diff --git a/clang/include/clang/Basic/CMakeLists.txt b/clang/include/clang/Basic/CMakeLists.txt
index 4d5e1eaa3fac..265ea1fc0649 100644
--- a/clang/include/clang/Basic/CMakeLists.txt
+++ b/clang/include/clang/Basic/CMakeLists.txt
@@ -13,6 +13,11 @@ macro(clang_diag_gen component)
     -gen-clang-diags-compat-ids -clang-component=${component}
     SOURCE Diagnostic.td
     TARGET ClangDiagnostic${component}CompatIDs)
+
+  clang_tablegen(Diagnostic${component}Interface.inc
+    -gen-clang-diags-iface -clang-component=${component}
+    SOURCE Diagnostic.td
+    TARGET ClangDiagnostic${component}Interface)
 endmacro(clang_diag_gen)
 
 clang_diag_gen(Analysis)
diff --git a/clang/include/clang/Basic/DiagnosticAST.h b/clang/include/clang/Basic/DiagnosticAST.h
index 41e2598f7cc3..be9e303d9262 100644
--- a/clang/include/clang/Basic/DiagnosticAST.h
+++ b/clang/include/clang/Basic/DiagnosticAST.h
@@ -10,44 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICAST_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define ASTSTART
-#include "clang/Basic/DiagnosticASTKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_AST_DIAGNOSTICS
-};
-
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticASTEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticASTCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticASTInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICAST_H
diff --git a/clang/include/clang/Basic/DiagnosticAnalysis.h b/clang/include/clang/Basic/DiagnosticAnalysis.h
index 5ead092b946c..8e2635ffbd78 100644
--- a/clang/include/clang/Basic/DiagnosticAnalysis.h
+++ b/clang/include/clang/Basic/DiagnosticAnalysis.h
@@ -10,43 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICANALYSIS_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define ANALYSISSTART
-#include "clang/Basic/DiagnosticAnalysisKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_ANALYSIS_DIAGNOSTICS
-};
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticAnalysisEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticAnalysisCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticAnalysisInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICANALYSIS_H
diff --git a/clang/include/clang/Basic/DiagnosticComment.h b/clang/include/clang/Basic/DiagnosticComment.h
index 08e66e805183..f2a325c4e167 100644
--- a/clang/include/clang/Basic/DiagnosticComment.h
+++ b/clang/include/clang/Basic/DiagnosticComment.h
@@ -10,44 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICCOMMENT_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define COMMENTSTART
-#include "clang/Basic/DiagnosticCommentKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_COMMENT_DIAGNOSTICS
-};
-
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticCommentEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticCommentCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticCommentInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICCOMMENT_H
diff --git a/clang/include/clang/Basic/DiagnosticCrossTU.h b/clang/include/clang/Basic/DiagnosticCrossTU.h
index 761716d78144..4c0aa8cd2669 100644
--- a/clang/include/clang/Basic/DiagnosticCrossTU.h
+++ b/clang/include/clang/Basic/DiagnosticCrossTU.h
@@ -10,44 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICCROSSTU_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define CROSSTUSTART
-#include "clang/Basic/DiagnosticCrossTUKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_CROSSTU_DIAGNOSTICS
-};
-
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticCrossTUEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticCrossTUCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticCrossTUInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICCROSSTU_H
diff --git a/clang/include/clang/Basic/DiagnosticDriver.h b/clang/include/clang/Basic/DiagnosticDriver.h
index 864a23a49e4c..e00dcedd68ab 100644
--- a/clang/include/clang/Basic/DiagnosticDriver.h
+++ b/clang/include/clang/Basic/DiagnosticDriver.h
@@ -10,44 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICDRIVER_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define DRIVERSTART
-#include "clang/Basic/DiagnosticDriverKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_DRIVER_DIAGNOSTICS
-};
-
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticDriverEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticDriverCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticDriverInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICDRIVER_H
diff --git a/clang/include/clang/Basic/DiagnosticFrontend.h b/clang/include/clang/Basic/DiagnosticFrontend.h
index 3506f05daae5..923ddd3b45ba 100644
--- a/clang/include/clang/Basic/DiagnosticFrontend.h
+++ b/clang/include/clang/Basic/DiagnosticFrontend.h
@@ -10,44 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICFRONTEND_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define FRONTENDSTART
-#include "clang/Basic/DiagnosticFrontendKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_FRONTEND_DIAGNOSTICS
-};
-
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticFrontendEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticFrontendCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticFrontendInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICFRONTEND_H
diff --git a/clang/include/clang/Basic/DiagnosticIDs.h b/clang/include/clang/Basic/DiagnosticIDs.h
index f936d4fb7a40..80d52a0d0111 100644
--- a/clang/include/clang/Basic/DiagnosticIDs.h
+++ b/clang/include/clang/Basic/DiagnosticIDs.h
@@ -71,17 +71,6 @@ namespace clang {
     /// All of the diagnostics that can be emitted by the frontend.
     typedef unsigned kind;
 
-    // Get typedefs for common diagnostics.
-    enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, CATEGORY,      \
-             NOWERROR, SHOWINSYSHEADER, SHOWINSYSMACRO, DEFFERABLE)            \
-  ENUM,
-#define COMMONSTART
-#include "clang/Basic/DiagnosticCommonKinds.inc"
-      NUM_BUILTIN_COMMON_DIAGNOSTICS
-#undef DIAG
-    };
-
     /// Enum values that allow the client to map NOTEs, WARNINGs, and EXTENSIONs
     /// to either Ignore (nothing), Remark (emit a remark), Warning
     /// (emit a warning) or Error (emit as an error).  It allows clients to
@@ -103,20 +92,13 @@ namespace clang {
       Remark          ///< A diagnostic that indicates normal progress through
                       ///< compilation.
     };
-  }
+  } // end namespace diag
+} // end namespace clang
 
-  namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                \
-    }                                                                          \
-    ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticCommonCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-  } // end namespace diag_compat
+// This has to be included *after* the DIAG_START_ enums above are defined.
+#include "clang/Basic/DiagnosticCommonInterface.inc"
 
+namespace clang {
 class DiagnosticMapping {
   LLVM_PREFERRED_TYPE(diag::Severity)
   unsigned Severity : 3;
diff --git a/clang/include/clang/Basic/DiagnosticInstallAPI.h b/clang/include/clang/Basic/DiagnosticInstallAPI.h
index 4619bfeea05a..9d814522270e 100644
--- a/clang/include/clang/Basic/DiagnosticInstallAPI.h
+++ b/clang/include/clang/Basic/DiagnosticInstallAPI.h
@@ -10,42 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICINSTALLAPI_H
 
 #include "clang/Basic/Diagnostic.h"
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define INSTALLAPISTART
-#include "clang/Basic/DiagnosticInstallAPIKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_INSTALLAPI_DIAGNOSTICS
-};
+#include "clang/Basic/DiagnosticInstallAPIInterface.inc"
 
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticInstallAPIEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticInstallAPICompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // namespace clang
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICINSTALLAPI_H
diff --git a/clang/include/clang/Basic/DiagnosticLex.h b/clang/include/clang/Basic/DiagnosticLex.h
index 6fa90f785bbf..f20f4fcd2d3d 100644
--- a/clang/include/clang/Basic/DiagnosticLex.h
+++ b/clang/include/clang/Basic/DiagnosticLex.h
@@ -10,43 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICLEX_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define LEXSTART
-#include "clang/Basic/DiagnosticLexKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_LEX_DIAGNOSTICS
-};
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticLexEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticLexCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticLexInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICLEX_H
diff --git a/clang/include/clang/Basic/DiagnosticParse.h b/clang/include/clang/Basic/DiagnosticParse.h
index e2a4368a59c4..1e025bdf0241 100644
--- a/clang/include/clang/Basic/DiagnosticParse.h
+++ b/clang/include/clang/Basic/DiagnosticParse.h
@@ -10,44 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICPARSE_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define PARSESTART
-#include "clang/Basic/DiagnosticParseKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_PARSE_DIAGNOSTICS
-};
-
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticParseEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticParseCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticParseInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICPARSE_H
diff --git a/clang/include/clang/Basic/DiagnosticRefactoring.h b/clang/include/clang/Basic/DiagnosticRefactoring.h
index b3f3a10925f0..380060e51d0f 100644
--- a/clang/include/clang/Basic/DiagnosticRefactoring.h
+++ b/clang/include/clang/Basic/DiagnosticRefactoring.h
@@ -10,44 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICREFACTORING_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define REFACTORINGSTART
-#include "clang/Basic/DiagnosticRefactoringKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_REFACTORING_DIAGNOSTICS
-};
-
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticRefactoringEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticRefactoringCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticRefactoringInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICREFACTORING_H
diff --git a/clang/include/clang/Basic/DiagnosticSema.h b/clang/include/clang/Basic/DiagnosticSema.h
index 943b2f64f427..26a5f719a299 100644
--- a/clang/include/clang/Basic/DiagnosticSema.h
+++ b/clang/include/clang/Basic/DiagnosticSema.h
@@ -10,45 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICSEMA_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define SEMASTART
-#include "clang/Basic/DiagnosticSemaKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_SEMA_DIAGNOSTICS
-};
-
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticSemaEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticSemaCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticSemaInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICSEMA_H
diff --git a/clang/include/clang/Basic/DiagnosticSerialization.h b/clang/include/clang/Basic/DiagnosticSerialization.h
index c8fb034e9bd4..27df12e5f098 100644
--- a/clang/include/clang/Basic/DiagnosticSerialization.h
+++ b/clang/include/clang/Basic/DiagnosticSerialization.h
@@ -10,44 +10,6 @@
 #define LLVM_CLANG_BASIC_DIAGNOSTICSERIALIZATION_H
 
 #include "clang/Basic/Diagnostic.h"
-
-namespace clang {
-namespace diag {
-enum {
-#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
-             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
-  ENUM,
-#define SERIALIZATIONSTART
-#include "clang/Basic/DiagnosticSerializationKinds.inc"
-#undef DIAG
-  NUM_BUILTIN_SERIALIZATION_DIAGNOSTICS
-};
-
-#define DIAG_ENUM(ENUM_NAME)                                                   \
-  namespace ENUM_NAME {                                                        \
-  enum {
-#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
-#define DIAG_ENUM_END()                                                        \
-  }                                                                            \
-  ;                                                                            \
-  }
-#include "clang/Basic/DiagnosticSerializationEnums.inc"
-#undef DIAG_ENUM_END
-#undef DIAG_ENUM_ITEM
-#undef DIAG_ENUM
-} // end namespace diag
-
-namespace diag_compat {
-#define DIAG_COMPAT_IDS_BEGIN() enum {
-#define DIAG_COMPAT_IDS_END()                                                  \
-  }                                                                            \
-  ;
-#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
-#include "clang/Basic/DiagnosticSerializationCompatIDs.inc"
-#undef DIAG_COMPAT_ID
-#undef DIAG_COMPAT_IDS_BEGIN
-#undef DIAG_COMPAT_IDS_END
-} // end namespace diag_compat
-} // end namespace clang
+#include "clang/Basic/DiagnosticSerializationInterface.inc"
 
 #endif // LLVM_CLANG_BASIC_DIAGNOSTICSERIALIZATION_H
diff --git a/clang/utils/TableGen/ClangDiagnosticsEmitter.cpp b/clang/utils/TableGen/ClangDiagnosticsEmitter.cpp
index 73facbc91671..cb309fb2e19e 100644
--- a/clang/utils/TableGen/ClangDiagnosticsEmitter.cpp
+++ b/clang/utils/TableGen/ClangDiagnosticsEmitter.cpp
@@ -20,6 +20,7 @@
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/Casting.h"
+#include "llvm/Support/Format.h"
 #include "llvm/TableGen/Error.h"
 #include "llvm/TableGen/Record.h"
 #include "llvm/TableGen/StringToOffsetTable.h"
@@ -1562,6 +1563,60 @@ void clang::EmitClangDiagsCompatIDs(const llvm::RecordKeeper &Records,
     OS << "DIAG_COMPAT_IDS_END()\n";
 }
 
+/// ClangDiagsIntefaceEmitter - Emit the diagnostics interface header for
+/// a Clang component.
+void clang::EmitClangDiagsInterface(llvm::raw_ostream &OS,
+                                    const std::string &Component) {
+  if (Component.empty())
+    PrintFatalError("'-gen-clang-diags-iface' requires a component name");
+
+  std::string ComponentUpper = StringRef(Component).upper();
+  const char *Comp = Component.c_str();
+  const char *Upper = ComponentUpper.c_str();
+
+  OS << llvm::format(R"c++(
+namespace clang {
+namespace diag {
+enum {
+#define DIAG(ENUM, FLAGS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
+             SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
+  ENUM,
+#define %sSTART
+#include "clang/Basic/Diagnostic%sKinds.inc"
+#undef DIAG
+  NUM_BUILTIN_%s_DIAGNOSTICS
+};
+
+#define DIAG_ENUM(ENUM_NAME)                                                   \
+  namespace ENUM_NAME {                                                        \
+  enum {
+#define DIAG_ENUM_ITEM(IDX, NAME) NAME = IDX,
+#define DIAG_ENUM_END()                                                        \
+  }                                                                            \
+  ;                                                                            \
+  }
+#include "clang/Basic/Diagnostic%sEnums.inc"
+#undef DIAG_ENUM_END
+#undef DIAG_ENUM_ITEM
+#undef DIAG_ENUM
+} // end namespace diag
+
+namespace diag_compat {
+#define DIAG_COMPAT_IDS_BEGIN() enum {
+#define DIAG_COMPAT_IDS_END()                                                  \
+  }                                                                            \
+  ;
+#define DIAG_COMPAT_ID(IDX, NAME, ...) NAME = IDX,
+#include "clang/Basic/Diagnostic%sCompatIDs.inc"
+#undef DIAG_COMPAT_ID
+#undef DIAG_COMPAT_IDS_BEGIN
+#undef DIAG_COMPAT_IDS_END
+} // end namespace diag_compat
+} // end namespace clang
+)c++",
+                     Upper, Comp, Upper, Comp, Comp);
+}
+
 /// ClangDiagsEnumsEmitter - The top-level class emits .def files containing
 /// declarations of Clang diagnostic enums for selects.
 void clang::EmitClangDiagsEnums(const RecordKeeper &Records, raw_ostream &OS,
diff --git a/clang/utils/TableGen/TableGen.cpp b/clang/utils/TableGen/TableGen.cpp
index 4d3d56ed4b9d..a2c6f002f735 100644
--- a/clang/utils/TableGen/TableGen.cpp
+++ b/clang/utils/TableGen/TableGen.cpp
@@ -53,6 +53,7 @@ enum ActionType {
   GenClangDiagsEnums,
   GenClangDiagGroups,
   GenClangDiagsIndexName,
+  GenClangDiagsInterface,
   GenClangCommentNodes,
   GenClangDeclNodes,
   GenClangStmtNodes,
@@ -187,6 +188,8 @@ cl::opt<ActionType> Action(
                    "Generate Clang diagnostic groups"),
         clEnumValN(GenClangDiagsIndexName, "gen-clang-diags-index-name",
                    "Generate Clang diagnostic name index"),
+        clEnumValN(GenClangDiagsInterface, "gen-clang-diags-iface",
+                   "Generate Clang diagnostic interface headers"),
         clEnumValN(GenClangBasicReader, "gen-clang-basic-reader",
                    "Generate Clang BasicReader classes"),
         clEnumValN(GenClangBasicWriter, "gen-clang-basic-writer",
@@ -417,6 +420,9 @@ bool ClangTableGenMain(raw_ostream &OS, const RecordKeeper &Records) {
   case GenClangDiagsIndexName:
     EmitClangDiagsIndexName(Records, OS);
     break;
+  case GenClangDiagsInterface:
+    EmitClangDiagsInterface(OS, ClangComponent);
+    break;
   case GenClangCommentNodes:
     EmitClangASTNodes(Records, OS, CommentNodeClassName, "");
     break;
diff --git a/clang/utils/TableGen/TableGenBackends.h b/clang/utils/TableGen/TableGenBackends.h
index c26ce2825ea9..54031147d38e 100644
--- a/clang/utils/TableGen/TableGenBackends.h
+++ b/clang/utils/TableGen/TableGenBackends.h
@@ -102,6 +102,8 @@ void EmitClangDiagGroups(const llvm::RecordKeeper &Records,
                          llvm::raw_ostream &OS);
 void EmitClangDiagsIndexName(const llvm::RecordKeeper &Records,
                              llvm::raw_ostream &OS);
+void EmitClangDiagsInterface(llvm::raw_ostream &OS,
+                             const std::string &Component);
 
 void EmitClangSACheckers(const llvm::RecordKeeper &Records,
                          llvm::raw_ostream &OS);