[clang] [flang] [Flang][Driver] Introduce -fopenmp-targets offloading option (PR #100152)

[Sergio Afonso via cfe-commits]

================
@@ -492,6 +493,18 @@ void Flang::addOffloadOptions(Compilation &C, const InputInfoList &Inputs,
     if (Args.hasArg(options::OPT_nogpulib))
       CmdArgs.push_back("-nogpulib");
   }
+
+  // For all the host OpenMP offloading compile jobs we need to pass the targets
+  // information using -fopenmp-targets= option.
+  if (JA.isHostOffloading(Action::OFK_OpenMP)) {
+    SmallString<128> Targets("-fopenmp-targets=");
----------------
skatrak wrote:

> For now, I would grudgingly accept the code as-is if this was done for the rest of the file, but hope that we can avoid all this code duplication in the future.
> 
> Did you consider to just extract the lines from `Clang.cpp` into another function to some location this is accessible to both?

I agree that we should try to avoid duplicating code like this as much as possible. In this case, I just followed what's been done for other similar options and just copied it from clang.

After a quick look, I don't see an obvious place to add this shared code, but it looks like one way to get there would be to create a `Driver` or similar class deriving from `Tool` and make that the shared parent for the `Clang` and `Flang` classes, putting in it common option processing code used by both. Something like this would probably be best done on its own patch after some discussion, though. In any case, I think @banach-space is the expert on this area, so maybe he knows of any plans already in place to improve this situation or can give us some pointers on how to better deal with this in the short term.

https://github.com/llvm/llvm-project/pull/100152