diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -2546,6 +2546,9 @@
       llvm::Function::Create(FnTy, getThreadLocalWrapperLinkage(VD, CGM),
                              WrapperName.str(), &CGM.getModule());
 
+  if (CGM.supportsCOMDAT() && Wrapper->isWeakForLinker())
+    Wrapper->setComdat(CGM.getModule().getOrInsertComdat(Wrapper->getName()));
+
   CGM.SetLLVMFunctionAttributes(GlobalDecl(), FI, Wrapper);
 
   // Always resolve references to the wrapper at link time.
diff --git a/clang/test/CodeGenCXX/cxx11-thread-local-reference.cpp b/clang/test/CodeGenCXX/cxx11-thread-local-reference.cpp
--- a/clang/test/CodeGenCXX/cxx11-thread-local-reference.cpp
+++ b/clang/test/CodeGenCXX/cxx11-thread-local-reference.cpp
@@ -21,7 +21,7 @@
 // DARWIN: call cxx_fast_tlscc i32* @_ZTW1r()
 // CHECK: ret i32* %{{.*}}
 
-// LINUX: define weak_odr hidden i32* @_ZTW1r() [[ATTR0:#[0-9]+]] {
+// LINUX: define weak_odr hidden i32* @_ZTW1r() [[ATTR0:#[0-9]+]] comdat {
 // DARWIN: define cxx_fast_tlscc i32* @_ZTW1r() [[ATTR1:#[0-9]+]] {
 // LINUX: call void @_ZTH1r()
 // DARWIN: call cxx_fast_tlscc void @_ZTH1r()
diff --git a/clang/test/CodeGenCXX/cxx11-thread-local.cpp b/clang/test/CodeGenCXX/cxx11-thread-local.cpp
--- a/clang/test/CodeGenCXX/cxx11-thread-local.cpp
+++ b/clang/test/CodeGenCXX/cxx11-thread-local.cpp
@@ -204,22 +204,19 @@
 // DARWIN: declare i32 @_tlv_atexit(void (i8*)*, i8*, i8*)
 
 // DARWIN: declare cxx_fast_tlscc i32* @_ZTWN1VIcE1mE()
-// LINUX: define linkonce_odr hidden i32* @_ZTWN1VIcE1mE()
-// LINUX-NOT: comdat
+// LINUX: define linkonce_odr hidden i32* @_ZTWN1VIcE1mE() {{#[0-9]+}} comdat {
 // LINUX: br i1 icmp ne (void ()* @_ZTHN1VIcE1mE,
 // LINUX: call void @_ZTHN1VIcE1mE()
 // LINUX: ret i32* @_ZN1VIcE1mE
 
 // DARWIN: declare cxx_fast_tlscc i32* @_ZTWN1WIcE1mE()
-// LINUX: define linkonce_odr hidden i32* @_ZTWN1WIcE1mE()
-// LINUX-NOT: comdat
+// LINUX: define linkonce_odr hidden i32* @_ZTWN1WIcE1mE() {{#[0-9]+}} comdat {
 // LINUX: br i1 icmp ne (void ()* @_ZTHN1WIcE1mE,
 // LINUX: call void @_ZTHN1WIcE1mE()
 // LINUX: ret i32* @_ZN1WIcE1mE
 
 // DARWIN: declare cxx_fast_tlscc {{.*}}* @_ZTWN1XIcE1mE()
-// LINUX: define linkonce_odr hidden {{.*}}* @_ZTWN1XIcE1mE()
-// LINUX-NOT: comdat
+// LINUX: define linkonce_odr hidden {{.*}}* @_ZTWN1XIcE1mE() {{#[0-9]+}} comdat {
 // LINUX: br i1 icmp ne (void ()* @_ZTHN1XIcE1mE,
 // LINUX: call void @_ZTHN1XIcE1mE()
 // LINUX: ret {{.*}}* @_ZN1XIcE1mE
diff --git a/clang/test/CodeGenCXX/tls-init-funcs.cpp b/clang/test/CodeGenCXX/tls-init-funcs.cpp
--- a/clang/test/CodeGenCXX/tls-init-funcs.cpp
+++ b/clang/test/CodeGenCXX/tls-init-funcs.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -triple x86_64-apple-macosx10.8 -std=c++1y -S -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-windows-gnu -std=c++1y -S -emit-llvm %s -o - | FileCheck %s --check-prefix=MINGW
 
 // CHECK: @a = internal thread_local global
 // CHECK: @_Z2vtIiE = linkonce_odr thread_local global i32 5
@@ -10,6 +11,9 @@
 // CHECK-DAG: define weak_odr hidden cxx_fast_tlscc i32* @_ZTW2vtIvE()
 // CHECK-DAG: define {{.*}} @_ZTW1a
 
+// MINGW-DAG: define weak_odr hidden i32* @_ZTW2vtIiE() {{.*}} comdat
+// MINGW-DAG: define weak_odr hidden i32* @_ZTW2vtIvE() {{.*}} comdat
+
 struct A {
   ~A();
 };
diff --git a/clang/test/OpenMP/threadprivate_codegen.cpp b/clang/test/OpenMP/threadprivate_codegen.cpp
--- a/clang/test/OpenMP/threadprivate_codegen.cpp
+++ b/clang/test/OpenMP/threadprivate_codegen.cpp
@@ -648,15 +648,15 @@
 // CHECK-TLS:   call void [[ARR_X_TLS_INIT]]
 // CHECK-TLS:   ret [2 x [3 x [[S1]]]]* [[ARR_X]]
 // CHECK-TLS: }
-// CHECK-TLS: define {{.*}} i32* [[ST_INT_ST_TLS_INITD]] {{#[0-9]+}} {
+// CHECK-TLS: define {{.*}} i32* [[ST_INT_ST_TLS_INITD]] {{#[0-9]+}} comdat {
 // CHECK-TLS-NOT:   call
 // CHECK-TLS:   ret i32* [[ST_INT_ST]]
 // CHECK-TLS: }
-// CHECK-TLS: define {{.*}} float* [[ST_FLOAT_ST_TLS_INITD]] {{#[0-9]+}} {
+// CHECK-TLS: define {{.*}} float* [[ST_FLOAT_ST_TLS_INITD]] {{#[0-9]+}} comdat {
 // CHECK-TLS-NOT:   call
 // CHECK-TLS:   ret float* [[ST_FLOAT_ST]]
 // CHECK-TLS: }
-// CHECK-TLS: define {{.*}} [[S4]]* [[ST_S4_ST_TLS_INITD]] {{#[0-9]+}} {
+// CHECK-TLS: define {{.*}} [[S4]]* [[ST_S4_ST_TLS_INITD]] {{#[0-9]+}} comdat {
 // CHECK-TLS:   call void [[ST_S4_ST_TLS_INIT]]
 // CHECK-TLS:   ret [[S4]]* [[ST_S4_ST]]
 // CHECK-TLS: }