Revert r49614.  As Dan pointed out, some of these aren't correct.

llvm-svn: 49657
diff --git a/llvm/lib/Transforms/Scalar/TailDuplication.cpp b/llvm/lib/Transforms/Scalar/TailDuplication.cpp
index 5d802a6..929d113 100644
--- a/llvm/lib/Transforms/Scalar/TailDuplication.cpp
+++ b/llvm/lib/Transforms/Scalar/TailDuplication.cpp
@@ -317,7 +317,7 @@
   //
   for (; BI != DestBlock->end(); ++BI) {
     Instruction *New = BI->clone();
-    New->takeName(BI);
+    New->setName(BI->getName());
     SourceBlock->getInstList().push_back(New);
     ValueMapping[BI] = New;
   }