r66870 missed this out.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@67082 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/RegAllocPBQP.cpp

@@ -83,6 +83,7 @@ namespace {
       au.addPreserved<LiveStacks>();
       au.addRequired<MachineLoopInfo>();
       au.addPreserved<MachineLoopInfo>();
+      au.addRequired<VirtRegMap>();
       MachineFunctionPass::getAnalysisUsage(au);
     }