1425 471223                   Email: jonathan.bromley@doulos.com
>Fax: +44 (0)1425 471573                           Web: http://www.doulos.com
>
>This e-mail and any  attachments are  confidential and Doulos Ltd. reserves
>all rights of privilege in  respect thereof. It is intended for the use of
>the addressee only. If you are not the intended recipient please delete it
>from  your  system, any  use, disclosure, or copying  of this  document is
>unauthorised. The contents of this message may contain personal views which
>are not the views of Doulos Ltd., unless specifically stated.

----------------------------------------------------
Cliff Cummings - Sunburst Design, Inc.
14314 SW Allen Blvd., PMB 501, Beaverton, OR 97005
Phone: 503-641-8446 / FAX: 503-641-8486
cliffc@sunburst-design.com / www.sunburst-design.com
Expert Verilog, SystemVerilog, Synthesis and Verification Training