diff --git a/llvm/include/llvm/Frontend/Directive/DirectiveBase.td b/llvm/include/llvm/Frontend/Directive/DirectiveBase.td
--- a/llvm/include/llvm/Frontend/Directive/DirectiveBase.td
+++ b/llvm/include/llvm/Frontend/Directive/DirectiveBase.td
@@ -39,6 +39,10 @@
 
   // Generate include and macro to enable LLVM BitmaskEnum.
   bit enableBitmaskEnumInNamespace = 0;
+
+  // Header file included in the implementation code generated. Ususally the
+  // output file of the declaration code generation. Can be left blank.
+  string includeHeader = "";
 }
 
 // Information about a specific clause.
diff --git a/llvm/include/llvm/Frontend/OpenMP/CMakeLists.txt b/llvm/include/llvm/Frontend/OpenMP/CMakeLists.txt
--- a/llvm/include/llvm/Frontend/OpenMP/CMakeLists.txt
+++ b/llvm/include/llvm/Frontend/OpenMP/CMakeLists.txt
@@ -1,4 +1,3 @@
 set(LLVM_TARGET_DEFINITIONS OMP.td)
 tablegen(LLVM OMP.h.inc --gen-directive-decl)
-tablegen(LLVM OMP.cpp.inc --gen-directive-impl)
 add_public_tablegen_target(omp_gen)
diff --git a/llvm/include/llvm/Frontend/OpenMP/OMP.td b/llvm/include/llvm/Frontend/OpenMP/OMP.td
--- a/llvm/include/llvm/Frontend/OpenMP/OMP.td
+++ b/llvm/include/llvm/Frontend/OpenMP/OMP.td
@@ -23,6 +23,7 @@
   let clausePrefix = "OMPC_";
   let makeEnumAvailableInNamespace = 1;
   let enableBitmaskEnumInNamespace = 1;
+  let includeHeader = "llvm/Frontend/OpenMP/OMP.h.inc";
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/llvm/lib/Frontend/OpenMP/CMakeLists.txt b/llvm/lib/Frontend/OpenMP/CMakeLists.txt
--- a/llvm/lib/Frontend/OpenMP/CMakeLists.txt
+++ b/llvm/lib/Frontend/OpenMP/CMakeLists.txt
@@ -1,5 +1,9 @@
+set(LLVM_TARGET_DEFINITIONS ${LLVM_MAIN_INCLUDE_DIR}/llvm/Frontend/OpenMP/OMP.td)
+tablegen(LLVM OMP.cpp --gen-directive-impl)
+add_public_tablegen_target(omp_cpp)
+
 add_llvm_component_library(LLVMFrontendOpenMP
-  OMPConstants.cpp
+  OMP.cpp # Generated by tablegen above
   OMPContext.cpp
   OMPIRBuilder.cpp
 
@@ -10,4 +14,5 @@
   DEPENDS
   intrinsics_gen
   omp_gen
-  )
+  omp_cpp
+  )
\ No newline at end of file
diff --git a/llvm/lib/Frontend/OpenMP/OMPConstants.cpp b/llvm/lib/Frontend/OpenMP/OMPConstants.cpp
deleted file mode 100644
--- a/llvm/lib/Frontend/OpenMP/OMPConstants.cpp
+++ /dev/null
@@ -1,21 +0,0 @@
-//===- OMPConstants.cpp - Helpers related to OpenMP code generation ---===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Frontend/OpenMP/OMPConstants.h"
-
-#include "llvm/ADT/StringRef.h"
-#include "llvm/ADT/StringSwitch.h"
-#include "llvm/IR/Module.h"
-#include "llvm/IR/Type.h"
-
-using namespace llvm;
-using namespace omp;
-
-#include "llvm/Frontend/OpenMP/OMP.cpp.inc"
diff --git a/llvm/test/TableGen/directive1.td b/llvm/test/TableGen/directive1.td
--- a/llvm/test/TableGen/directive1.td
+++ b/llvm/test/TableGen/directive1.td
@@ -72,7 +72,13 @@
 // CHECK-NEXT:  #endif // LLVM_Tdl_INC
 
 
-// IMPL:       Directive llvm::tdl::getTdlDirectiveKind(llvm::StringRef Str) {
+// IMPL:       #include "llvm/ADT/StringRef.h"
+// IMPL-NEXT:  #include "llvm/ADT/StringSwitch.h"
+// IMPL-EMPTY:
+// IMPL-NEXT:  using namespace llvm;
+// IMPL-NEXT:  using namespace tdl;
+// IMPL-EMPTY:
+// IMPL-NEXT:  Directive llvm::tdl::getTdlDirectiveKind(llvm::StringRef Str) {
 // IMPL-NEXT:    return llvm::StringSwitch<Directive>(Str)
 // IMPL-NEXT:      .Case("dira",TDLD_dira)
 // IMPL-NEXT:      .Default(TDLD_dira);
diff --git a/llvm/test/TableGen/directive2.td b/llvm/test/TableGen/directive2.td
--- a/llvm/test/TableGen/directive2.td
+++ b/llvm/test/TableGen/directive2.td
@@ -9,6 +9,7 @@
   let cppNamespace = "tdl";
   let directivePrefix = "TDLD_";
   let clausePrefix = "TDLC_";
+  let includeHeader = "tdl.h.inc";
 }
 
 def TDLC_ClauseA : Clause<"clausea"> {
@@ -62,7 +63,14 @@
 // CHECK-NEXT:  } // namespace llvm
 // CHECK-NEXT:  #endif // LLVM_Tdl_INC
 
-
+// IMPL:       #include "tdl.h.inc"
+// IMPL-EMPTY:
+// IMPL-NEXT:  #include "llvm/ADT/StringRef.h"
+// IMPL-NEXT:  #include "llvm/ADT/StringSwitch.h"
+// IMPL-EMPTY:
+// IMPL-NEXT:  using namespace llvm;
+// IMPL-NEXT:  using namespace tdl;
+// IMPL-EMPTY:
 // IMPL:       Directive llvm::tdl::getTdlDirectiveKind(llvm::StringRef Str) {
 // IMPL-NEXT:    return llvm::StringSwitch<Directive>(Str)
 // IMPL-NEXT:      .Case("dira",TDLD_dira)
diff --git a/llvm/utils/TableGen/DirectiveEmitter.cpp b/llvm/utils/TableGen/DirectiveEmitter.cpp
--- a/llvm/utils/TableGen/DirectiveEmitter.cpp
+++ b/llvm/utils/TableGen/DirectiveEmitter.cpp
@@ -284,10 +284,24 @@
   StringRef LanguageName = DirectiveLanguage->getValueAsString("name");
   StringRef ClausePrefix = DirectiveLanguage->getValueAsString("clausePrefix");
   StringRef CppNamespace = DirectiveLanguage->getValueAsString("cppNamespace");
+  StringRef IncludeHeader =
+      DirectiveLanguage->getValueAsString("includeHeader");
 
   const auto &Directives = Records.getAllDerivedDefinitions("Directive");
   const auto &Clauses = Records.getAllDerivedDefinitions("Clause");
 
+  if (!IncludeHeader.empty())
+    OS << "#include \"" << IncludeHeader << "\"\n\n";
+
+  OS << "#include \"llvm/ADT/StringRef.h\"\n";
+  OS << "#include \"llvm/ADT/StringSwitch.h\"\n";
+  OS << "\n";
+  OS << "using namespace llvm;\n";
+  llvm::SmallVector<StringRef, 2> Namespaces;
+  llvm::SplitString(CppNamespace, Namespaces, "::");
+  for (auto Ns : Namespaces)
+    OS << "using namespace " << Ns << ";\n";
+
   // getDirectiveKind(StringRef Str)
   GenerateGetKind(Directives, OS, "Directive", DirectivePrefix, LanguageName,
                   CppNamespace, /*ImplicitAsUnknown=*/false);