diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 8e076843849e..5f17a406ec4d 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -17,6 +17,7 @@ def : DiagGroup<"cast-align">;
 def : DiagGroup<"cast-qual">;
 def : DiagGroup<"char-align">;
 def : DiagGroup<"char-subscripts">;
+def Comment : DiagGroup<"comment">;
 def : DiagGroup<"declaration-after-statement">;
 def : DiagGroup<"error-implicit-function-declaration">;
 def : DiagGroup<"format-security">;
@@ -31,8 +32,6 @@ def : DiagGroup<"missing-declarations">;
 def : DiagGroup<"missing-format-attribute">;
 def : DiagGroup<"nested-externs">;
 def : DiagGroup<"newline-eof">;
-def : DiagGroup<"no-#warnings">;
-def : DiagGroup<"no-comment">;
 def : DiagGroup<"format-y2k">;
 def : DiagGroup<"long-long">;
 def : DiagGroup<"missing-field-initializers">;
@@ -69,6 +68,7 @@ def : DiagGroup<"", [Extra]>;  // -W = -Wextra
 
 // Aggregation warning settings.
 def Most : DiagGroup<"most", [
+    Comment,
     ImplicitFunctionDeclare,
     Switch,
     Trigraphs,
diff --git a/clang/include/clang/Basic/DiagnosticLexKinds.td b/clang/include/clang/Basic/DiagnosticLexKinds.td
index 32ce9e383eb8..77406f5652db 100644
--- a/clang/include/clang/Basic/DiagnosticLexKinds.td
+++ b/clang/include/clang/Basic/DiagnosticLexKinds.td
@@ -16,9 +16,11 @@ let Component = "Lex" in {
 def null_in_string : Warning<"null character(s) preserved in string literal">;
 def null_in_char : Warning<"null character(s) preserved in character literal">;
 def null_in_file : Warning<"null character ignored">;
-def warn_nested_block_comment : Warning<"'/*' within block comment">;
+def warn_nested_block_comment : Warning<"'/*' within block comment">,
+  InGroup<Comment>;
 def escaped_newline_block_comment_end : Warning<
-  "escaped newline between */ characters at block comment end">;
+  "escaped newline between */ characters at block comment end">,
+  InGroup<Comment>;
 def backslash_newline_space : Warning<
   "backslash and newline separated by space">;
 
@@ -31,9 +33,11 @@ def trigraph_ends_block_comment : Warning<"trigraph ends block comment">,
 def trigraph_converted : Warning<"trigraph converted to '%0' character">,
     InGroup<Trigraphs>;
 
-def ext_multi_line_bcpl_comment : Extension<"multi-line // comment">;
+def ext_multi_line_bcpl_comment : Extension<"multi-line // comment">,
+    InGroup<Comment>;
 def ext_bcpl_comment : Extension<
-  "// comments are not allowed in this language">;
+  "// comments are not allowed in this language">,
+  InGroup<Comment>;
 def ext_no_newline_eof : Extension<"no newline at end of file">;
 def ext_backslash_newline_eof : Extension<"backslash-newline at end of file">;
 def ext_dollar_in_identifier : Extension<"'$' in identifier">;