[llvm] [Analysis] Adding convert_from_arbitrary_fp support in computeKnownFPClass. (PR #208585)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm approved this pull request.

I'm not sure how you produced your "hack dump" but I think this code should handle it correctly 

https://github.com/llvm/llvm-project/pull/208585