Fix VC++ compilation error

llvm-svn: 19423
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 3b4694a..9c58304 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -19,6 +19,7 @@
 #include <iostream>
 #include <set>
 #include <cmath>
+#include <algorithm>
 using namespace llvm;
 
 /// getSetCCSwappedOperands - Return the operation corresponding to (Y op X)