diff --git a/clang/include/clang/Basic/AllDiagnosticKinds.inc b/clang/include/clang/Basic/AllDiagnosticKinds.inc
new file mode 100644
index 0000000000000..a946b4a640ac6
--- /dev/null
+++ b/clang/include/clang/Basic/AllDiagnosticKinds.inc
@@ -0,0 +1,33 @@
+//===--- AllDiagnosticKinds.inc----------------------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Defines the Diagnostic IDs in ID sorted order. The order is dictated by
+/// the enum in DiagnosticIDs.h#L49-L65.
+///
+//===----------------------------------------------------------------------===//
+
+// Turn off clang-format, as the order of the includes are important to make
+// sure tables based on Diagnostic IDs are partitioned/sorted based on
+// DiagID.
+
+// clang-format off
+#include "clang/Basic/DiagnosticCommonKinds.inc"
+#include "clang/Basic/DiagnosticDriverKinds.inc"
+#include "clang/Basic/DiagnosticFrontendKinds.inc"
+#include "clang/Basic/DiagnosticSerializationKinds.inc"
+#include "clang/Basic/DiagnosticLexKinds.inc"
+#include "clang/Basic/DiagnosticParseKinds.inc"
+#include "clang/Basic/DiagnosticASTKinds.inc"
+#include "clang/Basic/DiagnosticCommentKinds.inc"
+#include "clang/Basic/DiagnosticCrossTUKinds.inc"
+#include "clang/Basic/DiagnosticSemaKinds.inc"
+#include "clang/Basic/DiagnosticAnalysisKinds.inc"
+#include "clang/Basic/DiagnosticRefactoringKinds.inc"
+#include "clang/Basic/DiagnosticInstallAPIKinds.inc"
+// clang-format on
diff --git a/clang/lib/Basic/DiagnosticIDs.cpp b/clang/lib/Basic/DiagnosticIDs.cpp
index d77f28c80b2eb..81194bbf2538e 100644
--- a/clang/lib/Basic/DiagnosticIDs.cpp
+++ b/clang/lib/Basic/DiagnosticIDs.cpp
@@ -37,21 +37,7 @@ struct StaticDiagInfoDescriptionStringTable {
 #define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
              SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
   char ENUM##_desc[sizeof(DESC)];
-  // clang-format off
-#include "clang/Basic/DiagnosticCommonKinds.inc"
-#include "clang/Basic/DiagnosticDriverKinds.inc"
-#include "clang/Basic/DiagnosticFrontendKinds.inc"
-#include "clang/Basic/DiagnosticSerializationKinds.inc"
-#include "clang/Basic/DiagnosticLexKinds.inc"
-#include "clang/Basic/DiagnosticParseKinds.inc"
-#include "clang/Basic/DiagnosticASTKinds.inc"
-#include "clang/Basic/DiagnosticCommentKinds.inc"
-#include "clang/Basic/DiagnosticCrossTUKinds.inc"
-#include "clang/Basic/DiagnosticSemaKinds.inc"
-#include "clang/Basic/DiagnosticAnalysisKinds.inc"
-#include "clang/Basic/DiagnosticRefactoringKinds.inc"
-#include "clang/Basic/DiagnosticInstallAPIKinds.inc"
-  // clang-format on
+#include "clang/Basic/AllDiagnosticKinds.inc"
 #undef DIAG
 };
 
@@ -59,21 +45,7 @@ const StaticDiagInfoDescriptionStringTable StaticDiagInfoDescriptions = {
 #define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
              SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
   DESC,
-// clang-format off
-#include "clang/Basic/DiagnosticCommonKinds.inc"
-#include "clang/Basic/DiagnosticDriverKinds.inc"
-#include "clang/Basic/DiagnosticFrontendKinds.inc"
-#include "clang/Basic/DiagnosticSerializationKinds.inc"
-#include "clang/Basic/DiagnosticLexKinds.inc"
-#include "clang/Basic/DiagnosticParseKinds.inc"
-#include "clang/Basic/DiagnosticASTKinds.inc"
-#include "clang/Basic/DiagnosticCommentKinds.inc"
-#include "clang/Basic/DiagnosticCrossTUKinds.inc"
-#include "clang/Basic/DiagnosticSemaKinds.inc"
-#include "clang/Basic/DiagnosticAnalysisKinds.inc"
-#include "clang/Basic/DiagnosticRefactoringKinds.inc"
-#include "clang/Basic/DiagnosticInstallAPIKinds.inc"
-// clang-format on
+#include "clang/Basic/AllDiagnosticKinds.inc"
 #undef DIAG
 };
 
@@ -85,21 +57,7 @@ const uint32_t StaticDiagInfoDescriptionOffsets[] = {
 #define DIAG(ENUM, CLASS, DEFAULT_SEVERITY, DESC, GROUP, SFINAE, NOWERROR,     \
              SHOWINSYSHEADER, SHOWINSYSMACRO, DEFERRABLE, CATEGORY)            \
   offsetof(StaticDiagInfoDescriptionStringTable, ENUM##_desc),
-// clang-format off
-#include "clang/Basic/DiagnosticCommonKinds.inc"
-#include "clang/Basic/DiagnosticDriverKinds.inc"
-#include "clang/Basic/DiagnosticFrontendKinds.inc"
-#include "clang/Basic/DiagnosticSerializationKinds.inc"
-#include "clang/Basic/DiagnosticLexKinds.inc"
-#include "clang/Basic/DiagnosticParseKinds.inc"
-#include "clang/Basic/DiagnosticASTKinds.inc"
-#include "clang/Basic/DiagnosticCommentKinds.inc"
-#include "clang/Basic/DiagnosticCrossTUKinds.inc"
-#include "clang/Basic/DiagnosticSemaKinds.inc"
-#include "clang/Basic/DiagnosticAnalysisKinds.inc"
-#include "clang/Basic/DiagnosticRefactoringKinds.inc"
-#include "clang/Basic/DiagnosticInstallAPIKinds.inc"
-// clang-format on
+#include "clang/Basic/AllDiagnosticKinds.inc"
 #undef DIAG
 };
 
diff --git a/clang/tools/diagtool/DiagnosticNames.cpp b/clang/tools/diagtool/DiagnosticNames.cpp
index eb90f082437b3..c3a3002889c73 100644
--- a/clang/tools/diagtool/DiagnosticNames.cpp
+++ b/clang/tools/diagtool/DiagnosticNames.cpp
@@ -23,26 +23,13 @@ llvm::ArrayRef<DiagnosticRecord> diagtool::getBuiltinDiagnosticsByName() {
   return llvm::ArrayRef(BuiltinDiagnosticsByName);
 }
 
-
 // FIXME: Is it worth having two tables, especially when this one can get
 // out of sync easily?
 static const DiagnosticRecord BuiltinDiagnosticsByID[] = {
 #define DIAG(ENUM, CLASS, DEFAULT_MAPPING, DESC, GROUP, SFINAE, NOWERROR,      \
              SHOWINSYSHEADER, SHOWINSYSMACRO, DEFER, CATEGORY)                 \
   {#ENUM, diag::ENUM, STR_SIZE(#ENUM, uint8_t)},
-#include "clang/Basic/DiagnosticCommonKinds.inc"
-#include "clang/Basic/DiagnosticCrossTUKinds.inc"
-#include "clang/Basic/DiagnosticDriverKinds.inc"
-#include "clang/Basic/DiagnosticFrontendKinds.inc"
-#include "clang/Basic/DiagnosticSerializationKinds.inc"
-#include "clang/Basic/DiagnosticLexKinds.inc"
-#include "clang/Basic/DiagnosticParseKinds.inc"
-#include "clang/Basic/DiagnosticASTKinds.inc"
-#include "clang/Basic/DiagnosticCommentKinds.inc"
-#include "clang/Basic/DiagnosticSemaKinds.inc"
-#include "clang/Basic/DiagnosticAnalysisKinds.inc"
-#include "clang/Basic/DiagnosticRefactoringKinds.inc"
-#include "clang/Basic/DiagnosticInstallAPIKinds.inc"
+#include "clang/Basic/AllDiagnosticKinds.inc"
 #undef DIAG
 };
 
@@ -54,6 +41,13 @@ static bool orderByID(const DiagnosticRecord &Left,
 const DiagnosticRecord &diagtool::getDiagnosticForID(short DiagID) {
   DiagnosticRecord Key = {nullptr, DiagID, 0};
 
+  // The requirement for lower_bound to produce a valid result it is
+  // enough if the BuiltinDiagnosticsByID is partitioned (by DiagID),
+  // but as we want this function to work for all possible values of
+  // DiagID sent in as argument it is better to right away check if
+  // BuiltinDiagnosticsByID is sorted.
+  assert(llvm::is_sorted(BuiltinDiagnosticsByID, orderByID) &&
+         "IDs in BuiltinDiagnosticsByID must be sorted.");
   const DiagnosticRecord *Result =
       llvm::lower_bound(BuiltinDiagnosticsByID, Key, orderByID);
   assert(Result && "diagnostic not found; table may be out of date");