diff --git a/clang/include/clang/Basic/DiagnosticCategories.h b/clang/include/clang/Basic/DiagnosticCategories.h
--- a/clang/include/clang/Basic/DiagnosticCategories.h
+++ b/clang/include/clang/Basic/DiagnosticCategories.h
@@ -21,7 +21,8 @@
     };
 
     enum class Group {
-#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups) GroupName,
+#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs)        \
+  GroupName,
 #include "clang/Basic/DiagnosticGroups.inc"
 #undef CATEGORY
 #undef DIAG_ENTRY
diff --git a/clang/include/clang/Basic/DiagnosticIDs.h b/clang/include/clang/Basic/DiagnosticIDs.h
--- a/clang/include/clang/Basic/DiagnosticIDs.h
+++ b/clang/include/clang/Basic/DiagnosticIDs.h
@@ -231,6 +231,9 @@
   /// "deprecated-declarations".
   static StringRef getWarningOptionForGroup(diag::Group);
 
+  /// Given a diagnostic group ID, return its documentation.
+  static StringRef getWarningOptionDocumentation(diag::Group GroupID);
+
   /// Given a group ID, returns the flag that toggles the group.
   /// For example, for "deprecated-declarations", returns
   /// Group::DeprecatedDeclarations.
diff --git a/clang/lib/Basic/DiagnosticIDs.cpp b/clang/lib/Basic/DiagnosticIDs.cpp
--- a/clang/lib/Basic/DiagnosticIDs.cpp
+++ b/clang/lib/Basic/DiagnosticIDs.cpp
@@ -607,6 +607,7 @@
     uint16_t NameOffset;
     uint16_t Members;
     uint16_t SubGroups;
+    StringRef Documentation;
 
     // String is stored with a pascal-style length byte.
     StringRef getName() const {
@@ -618,12 +619,17 @@
 
 // Second the table of options, sorted by name for fast binary lookup.
 static const WarningOption OptionTable[] = {
-#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups)              \
-  {FlagNameOffset, Members, SubGroups},
+#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs)        \
+  {FlagNameOffset, Members, SubGroups, Docs},
 #include "clang/Basic/DiagnosticGroups.inc"
 #undef DIAG_ENTRY
 };
 
+/// Given a diagnostic group ID, return its documentation.
+StringRef DiagnosticIDs::getWarningOptionDocumentation(diag::Group Group) {
+  return OptionTable[static_cast<int>(Group)].Documentation;
+}
+
 StringRef DiagnosticIDs::getWarningOptionForGroup(diag::Group Group) {
   return OptionTable[static_cast<int>(Group)].getName();
 }
diff --git a/clang/tools/diagtool/DiagnosticNames.cpp b/clang/tools/diagtool/DiagnosticNames.cpp
--- a/clang/tools/diagtool/DiagnosticNames.cpp
+++ b/clang/tools/diagtool/DiagnosticNames.cpp
@@ -66,7 +66,7 @@
 
 // Second the table of options, sorted by name for fast binary lookup.
 static const GroupRecord OptionTable[] = {
-#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups)              \
+#define DIAG_ENTRY(GroupName, FlagNameOffset, Members, SubGroups, Docs)        \
   {FlagNameOffset, Members, SubGroups},
 #include "clang/Basic/DiagnosticGroups.inc"
 #undef DIAG_ENTRY
diff --git a/clang/utils/TableGen/ClangDiagnosticsEmitter.cpp b/clang/utils/TableGen/ClangDiagnosticsEmitter.cpp
--- a/clang/utils/TableGen/ClangDiagnosticsEmitter.cpp
+++ b/clang/utils/TableGen/ClangDiagnosticsEmitter.cpp
@@ -1534,14 +1534,22 @@
     const bool hasSubGroups =
         !SubGroups.empty() || (IsPedantic && !GroupsInPedantic.empty());
     if (hasSubGroups) {
-      OS << "/* DiagSubGroup" << I.second.IDNo << " */ " << SubGroupIndex;
+      OS << "/* DiagSubGroup" << I.second.IDNo << " */ " << SubGroupIndex
+         << ", ";
       if (IsPedantic)
         SubGroupIndex += GroupsInPedantic.size();
       SubGroupIndex += SubGroups.size() + 1;
     } else {
-      OS << "0";
+      OS << "0, ";
     }
 
+    std::string Documentation = I.second.Defs.back()
+                                    ->getValue("Documentation")
+                                    ->getValue()
+                                    ->getAsUnquotedString();
+
+    OS << "R\"(" << StringRef(Documentation).trim() << ")\"";
+
     OS << ")\n";
   }
   OS << "#endif // DIAG_ENTRY\n\n";