How should I do to link a port declaration using SV interface to the actual interface ?

[suzizecat]

Hi there !

In the context of my Language server, I started trying to handle scoped references.
While I found some methods to handle a 'normal' scoped reference such as an interface binding when the interface is declared within a module body, I'm struggling with the situation where the interface 'instance' is actually a module port such as the following tiny example:

module my_mod (
    my_itf.mport sif_foo
);

assign sif_foo.bar = 1'b0;

endmodule

My approach would be to handle the interface port in the same way as I would for a proper instance, that is:

• Generate a "LSPScope" named sif_foo (mind you, this is not exactly the same as a Scope in slang, but consider it a collection of symbols, references and other scopes)
• Process the body of my_itf as if it was an instance body, filling the LSPScope sif_foo with all the symbols / subscopes of my_itf
• Upon reaching the scoped assignment, looking for the sif_foo subscope, then for the bar symbol in this subscope.

However the slang::ast::InterfacePortSymbol is not a scope nor does it have a member that would link to slang::ast::InstanceSymbol defining my_itf. Moreover, this slang::ast::InstanceSymbol seems to not be consistent in the AST with regards to my module (if the module is alone, the symbol is under the root of the AST after the module, if an instance of this interface is defined before, it will be declared here).

What would be the consistent/reliable way to get the slang::ast::InstanceSymbol linked to the slang::ast::InterfacePortSymbol ?

Best regards !

[MikePopoloski]

You can get to the instance by looking at what the port connects to outside the module. If there's no connection then there's no instance, which is why SV makes it illegal to have top-level modules with interface ports.

[suzizecat]

Thanks for the answer.

It was not very straight forward, but I managed to implement it (by omitting the top-level interface situation).

For the sake of completeness here is how I proceeded:

While processing an instance declaration (InstanceSymbol):

1. Iterate through all its ports using node.getPortConnections().
2. If an interface connection object is valid (pconn->getIfaceConn().first != nullptr) preemptively create the instance scope (unrelated to slang)
3. Lookup from the parent scope pconn->getIfaceConn().first->name
4. If found, copy is in the instance scope with the name port_connection->port.name
5. Process the instance as normal.