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• Parse-property

Vl-parse-property-list-of-arguments

Heuristically match a property_list_of_arguments.

Signature

(vl-parse-property-list-of-arguments &key (tokstream 'tokstream) 
                                     (config 'config)) 
 
  → 
(mv errmsg? value new-tokstream)

Arguments

config — Guard (vl-loadconfig-p config).

Our goal is to match property_list_of_arguments, defined in the SystemVerilog-2012 grammar as follows:

property_list_of_arguments ::=

    [property_actual_arg] { ',' [property_actual_arg] }
                          { ',' '.' identifier '(' [property_actual_arg] ')' }

  | '.' identifier ( [property_actual_arg] )
       { ',' '.' identifier ( [property_actual_arg] ) }

Here is a slightly revised, equivalent grammar:

named_property_list_of_arguments ::=
               '.' identifier ( [property_actual_arg] )
         { ',' '.' identifier ( [property_actual_arg] ) }

property_list_of_arguments ::=
    [property_actual_arg] { ',' [property_actual_arg] } [named_property_list_of_arguments]
  | named_property_list_of_arguments

Note that we can match named_property_list_of_arguments with vl-parse-1+-named-property-list-of-arguments and we know that such a thing always starts with a dot. Note also that by inspecting the grammar, we can see that property_list_of_arguments always occurs within parens, so we know that we should end on a right paren.

Distressingly this rule is quite ambiguous. We describe some of the basic property_actual_arg ambiguities in vl-parse-property-actual-arg. But beyond that, here we have property_actual_args being separated by commas, which is even more ambiguous because an event_expression can itself be a comma-delimited list of expressions!

So how can we handle this. One option would be to try to aggressively use backtracking to find a match. But even then we have to make rather arbitrary distinctions for expressions like a or b---is it an event expression or is it a property expression?

So I think something I like better is to be a little more restrictive. Suppose that instead of the full event_expression grammar, we only support edge expressions that have an explicit posedge or negedge, and otherwise we require a property expression. This will still allow us to match most of the grammar and will probably lead to mostly correct interpretations.

Coming up with a proper solution to this would probably require a lot of experimentation. This language is so awful...

Subtopics

Vl-parse-event-expression-fragment

Special subset of event_expression for use only in sequence_list_of_actuals.