[Flang][OpenMP] Add TODO message for common block privatisation

[kiranchandramohan]

Summary

This is a temporary message until the feature is implemented and
merged.

Note: There is a proposed patch (https://reviews.llvm.org/D127215)

[peixin]

LGTM except one small problem

flang/lib/Lower/OpenMP.cpp

178

I think commonDet may cause a warning of unused variable.

[kiranchandramohan]

flang/lib/Lower/OpenMP.cpp

178

Thanks for pointing that out. Will fix it before I submit it.

flang/lib/Lower/OpenMP.cpp

if (const auto &privateClause =
                        &clause.u)) {
       collectOmpObjectListSymbol(lastPrivateClause->v, privatizedSymbols);
       hasLastPrivateOp = true;
     } else if (std::get_if<Fortran::parser::OmpClause::Collapse>(&clause.u)) {
       hasCollapse = true;
     }
   }
 
+  for (auto *ps : privatizedSymbols) {
+    if (const auto *commonDet =
+            ps->detailsIf<Fortran::semantics::CommonBlockDetails>())
+      TODO(converter.getCurrentLocation(),
+           "Common Block in privatization clause");
+  }
+
   if (hasCollapse && hasLastPrivateOp)
     TODO(converter.getCurrentLocation(), "Collapse clause with lastprivate");
 }
 
 bool DataSharingProcessor ::needBarrier() {
   for (auto sym : privatizedSymbols) {
     if (sym->test(Fortran::semantics::Symbol::Flag::OmpFirstPrivate) &&
         sym->test(Fortran::semantics::Symbol::Flag::OmpLastPrivate))

flang/test/Lower/OpenMP/Todo/firstprivate-commonblock.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: Common Block in privatization clause
+subroutine firstprivate_common
+  common /c/ x, y
+  real x, y
+  !$omp parallel firstprivate(/c/)
+  !$omp end parallel
+end subroutine

flang/test/Lower/OpenMP/Todo/lastprivate-commonblock.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: Common Block in privatization clause
+subroutine lastprivate_common
+  common /c/ x, y
+  real x, y
+  !$omp do lastprivate(/c/)
+  do i=1,100
+  end do
+  !$omp end do
+end subroutine

flang/test/Lower/OpenMP/Todo/private-commonblock.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: Common Block in privatization clause
+subroutine private_common
+  common /c/ x, y
+  real x, y
+  !$omp parallel private(/c/)
+  !$omp end parallel
+end subroutine