Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -7696,7 +7696,7 @@
 def err_opencl_implicit_vector_conversion : Error<
   "implicit conversions between vector types (%0 and %1) are not permitted">;
 
-// OpenCL v2.0 s6.13.6 -- Builtin Pipe Functions
+// OpenCL v2.0 s6.13.6 - Builtin Pipe Functions
 def err_opencl_builtin_pipe_first_arg : Error<
   "first argument to %0 must be a pipe type">;
 def err_opencl_builtin_pipe_arg_num : Error<
@@ -7706,7 +7706,8 @@
 def err_opencl_builtin_pipe_invalid_access_modifier : Error<
   "invalid pipe access modifier (expecting %0)">;
 
-// OpenCL Section 6.8.g
+// OpenCL v1.1 s6.8.g - extern, static, auto, register is not supported
+// OpenCL v1.2/2.0 s6.8 -  auto, register is not supported
 def err_opencl_unknown_type_specifier : Error<
   "OpenCL does not support the '%0' %select{type qualifier|storage class specifier}1">;
 
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -6611,9 +6611,12 @@
         NewVD->setInvalidDecl();
         return;
       }
-      // OpenCL v1.1 s6.5.2 and s6.5.3 no local or constant variables
+      // OpenCL v1.1 s6.5.2 and s6.5.3 - No local or constant variables
       // in functions.
-      if (T.getAddressSpace() == LangAS::opencl_constant ||
+      // OpenCL v1.2 s6.8.p2 - Extern can be used for variables declared
+      // in functions.
+      if ((T.getAddressSpace() == LangAS::opencl_constant &&
+           !NewVD->isLocalExternDecl()) ||
           T.getAddressSpace() == LangAS::opencl_local) {
         FunctionDecl *FD = getCurFunctionDecl();
         if (FD && !FD->hasAttr<OpenCLKernelAttr>()) {
Index: test/CodeGenOpenCL/extern.cl
===================================================================
--- /dev/null
+++ test/CodeGenOpenCL/extern.cl
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -x cl -cl-std=CL1.2 -emit-llvm -ffake-address-space-map %s -o - | FileCheck %s
+
+// CHECK: @foo = external addrspace(3) constant float
+extern constant float foo;
+
+kernel void test(global float* buf) {
+  buf[0] += foo;
+}
+
+void test2(global float* buf) {
+// CHECK: @bar = external addrspace(3) constant [0 x float]
+  extern constant float bar[];
+  buf[0] += bar[0];
+}
+
Index: test/SemaOpenCL/extern.cl
===================================================================
--- test/SemaOpenCL/extern.cl
+++ test/SemaOpenCL/extern.cl
@@ -1,9 +1,8 @@
-// RUN: %clang_cc1 -x cl -cl-std=CL1.2 -emit-llvm -ffake-address-space-map %s -o - -verify | FileCheck %s
-// expected-no-diagnostics
+// RUN: %clang_cc1 -x cl -emit-llvm -ffake-address-space-map %s -o - -verify
 
-// CHECK: @foo = external addrspace(3) constant float
-extern constant float foo;
+extern constant float foo; // expected-error{{OpenCL does not support the 'extern' storage class specifier}} expected-error{{variable in constant address space must be initialized}}
 
 kernel void test(global float* buf) {
-  buf[0] += foo;
+  extern constant float bar[10]; // expected-error{{OpenCL does not support the 'extern' storage class specifier}} expected-error{{variable in constant address space must be initialized}}
 }
+