Re: [sv-ac] 1678

Hi Bassam,

before we get into that discussion, note that with the current semantics
you can instantiate two instances of the same sequence in the same scope.
For example

sequence r2;

logic [7:0] lv1;

(b, lv1 = c) ##1
r1(lv1) ##1 r1(lv1)
##1 (lv1 == d);
endsequence


Thus you cannot use the sequence declared name as an identifier.

r1.lv1 is ambiguous in this example.


Doron


Bassam Tabbara wrote:

>Hi Doron,
>
>May be use r1_lv1 instead of unique below ... (r1.lv1 might be
>misleading scope/namespace creation issues) to be r1's lv1:
>
>sequence r2;
>
>logic [7:0] lv1;
>logic [7:0] unique_lv1;
>
>(b, lv1 = c) ##1
>(a, r1_lv1 = 0) ##1 (!a, r1_lv1 = r1_lv1 +lv1)[*0:$] ##1 a ##0 (1, lv1 =
>r1_lv1)
>##1 (lv1 == d);
>endsequence
>
>The adjacent idea (I mentioned on call yesterday) is to *add* (we still
>need to explain above for backward compatibility) visibility notions,
>instead of just explaining how substitution/passing should work, similar
>to classes with a "local"/"public" (default) access to r1's lv1, or
>simply just add scoping (drop the local bit :)) so you can say to begin
>with:
>
>sequence r2;
>//logic [7:0] lv1; // no need ...
>
>(b) ##1
>r1 (c) // "c" just an input not inout 
>##1 (r1.lv1 == d);
>endsequence
>
>This would have same "substitution" semantics but clearer, avoids
>shadowing issues, cleaner, easier to write ... BTW, I am not too keen on
>adding things, we have to clarify/interpret current LRM anyway, so food
>for thought in case we encounter more severe issues in this area.
>
>Thx.
>-Bassam.
>
>-----Original Message-----
>From: owner-sv-ac@eda.org [mailto:owner-sv-ac@eda.org] On Behalf Of
>Doron Bustan
>Sent: Wednesday, November 15, 2006 8:55 AM
>To: sv-ac@eda.org
>Subject: [sv-ac] 1678
>
>I open a new bug - 1678 for local variables name clashes:
>
>-------------------------------------------------------------
>
>A naive interpretation of substitution may lead to local variables name
>clashing.
>
>Here is an example of name clashing.
>
>sequence r1(lv);
>logic [7:0] lv1;
>
>(a, lv1 = 0) ##1 (!a, lv1 = lv1 +lv)[*0:$] ##1 a ##0 (1, lv = lv1); 
>endsequence
>
>
>
>sequence r2;
>
>logic [7:0] lv1;
>
>(b, lv1 = c) ##1
>r1(lv1) 
>##1 (lv1 == d);
>endsequence
>
>
>
>A naive substitution will result in the following:
>
>sequence r2;
>
>logic [7:0] lv1;
>logic [7:0] lv1;
>
>(b, lv1 = c) ##1
>(a, lv1 = 0) ##1 (!a, lv1 = lv1 +lv1)[*0:$] ##1 a ##0 (1, lv1 = lv1)
>##1 (lv1 == d);
>endsequence
>
>
>what we really want is to rename lv1 in r1 to a unique name before the
>substitution occurs. Then we get
>
>sequence r2;
>
>logic [7:0] lv1;
>logic [7:0] unique_lv1;
>
>(b, lv1 = c) ##1
>(a, unique_lv1 = 0) ##1 (!a, unique_lv1 = unique_lv1 +lv1)[*0:$] ##1 a
>##0 (1, lv1 = unique_lv1)
>##1 (lv1 == d);
>endsequence
>
>
>  
>