Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -2211,9 +2211,13 @@
         // FIXME: Diagnostic!
         return false;
 
-      // A dllimport variable never acts like a constant, unless we're
-      // evaluating a value for use only in name mangling.
-      if (!isForManglingOnly(Kind) && Var->hasAttr<DLLImportAttr>())
+      // A dllimport variable in C99, or a dllexport variable in C++ never acts
+      // like a constant, unless we're evaluating a value for use only in name
+      // mangling.
+      if (Info.getLangOpts().C99 && !isForManglingOnly(Kind) &&
+              Var->hasAttr<DLLImportAttr>() ||
+          Info.getLangOpts().CPlusPlus && !isForManglingOnly(Kind) &&
+              Var->hasAttr<DLLExportAttr>())
         // FIXME: Diagnostic!
         return false;
 
Index: clang/test/CodeGenCXX/PR19955.cpp
===================================================================
--- clang/test/CodeGenCXX/PR19955.cpp
+++ clang/test/CodeGenCXX/PR19955.cpp
@@ -6,20 +6,16 @@
 
 extern int *varp;
 int *varp = &var;
-// CHECK-DAG: @"?varp@@3PAHA" = dso_local global i32* null
-// X64-DAG: @"?varp@@3PEAHEA" = dso_local global i32* null
+// CHECK-DAG: @"?var@@3HA" = external dllimport global i32
+// CHECK-DAG: @"?varp@@3PAHA" = dso_local global i32* @"?var@@3HA"
+// X64-DAG: @"?var@@3HA" = external dllimport global i32, align 4
+// X64-DAG: @"?varp@@3PEAHEA" = dso_local global i32* @"?var@@3HA"
 
 extern void (*funp)();
 void (*funp)() = &fun;
 // CHECK-DAG: @"?funp@@3P6AXXZA" = dso_local global void ()* null
 // X64-DAG: @"?funp@@3P6AXXZEA" = dso_local global void ()* null
 
-// CHECK-LABEL: @"??__Evarp@@YAXXZ"
-// CHECK-DAG: store i32* @"?var@@3HA", i32** @"?varp@@3PAHA"
-
-// X64-LABEL: @"??__Evarp@@YAXXZ"
-// X64-DAG: store i32* @"?var@@3HA", i32** @"?varp@@3PEAHEA"
-
 // CHECK-LABEL: @"??__Efunp@@YAXXZ"()
 // CHECK-DAG: store void ()* @"?fun@@YAXXZ", void ()** @"?funp@@3P6AXXZA"
 
Index: clang/test/CodeGenCXX/dllimport.cpp
===================================================================
--- clang/test/CodeGenCXX/dllimport.cpp
+++ clang/test/CodeGenCXX/dllimport.cpp
@@ -98,8 +98,8 @@
 USE(inlineStaticLocalsFunc);
 
 // The address of a dllimport global cannot be used in constant initialization.
-// M32-DAG: @"?arr@?1??initializationFunc@@YAPAHXZ@4QBQAHB" = internal global [1 x i32*] zeroinitializer
-// GNU-DAG: @_ZZ18initializationFuncvE3arr = internal global [1 x i32*] zeroinitializer
+// M32-DAG: @"?arr@?1??initializationFunc@@YAPAHXZ@4QBQAHB" = internal constant [1 x i32*] [i32* @"?ExternGlobalDecl@@3HA"]
+// GNU-DAG: @_ZZ18initializationFuncvE3arr = internal constant [1 x i32*] [i32* @ExternGlobalDecl]
 int *initializationFunc() {
   static int *const arr[] = {&ExternGlobalDecl};
   return arr[0];
Index: clang/test/SemaCXX/PR19955.cpp
===================================================================
--- clang/test/SemaCXX/PR19955.cpp
+++ clang/test/SemaCXX/PR19955.cpp
@@ -2,7 +2,7 @@
 // RUN: %clang_cc1 -triple i686-mingw32 -verify -std=c++11 %s
 
 extern int __attribute__((dllimport)) var;
-constexpr int *varp = &var; // expected-error {{must be initialized by a constant expression}}
+constexpr int *varp = &var;
 
 extern __attribute__((dllimport)) void fun();
 constexpr void (*funp)(void) = &fun; // expected-error {{must be initialized by a constant expression}}
Index: clang/test/SemaCXX/dllimport-constexpr.cpp
===================================================================
--- clang/test/SemaCXX/dllimport-constexpr.cpp
+++ clang/test/SemaCXX/dllimport-constexpr.cpp
@@ -40,7 +40,6 @@
 // constexpr initialization doesn't work for dllimport things.
 // expected-error@+1{{must be initialized by a constant expression}}
 constexpr void (*constexpr_import_func)() = &imported_func;
-// expected-error@+1{{must be initialized by a constant expression}}
 constexpr int *constexpr_import_int = &imported_int;
 // expected-error@+1{{must be initialized by a constant expression}}
 constexpr void (Foo::*constexpr_memptr)() = &Foo::imported_method;
@@ -60,3 +59,14 @@
   // expected-note@+1 {{requested here}}
   StaticConstexpr<imported_func>::g_fp();
 }
+
+void foo() {
+  extern int __declspec(dllimport) dll_import_int;
+  constexpr int &dll_import_constexpr_ref = dll_import_int;
+}
+
+extern int __declspec(dllimport) dll_import_int;
+constexpr int &dll_import_constexpr_ref = dll_import_int;
+int goo() {
+  return dll_import_constexpr_ref;
+}