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

[Shunsuke Watanabe via cfe-commits]

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@@ -9,6 +9,7 @@
 #ifndef FORTRAN_OPTIMIZER_CODEGEN_CODEGEN_H
 #define FORTRAN_OPTIMIZER_CODEGEN_CODEGEN_H
 
+#include "flang/Frontend/CodeGenOptions.h"
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s-watanabe314 wrote:

Thank you for the reviews!
> Not requesting to do that here, but I feel the CodeGenOptions should be defined in Codegen and used/set in Frontend rather than having Codegen depends on Frontend things I think.

Does this mean that `ComplexRangeKind` should be defined in `CodeGen.h` instead of `CodeGenOptions.h`, and that CodeGenOptions should reference it?

>I think the CodeGenOptions.h header is included because of the ComplexRangeKind enum. If that is moved to llvm/Frontend/Driver/CodeGenOptions.h, we don't have this issue. It may be worth doing it in this PR, but I am ok with moving it in a separate PR as well.

Yes, I'm including `CodeGenOptions.h` to use the `ComplexRangeKind` enum. I'll also try moving it to `llvm/Frontend/Driver/CodeGenOptions.h`,  but I think that would be a separate PR.

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