run mem2reg after the second jump threading pass in llvm-ld.

llvm-svn: 52728
diff --git a/llvm/tools/llvm-ld/Optimize.cpp b/llvm/tools/llvm-ld/Optimize.cpp
index 0dc3857..a3f1986 100644
--- a/llvm/tools/llvm-ld/Optimize.cpp
+++ b/llvm/tools/llvm-ld/Optimize.cpp
@@ -148,7 +148,8 @@
     addPass(Passes, createInstructionCombiningPass());
 
     addPass(Passes, createJumpThreadingPass());        // Thread jumps.
-
+    addPass(Passes, createPromoteMemoryToRegisterPass()); // Cleanup jumpthread.
+    
     // Delete basic blocks, which optimization passes may have killed...
     addPass(Passes, createCFGSimplificationPass());