Index: lib/Transforms/Scalar/LoopIdiomRecognize.cpp
===================================================================
--- lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -441,6 +441,13 @@
   if (!C)
     return nullptr;
 
+  // While technically constant, the address of a thread_local GlobalVariable
+  // isn't known until runtime and would require additional tls init code to
+  // handle correctly.
+  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
+    if (GV->isThreadDependent())
+      return nullptr;
+
   // Only handle simple values that are a power of two bytes in size.
   uint64_t Size = DL->getTypeSizeInBits(V->getType());
   if (Size == 0 || (Size & 7) || (Size & (Size - 1)))
Index: test/Transforms/LoopIdiom/thread-local.ll
===================================================================
--- test/Transforms/LoopIdiom/thread-local.ll
+++ test/Transforms/LoopIdiom/thread-local.ll
@@ -0,0 +1,29 @@
+; RUN: opt -loop-idiom < %s -S | FileCheck %s
+
+target triple = "x86_64-apple-darwin10.0.0"
+
+;void test_tls(int **ptrs) {
+;  thread_local int tls_var;
+;  for (int i = 0; i < 1000; i++) {
+;    p[i] = &tls_var;
+;  }
+;}
+@tls_var = internal thread_local global i32 0, align 4
+
+define void @test_tls(i32** nocapture %ptrs) nounwind ssp {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %indvar = phi i64 [ 0, %entry ], [ %indvar.next, %for.body ]
+  %arrayidx = getelementptr i32*, i32** %ptrs, i64 %indvar
+  store i32* @tls_var, i32** %arrayidx, align 8
+  %indvar.next = add i64 %indvar, 1
+  %exitcond = icmp eq i64 %indvar.next, 1000
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:                                          ; preds = %for.body
+  ret void
+; CHECK-LABEL: @test_tls(
+; CHECK-NOT: call void @memset_pattern
+}