Update to LLVM 3.5a.

Change-Id: Ifadecab779f128e62e430c2b4f6ddd84953ed617
diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
index 054e3dd..5639894 100644
--- a/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
+++ b/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.cpp
@@ -738,13 +738,13 @@
   if (Emitter.getInsertPos() == BB->begin() || BB->back().isPHI() ||
       // Fast-isel may have inserted some instructions, in which case the
       // BB->back().isPHI() test will not fire when we want it to.
-      prior(Emitter.getInsertPos())->isPHI()) {
+      std::prev(Emitter.getInsertPos())->isPHI()) {
     // Did not insert any instruction.
     Orders.push_back(std::make_pair(Order, (MachineInstr*)0));
     return;
   }
 
-  Orders.push_back(std::make_pair(Order, prior(Emitter.getInsertPos())));
+  Orders.push_back(std::make_pair(Order, std::prev(Emitter.getInsertPos())));
   ProcessSDDbgValues(N, DAG, Emitter, Orders, VRBaseMap, Order);
 }