Add #includes to make some dependencies explicit.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@51496 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 066952d..31cbdb9 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -29,6 +29,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/MathExtras.h"
 #include <algorithm>
+#include <set>
 using namespace llvm;
 
 STATISTIC(NodesCombined   , "Number of dag nodes combined");