[flang][CodeGen][NFC] Reduce TargetRewrite pass boilerplate (llvm#94450)

Tablegen can automatically generate the pass constructor. Tablegen will
create a constructor for all of the pass options (not only the subset in
the old constructor), but the pass options seem unused anyway.

This pass does not require any modification to support alternative
top-level ops. It walks all operations in the module. Functions have
special handling (adding attributes, converting signatures) but this
wouldn't make sense for top level operations in general.

Author: tblah

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

@@ -61,7 +61,6 @@ def TargetRewritePass : Pass<"target-rewrite", "mlir::ModuleOp"> {
       Certain abstractions in the FIR dialect need to be rewritten to reflect
       representations that may differ based on the target machine.
   }];
-  let constructor = "::fir::createFirTargetRewritePass()";
   let dependentDialects = [ "fir::FIROpsDialect", "mlir::func::FuncDialect",
                             "mlir::DLTIDialect" ];
   let options = [

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

@@ -28,18 +28,6 @@ struct NameUniquer;
 #define GEN_PASS_DECL_BOXEDPROCEDUREPASS
 #include "flang/Optimizer/CodeGen/CGPasses.h.inc"
 
-/// FirTargetRewritePass options.
-struct TargetRewriteOptions {
-  bool noCharacterConversion{};
-  bool noComplexConversion{};
-  bool noStructConversion{};
-};
-
-/// Prerequiste pass for code gen. Perform intermediate rewrites to tailor the
-/// FIR for the chosen target.
-std::unique_ptr<mlir::OperationPass<mlir::ModuleOp>> createFirTargetRewritePass(
-    const TargetRewriteOptions &options = TargetRewriteOptions());
-
 /// FIR to LLVM translation pass options.
 struct FIRToLLVMPassOptions {
   // Do not fail when type descriptors are not found when translating

flang/include/flang/Tools/CLOptions.inc

@@ -182,9 +182,8 @@ inline void addCodeGenRewritePass(mlir::PassManager &pm, bool preserveDeclare) {
 }
 
 inline void addTargetRewritePass(mlir::PassManager &pm) {
-  addPassConditionally(pm, disableTargetRewrite, []() {
-    return fir::createFirTargetRewritePass(fir::TargetRewriteOptions{});
-  });
+  addPassConditionally(pm, disableTargetRewrite,
+      []() { return fir::createTargetRewritePass(); });
 }
 
 inline mlir::LLVM::DIEmissionKind getEmissionKind(

flang/lib/Optimizer/CodeGen/TargetRewrite.cpp

@@ -76,11 +76,7 @@ struct FixupTy {
 /// idioms that are used for distinct target processor and ABI combinations.
 class TargetRewrite : public fir::impl::TargetRewritePassBase<TargetRewrite> {
 public:
-  TargetRewrite(const fir::TargetRewriteOptions &options) {
-    noCharacterConversion = options.noCharacterConversion;
-    noComplexConversion = options.noComplexConversion;
-    noStructConversion = options.noStructConversion;
-  }
+  using TargetRewritePassBase<TargetRewrite>::TargetRewritePassBase;
 
   void runOnOperation() override final {
     auto &context = getContext();
@@ -1255,8 +1251,3 @@ class TargetRewrite : public fir::impl::TargetRewritePassBase<TargetRewrite> {
   mlir::func::FuncOp stackRestoreFn = nullptr;
 };
 } // namespace
-
-std::unique_ptr<mlir::OperationPass<mlir::ModuleOp>>
-fir::createFirTargetRewritePass(const fir::TargetRewriteOptions &options) {
-  return std::make_unique<TargetRewrite>(options);
-}