[flang][OpenMP][NFC] Reduce FunctionFiltering pass boilerplate (#93951)

The pass constructor can be generated automatically.

This pass doesn't need to be adapted to support other top level
operations because it is specifically supposed to filter functions. We
don't need to filter non-function top level operations because without
use inside of functions they shouldn't lead to any codegen.

Author: tblah

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

@@ -53,6 +53,7 @@ namespace fir {
 #define GEN_PASS_DECL_ADDALIASTAGS
 #define GEN_PASS_DECL_OMPMAPINFOFINALIZATIONPASS
 #define GEN_PASS_DECL_OMPMARKDECLARETARGETPASS
+#define GEN_PASS_DECL_OMPFUNCTIONFILTERING
 #include "flang/Optimizer/Transforms/Passes.h.inc"
 
 std::unique_ptr<mlir::Pass> createAffineDemotionPass();
@@ -72,8 +73,6 @@ std::unique_ptr<mlir::Pass> createAlgebraicSimplificationPass();
 std::unique_ptr<mlir::Pass>
 createAlgebraicSimplificationPass(const mlir::GreedyRewriteConfig &config);
 
-std::unique_ptr<mlir::Pass> createOMPFunctionFilteringPass();
-
 std::unique_ptr<mlir::Pass> createVScaleAttrPass();
 std::unique_ptr<mlir::Pass>
 createVScaleAttrPass(std::pair<unsigned, unsigned> vscaleAttr);

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

@@ -343,7 +343,6 @@ def OMPMarkDeclareTargetPass
 def OMPFunctionFiltering : Pass<"omp-function-filtering"> {
   let summary = "Filters out functions intended for the host when compiling "
                 "for the target device.";
-  let constructor = "::fir::createOMPFunctionFilteringPass()";
   let dependentDialects = [
     "mlir::func::FuncDialect",
     "fir::FIROpsDialect"

flang/include/flang/Tools/CLOptions.inc

@@ -349,7 +349,7 @@ inline void createOpenMPFIRPassPipeline(
       pm, fir::createOMPMapInfoFinalizationPass);
   pm.addPass(fir::createOMPMarkDeclareTargetPass());
   if (isTargetDevice)
-    pm.addPass(fir::createOMPFunctionFilteringPass());
+    pm.addPass(fir::createOMPFunctionFiltering());
 }
 
 #if !defined(FLANG_EXCLUDE_CODEGEN)

flang/lib/Optimizer/Transforms/OMPFunctionFiltering.cpp

@@ -103,7 +103,3 @@ class OMPFunctionFilteringPass
   }
 };
 } // namespace
-
-std::unique_ptr<Pass> fir::createOMPFunctionFilteringPass() {
-  return std::make_unique<OMPFunctionFilteringPass>();
-}