CodeGen: Don't emit a thread-wrapper if we can't touch the backing variable

OS X TLS has all accesses going through the thread-wrapper function and
gives the backing thread-local variable internal linkage.  This means
that thread-wrappers must have WeakAnyLinkage so that references to the
internal thread-local variables do not get propagated to other code.

It also means that translation units which do not provide a definition
for the thread-local variable cannot attempt to emit a thread-wrapper
because the thread wrapper will attempt to reference the backing
variable.

Differential Revision: http://reviews.llvm.org/D4109

llvm-svn: 212841

1 files changed, 25 insertions, 2 deletions

diff --git a/clang/test/CodeGenCXX/tls-init-funcs.cpp b/clang/test/CodeGenCXX/tls-init-funcs.cpp
index 99fe75f7..d47329c 100644
--- a/clang/test/CodeGenCXX/tls-init-funcs.cpp
+++ b/clang/test/CodeGenCXX/tls-init-funcs.cpp
@@ -1,11 +1,34 @@
-// RUN: %clang_cc1 -triple x86_64-apple-macosx10.8 -std=c++11 -S -emit-llvm %s -o - | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.8 -std=c++1y -S -emit-llvm %s -o - | FileCheck %s
 
 // CHECK: @a = internal thread_local global
+// CHECK: @_Z2vtIiE = internal thread_local global i32 5
+// CHECK: @_ZZ3inlvE3loc = linkonce_odr thread_local global i32 0
 // CHECK: @_tlv_atexit({{.*}}@_ZN1AD1Ev
-// CHECK: define weak hidden {{.*}} @_ZTW1a
+// CHECK: call i32* @_ZTW3ext()
+// CHECK: declare i32* @_ZTW3ext()
+// CHECK: define weak i32* @_ZTW2vtIiE()
+// CHECK: define weak i32* @_ZTW2vtIvE()
+// CHECK: define {{.*}} @_ZTW1a
 
 struct A {
   ~A();
 };
 
 thread_local A a;
+
+extern thread_local int ext;
+int &get_ext() { return ext; }
+
+template <typename T>
+thread_local int vt = 5;
+
+int get_vt() { return vt<int>; }
+
+inline int &inl() {
+  thread_local int loc;
+  return loc;
+}
+int &use_inl() { return inl(); }
+
+template int vt<void>;
+int &get_vt_void() { return vt<void>; }