PARALLEL_CASE specifies that the case statement
must be built as a parallel structure. No logic is created for the if-elsif structure. Because this attribute affects the
compiler and the design's logical behavior, it is only available as an RTL
attribute.
(* parallel_case *) case select
3'b100 : sig = val1;
3'b010 : sig = val2;
3'b001 : sig = val3;
endcase