[flang][CodeGen][NFC] Reduce boilerplatre for ExternalNameConversion (#94474)

Use tablegen to generate the pass constructor.

I removed the duplicated pass option handling. I don't understand why
the manual instantiation of the pass needs its own duplicate of the pass
options in the (automatically generated) base class (even with the
option to ignore the pass options in the base class).

This pass doesn't need changes to support other top level operations.

Author: tblah

flang/include/flang/Optimizer/Transforms/Passes.h

@@ -60,9 +60,6 @@ std::unique_ptr<mlir::Pass> createAffineDemotionPass();
 std::unique_ptr<mlir::Pass>
 createArrayValueCopyPass(fir::ArrayValueCopyOptions options = {});
 std::unique_ptr<mlir::Pass> createCFGConversionPassWithNSW();
-std::unique_ptr<mlir::Pass> createExternalNameConversionPass();
-std::unique_ptr<mlir::Pass>
-createExternalNameConversionPass(bool appendUnderscore);
 std::unique_ptr<mlir::Pass> createMemDataFlowOptPass();
 std::unique_ptr<mlir::Pass> createPromoteToAffinePass();
 std::unique_ptr<mlir::Pass>

flang/include/flang/Optimizer/Transforms/Passes.td

@@ -163,7 +163,6 @@ def ExternalNameConversion : Pass<"external-name-interop", "mlir::ModuleOp"> {
   let description = [{
     Demangle FIR internal name and mangle them for external interoperability.
   }];
-  let constructor = "::fir::createExternalNameConversionPass()";
   let options = [
     Option<"appendUnderscoreOpt", "append-underscore",
            "bool", /*default=*/"true",

flang/include/flang/Tools/CLOptions.inc

@@ -233,9 +233,8 @@ inline void addBoxedProcedurePass(mlir::PassManager &pm) {
 
 inline void addExternalNameConversionPass(
     mlir::PassManager &pm, bool appendUnderscore = true) {
-  addPassConditionally(pm, disableExternalNameConversion, [&]() {
-    return fir::createExternalNameConversionPass(appendUnderscore);
-  });
+  addPassConditionally(pm, disableExternalNameConversion,
+      [&]() { return fir::createExternalNameConversion({appendUnderscore}); });
 }
 
 // Use inliner extension point callback to register the default inliner pass.

flang/lib/Optimizer/Transforms/ExternalNameConversion.cpp

@@ -45,25 +45,18 @@ namespace {
 class ExternalNameConversionPass
     : public fir::impl::ExternalNameConversionBase<ExternalNameConversionPass> {
 public:
-  ExternalNameConversionPass(bool appendUnderscoring)
-      : appendUnderscores(appendUnderscoring) {}
-
-  ExternalNameConversionPass() { usePassOpt = true; }
+  using ExternalNameConversionBase<
+      ExternalNameConversionPass>::ExternalNameConversionBase;
 
   mlir::ModuleOp getModule() { return getOperation(); }
   void runOnOperation() override;
-
-private:
-  bool appendUnderscores;
-  bool usePassOpt = false;
 };
 } // namespace
 
 void ExternalNameConversionPass::runOnOperation() {
   auto op = getOperation();
   auto *context = &getContext();
 
-  appendUnderscores = (usePassOpt) ? appendUnderscoreOpt : appendUnderscores;
   llvm::DenseMap<mlir::StringAttr, mlir::FlatSymbolRefAttr> remappings;
   // Update names of external Fortran functions and names of Common Block
   // globals.
@@ -74,7 +67,8 @@ void ExternalNameConversionPass::runOnOperation() {
           mlir::SymbolTable::getSymbolAttrName());
       auto deconstructedName = fir::NameUniquer::deconstruct(symName);
       if (fir::NameUniquer::isExternalFacingUniquedName(deconstructedName)) {
-        auto newName = mangleExternalName(deconstructedName, appendUnderscores);
+        auto newName =
+            mangleExternalName(deconstructedName, appendUnderscoreOpt);
         auto newAttr = mlir::StringAttr::get(context, newName);
         mlir::SymbolTable::setSymbolName(&funcOrGlobal, newAttr);
         auto newSymRef = mlir::FlatSymbolRefAttr::get(newAttr);
@@ -101,12 +95,3 @@ void ExternalNameConversionPass::runOnOperation() {
       nestedOp->setAttr(update.first, update.second);
   });
 }
-
-std::unique_ptr<mlir::Pass> fir::createExternalNameConversionPass() {
-  return std::make_unique<ExternalNameConversionPass>();
-}
-
-std::unique_ptr<mlir::Pass>
-fir::createExternalNameConversionPass(bool appendUnderscoring) {
-  return std::make_unique<ExternalNameConversionPass>(appendUnderscoring);
-}