Can someone help with a comparison between std:: unordered_set and llvm:: FoldingSet?

I need a data structure to store a large number of objects and retrieve them. Retrievals will be far more than stores.

I was planning to use std::unordered_set but I came across llvm:: FoldingSet.

I couldn't find much literature or articles on a comparison between the two or information about the benefits of the latter.

Can someone shed light on this?