Revert "Remove DirectiveSpecification"

This reverts commit 0e317db.

Author: kparzysz

flang/include/flang/Parser/parse-tree.h

@@ -3456,6 +3456,14 @@ WRAPPER_CLASS(PauseStmt, std::optional<StopCode>);
 struct OmpClause;
 struct OmpClauseList;
 
+struct OmpDirectiveSpecification {
+  TUPLE_CLASS_BOILERPLATE(OmpDirectiveSpecification);
+  std::tuple<llvm::omp::Directive,
+      std::optional<common::Indirection<OmpClauseList>>>
+      t;
+  CharBlock source;
+};
+
 // 2.1 Directives or clauses may accept a list or extended-list.
 //     A list item is a variable, array section or common block name (enclosed
 //     in slashes). An extended list item is a list item or a procedure Name.

flang/lib/Parser/openmp-parsers.cpp

@@ -153,6 +153,9 @@ static TypeDeclarationStmt makeIterSpecDecl(std::list<ObjectName> &&names) {
       makeEntityList(std::move(names)));
 }
 
+TYPE_PARSER(sourced(construct<OmpDirectiveSpecification>(
+    OmpDirectiveNameParser{}, maybe(indirect(Parser<OmpClauseList>{})))))
+
 // --- Parsers for context traits -------------------------------------
 
 TYPE_PARSER(construct<OmpTraitPropertyName>( //

flang/lib/Parser/unparse.cpp

@@ -2070,6 +2070,10 @@ class UnparseVisitor {
   void Unparse(const llvm::omp::Directive &x) {
     Word(llvm::omp::getOpenMPDirectiveName(x).str());
   }
+  void Unparse(const OmpDirectiveSpecification &x) {
+    Walk(std::get<llvm::omp::Directive>(x.t));
+    Walk(std::get<std::optional<common::Indirection<OmpClauseList>>>(x.t));
+  }
   void Unparse(const OmpTraitScore &x) {
     Word("SCORE(");
     Walk(x.v);