diff --git a/llvm/lib/Transforms/IPO/ConstantMerge.cpp b/llvm/lib/Transforms/IPO/ConstantMerge.cpp
--- a/llvm/lib/Transforms/IPO/ConstantMerge.cpp
+++ b/llvm/lib/Transforms/IPO/ConstantMerge.cpp
@@ -95,6 +95,8 @@
   // Only process constants with initializers in the default address space.
   return !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
          GV->getType()->getAddressSpace() != 0 || GV->hasSection() ||
+         // Don't touch thread-local variables.
+         GV->isThreadLocal() ||
          // Don't touch values marked with attribute(used).
          UsedGlobals.count(GV);
 }
diff --git a/llvm/test/Transforms/ConstantMerge/dont-merge.ll b/llvm/test/Transforms/ConstantMerge/dont-merge.ll
--- a/llvm/test/Transforms/ConstantMerge/dont-merge.ll
+++ b/llvm/test/Transforms/ConstantMerge/dont-merge.ll
@@ -80,3 +80,15 @@
         store i32* @T4D2, i32** %P8
         ret void
 }
+
+; CHECK: @T5tls
+; CHECK: @T5ua
+
+@T5tls = private thread_local constant i32 555
+@T5ua = private unnamed_addr constant i32 555
+
+define void @test5(i32** %P1, i32** %P2) {
+        store i32* @T5tls, i32** %P1
+        store i32* @T5ua, i32** %P2
+        ret void
+}