[clang] [flang] [mlir] [flang] Add basic -mtune support (PR #95043)

[Alexis Perry-Holby via cfe-commits]

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@@ -1796,6 +1797,10 @@ void ModuleImport::processFunctionAttributes(llvm::Function *func,
       attr.isStringAttribute())
     funcOp.setTargetCpuAttr(StringAttr::get(context, attr.getValueAsString()));
 
+  if (llvm::Attribute attr = func->getFnAttribute("tune-cpu");
+      attr.isStringAttribute())
+    funcOp.setTuneCpuAttr(StringAttr::get(context, attr.getValueAsString()));
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AlexisPerry wrote:

Thank you so much for this suggestion and for the pointers for how to do this kind of test.  I was struggling to figure out the proper mechanism and you helped greatly.  I have added two separate tests for tune-cpu instead of combining with the target-cpu ones because I think it's cleaner, but I am happy to combine if you prefer. Just let me know.  Thanks again for your help! 

https://github.com/llvm/llvm-project/pull/95043