From: Surya Pratik
Saha [mailto:spsaha@cal.interrasystems.com]
Sent: Wednesday,
January 07, 2009
2:30 PM
To: Bresticker,
Shalom
Cc: sv-bc@eda.org
Subject: Re: [sv-bc]
Member select
or hierarchical name
Hi Shalom,
An identifier can't be used as forward reference like task enable or
function
call. So for the following example:
module top;
int x;
if (1) begin : b // generate block
initial x = 1; // pointing to 'int x' inside module
bit x;
end
endmodule
The reference 'x' inside initial block is 'int x;' inside module, not
'bit x'
inside generate block.
Now for my earlier example, 'bl' as struct is not yet declared when
'bl.x' is
referred, and it must hit generate block 'bl'. So I am not sure how you
derive
rule <1> will be applied here.
Regards
Surya
-------- Original Message --------
Subject: Re:[sv-bc] Member select or hierarchical name
From: Bresticker, Shalom <shalom.bresticker@intel.com>
To: Surya Pratik Saha <spsaha@cal.interrasystems.com>
Cc: "sv-bc@eda.org"
<sv-bc@eda.org>
Date: Wednesday, January 07, 2009 5:41:54 PM
I can see where
you get confused. As I
wrote, we still have a long way to go before the description is
complete,
precise, and clear.
In this case, "the first name in the sequence is resolved as
though it
were a simple identifier"
should point
you to 23.9, where it says,
"If
an identifier is
referenced directly (without a hierarchical path) within a task,
function,
named block, or generate block, it shall be declared either within the
task,
function, named block, or generate block locally or within a module,
interface,
program, checker, task, function, named block, or generate block that
is higher
in the same branch of the name tree that contains the task, function,
named
block, or generate block. If it is declared locally, then the local
item shall
be used; if not, the search shall continue upward until an item by that
name is
found or until a module, interface, program, or checker boundary is
encountered."
As a result bl
resolves to the variable declaration.
Then rule <1> applies.
From: Surya
Pratik Saha [mailto:spsaha@cal.interrasystems.com]
Sent: Wednesday,
January 07, 2009
2:04 PM
To: Bresticker,
Shalom
Cc: sv-bc@eda.org
Subject: Re:
[sv-bc] Member select
or hierarchical name
Hi Shalom,
Darft LRM mentioned:
When a dotted name is
encountered at its
point of appearance, the first name in the sequence is resolved as
though it were
a simple identifier.
And if we go by simple identifier searching rule, then
'b1' to be
selected as generate block, as the struct is not yet declared. So the
'bl.x'
has to be considered as 'hierarchical name' as per the rule <2>
mentioned
in the section. So your comment saying "bl.x is considered to be a
member
select of bl.x." is not correct. But my query is - after traversing the
whole design, is it required to double check the 'hierarchical name's
to
convert to 'member select'. In that way, LRM is silent.
Regards
Surya
-------- Original Message --------
Subject: Re:[sv-bc] Member select or hierarchical name
From: Bresticker, Shalom <shalom.bresticker@intel.com>
To: Surya Pratik Saha <spsaha@cal.interrasystems.com>, sv-bc@eda.org <sv-bc@eda.org>
Date: Wednesday, January 07, 2009 5:21:31 PM
Hi,
This is actually one of the simpler cases and is connected to sections 23.8 and 23.9 as well.
This whole subject is still far from being adequately described in the LRM, but we try to improve each time.
One of the basic rules is that you look for the first component of the name in the local scope. If you find it, then you go downward from there. If not, then you go upward and try again.
In this case, the first component of bl.x is bl. bl is not declared within the initial procedure, so you go up to the generate block. In this case, bl is declared inside the generate block, as the name of the struct. Then bl.x is considered to be a member select of bl.x.
A more complex case would be if struct bl did not contain a member x. Would it go up to the generate block called bl and the variable int x inside it or would it still consider bl to be a reference to the struct bl and then bl.x would be an error because it does not exist?
This was ambiguous in previous versions of the standard. This revision attempts to resolve that ambiguity. I believe that the rules defined in 23.7 in this draft will define that bl would resolve to the struct in any case and bl.x would be an error.
Regards,
Shalom
-----Original Message-----
From: owner-sv-bc@server.eda.org
[mailto:owner-sv-bc@server.eda.org] On Behalf Of Surya Pratik Saha
Sent: Wednesday, January 07, 2009 1:26 PM
To: sv-bc@eda.org
Subject: [sv-bc] Member select or hierarchical name
Hi,
I have just gone through the section 23.7 (Member selects and
hierarchical names). The section seems very interesting.
However, I am not sure if a hierarchical name will be
converted to member select or not when the whole scope is
traversed. For e.g.
module top;
generate
begin:bl
int x;
initial begin
bl.x = 1; // will it be converted to member
select of struct after the full scope is traversed
end
struct {int x;} bl;
end
endgenerate
endmodule
Please let me know.
Currently all standard simulators consider 'bl.x' as member select.
--
Regards
Surya
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