Index: include/clang/Basic/DiagnosticASTKinds.td
===================================================================
--- include/clang/Basic/DiagnosticASTKinds.td
+++ include/clang/Basic/DiagnosticASTKinds.td
@@ -173,6 +173,9 @@
 def note_constexpr_memcpy_nontrivial : Note<
   "cannot constant evaluate '%select{memcpy|memmove}0' between objects of "
   "non-trivially-copyable type %1">;
+def note_constexpr_memcpy_incomplete_type : Note<
+  "cannot constant evaluate '%select{memcpy|memmove}0' between objects of "
+  "incomplete type %1">;
 def note_constexpr_memcpy_overlap : Note<
   "'%select{memcpy|wmemcpy}0' between overlapping memory regions">;
 def note_constexpr_memcpy_unsupported : Note<
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -6232,6 +6232,10 @@
       Info.FFDiag(E, diag::note_constexpr_memcpy_type_pun) << Move << SrcT << T;
       return false;
     }
+    if (T->isIncompleteType()) {
+      Info.FFDiag(E, diag::note_constexpr_memcpy_incomplete_type) << Move << T;
+      return false;
+    }
     if (!T.isTriviallyCopyableType(Info.Ctx)) {
       Info.FFDiag(E, diag::note_constexpr_memcpy_nontrivial) << Move << T;
       return false;
Index: test/CodeGen/builtin-memfns.c
===================================================================
--- test/CodeGen/builtin-memfns.c
+++ test/CodeGen/builtin-memfns.c
@@ -111,3 +111,10 @@
   memcpy(&d, (char *)&e.a, sizeof(e));
 }
 
+// CHECK-LABEL: @test12
+extern char dest_array[];
+extern char src_array[];
+void test12() {
+  // CHECK: call void @llvm.memcpy{{.*}}(
+  memcpy(&dest_array, &dest_array, 2);
+}
Index: test/SemaCXX/constexpr-string.cpp
===================================================================
--- test/SemaCXX/constexpr-string.cpp
+++ test/SemaCXX/constexpr-string.cpp
@@ -387,4 +387,41 @@
   // designators until we have a long enough matching size, if both designators
   // point to the start of their respective final elements.
   static_assert(test_derived_to_base(2) == 3434); // expected-error {{constant}} expected-note {{in call}}
+
+  // Check that when address-of an array is passed to a tested function the
+  // array can be fully copied.
+  constexpr int test_address_of_const_array_type() {
+    int arr[4] = {1, 2, 3, 4};
+    __builtin_memmove(&arr, &arr, sizeof(arr));
+    return arr[0] * 1000 + arr[1] * 100 + arr[2] * 10 + arr[3];
+  }
+  static_assert(test_address_of_const_array_type() == 1234);
+
+  // Check that an incomplete array is rejected.
+  constexpr int test_incomplete_array_type() { // expected-error {{never produces a constant}}
+    extern int arr[];
+    __builtin_memmove(arr, arr, 4 * sizeof(arr[0]));
+    // expected-note@-1 2{{'memmove' not supported: source is not a contiguous array of at least 4 elements of type 'int'}}
+    return arr[0] * 1000 + arr[1] * 100 + arr[2] * 10 + arr[3];
+  }
+  static_assert(test_incomplete_array_type() == 1234); // expected-error {{constant}} expected-note {{in call}}
+
+  // Check that a pointer to an incomplete array is rejected.
+  constexpr int test_address_of_incomplete_array_type() { // expected-error {{never produces a constant}}
+    extern int arr[];
+    __builtin_memmove(&arr, &arr, 4 * sizeof(arr[0]));
+    // expected-note@-1 2{{cannot constant evaluate 'memmove' between objects of incomplete type 'int []'}}
+    return arr[0] * 1000 + arr[1] * 100 + arr[2] * 10 + arr[3];
+  }
+  static_assert(test_address_of_incomplete_array_type() == 1234); // expected-error {{constant}} expected-note {{in call}}
+
+  // Check that a pointer to an incomplete struct is rejected.
+  constexpr bool test_address_of_incomplete_struct_type() { // expected-error {{never produces a constant}}
+    struct Incomplete;
+    extern Incomplete x, y;
+    __builtin_memcpy(&x, &x, 4);
+    // expected-note@-1 2{{cannot constant evaluate 'memcpy' between objects of incomplete type 'Incomplete'}}
+    return true;
+  }
+  static_assert(test_address_of_incomplete_struct_type()); // expected-error {{constant}} expected-note {{in call}}
 }