diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -821,8 +821,10 @@
 //  under separate flags.
 //
 def UnreachableCodeLoopIncrement : DiagGroup<"unreachable-code-loop-increment">;
+def UnreachableCodeFallthrough : DiagGroup<"unreachable-code-fallthrough">;
 def UnreachableCode : DiagGroup<"unreachable-code",
-                                [UnreachableCodeLoopIncrement]>;
+                                [UnreachableCodeLoopIncrement,
+                                 UnreachableCodeFallthrough]>;
 def UnreachableCodeBreak : DiagGroup<"unreachable-code-break">;
 def UnreachableCodeReturn : DiagGroup<"unreachable-code-return">;
 def UnreachableCodeAggressive : DiagGroup<"unreachable-code-aggressive",
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -682,6 +682,9 @@
 def warn_unreachable_loop_increment : Warning<
   "loop will run at most once (loop increment never executed)">,
   InGroup<UnreachableCodeLoopIncrement>, DefaultIgnore;
+def warn_unreachable_fallthrough_attr : Warning<
+  "fallthrough annotation in unreachable code">,
+  InGroup<UnreachableCodeFallthrough>, DefaultIgnore;
 def note_unreachable_silence : Note<
   "silence by adding parentheses to mark code as explicitly dead">;
 
@@ -9578,9 +9581,6 @@
   "fallthrough annotation is outside switch statement">;
 def err_fallthrough_attr_invalid_placement : Error<
   "fallthrough annotation does not directly precede switch label">;
-def warn_fallthrough_attr_unreachable : Warning<
-  "fallthrough annotation in unreachable code">,
-  InGroup<ImplicitFallthrough>, DefaultIgnore;
 
 def warn_unreachable_default : Warning<
   "default label in switch which covers all enumeration values">,
diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -1125,7 +1125,7 @@
                 // unreachable in all instantiations of the template.
                 if (!IsTemplateInstantiation)
                   S.Diag(AS->getBeginLoc(),
-                         diag::warn_fallthrough_attr_unreachable);
+                         diag::warn_unreachable_fallthrough_attr);
                 markFallthroughVisited(AS);
                 ++AnnotatedCnt;
                 break;
diff --git a/clang/test/SemaCXX/P30636.cpp b/clang/test/SemaCXX/P30636.cpp
--- a/clang/test/SemaCXX/P30636.cpp
+++ b/clang/test/SemaCXX/P30636.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wimplicit-fallthrough %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wimplicit-fallthrough -Wunreachable-code-fallthrough %s
 // expected-no-diagnostics
 
 template<bool param>
diff --git a/clang/test/SemaCXX/switch-implicit-fallthrough.cpp b/clang/test/SemaCXX/switch-implicit-fallthrough.cpp
--- a/clang/test/SemaCXX/switch-implicit-fallthrough.cpp
+++ b/clang/test/SemaCXX/switch-implicit-fallthrough.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wimplicit-fallthrough %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 -Wimplicit-fallthrough -Wunreachable-code-fallthrough %s
 
 
 int fallthrough(int n) {
@@ -193,6 +193,26 @@
         ;
   }
 
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunreachable-code-fallthrough"
+  switch (n) {
+      n += 300;
+      [[clang::fallthrough]];  // no warning here
+    case 221:
+      return 1;
+      [[clang::fallthrough]];  // no warning here
+    case 222:
+      return 2;
+      __attribute__((fallthrough)); // no warning here
+    case 223:
+      if (1)
+        return 3;
+      __attribute__((fallthrough)); // no warning here
+    case 224:
+      n += 400;
+  }
+#pragma clang diagnostic pop
+
   long p = static_cast<long>(n) * n;
   switch (sizeof(p)) {
     case 9: