Index: lib/Transforms/Scalar/TailRecursionElimination.cpp
===================================================================
--- lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -252,8 +252,10 @@
       for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
         if (CallInst *CI = dyn_cast<CallInst>(I)) {
           if (!ACT.UsesAlloca.count(CI)) {
-            CI->setTailCall();
-            MadeChange = true;
+            if (!CI->isTailCall()) {
+              CI->setTailCall();
+              MadeChange = true;
+            }
           }
         }
       }