Subject: RE: [sv-bc] Erratum and PROPOSAL -- 3.9 -- 'complex data types' as parameters
From: Mark Hartoog (Mark.Hartoog@synopsys.com)
Date: Tue Nov 11 2003 - 20:24:41 PST
What is the reason for making this BNF change? I believe that the wording in
section 3.9 is a little unclear, but I see no reason to change the BNF.
For example:
module m #(parameter type T = logic [7:0) (input T i, output T o);
always @(i) o = i;
endmodule
module top();
bit [15:0] a, b;
m #(bit [15:0]) u1(a, b);
endmodule
I see nothing wrong with this syntax. Why should we force users to create
a typedef for this, and change this too:
typedef logic [7:0] logic8;
typedef bit [15:0] bit16;
module m #(parameter type T = logic8) (input T i, output T o);
always @(i) o = i;
endmodule
module top();
bit [15:0] a, b;
m #(bit16) u1(a, b);
endmodule
Does this really make it easier to code or understand the code?
I believe that the meaning of the sentence in section 3.9 is that there are
types that are too complex to express in either a cast or a type parameter
value, which is true. What is left out is that the restrictions on casts
and type parameter values are different. The cast type must be a simple
name. A type parameter value is less restrictive, but still cannot represent
an array type. For example, if I wanted to change the ports above to array
ports like this:
module m #(parameter type T = logic [7:0) (input T i, output T o);
always @(i) o = i;
endmodule
module top();
typedef bit [7:0] myarray[0:1];
myarray a, b;
m #(myarray) u1(a, b);
endmodule
Here you have to use a typedef, because an unpacked array type is "too complex"
for the data_type BNF rule.
I see no reason for making type parameter values as restrictive as cast types.
I would rather see the sentence in 3.9 changed to something like:
"User-defined type names must be used for complex data types in casting
(see Section 3.14, below), which only allows simple type names, and
as type parameters values when unpacked array types are used."
> -----Original Message-----
> From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org]On Behalf Of Brad
> Pierce
> Sent: Tuesday, November 11, 2003 7:02 PM
> To: sv-bc@eda.org
> Subject: [sv-bc] Erratum and PROPOSAL -- 3.9 -- 'complex data types' as
> parameters
>
>
> According to 3.9,
>
> "User-defined type names must be used for complex data types in casting
> (see Section 3.14, below), and as parameters."
>
> The BNF implements this sentence for casting, but not for parameters,
> because
> according to A.4.1.1, a parameter assignment can take any data_type, and
> according to A.2.4, so can a type_assignment.
>
> PROPOSAL
>
> In A.4.1.1 and Syntax 18-3 in ordered_parameter_assignment
> and in named_parameter_assignment, REPLACE
>
> data_type
>
> WITH
>
> simple_type
>
>
> In A.2.4 and Syntax 20-1, in type_assignment, REPLACE
>
> data_type
>
> WITH
> simple_type
>
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