Add preservation of SlotIndexes to PHIElimination.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175596 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index abad5c1..37e2ee1 100644
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -116,6 +116,7 @@
 
 void PHIElimination::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addPreserved<LiveVariables>();
+  AU.addPreserved<SlotIndexes>();
   AU.addPreserved<LiveIntervals>();
   AU.addPreserved<MachineDominatorTree>();
   AU.addPreserved<MachineLoopInfo>();