Guard private fields that are unused in Release builds with #ifndef NDEBUG.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158608 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/RegAllocBasic.cpp b/lib/CodeGen/RegAllocBasic.cpp
index 1fa54cd..73059ec 100644
--- a/lib/CodeGen/RegAllocBasic.cpp
+++ b/lib/CodeGen/RegAllocBasic.cpp
@@ -64,8 +64,10 @@
   // context
   MachineFunction *MF;
 
+#ifndef NDEBUG
   // analyses
   RenderMachineFunction *RMF;
+#endif
 
   // state
   std::auto_ptr<Spiller> SpillerInstance;