Re: [sv-ec] Re: Arguments to "randomize" method calls

Arturo Salz wrote:

 > Gord,
 >
 > My expectation as to the legality of your example is the same as yours:
 > It should be illegal. And, b.randomize(c) is legal. Hence, the name
 > binding is static and not at run-time.
 >
 > By "nasty" I assume you mean problems related to a separately compiled
 > unit that does not include the full class declaration. But, I assume the
 > same problems exist with the rand_mode and constraint_mode methods,
 > right?

rand_mode and constraint_mode are different in that they don't
require you to ignore normal lexical binding for actuals
in a call.

randomize is not an issue when you have inline constraints
since you can use that to disambiguate the nature of the call
("randomize" must mean the method when there are inline
constraints).

The nastiness is that you can't determine in a separately
compiled module whether a simple call to randomize is to the class
method randomize (requiring "pass by name") or to a non-class task
(requiring normal actual evaluation).

Example:

module D;
    int x;
    initial a.b.randomize(x);
endmodule

If D is a separately compiled module, what do you do?
You can't determine what to do with "x" in the call.

Context 1:
    module top;
       A a();
       D d();
    endmodule
    module A;
       begin : b;  // generate block
           task randomize(int arg);
           endtask
       end
    endmodule


Context 2:
     module top;
        A a();
        D d();
     endmodule
     module A;
        class B;
            rand int x;
        endclass
        B b = new;
     endmodule


I believe that both "Context 1" and "Context 2" are legal
contexts for instance d.  But the meaning of "x" in
the a.b.randomize(x) is vastly different and there is no
way to determine which one is required until elaboration.
In fact, to be more nasty, I could merge Context 1 and
Context 2 with some renaming and create two different
contexts in which a.b.randomize(x) would mean two
very different things in different instantiations of D.

Gord.


> 	Arturo
> 
> -----Original Message-----
> From: owner-sv-ec@eda.org [mailto:owner-sv-ec@eda.org] On Behalf Of
> Gordon Vreugdenhil
> Sent: Tuesday, March 07, 2006 7:49 AM
> To: Gordon Vreugdenhil
> Cc: SV_EC List
> Subject: [sv-ec] Re: Arguments to "randomize" method calls
> 
> 
> 
> Gordon Vreugdenhil wrote:
> 
> 
>>In 1800-2005, 13.10 we have:
>>   The scope of the arguments to the randomize method is the object
>>   class. Arguments are limited to the names of properties of the
>>   calling object; expressions are not allowed.
>>
>>I just want to clarify whether the name binding is static based on
>>the type of the reference or dynamic based on the actual object.
>>Specifically, is the following legal:
>>
>>   class A;
>>   endclass
>>   class B extends A;
>>     rand int c;
>>   endclass
>>   A a;
>>   B b;
>>   initial begin
>>      b = new;
>>      a = b;
>>      a.randomize(c);   // randomize member "c" - legal?
>>   end
>>
>>For a normal reference "a.c" is illegal but the text in 13.10
>>talks about both the "object class" and the "calling object".
>>At this point, I'm assuming that this example should be illegal.
>>
>>BTW, there are some very nasty separate compilation issues
>>involving randomize since the formals of the class method
> 
>                                  ^^^^^^^
> Should be "actuals" of course.
> 
> Gord
> 
> 
>>randomize are member names while in a hierarchical call
>>to a task randomize they would be normal actuals.
>>
>>Gord.
> 
> 

-- 
--------------------------------------------------------------------
Gordon Vreugdenhil                                503-685-0808
Model Technology (Mentor Graphics)                gordonv@model.com