diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -420,6 +420,13 @@
     if (GV.hasAppendingLinkage() || GV.hasLocalLinkage())
       continue;
 
+    // Reset DSO locality before setting the visibility. This removes
+    // any effects that visibility options and annotations may have
+    // had on the DSO locality. Setting the visibility will implicitly set
+    // appropriate globals to DSO Local; however, this will be pessimistic
+    // w.r.t. to the normal compiler IRGen.
+    GV.setDSOLocal(false);
+
     if (GV.isDeclarationForLinker()) {
       GV.setVisibility(GV.getDLLStorageClass() ==
                                llvm::GlobalValue::DLLImportStorageClass
diff --git a/clang/test/CodeGenCXX/visibility-dllstorageclass.cpp b/clang/test/CodeGenCXX/visibility-dllstorageclass.cpp
--- a/clang/test/CodeGenCXX/visibility-dllstorageclass.cpp
+++ b/clang/test/CodeGenCXX/visibility-dllstorageclass.cpp
@@ -5,12 +5,14 @@
 
 // RUN: %clang_cc1 -triple x86_64-unknown-windows-itanium -fdeclspec \
 // RUN:     -fvisibility hidden \
+// RUN:     -fapply-global-visibility-to-externs \
 // RUN:     -fvisibility-from-dllstorageclass \
 // RUN:     -x c++ %s -S -emit-llvm -o - | \
-// RUN:   FileCheck %s --check-prefixes=DEFAULT
+// RUN:   FileCheck %s --check-prefixes=DEFAULTS
 
 // RUN: %clang_cc1 -triple x86_64-unknown-windows-itanium -fdeclspec \
 // RUN:     -fvisibility hidden \
+// RUN:     -fapply-global-visibility-to-externs \
 // RUN:     -fvisibility-from-dllstorageclass \
 // RUN:     -fvisibility-dllexport=hidden \
 // RUN:     -fvisibility-nodllstorageclass=protected \
@@ -19,45 +21,78 @@
 // RUN:     -x c++  %s -S -emit-llvm -o - | \
 // RUN:   FileCheck %s --check-prefixes=EXPLICIT
 
+// RUN: %clang_cc1 -triple x86_64-unknown-windows-itanium -fdeclspec \
+// RUN:     -fvisibility hidden \
+// RUN:     -fapply-global-visibility-to-externs \
+// RUN:     -fvisibility-from-dllstorageclass \
+// RUN:     -fvisibility-dllexport=default \
+// RUN:     -fvisibility-nodllstorageclass=default \
+// RUN:     -fvisibility-externs-dllimport=default \
+// RUN:     -fvisibility-externs-nodllstorageclass=default \
+// RUN:     -x c++  %s -S -emit-llvm -o - | \
+// RUN:   FileCheck %s --check-prefixes=ALL_DEFAULT
+
 // Local
 static void l() {}
 void use_locals(){l();}
-// DEFAULT-DAG: define internal void @_ZL1lv()
+// DEFAULTS-DAG: define internal void @_ZL1lv()
 // EXPLICIT-DAG: define internal void @_ZL1lv()
+// ALL_DEFAULT-DAG: define internal void @_ZL1lv()
 
 // Function
 void f() {}
 void __declspec(dllexport) exported_f() {}
-// DEFAULT-DAG: define hidden void @_Z1fv()
-// DEFAULT-DAG: define dso_local void @_Z10exported_fv()
+// DEFAULTS-DAG: define hidden void @_Z1fv()
+// DEFAULTS-DAG: define void @_Z10exported_fv()
 // EXPLICIT-DAG: define protected void @_Z1fv()
 // EXPLICIT-DAG: define hidden void @_Z10exported_fv()
+// ALL_DEFAULT-DAG: define void @_Z1fv()
+// ALL_DEFAULT-DAG: define void @_Z10exported_fv()
 
 // Variable
 int d = 123;
 __declspec(dllexport) int exported_d = 123;
-// DEFAULT-DAG: @d = hidden global
-// DEFAULT-DAG: @exported_d = dso_local global
+// DEFAULTS-DAG: @d = hidden global
+// DEFAULTS-DAG: @exported_d = global
 // EXPLICIT-DAG: @d = protected global
 // EXPLICIT-DAG: @exported_d = hidden global
+// ALL_DEFAULT-DAG: @d = global
+// ALL_DEFAULT-DAG: @exported_d = global
 
 // Alias
 extern "C" void aliased() {}
 void a() __attribute__((alias("aliased")));
 void __declspec(dllexport) a_exported() __attribute__((alias("aliased")));
-// DEFAULT-DAG: @_Z1av = hidden alias
-// DEFAULT-DAG: @_Z10a_exportedv = dso_local alias
+// DEFAULTS-DAG: @_Z1av = hidden alias
+// DEFAULTS-DAG: @_Z10a_exportedv = alias
 // EXPLICIT-DAG: @_Z1av = protected alias
 // EXPLICIT-DAG: @_Z10a_exportedv = hidden alias
+// ALL_DEFAULT-DAG: @_Z1av = alias
+// ALL_DEFAULT-DAG: @_Z10a_exportedv = alias
 
 // Declaration
 extern void e();
 extern void __declspec(dllimport) imported_e();
-void use_declarations(){e(); imported_e();}
-// DEFAULT-DAG: declare hidden void @_Z1ev()
-// DEFAULT-DAG: declare void @_Z10imported_ev()
+// DEFAULTS-DAG: declare hidden void @_Z1ev()
+// DEFAULTS-DAG: declare void @_Z10imported_ev()
 // EXPLICIT-DAG: declare protected void @_Z1ev()
 // EXPLICIT-DAG: declare hidden void @_Z10imported_ev()
+// ALL_DEFAULT-DAG: declare void @_Z1ev()
+// ALL_DEFAULT-DAG: declare void @_Z10imported_ev()
+
+// Weak Declaration
+__attribute__((weak))
+extern void w();
+__attribute__((weak))
+extern void __declspec(dllimport) imported_w();
+// DEFAULTS-DAG: declare extern_weak hidden void @_Z1wv()
+// DEFAULTS-DAG: declare extern_weak void @_Z10imported_wv()
+// EXPLICIT-DAG: declare extern_weak protected void @_Z1wv()
+// EXPLICIT-DAG: declare extern_weak hidden void @_Z10imported_wv()
+// ALL_DEFAULT-DAG: declare extern_weak void @_Z1wv()
+// ALL_DEFAULT-DAG: declare extern_weak void @_Z10imported_wv()
+
+void use_declarations(){e(); imported_e(); w(); imported_w();}
 
 // Show that -fvisibility-from-dllstorageclass overrides the effect of visibility annotations.
 
@@ -65,12 +100,12 @@
   virtual void foo();
 };
 void t::foo() {}
-// DEFAULT-DAG: @_ZTV1t = hidden unnamed_addr constant
+// DEFAULTS-DAG: @_ZTV1t = hidden unnamed_addr constant
 
 int v __attribute__ ((__visibility__ ("protected"))) = 123;
-// DEFAULT-DAG: @v = hidden global
+// DEFAULTS-DAG: @v = hidden global
 
 #pragma GCC visibility push(protected)
 int p = 345;
 #pragma GCC visibility pop
-// DEFAULT-DAG: @p = hidden global
+// DEFAULTS-DAG: @p = hidden global