[PATCH] D21462: [PM] Make the the new pass manageg support fully generic extra arguments to run methods, both for transform passes and analysis passes.

[Sean Silva via llvm-commits]

silvas added a comment.

In https://reviews.llvm.org/D21462#505454, @chandlerc wrote:

> > I hear your argument (IIRC we discussed this at a social) about back pointers being somewhat annoying, but the ability to use just a `void*` to represent the information passed to an analysis makes it much easier to have a unified analysis manager.
>
>
> I don't think I understand the connection you see between up pointers and using a 'void*' to represent the information passed to an analysis. Can you re-explain this? Sorry if it just isn't clicking for me....
>
> That said, in general I would like to not sacrifice type safety because of concerns around mapping arguments from one interface to another though.


The issue is that for a unified analysis manager, AnalysisPassConcept is not templated (on IRUnitT and couldn't be on the ExtraArgTs). Therefore, we need to pass a type-erased object through its `run` method. Currently, the type-erased IRUnit can be passed as a void*, and then the AnalysisPassModel (which *is* templated on IRUnitT) just casts it back since it knows the right type.
At least with the current registration stuff, all we need right now for type-safety is tracking which IRUnit it is (and there are 4 discrete values which is easy to track).

Or to put it another way, the ideas you are running with in this patch is very intimately tied to having the analysis manager templated on the signature of the associated `run` method for analyses it manages. A unified analysis manager (which seems like it was the agreed upon design for solving dependency tracking) must type-erase the information you have baked into the template arguments of AnalysisPassConcept here.
At least with the way that the registration stuff works now, you would need to find a way to type-erase the exact signature of the `run` method in order to get type-safety.


https://reviews.llvm.org/D21462