diff --git a/tools/opt/opt.cpp b/tools/opt/opt.cpp
index 2639a802e8d..e3ea59e26bf 100644
--- a/tools/opt/opt.cpp
+++ b/tools/opt/opt.cpp
@@ -264,6 +264,7 @@ void AddStandardCompilePasses(PassManager &PM) {
     addPass(PM, createFunctionInliningPass());   // Inline small functions
   addPass(PM, createArgumentPromotionPass());    // Scalarize uninlined fn args
 
+  addPass(PM, createTailDuplicationPass());      // Simplify cfg by copying code
   addPass(PM, createSimplifyLibCallsPass());     // Library Call Optimizations
   addPass(PM, createInstructionCombiningPass()); // Cleanup for scalarrepl.
   addPass(PM, createJumpThreadingPass());        // Thread jumps.