[clang] [flang] [mlir] [flang] Add support for -mprefer-vector-width=<value> (PR #141380)

[Tarun Prabhu via cfe-commits]

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@@ -309,6 +309,20 @@ static void parseCodeGenArgs(Fortran::frontend::CodeGenOptions &opts,
   for (auto *a : args.filtered(clang::driver::options::OPT_fpass_plugin_EQ))
     opts.LLVMPassPlugins.push_back(a->getValue());
 
+  // -mprefer_vector_width option
+  if (const llvm::opt::Arg *a = args.getLastArg(
+          clang::driver::options::OPT_mprefer_vector_width_EQ)) {
+    llvm::StringRef s = a->getValue();
+    unsigned Width;
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tarunprabhu wrote:

Flang's coding conventions are a bit different from clang. Variables names should start with a lowercase letter

```suggestion
    unsigned width;
```

https://github.com/llvm/llvm-project/pull/141380