Given an Expression, get the effective TimeScale

[fabianschuiki]

Hey! I'm walking the AST and when I encounter a TimeLiteral expression, I would like to determine what TimeScale is in effect for that expression. I see that TimeLiteral::fromSyntax gets this information from context.scope, but I'm not sure how I can determine which Scope an expression is in once the AST has been constructed. Any ideas?

[MikePopoloski]

You can only reach an expression via some scope, so you have to remember it during visitation such that it's available when you reach the expression you're interested in. Once you have the scope the getTimeScale method will give you what you need.

[fabianschuiki]

Would it make sense to have the TimeLiteral AST node also track the applicable time scale? It feels like a relevant piece of information, and the time scale is used to compute its value anyway in that initial AST walk, so we might just store a reference to it as well.

In CIRCT for example we only ever care about the time scale specifically when dealing with these time literals. We also never have to track any scopes explicitly, except for this one use case. If we could just ask the time literal for the time scale that was in effect, that would go away.

[MikePopoloski]

Yes, that seems fine to me and should be easy to do.

[MikePopoloski]

c548f2c

[fabianschuiki]

That's fantastic! Thanks 🥳