[clang] [flang] [Flang] Add -ffast-real-mod and direct code for MOD on REAL types (PR #160660)

[Slava Zakharin via cfe-commits]

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@@ -2750,6 +2750,7 @@ def fno_unsafe_math_optimizations : Flag<["-"], "fno-unsafe-math-optimizations">
   Group<f_Group>;
 def fassociative_math : Flag<["-"], "fassociative-math">, Visibility<[ClangOption, FlangOption]>, Group<f_Group>;
 def fno_associative_math : Flag<["-"], "fno-associative-math">, Visibility<[ClangOption, FlangOption]>, Group<f_Group>;
+def ffast_real_mod : Flag<["-"], "ffast-real-mod">, Visibility<[FlangOption, FC1Option]>, Group<f_Group>;
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vzakhari wrote:

Can you please also add `-fno-fast-real-mod`?

https://github.com/llvm/llvm-project/pull/160660