Allow do concurrent in loop constructs, but not loop nests

Author: tblah

flang/lib/Semantics/resolve-directives.cpp

@@ -1952,7 +1952,8 @@ void OmpAttributeVisitor::PrivatizeAssociatedLoopIndexAndCheckLoopLevel(
   const auto &outer{std::get<std::optional<parser::DoConstruct>>(x.t)};
   if (outer.has_value()) {
     for (const parser::DoConstruct *loop{&*outer}; loop && level > 0; --level) {
-      if (loop->IsDoConcurrent()) {
+      // DO CONCURRENT is allowed for loop constructs but not loop nests
+      if (loop->IsDoConcurrent() && GetContext().associatedLoopLevel != 1) {
         auto &stmt =
             std::get<parser::Statement<parser::NonLabelDoStmt>>(loop->t);
         context_.Say(stmt.source,

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

@@ -0,0 +1,10 @@
+! 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