[flang][openxx][NFC] Remove duplicated function to check required clauses

[clementval]

Summary

Remove duplicated function to check for required clauses on a directive. This was
still there from the merging of OpenACC and OpenMP common semantic checks and it can now be
removed so we use only one function.

[sameeranjoshi]

LGMT. Thanks for cleaning that up.

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

template <typename B> void CheckMatching(const B &beginDir, const B &endDir) {
     }
   }
   void CheckNoBranching(const parser::Block &block, D directive,
       const parser::CharBlock &directiveSource);
 
   // Check that only clauses in set are after the specific clauses.
   void CheckOnlyAllowedAfter(C clause, common::EnumSet<C, ClauseEnumSize> set);
 
-  void CheckRequired(C clause);
-
   void CheckRequireAtLeastOneOf();
 
   void CheckAllowed(C clause);
 
   void CheckAtLeastOneClause();
 
   void CheckNotAllowedIfClause(
       C clause, common::EnumSet<C, ClauseEnumSize> set);
DirectiveStructureChecker<D, C, PC, ClauseEnumSize>::ClauseSetToString(
   return list;
 }
 
 // Check that at least one clause in the required set is present on the
 // directive.
 template <typename D, typename C, typename PC, std::size_t ClauseEnumSize>
 void DirectiveStructureChecker<D, C, PC,
     ClauseEnumSize>::CheckRequireAtLeastOneOf() {
+  if (GetContext().requiredClauses.empty())
+    return;
   for (auto cl : GetContext().actualClauses) {
     if (GetContext().requiredClauses.test(cl))
       return;
   }
   // No clause matched in the actual clauses list
   context_.Say(GetContext().directiveSource,
       "At least one of %s clause must appear on the %s directive"_err_en_US,
       ClauseSetToString(GetContext().requiredClauses),

 void DirectiveStructureChecker<D, C, PC, ClauseEnumSize>::SayNotMatching(
     const parser::CharBlock &beginSource, const parser::CharBlock &endSource) {
   context_
       .Say(endSource, "Unmatched %s directive"_err_en_US,
           parser::ToUpperCaseLetters(endSource.ToString()))
       .Attach(beginSource, "Does not match directive"_en_US);
 }
 
-// Check that at least one of the required clauses is present on the directive.
-template <typename D, typename C, typename PC, std::size_t ClauseEnumSize>
-void DirectiveStructureChecker<D, C, PC, ClauseEnumSize>::CheckRequired(C c) {
-  if (!FindClause(c)) {
-    context_.Say(GetContext().directiveSource,
-        "At least one %s clause must appear on the %s directive"_err_en_US,
-        parser::ToUpperCaseLetters(getClauseName(c).str()),
-        ContextDirectiveAsFortran());
-  }
-}
-
 // Check the value of the clause is a positive parameter.
 template <typename D, typename C, typename PC, std::size_t ClauseEnumSize>
 void DirectiveStructureChecker<D, C, PC,
     ClauseEnumSize>::RequiresPositiveParameter(const C &clause,
     const parser::ScalarIntExpr &i, llvm::StringRef paramName) {
   if (const auto v{GetIntValue(i)}) {
     if (*v <= 0) {
       context_.Say(GetContext().clauseSource,

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

void OmpStructureChecker::Leave(const parser::OmpClauseList &) {
   } // SIMD
 
   // 2.7.3 Single Construct Restriction
   if (GetContext().directive == llvm::omp::Directive::OMPD_end_single) {
     CheckNotAllowedIfClause(
         llvm::omp::Clause::OMPC_copyprivate, {llvm::omp::Clause::OMPC_nowait});
   }
 
-  GetContext().requiredClauses.IterateOverMembers(
-      [this](llvm::omp::Clause c) { CheckRequired(c); });
+  CheckRequireAtLeastOneOf();
 }
 
 void OmpStructureChecker::Enter(const parser::OmpClause &x) {
   SetContextClause(x);
 }
 
 // Following clauses do not have a seperate node in parse-tree.h.
 // They fall under 'struct OmpClause' in parse-tree.h.

flang/test/Semantics/omp-device-constructs.f90

program main
   !$omp end target
 
   !$omp target data device(0) map(to:a)
   do i = 1, N
     a = 3.14
   enddo
   !$omp end target data
 
-  !ERROR: At least one MAP clause must appear on the TARGET DATA directive
+  !ERROR: At least one of MAP clause must appear on the TARGET DATA directive
   !$omp target data device(0)
   do i = 1, N
      a = 3.14
   enddo
   !$omp end target data
 
   !ERROR: At most one IF clause can appear on the TARGET ENTER DATA directive
   !$omp target enter data map(to:a) if(.true.) if(.false.)