[flang] [llvm] [mlir] [Flang] [OpenMP] atomic compare (PR #184761)

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SunilKuravinakop wrote:

> That's an interesting solution. I think if we are going to handle special cases directly then the other case is that `NaN == NaN` evaluates to false.

I have added a check for NaN == NaN. @tblah can you please review?

https://github.com/llvm/llvm-project/pull/184761