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

 How about creating a new format which would return the aggregate constant
value
for the struct by displaying the struct aggregate value 
using the positional aggregate form and default formats for each member
type.
Ex:

 typedef struct {
    bit  [3:0] dst_addr;
    bit  [3:0] src_addr;
    bit [31:0] data;
    bit  [7:0] crc;
 } pkt_s;

$display("pkt1 = %a", pkt1)

pkt1 = '{4'b0, 4'b0, 32'b0, 8'b0}

We could be defining a default format for datatype, unless there is already
an
existing mapping.

Francoise
    ' 
-----Original Message-----
From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of Clifford
E. Cummings
Sent: Monday, February 27, 2006 12:55 PM
To: sv-bc@eda.org
Cc: nikhil@bluespec.com; Brad Pierce; matthew.r.maidment@intel.com
Subject: 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

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>Jonathan Bromley, Consultant
>
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Cliff Cummings - Sunburst Design, Inc.
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