diff --git a/clang/lib/Headers/opencl-c-base.h b/clang/lib/Headers/opencl-c-base.h
--- a/clang/lib/Headers/opencl-c-base.h
+++ b/clang/lib/Headers/opencl-c-base.h
@@ -202,6 +202,9 @@
 typedef double double16 __attribute__((ext_vector_type(16)));
 #endif
 
+// An internal alias for half, for use by OpenCLBuiltins.td.
+#define __half half
+
 #if defined(__OPENCL_CPP_VERSION__)
 #define NULL nullptr
 #elif defined(__OPENCL_C_VERSION__)
diff --git a/clang/lib/Sema/OpenCLBuiltins.td b/clang/lib/Sema/OpenCLBuiltins.td
--- a/clang/lib/Sema/OpenCLBuiltins.td
+++ b/clang/lib/Sema/OpenCLBuiltins.td
@@ -352,9 +352,22 @@
 let Extension = Fp64TypeExt in {
   def Double    : Type<"double",    QualType<"Context.DoubleTy">>;
 }
+
+// The half type for builtins that require the cl_khr_fp16 extension.
 let Extension = Fp16TypeExt in {
   def Half      : Type<"half",      QualType<"Context.HalfTy">>;
 }
+
+// Without the cl_khr_fp16 extension, the half type can only be used to declare
+// a pointer.  Define const and non-const pointer types in all address spaces.
+// Use the "__half" alias to allow the TableGen emitter to distinguish the
+// (extensionless) pointee type of these pointer-to-half types from the "half"
+// type defined above that already carries the cl_khr_fp16 extension.
+foreach AS = [PrivateAS, GlobalAS, ConstantAS, LocalAS, GenericAS] in {
+  def "HalfPtr" # AS      : PointerType<Type<"__half", QualType<"Context.HalfTy">>, AS>;
+  def "HalfPtrConst" # AS : PointerType<ConstType<Type<"__half", QualType<"Context.HalfTy">>>, AS>;
+}
+
 def Size      : Type<"size_t",    QualType<"Context.getSizeType()">>;
 def PtrDiff   : Type<"ptrdiff_t", QualType<"Context.getPointerDiffType()">>;
 def IntPtr    : Type<"intptr_t",  QualType<"Context.getIntPtrType()">>;
@@ -877,22 +890,22 @@
 
 multiclass VloadVstoreHalf<list<AddressSpace> addrspaces, bit defStores> {
   foreach AS = addrspaces in {
-    def : Builtin<"vload_half", [Float, Size, PointerType<ConstType<Half>, AS>], Attr.Pure>;
+    def : Builtin<"vload_half", [Float, Size, !cast<Type>("HalfPtrConst" # AS)], Attr.Pure>;
     foreach VSize = [2, 3, 4, 8, 16] in {
       foreach name = ["vload_half" # VSize, "vloada_half" # VSize] in {
-        def : Builtin<name, [VectorType<Float, VSize>, Size, PointerType<ConstType<Half>, AS>], Attr.Pure>;
+        def : Builtin<name, [VectorType<Float, VSize>, Size, !cast<Type>("HalfPtrConst" # AS)], Attr.Pure>;
       }
     }
     if defStores then {
       foreach rnd = ["", "_rte", "_rtz", "_rtp", "_rtn"] in {
         foreach name = ["vstore_half" # rnd] in {
-          def : Builtin<name, [Void, Float, Size, PointerType<Half, AS>]>;
-          def : Builtin<name, [Void, Double, Size, PointerType<Half, AS>]>;
+          def : Builtin<name, [Void, Float, Size, !cast<Type>("HalfPtr" # AS)]>;
+          def : Builtin<name, [Void, Double, Size, !cast<Type>("HalfPtr" # AS)]>;
         }
         foreach VSize = [2, 3, 4, 8, 16] in {
           foreach name = ["vstore_half" # VSize # rnd, "vstorea_half" # VSize # rnd] in {
-            def : Builtin<name, [Void, VectorType<Float, VSize>, Size, PointerType<Half, AS>]>;
-            def : Builtin<name, [Void, VectorType<Double, VSize>, Size, PointerType<Half, AS>]>;
+            def : Builtin<name, [Void, VectorType<Float, VSize>, Size, !cast<Type>("HalfPtr" # AS)]>;
+            def : Builtin<name, [Void, VectorType<Double, VSize>, Size, !cast<Type>("HalfPtr" # AS)]>;
           }
         }
       }
diff --git a/clang/test/SemaOpenCL/half.cl b/clang/test/SemaOpenCL/half.cl
--- a/clang/test/SemaOpenCL/half.cl
+++ b/clang/test/SemaOpenCL/half.cl
@@ -1,5 +1,5 @@
 // RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -Wno-unused-value -triple spir-unknown-unknown
-// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -Wno-unused-value -triple spir-unknown-unknown -fdeclare-opencl-builtins -finclude-default-header
+// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -Wno-unused-value -triple spir-unknown-unknown -fdeclare-opencl-builtins -finclude-default-header -DHAVE_BUILTINS
 
 constant float f = 1.0h; // expected-error{{half precision constant requires cl_khr_fp16}}
 
@@ -22,6 +22,11 @@
   half *allowed2 = &*p;
   half *allowed3 = p + 1;
 
+#ifdef HAVE_BUILTINS
+  (void)ilogb(*p); // expected-error{{loading directly from pointer to type '__private half' requires cl_khr_fp16. Use vector data load builtin functions instead}}
+  vstore_half(42.0f, 0, p);
+#endif
+
   return h;
 }
 
@@ -49,6 +54,11 @@
   half *allowed2 = &*p;
   half *allowed3 = p + 1;
 
+#ifdef HAVE_BUILTINS
+  (void)ilogb(*p);
+  vstore_half(42.0f, 0, p);
+#endif
+
   return h;
 }