RE: [sv-bc] DataTypes: BNF changes

From: Mark Hartoog (Mark.Hartoog@synopsys.com)
Date: Wed Nov 10 2004 - 14:43:33 PST

  • Next message: Steven Sharp: "RE: [sv-bc] DataTypes: BNF changes"

    > The datatypes groups voted to disallow <nettype> followed by 'reg' as a
    > lexical restriction.

    I cannot find this restriction anyplace in the proposed BNF, chapter 4 or 5
    changes to the LRM.

    Is it an oversight that this was left out?

    How exactly was this restriction formulated?

     

    > -----Original Message-----
    > From: Rich, Dave [mailto:Dave_Rich@mentorg.com]
    > Sent: Wednesday, November 10, 2004 2:32 PM
    > To: Mark Hartoog; Steven Sharp; btf-dtype@boyd.com; sv-bc@eda.org
    > Subject: RE: [sv-bc] DataTypes: BNF changes
    >
    >
    > Mark,
    >
    > The datatypes groups voted to disallow <nettype> followed by 'reg' as a
    > lexical restriction.
    >
    > This would still allow
    >
    > typedef reg T;
    >
    > tri T w;
    >
    >
    > But I was in favour of
    >
    > tri <T> w;
    >
    > for other reasons you mentioned.
    >
    > Dave
    >
    >
    >
    > -----Original Message-----
    > From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of Mark
    > Hartoog
    > Sent: Wednesday, November 10, 2004 2:21 PM
    > To: Steven Sharp; btf-dtype@boyd.com; sv-bc@eda.org
    > Subject: RE: [sv-bc] DataTypes: BNF changes
    >
    > There are some unfortunate corner cases in the syntax for data types
    > on wires.
    >
    > tri reg w1; // declares a net with tri resolution and reg data type.
    > trireg w2; // declares a net with trireg resolution and default (logic)
    > // data type.
    > trireg reg w3; // declares a net with trireg resolution and reg data
    > type.
    >
    > I'm not sure there is anything that can be done about this. I notice at
    > one time some of the emails were using a template like syntax:
    >
    > tri<reg> w1;
    > trireg w2;
    > trireg<reg> w3;
    >
    > which is syntactically clearer on this point, but I think has other
    > problems.
    > Declarations like:
    >
    > tri signed [7:0] w1;
    >
    > are legal v2k, but "signed [7:0]" is now the data type specifier with
    > default logic data type. We can not force <> here for backwards
    > compatibility, so it would be funny if
    >
    > tri <logic signed [7:0]> w1;
    >
    > putting in the default data type now required <>.
    >
    > Another alternative would be to outlaw 'reg' data type on wires
    > and only allow logic. I don't really like that either.
    >
    > Since wire types tri and trireg are not commonly used, I don't expect
    > this to be a very serious practical problem, and I guess I would rather
    > live with this problem then any of the solutions I can think of.
    >
    > Mark Hartoog
    > 700 E. Middlefield Road
    > Mountain View, CA 94043
    > 650 584-5404
    > markh@synopsys.com
    >
    >
    >
    >

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