[flang][OpenMP] Lower standalone ops via OMP dispatch, NFC (#92045)

This moves lowering of standalone OpenMP ops into the dispatch function.
Follow-up to PR90098.

Author: kparzysz

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -1959,6 +1959,9 @@ static void genOMPDispatch(Fortran::lower::AbstractConverter &converter,
   const List<Clause> &clauses = item->clauses;
 
   switch (llvm::omp::Directive dir = item->id) {
+  case llvm::omp::Directive::OMPD_barrier:
+    genBarrierOp(converter, symTable, semaCtx, eval, loc, queue, item);
+    break;
   case llvm::omp::Directive::OMPD_distribute:
     genDistributeOp(converter, symTable, semaCtx, eval, loc, clauses, queue,
                     item);
@@ -1968,22 +1971,25 @@ static void genOMPDispatch(Fortran::lower::AbstractConverter &converter,
     break;
   case llvm::omp::Directive::OMPD_loop:
   case llvm::omp::Directive::OMPD_masked:
-  case llvm::omp::Directive::OMPD_tile:
-  case llvm::omp::Directive::OMPD_unroll:
     TODO(loc, "Unhandled loop directive (" +
                   llvm::omp::getOpenMPDirectiveName(dir) + ")");
     break;
   case llvm::omp::Directive::OMPD_master:
     genMasterOp(converter, symTable, semaCtx, eval, loc, clauses, queue, item);
     break;
   case llvm::omp::Directive::OMPD_ordered:
+    // Block-associated "ordered" construct.
     genOrderedRegionOp(converter, symTable, semaCtx, eval, loc, clauses, queue,
                        item);
     break;
   case llvm::omp::Directive::OMPD_parallel:
     genParallelOp(converter, symTable, semaCtx, eval, loc, clauses, queue, item,
                   /*outerCombined=*/false);
     break;
+  case llvm::omp::Directive::OMPD_section:
+    genSectionOp(converter, symTable, semaCtx, eval, loc, /*clauses=*/{}, queue,
+                 item);
+    break;
   case llvm::omp::Directive::OMPD_sections:
     genSectionsOp(converter, symTable, semaCtx, eval, loc, clauses, queue,
                   item);
@@ -2025,16 +2031,28 @@ static void genOMPDispatch(Fortran::lower::AbstractConverter &converter,
     genTaskloopOp(converter, symTable, semaCtx, eval, loc, clauses, queue,
                   item);
     break;
+  case llvm::omp::Directive::OMPD_taskwait:
+    genTaskwaitOp(converter, symTable, semaCtx, eval, loc, clauses, queue,
+                  item);
+    break;
+  case llvm::omp::Directive::OMPD_taskyield:
+    genTaskyieldOp(converter, symTable, semaCtx, eval, loc, queue, item);
+    break;
   case llvm::omp::Directive::OMPD_teams:
     genTeamsOp(converter, symTable, semaCtx, eval, loc, clauses, queue, item);
     break;
+  case llvm::omp::Directive::OMPD_tile:
+  case llvm::omp::Directive::OMPD_unroll:
+    TODO(loc, "Unhandled loop directive (" +
+                  llvm::omp::getOpenMPDirectiveName(dir) + ")");
   // case llvm::omp::Directive::OMPD_workdistribute:
   case llvm::omp::Directive::OMPD_workshare:
     // FIXME: Workshare is not a commonly used OpenMP construct, an
     // implementation for this feature will come later. For the codes
     // that use this construct, add a single construct for now.
     genSingleOp(converter, symTable, semaCtx, eval, loc, clauses, queue, item);
     break;
+
   // Composite constructs
   case llvm::omp::Directive::OMPD_distribute_parallel_do:
     genCompositeDistributeParallelDo(converter, symTable, semaCtx, eval, loc,
@@ -2174,45 +2192,14 @@ static void genOMP(Fortran::lower::AbstractConverter &converter,
   ConstructQueue queue{
       buildConstructQueue(converter.getFirOpBuilder().getModule(), semaCtx,
                           eval, directive.source, directive.v, clauses)};
-
-  switch (directive.v) {
-  default:
-    break;
-  case llvm::omp::Directive::OMPD_barrier:
-    genBarrierOp(converter, symTable, semaCtx, eval, currentLocation, queue,
-                 queue.begin());
-    break;
-  case llvm::omp::Directive::OMPD_taskwait:
-    genTaskwaitOp(converter, symTable, semaCtx, eval, currentLocation, clauses,
-                  queue, queue.begin());
-    break;
-  case llvm::omp::Directive::OMPD_taskyield:
-    genTaskyieldOp(converter, symTable, semaCtx, eval, currentLocation, queue,
-                   queue.begin());
-    break;
-  case llvm::omp::Directive::OMPD_target_data:
-    genTargetDataOp(converter, symTable, semaCtx, eval, currentLocation,
-                    clauses, queue, queue.begin());
-    break;
-  case llvm::omp::Directive::OMPD_target_enter_data:
-    genTargetEnterExitUpdateDataOp<mlir::omp::TargetEnterDataOp>(
-        converter, symTable, semaCtx, currentLocation, clauses, queue,
-        queue.begin());
-    break;
-  case llvm::omp::Directive::OMPD_target_exit_data:
-    genTargetEnterExitUpdateDataOp<mlir::omp::TargetExitDataOp>(
-        converter, symTable, semaCtx, currentLocation, clauses, queue,
-        queue.begin());
-    break;
-  case llvm::omp::Directive::OMPD_target_update:
-    genTargetEnterExitUpdateDataOp<mlir::omp::TargetUpdateOp>(
-        converter, symTable, semaCtx, currentLocation, clauses, queue,
-        queue.begin());
-    break;
-  case llvm::omp::Directive::OMPD_ordered:
+  if (directive.v == llvm::omp::Directive::OMPD_ordered) {
+    // Standalone "ordered" directive.
     genOrderedOp(converter, symTable, semaCtx, eval, currentLocation, clauses,
                  queue, queue.begin());
-    break;
+  } else {
+    // Dispatch handles the "block-associated" variant of "ordered".
+    genOMPDispatch(converter, symTable, semaCtx, eval, currentLocation, queue,
+                   queue.begin());
   }
 }
 
@@ -2466,8 +2453,7 @@ genOMP(Fortran::lower::AbstractConverter &converter,
   ConstructQueue queue{buildConstructQueue(
       converter.getFirOpBuilder().getModule(), semaCtx, eval,
       sectionConstruct.source, llvm::omp::Directive::OMPD_section, {})};
-  genSectionOp(converter, symTable, semaCtx, eval, loc,
-               /*clauses=*/{}, queue, queue.begin());
+  genOMPDispatch(converter, symTable, semaCtx, eval, loc, queue, queue.begin());
 }
 
 static void