[clang] [CLANG] Add warning when INF or NAN are used in a binary operation or as function argument in fast math mode. (PR #76873)

[Zahira Ammarguellat via cfe-commits]

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@@ -6771,6 +6771,11 @@ def warn_pointer_sub_null_ptr : Warning<
 def warn_floatingpoint_eq : Warning<
   "comparing floating point with == or != is unsafe">,
   InGroup<DiagGroup<"float-equal">>, DefaultIgnore;
+def warn_fast_floatingpoint_eq : Warning<
+  "use of %select{infinity|NaN}0 will always be 'false' because "
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zahiraam wrote:

Yea! not happy with this either. 
May be saying something like this to warn the user the existence of inf/nan use: "use of inf/nan when the program will not be producing inf/nan according to the currently enabled floating-point options"?

https://github.com/llvm/llvm-project/pull/76873