[llvm] [NFC][TableGen] Adopt NamespaceEmitter in DirectiveEmitter (PR #165600)

[Rahul Joshi via llvm-commits]

https://github.com/jurahul updated https://github.com/llvm/llvm-project/pull/165600

>From 67afd76722941b798879f6f02e1bdedc992d3088 Mon Sep 17 00:00:00 2001
From: Rahul Joshi <rjoshi at nvidia.com>
Date: Wed, 29 Oct 2025 10:16:55 -0700
Subject: [PATCH] [NFC][TableGen] Adopt NamespaceEmitter in DirectiveEmitter

---
 llvm/test/TableGen/directive1.td              |  7 ++--
 llvm/test/TableGen/directive2.td              |  7 ++--
 .../utils/TableGen/Basic/DirectiveEmitter.cpp | 36 ++++++-------------
 3 files changed, 16 insertions(+), 34 deletions(-)

diff --git a/llvm/test/TableGen/directive1.td b/llvm/test/TableGen/directive1.td
index 8648651f3d714..5bd7890e0ddd1 100644
--- a/llvm/test/TableGen/directive1.td
+++ b/llvm/test/TableGen/directive1.td
@@ -186,8 +186,7 @@ def TDL_DirA : Directive<[Spelling<"dira">]> {
 // IMPL:       #ifdef GEN_FLANG_DIRECTIVE_CLAUSE_SETS
 // IMPL-NEXT:  #undef GEN_FLANG_DIRECTIVE_CLAUSE_SETS
 // IMPL-EMPTY:
-// IMPL-NEXT:  namespace llvm {
-// IMPL-NEXT:  namespace tdl {
+// IMPL-NEXT:  namespace llvm::tdl {
 // IMPL-EMPTY:
 // IMPL-NEXT:    // Sets for dira
 // IMPL-EMPTY:
@@ -204,8 +203,8 @@ def TDL_DirA : Directive<[Spelling<"dira">]> {
 // IMPL-EMPTY:
 // IMPL-NEXT:    static  requiredClauses_TDLD_dira {
 // IMPL-NEXT:    };
-// IMPL-NEXT:  } // namespace tdl
-// IMPL-NEXT:  } // namespace llvm
+// IMPL-EMPTY:
+// IMPL-NEXT:  } // namespace llvm::tdl
 // IMPL-EMPTY:
 // IMPL-NEXT:  #endif // GEN_FLANG_DIRECTIVE_CLAUSE_SETS
 // IMPL-EMPTY:
diff --git a/llvm/test/TableGen/directive2.td b/llvm/test/TableGen/directive2.td
index 96022d7647440..eaaf82ddaaf41 100644
--- a/llvm/test/TableGen/directive2.td
+++ b/llvm/test/TableGen/directive2.td
@@ -159,8 +159,7 @@ def TDL_DirA : Directive<[Spelling<"dira">]> {
 // IMPL:      #ifdef GEN_FLANG_DIRECTIVE_CLAUSE_SETS
 // IMPL-NEXT: #undef GEN_FLANG_DIRECTIVE_CLAUSE_SETS
 // IMPL-EMPTY:
-// IMPL-NEXT: namespace llvm {
-// IMPL-NEXT: namespace tdl {
+// IMPL-NEXT: namespace llvm::tdl {
 // IMPL-EMPTY:
 // IMPL-NEXT:   // Sets for dira
 // IMPL-EMPTY:
@@ -177,8 +176,8 @@ def TDL_DirA : Directive<[Spelling<"dira">]> {
 // IMPL-EMPTY:
 // IMPL-NEXT:   static  requiredClauses_TDLD_dira {
 // IMPL-NEXT:   };
-// IMPL-NEXT: } // namespace tdl
-// IMPL-NEXT: } // namespace llvm
+// IMPL-EMPTY:
+// IMPL-NEXT: } // namespace llvm::tdl
 // IMPL-EMPTY:
 // IMPL-NEXT: #endif // GEN_FLANG_DIRECTIVE_CLAUSE_SETS
 // IMPL-EMPTY:
diff --git a/llvm/utils/TableGen/Basic/DirectiveEmitter.cpp b/llvm/utils/TableGen/Basic/DirectiveEmitter.cpp
index d33bf45595e2e..0bb743dc8a7f5 100644
--- a/llvm/utils/TableGen/Basic/DirectiveEmitter.cpp
+++ b/llvm/utils/TableGen/Basic/DirectiveEmitter.cpp
@@ -359,7 +359,6 @@ static void emitDirectivesDecl(const RecordKeeper &Records, raw_ostream &OS) {
     OS << "  static constexpr bool is_iterable = true;\n";
     OS << "};\n";
   }
-  LlvmNS.close();
 }
 
 // Given a list of spellings (for a given clause/directive), order them
@@ -931,27 +930,20 @@ static void generateClauseSet(ArrayRef<const Record *> VerClauses,
 // Generate an enum set for the 4 kinds of clauses linked to a directive.
 static void generateDirectiveClauseSets(const DirectiveLanguage &DirLang,
                                         Frontend FE, raw_ostream &OS) {
+  IfDefEmitter Scope(OS, "GEN_" + getFESpelling(FE).upper() +
+                             "_DIRECTIVE_CLAUSE_SETS");
 
-  std::string IfDefName{"GEN_"};
-  IfDefName += getFESpelling(FE).upper();
-  IfDefName += "_DIRECTIVE_CLAUSE_SETS";
-  IfDefEmitter Scope(OS, IfDefName);
-
-  StringRef Namespace =
-      getFESpelling(FE == Frontend::Flang ? Frontend::LLVM : FE);
+  std::string Namespace =
+      getFESpelling(FE == Frontend::Flang ? Frontend::LLVM : FE).str();
   // The namespace has to be different for clang vs flang, as 2 structs with the
   // same name but different layout is UB.  So just put the 'clang' on in the
   // clang namespace.
-  OS << "namespace " << Namespace << " {\n";
-
-  // Open namespaces defined in the directive language.
-  SmallVector<StringRef, 2> Namespaces;
-  SplitString(DirLang.getCppNamespace(), Namespaces, "::");
-  for (auto Ns : Namespaces)
-    OS << "namespace " << Ns << " {\n";
+  // Additionally, open namespaces defined in the directive language.
+  if (!DirLang.getCppNamespace().empty())
+    Namespace += "::" + DirLang.getCppNamespace().str();
+  NamespaceEmitter NS(OS, Namespace);
 
   for (const Directive Dir : DirLang.getDirectives()) {
-    OS << "\n";
     OS << "// Sets for " << Dir.getSpellingForIdentifier() << "\n";
 
     generateClauseSet(Dir.getAllowedClauses(), OS, "allowedClauses_", Dir,
@@ -963,12 +955,6 @@ static void generateDirectiveClauseSets(const DirectiveLanguage &DirLang,
     generateClauseSet(Dir.getRequiredClauses(), OS, "requiredClauses_", Dir,
                       DirLang, FE);
   }
-
-  // Closing namespaces
-  for (auto Ns : reverse(Namespaces))
-    OS << "} // namespace " << Ns << "\n";
-
-  OS << "} // namespace " << Namespace << "\n";
 }
 
 // Generate a map of directive (key) with DirectiveClauses struct as values.
@@ -976,10 +962,8 @@ static void generateDirectiveClauseSets(const DirectiveLanguage &DirLang,
 // allowances (allowed, allowed once, allowed exclusive and required).
 static void generateDirectiveClauseMap(const DirectiveLanguage &DirLang,
                                        Frontend FE, raw_ostream &OS) {
-  std::string IfDefName{"GEN_"};
-  IfDefName += getFESpelling(FE).upper();
-  IfDefName += "_DIRECTIVE_CLAUSE_MAP";
-  IfDefEmitter Scope(OS, IfDefName);
+  IfDefEmitter Scope(OS, "GEN_" + getFESpelling(FE).upper() +
+                             "_DIRECTIVE_CLAUSE_MAP");
 
   OS << "{\n";