[flang] Add support for -mprefer-vector-width=<value> (#142073)

This patch adds support for the -mprefer-vector-width= command line
option. The parsing of this options is equivalent to Clang's and it is
implemented by setting the "prefer-vector-width" function attribute.

Co-authored-by: Cameron McInally <cmcinally@nvidia.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index ba25318..90a0029 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -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;
+    if (s == "none")
+      opts.PreferVectorWidth = "none";
+    else if (s.getAsInteger(10, width))
+      diags.Report(clang::diag::err_drv_invalid_value)
+          << a->getAsString(args) << a->getValue();
+    else
+      opts.PreferVectorWidth = s.str();
+  }
+
   // -fembed-offload-object option
   for (auto *a :
        args.filtered(clang::driver::options::OPT_fembed_offload_object_EQ))