Don't recalculate the loop info and loop dominators analyses if they're
preserved.

llvm-svn: 45596
diff --git a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
index 46cdec7..5c9d69a 100644
--- a/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -60,6 +60,8 @@
 void LiveIntervals::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addPreserved<LiveVariables>();
   AU.addRequired<LiveVariables>();
+  AU.addPreservedID(MachineLoopInfoID);
+  AU.addPreservedID(MachineDominatorsID);
   AU.addPreservedID(PHIEliminationID);
   AU.addRequiredID(PHIEliminationID);
   AU.addRequiredID(TwoAddressInstructionPassID);