[clang] [flang] [flang] Add -fcomplex-arithmetic= option and select complex division algorithm (PR #146641)

[Tarun Prabhu via cfe-commits]

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@@ -3409,3 +3409,30 @@ StringRef tools::parseMRecipOption(clang::DiagnosticsEngine &Diags,
 
   return Out;
 }
+
+std::string tools::ComplexRangeKindToStr(LangOptions::ComplexRangeKind Range) {
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tarunprabhu wrote:

The functions in `CommonArgs.cpp` use a lower-case letter as the first letter in the function name, unlike clang which often uses upper case. 

```suggestion
std::string tools::complexRangeKindToStr(LangOptions::ComplexRangeKind Range) {
```

https://github.com/llvm/llvm-project/pull/146641