RE: [sv-bc] Signed after typedef

He isn't trying to modify the signedness of T, or create a new type that is like T but with a different signedness.  He is trying to construct a packed array with elements of type T, and set the signedness of that new packed array type.

This is related to another deficiency in the language.  When you compose packed arrays of packed arrays, there is no way to independently control the signedness of each level.  The language only allows you to set the array to signed at one level.  You can declare an unsigned word that is an array of 4 signed bytes, or a signed word that is an array of unsigned bytes.  But there is no way to declare a signed word that is an array of signed bytes.

For the 2005 standard, Cadence proposed a syntax for declaring packed arrays that would allow separately specifying the signedness at each dimension. But nobody else seemed to understand what that meant, until after something had been standardized that was incompatible with it and it was too late.  It should still be possible to support it in a backward compatible way using typedefs for each level that needs to be signed, but it requires allowing the syntax Radoslaw is trying to use here, i.e.

typedef logic signed [7:0] mybyte;
typedef mybyte signed [3:0] myword; //signed word composed of signed bytes


From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of Rich, Dave
Sent: Wednesday, May 21, 2014 5:13 PM
To: Bresticker, Shalom; Radosław Nawrot; 'SV_BC List'
Subject: RE: [sv-bc] Signed after typedef

And type T is implicitly unsigned. There are no rules to explain how you could override the signedness of a type.

From: owner-sv-bc@eda.org [mailto:owner-sv-bc@eda.org] On Behalf Of Bresticker, Shalom
Sent: Wednesday, May 21, 2014 5:18 AM
To: Radosław Nawrot; 'SV_BC List'
Subject: RE: [sv-bc] Signed after typedef

I don't see that the BNF allows it.

type_identifier can be followed by packed_dimension, but I don't see that it can be followed by 'signing'.

Shalom

From: owner-sv-bc@eda.org<mailto:owner-sv-bc@eda.org> [mailto:owner-sv-bc@eda.org] On Behalf Of Rados?aw Nawrot
Sent: Wednesday, May 21, 2014 15:02
To: 'SV_BC List'
Subject: [sv-bc] Signed after typedef

Hi,
I have a code:

typedef reg T;
T signed [1:0] r;

Is it legal ?
I cannot find reason why nobody supports it

Regards,
Radek


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