[Flang][OpenMP] Add Todo for doconcurrent with worksharing loop

[kiranchandramohan]

Summary

This is a valid usage. We do not handle it as of now. Gfortran/Ifx produces an error, possibly because do concurrent was not allowed in previous versions of the OpenMP standard.

Fixes #62649

flang/lib/Lower/OpenMP.cpp

createCombinedParallelOp<Fortran::parser::OmpBeginLoopDirective>(
         std::get<Fortran::parser::OmpBeginLoopDirective>(loopConstruct.t));
   } else if (llvm::omp::OMPD_do != ompDirective &&
              llvm::omp::OMPD_simd != ompDirective) {
     TODO(converter.getCurrentLocation(), "Construct enclosing do loop");
   }
 
   // Collect the loops to collapse.
   auto *doConstructEval = &eval.getFirstNestedEvaluation();
+  if (doConstructEval->getIf<Fortran::parser::DoConstruct>()
+          ->IsDoConcurrent()) {
+    TODO(converter.getCurrentLocation(),
+         "Do Concurrent in Worksharing loop construct");
+  }
 
   std::int64_t collapseValue =
       Fortran::lower::getCollapseValue(loopOpClauseList);
   std::size_t loopVarTypeSize = 0;
   SmallVector<const Fortran::semantics::Symbol *> iv;
   do {
     auto *doLoop = &doConstructEval->getFirstNestedEvaluation();
     auto *doStmt = doLoop->getIf<Fortran::parser::NonLabelDoStmt>();

flang/lib/Semantics/resolve-directives.cpp

bool DirectiveAttributeVisitor<T>::HasDataSharingAttributeObject(
   return it != dataSharingAttributeObjects_.end();
 }
 
 template <typename T>
 const parser::Name *DirectiveAttributeVisitor<T>::GetLoopIndex(
     const parser::DoConstruct &x) {
   using Bounds = parser::LoopControl::Bounds;
   if (x.GetLoopControl()) {
-    return &std::get<Bounds>(x.GetLoopControl()->u).name.thing;
+    if (const Bounds * b{std::get_if<Bounds>(&x.GetLoopControl()->u)}) {
+      return &b->name.thing;
+    } else {
+      return nullptr;
+    }
   } else {
     context_
         .Say(std::get<parser::Statement<parser::NonLabelDoStmt>>(x.t).source,
             "Loop control is not present in the DO LOOP"_err_en_US)
         .Attach(GetContext().directiveSource,
             "associated with the enclosing LOOP construct"_en_US);
     return nullptr;
   }

flang/test/Lower/OpenMP/Todo/omp-doconcurrent.f90

+! RUN: %not_todo_cmd bbc -emit-fir -fopenmp -o - %s 2>&1 | FileCheck %s
+! RUN: %not_todo_cmd %flang_fc1 -emit-fir -fopenmp -o - %s 2>&1 | FileCheck %s
+
+! CHECK: not yet implemented: Do Concurrent in Worksharing loop construct
+subroutine sb()
+  !$omp do
+  do concurrent(i=1:10)
+    print *, i
+  end do
+end subroutine