[flang][CodeGen][NFC] Reduce BoxedProcedurePass boilerplate (#94200)

The pass constructor can be generated automatically by tablegen.

The pass is module-level and iterates over every operation within the
module so it should not need any changes to support alternative top
level operations.

Author: tblah

flang/include/flang/Optimizer/CodeGen/CGPasses.td

@@ -85,7 +85,6 @@ def TargetRewritePass : Pass<"target-rewrite", "mlir::ModuleOp"> {
 }
 
 def BoxedProcedurePass : Pass<"boxed-procedure", "mlir::ModuleOp"> {
-  let constructor = "::fir::createBoxedProcedurePass()";
   let options = [
     Option<"useThunks", "use-thunks",
            "bool", /*default=*/"true",

flang/include/flang/Optimizer/CodeGen/CodeGen.h

@@ -78,11 +78,6 @@ std::unique_ptr<mlir::Pass> createLLVMDialectToLLVMPass(
     LLVMIRLoweringPrinter printer =
         [](llvm::Module &m, llvm::raw_ostream &out) { m.print(out, nullptr); });
 
-/// Convert boxproc values to a lower level representation. The default is to
-/// use function pointers and thunks.
-std::unique_ptr<mlir::Pass> createBoxedProcedurePass();
-std::unique_ptr<mlir::Pass> createBoxedProcedurePass(bool useThunks);
-
 /// Populate the given list with patterns that convert from FIR to LLVM.
 void populateFIRToLLVMConversionPatterns(fir::LLVMTypeConverter &converter,
                                          mlir::RewritePatternSet &patterns,

flang/lib/Optimizer/CodeGen/BoxedProcedure.cpp

@@ -211,8 +211,7 @@ class BoxprocTypeRewriter : public mlir::TypeConverter {
 class BoxedProcedurePass
     : public fir::impl::BoxedProcedurePassBase<BoxedProcedurePass> {
 public:
-  BoxedProcedurePass() { options = {true}; }
-  BoxedProcedurePass(bool useThunks) { options = {useThunks}; }
+  using BoxedProcedurePassBase<BoxedProcedurePass>::BoxedProcedurePassBase;
 
   inline mlir::ModuleOp getModule() { return getOperation(); }
 
@@ -397,11 +396,3 @@ class BoxedProcedurePass
   BoxedProcedureOptions options;
 };
 } // namespace
-
-std::unique_ptr<mlir::Pass> fir::createBoxedProcedurePass() {
-  return std::make_unique<BoxedProcedurePass>();
-}
-
-std::unique_ptr<mlir::Pass> fir::createBoxedProcedurePass(bool useThunks) {
-  return std::make_unique<BoxedProcedurePass>(useThunks);
-}