Index: clang/include/clang/Basic/TokenKinds.def
===================================================================
--- clang/include/clang/Basic/TokenKinds.def
+++ clang/include/clang/Basic/TokenKinds.def
@@ -586,7 +586,7 @@
 ALIAS("read_write", __read_write    , KEYOPENCLC | KEYOPENCLCXX)
 // OpenCL builtins
 KEYWORD(__builtin_astype            , KEYOPENCLC | KEYOPENCLCXX)
-UNARY_EXPR_OR_TYPE_TRAIT(vec_step, VecStep, KEYOPENCLC | KEYALTIVEC | KEYZVECTOR)
+UNARY_EXPR_OR_TYPE_TRAIT(vec_step, VecStep, KEYOPENCLC | KEYOPENCLCXX | KEYALTIVEC | KEYZVECTOR)
 #define GENERIC_IMAGE_TYPE(ImgType, Id) KEYWORD(ImgType##_t, KEYOPENCLC | KEYOPENCLCXX)
 #include "clang/Basic/OpenCLImageTypes.def"
 KEYWORD(pipe                        , KEYOPENCLC | KEYOPENCLCXX)
Index: clang/test/CodeGenOpenCLCXX/constexpr.cl
===================================================================
--- clang/test/CodeGenOpenCLCXX/constexpr.cl
+++ clang/test/CodeGenOpenCLCXX/constexpr.cl
@@ -52,3 +52,13 @@
 kernel void vecEval2(global int2 *x) {
   *x = fromConstexprFunc;
 }
+
+// Test evaluation of vec_step
+// CHECK-LABEL: define spir_kernel void @vec_step_test
+// CHECK: store i32 6
+constexpr int vsize1 = vec_step(fromConstexprFunc);
+constexpr int vsize2 = vec_step(int4);
+
+kernel void vec_step_test(global int *x) {
+  *x = vsize1 + vsize2;
+}