Index: include/clang/Basic/LangOptions.def
===================================================================
--- include/clang/Basic/LangOptions.def
+++ include/clang/Basic/LangOptions.def
@@ -167,6 +167,7 @@
 
 LANGOPT(AssumeSaneOperatorNew , 1, 1, "implicit __attribute__((malloc)) for C++'s new operators")
 LANGOPT(SizedDeallocation , 1, 0, "enable sized deallocation functions")
+LANGOPT(ConceptsTS , 1, 0, "enable C++ Extensions for Concepts")
 BENIGN_LANGOPT(ElideConstructors , 1, 1, "C++ copy constructor elision")
 BENIGN_LANGOPT(DumpRecordLayouts , 1, 0, "dumping the layout of IRgen'd records")
 BENIGN_LANGOPT(DumpRecordLayoutsSimple , 1, 0, "dumping the layout of IRgen'd records in a simple form")
Index: include/clang/Driver/CC1Options.td
===================================================================
--- include/clang/Driver/CC1Options.td
+++ include/clang/Driver/CC1Options.td
@@ -365,6 +365,8 @@
   Flag<["-"], "fmodules-local-submodule-visibility">,
   HelpText<"Enforce name visibility rules across submodules of the same "
            "top-level module.">;
+def fconcepts_ts : Flag<["-"], "fconcepts-ts">,
+  HelpText<"Enable C++ Extensions for Concepts.">;
 
 let Group = Action_Group in {
 
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -1537,6 +1537,7 @@
   Opts.NoMathBuiltin = Args.hasArg(OPT_fno_math_builtin);
   Opts.AssumeSaneOperatorNew = !Args.hasArg(OPT_fno_assume_sane_operator_new);
   Opts.SizedDeallocation = Args.hasArg(OPT_fsized_deallocation);
+  Opts.ConceptsTS = Args.hasArg(OPT_fconcepts_ts);
   Opts.HeinousExtensions = Args.hasArg(OPT_fheinous_gnu_extensions);
   Opts.AccessControl = !Args.hasArg(OPT_fno_access_control);
   Opts.ElideConstructors = !Args.hasArg(OPT_fno_elide_constructors);
Index: lib/Frontend/InitPreprocessor.cpp
===================================================================
--- lib/Frontend/InitPreprocessor.cpp
+++ lib/Frontend/InitPreprocessor.cpp
@@ -453,6 +453,8 @@
   }
   if (LangOpts.SizedDeallocation)
     Builder.defineMacro("__cpp_sized_deallocation", "201309");
+  if (LangOpts.ConceptsTS)
+    Builder.defineMacro("__cpp_experimental_concepts", "1");
 }
 
 static void InitializePredefinedMacros(const TargetInfo &TI,
Index: test/Lexer/cxx-features.cpp
===================================================================
--- test/Lexer/cxx-features.cpp
+++ test/Lexer/cxx-features.cpp
@@ -1,6 +1,7 @@
 // RUN: %clang_cc1 -std=c++98 -verify %s
 // RUN: %clang_cc1 -std=c++11 -verify %s
 // RUN: %clang_cc1 -std=c++1y -fsized-deallocation -verify %s
+// RUN: %clang_cc1 -std=c++1y -fsized-deallocation -fconcepts-ts -DCONCEPTS_TS=1 -verify %s
 
 // expected-no-diagnostics
 
@@ -123,3 +124,7 @@
 #if check(alias_templates, 0, 200704, 200704)
 #error "wrong value for __cpp_alias_templates"
 #endif
+
+#if check(experimental_concepts, 0, 0, CONCEPTS_TS)
+#error "wrong value for __cpp_experimental_concepts"
+#endif
Index: www/cxx_status.html
===================================================================
--- www/cxx_status.html
+++ www/cxx_status.html
@@ -631,7 +631,7 @@
     </tr>
     <tr>
       <td>[DRAFT TS] Concepts</td>
-      <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3929.pdf">N3929</a></td>
+      <td><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4377.pdf">N4377</a></td>
       <td class="none" align="center">No</td>
     </tr>
 </table>