Eliminate PromoteMemoryToRegisterID; just use addPreserved("mem2reg")
instead, as an example of what this looks like.

llvm-svn: 110478
diff --git a/llvm/lib/Transforms/Utils/LowerSwitch.cpp b/llvm/lib/Transforms/Utils/LowerSwitch.cpp
index 1910fd9..0caeff9 100644
--- a/llvm/lib/Transforms/Utils/LowerSwitch.cpp
+++ b/llvm/lib/Transforms/Utils/LowerSwitch.cpp
@@ -41,7 +41,7 @@
     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       // This is a cluster of orthogonal Transforms
       AU.addPreserved<UnifyFunctionExitNodes>();
-      AU.addPreservedID(PromoteMemoryToRegisterID);
+      AU.addPreserved("mem2reg");
       AU.addPreservedID(LowerInvokePassID);
     }