[llvm] [TableGen] Allow emitter callbacks to use `const RecordKeeper &` (PR #104716)

[Pierre van Houtryve via llvm-commits]

" + sys::path::filename(Record.getInputFilename()),"
In-Reply-To: <llvm.org/llvm/llvm-project/pull/104716 at github.com>


================
@@ -12,22 +12,65 @@
 
 #include "llvm/TableGen/TableGenBackend.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
 #include <cstddef>
 
 using namespace llvm;
+using namespace TableGen::Emitter;
 
 const size_t MAX_LINE_LEN = 80U;
 
-namespace llvm::TableGen::Emitter {
-ManagedStatic<cl::opt<FnT>, OptCreatorT> Action;
-void *OptCreatorT::call() {
-  return new cl::opt<FnT>(cl::desc("Action to perform:"));
+// CommandLine options of class type are not directly supported with some
+// specific exceptions like std::string which are safe to copy. In our case,
+// the `FnT` function_ref object is also safe to copy. So provide a
+// specialization of `OptionValue` for `FnT` type that stores it as a copy.
+// This is essentially similar to OptionValue<std::string> specialization for
+// strings.
+template <> struct cl::OptionValue<FnT> final : cl::OptionValueCopy<FnT> {
+  OptionValue() = default;
+
+  OptionValue(const FnT &V) { this->setValue(V); }
+
+  OptionValue<FnT> &operator=(const FnT &V) {
+    setValue(V);
+    return *this;
+  }
+
+private:
+  void anchor() override {}
----------------
Pierre-vh wrote:

I don't think you need an anchor if the class is contained inside a .cpp file, it's just useful in headers IIRC

https://github.com/llvm/llvm-project/pull/104716