Fix a significant recent(?) regression. StackSlotColoring no longer did anything
because LiveStackAnalysis was not preserved by VirtRegWriter. This caused
big stack usage regression in some cases.

rdar://12340383


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164408 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocGreedy.cpp b/lib/CodeGen/RegAllocGreedy.cpp
index 20ba804..06f69c1 100644
--- a/lib/CodeGen/RegAllocGreedy.cpp
+++ b/lib/CodeGen/RegAllocGreedy.cpp
@@ -330,9 +330,9 @@
   AU.addPreserved<SlotIndexes>();
   AU.addRequired<LiveDebugVariables>();
   AU.addPreserved<LiveDebugVariables>();
-  AU.addRequired<CalculateSpillWeights>();
   AU.addRequired<LiveStacks>();
   AU.addPreserved<LiveStacks>();
+  AU.addRequired<CalculateSpillWeights>();
   AU.addRequired<MachineDominatorTree>();
   AU.addPreserved<MachineDominatorTree>();
   AU.addRequired<MachineLoopInfo>();