Is value_set's size compile-time known?

[jaehyun1ee]

The spec mentions about the size argument to a value_set constructor:

Parser Value Sets support a size argument to provide hints to the compiler to reserve hardware resources to implement the value set.

Although the phrase "hints to the compiler" already implies that the size argument should be a local** compile-time known value, can we make it clearly written in the spec? (** edited)

[jafingerhut]

Does p4c currently support using a constructor parameter of a control as the size of a value_set? Or the size of a P4 table?

I hope that the answer is "yes". At least, I can imagine scenarios where that would be a nice-to-have choice available, as a P4 developer.

If yes, then I would recommend against specifying that these should be local compile-time known values.

[jaehyun1ee]

Ah, yes, thank you for the comment :) The P4 spec mentions about the size property of a table,

When present, its value must always be a compile-time known value that is an integer.

So I would instead propose: size argument to a value_set constructor should be a compile-time known value.

[jafingerhut]

Adding an explicit restriction that the size parameter of a value_set must be compile-time known seems reasonable to me. If it is not already explicitly stated that the value of a table's size property must be compile-time known, that also seems like a reasonable addition.

[jaehyun1ee]

Thank you for the comment! I made a related PR :)