[flang] [llvm] [flang]- Fix for IEEE_IS_NAN sets IEEE_INVALID after inspecting a sNaN (PR #205276)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

This is not a flang patch. This is also a valid optimization with not-strictfp, which is the case in this test 

https://github.com/llvm/llvm-project/pull/205276