[Flang][OpenMP] Add semantic checks for OpenMP Private clause.

Add the semantic checks for the OpenMP 4.5 - 2.15.3.3 Private clause.

1. Pointers with the INTENT(IN) attribute may not appear in a private clause.
2. Variables that appear in namelist statements may not appear in a private clause.
   A flag 'InNamelist' is added to the Symbol::Flag to identify the symbols
   in Namelist statemnts.

Test cases : omp-private01.f90, omp-private02.f90

Reviewed By: kiranchandramohan

Differential Revision: https://reviews.llvm.org/D90210

flang/include/flang/Semantics/symbol.h

@@ -493,6 +493,7 @@ public:
       LocalityLocalInit, // named in LOCAL_INIT locality-spec
       LocalityShared, // named in SHARED locality-spec
       InDataStmt, // initialized in a DATA statement
+      InNamelist, // flag is set if the symbol is in Namelist statement
       // OpenACC data-sharing attribute
       AccPrivate, AccFirstPrivate, AccShared,
       // OpenACC data-mapping attribute

flang/lib/Semantics/check-omp-structure.cpp

@@ -417,6 +417,7 @@ void OmpStructureChecker::Enter(const parser::OmpClause::Shared &x) {
 void OmpStructureChecker::Enter(const parser::OmpClause::Private &x) {
   CheckAllowed(llvm::omp::Clause::OMPC_private);
   CheckIsVarPartOfAnotherVar(x.v);
+  CheckIntentInPointer(x.v, llvm::omp::Clause::OMPC_private);
 }
 
 void OmpStructureChecker::CheckIsVarPartOfAnotherVar(
@@ -693,4 +694,38 @@ void OmpStructureChecker::CheckDependArraySection(
   }
 }
 
+void OmpStructureChecker::CheckIntentInPointer(
+    const parser::OmpObjectList &objectList, const llvm::omp::Clause clause) {
+  std::vector<const Symbol *> symbols;
+  GetSymbolsInObjectList(objectList, symbols);
+  for (const auto *symbol : symbols) {
+    if (IsPointer(*symbol) && IsIntentIn(*symbol)) {
+      context_.Say(GetContext().clauseSource,
+          "Pointer '%s' with the INTENT(IN) attribute may not appear "
+          "in a %s clause"_err_en_US,
+          symbol->name(),
+          parser::ToUpperCaseLetters(getClauseName(clause).str()));
+    }
+  }
+}
+
+void OmpStructureChecker::GetSymbolsInObjectList(
+    const parser::OmpObjectList &objectList,
+    std::vector<const Symbol *> &symbols) {
+  for (const auto &ompObject : objectList.v) {
+    if (const auto *name{parser::Unwrap<parser::Name>(ompObject)}) {
+      if (const auto *symbol{name->symbol}) {
+        if (const auto *commonBlockDetails{
+                symbol->detailsIf<CommonBlockDetails>()}) {
+          for (const auto &object : commonBlockDetails->objects()) {
+            symbols.emplace_back(&object->GetUltimate());
+          }
+        } else {
+          symbols.emplace_back(&symbol->GetUltimate());
+        }
+      }
+    }
+  }
+}
+
 } // namespace Fortran::semantics

flang/lib/Semantics/check-omp-structure.h

@@ -185,8 +185,11 @@ private:
   void CheckDependList(const parser::DataRef &);
   void CheckDependArraySection(
       const common::Indirection<parser::ArrayElement> &, const parser::Name &);
-
   void CheckIsVarPartOfAnotherVar(const parser::OmpObjectList &objList);
+  void CheckIntentInPointer(
+      const parser::OmpObjectList &, const llvm::omp::Clause);
+  void GetSymbolsInObjectList(
+      const parser::OmpObjectList &, std::vector<const Symbol *> &);
 };
 } // namespace Fortran::semantics
 #endif // FORTRAN_SEMANTICS_CHECK_OMP_STRUCTURE_H_

flang/lib/Semantics/resolve-directives.cpp

@@ -375,6 +375,8 @@ private:
       const parser::Name &, const Symbol &, Symbol::Flag);
 
   void CheckAssocLoopLevel(std::int64_t level, const parser::OmpClause *clause);
+  void CheckObjectInNamelist(
+      const parser::Name &, const Symbol &, Symbol::Flag);
 };
 
 template <typename T>
@@ -1107,6 +1109,10 @@ void OmpAttributeVisitor::ResolveOmpObject(
                   if (dataSharingAttributeFlags.test(ompFlag)) {
                     CheckMultipleAppearances(*name, *symbol, ompFlag);
                   }
+                  if (privateDataSharingAttributeFlags.test(ompFlag)) {
+                    CheckObjectInNamelist(*name, *symbol, ompFlag);
+                  }
+
                   if (ompFlag == Symbol::Flag::OmpAllocate) {
                     AddAllocateName(name);
                   }
@@ -1258,4 +1264,18 @@ void OmpAttributeVisitor::CheckDataCopyingClause(
   }
 }
 
+void OmpAttributeVisitor::CheckObjectInNamelist(
+    const parser::Name &name, const Symbol &symbol, Symbol::Flag ompFlag) {
+  if (symbol.GetUltimate().test(Symbol::Flag::InNamelist)) {
+    llvm::StringRef clauseName{"PRIVATE"};
+    if (ompFlag == Symbol::Flag::OmpFirstPrivate)
+      clauseName = "FIRSTPRIVATE";
+    else if (ompFlag == Symbol::Flag::OmpLastPrivate)
+      clauseName = "LASTPRIVATE";
+    context_.Say(name.source,
+        "Variable '%s' in NAMELIST cannot be in a %s clause"_err_en_US,
+        name.ToString(), clauseName.str());
+  }
+}
+
 } // namespace Fortran::semantics

flang/lib/Semantics/resolve-names.cpp

@@ -4289,6 +4289,7 @@ bool DeclarationVisitor::Pre(const parser::NamelistStmt::Group &x) {
     } else if (!ConvertToObjectEntity(*symbol)) {
       SayWithDecl(name, *symbol, "'%s' is not a variable"_err_en_US);
     }
+    symbol->GetUltimate().set(Symbol::Flag::InNamelist);
     details.add_object(*symbol);
   }
 

flang/test/Semantics/omp-private01.f90

@@ -0,0 +1,20 @@
+! RUN: %S/test_errors.sh %s %t %f18 -fopenmp
+! OpenMP Version 4.5
+! 2.15.3.3 private Clause
+! Pointers with the INTENT(IN) attribute may not appear in a private clause.
+
+subroutine omp_private(p)
+  integer :: a(10), b(10), c(10)
+  integer, pointer, intent(in) :: p
+
+  a = 10
+  b = 20
+
+  !ERROR: Pointer 'p' with the INTENT(IN) attribute may not appear in a PRIVATE clause
+  !$omp parallel private(p)
+  c = a + b + p
+  !$omp end parallel
+
+  print *, c
+
+end subroutine omp_private

flang/test/Semantics/omp-private02.f90

@@ -0,0 +1,46 @@
+! RUN: %S/test_errors.sh %s %t %f18 -fopenmp
+! OpenMP Version 4.5
+! 2.15.3.3 private Clause
+! Variables that appear in namelist statements may not appear in a private clause.
+
+module test
+  integer :: a, b, c
+  namelist /nlist1/ a, b
+end module
+
+program omp_private
+  use test
+
+  integer :: p(10) ,q(10)
+  namelist /nlist2/ c, d
+
+  a = 5
+  b = 10
+  c = 100
+
+  !ERROR: Variable 'a' in NAMELIST cannot be in a PRIVATE clause
+  !ERROR: Variable 'c' in NAMELIST cannot be in a PRIVATE clause
+  !$omp parallel private(a, c)
+  d = a + b
+  !$omp end parallel
+
+  call sb()
+
+  contains
+    subroutine sb()
+      namelist /nlist3/ p, q
+
+      !ERROR: Variable 'p' in NAMELIST cannot be in a PRIVATE clause
+      !ERROR: Variable 'd' in NAMELIST cannot be in a PRIVATE clause
+      !$omp parallel private(p, d)
+      p = c * b
+      q = p * d
+      !$omp end parallel
+
+      write(*, nlist1)
+      write(*, nlist2)
+      write(*, nlist3)
+
+    end subroutine
+
+end program omp_private