[llvm] [ADT] Speed up FoldingSet with linear probing and Algorithm R deletion (PR #218190)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

> > @MaskRay @kazutakahirata Maybe summarize all 3 approaches on discourse? I find it difficult to keep track of 3 competing PRs...
> 
> I'll do that. Thanks!

@kuhar Posted https://discourse.llvm.org/t/rfc-modernizing-llvms-foldingset-open-addressing-with-swiss-table-and-algorithm-r/91637.  Thanks!

https://github.com/llvm/llvm-project/pull/218190