[sv-bc] RE: Value propagation in Parameter with Type

Shalom,

Does parameter override happens following assignment evaluation rule?
As section 23.10 says if a parameter has range specification then it should be unsigned and an override value shall be converted to the type and range of parameter.
For any typed parameter I think size is implicitly defined.

Thanks
Kausik


23.10 Overriding module parameters
A value parameter (see 6.20.2) can have a type specification and a range specification. The effect of
parameter overrides on a value parameter's type and range shall be in accordance with the following rules:
- A value parameter declaration with no type or range specification shall default to the type and range
of the final override value assigned to the parameter.
- A value parameter with a range specification, but with no type specification, shall have the range of
the parameter declaration and shall be unsigned. An override value shall be converted to the type
and range of the parameter.
- A value parameter with a type specification, but with no range specification, shall be of the type
specified. An override value shall be converted to the type of the parameter. A signed parameter
shall default to the range of the final override value assigned to the parameter.
- A value parameter with a signed type specification and with a range specification shall be signed
and shall have the range of its declaration. An override value shall be converted to the type and
range of the parameter.



From: Bresticker, Shalom [mailto:shalom.bresticker@intel.com]
Sent: Wednesday, March 19, 2014 8:23 PM
To: Datta, Kausik; sv-bc@eda.org
Subject: RE: Value propagation in Parameter with Type

11.8.3 says,

11.8.3 Steps for evaluating an assignment
The following are the steps for evaluating an assignment:
- Determine the size of the right-hand side by the standard assignment size determination rules (see 11.6).
- If needed, extend the size of the right-hand side, performing sign extension if, and only if, the type of the right-hand side is signed.

So you get

parameter UTR p2 = 2'sb11 ;

In this case, the RHS is signed.
According to 11.8.3, when size-extending the RHS, it does not matter whether or not the LHS is signed or unsigned. If the RHS is signed, as in this case, sign-extension is performed.
So you should get 8'b11111111.

Regards,
Shalom

From: owner-sv-bc@eda.org<mailto:owner-sv-bc@eda.org> [mailto:owner-sv-bc@eda.org] On Behalf Of Datta, Kausik
Sent: Wednesday, March 19, 2014 16:46
To: sv-bc@eda.org<mailto:sv-bc@eda.org>
Subject: [sv-bc] Value propagation in Parameter with Type

Hi,
For the following testcase what should be the value of p2?

Will it be 8'b00000011 or 8'b11111111?

Thanks
Kausik


module bot #(parameter type p1 = logic, parameter p1 p2 = 7)
                  (input in1, output integer out1);
assign out1 = p2;

endmodule

module top(input  in1, output integer out1);

typedef union packed {
        byte      a;
        bit [7:0] b;
}UTR;

bot #(UTR, 2'sb11) inst(in1, out1);

endmodule



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