Add explicit keywords.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43464 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ValueNumbering.cpp b/lib/Analysis/ValueNumbering.cpp
index bdb9422..8665acd 100644
--- a/lib/Analysis/ValueNumbering.cpp
+++ b/lib/Analysis/ValueNumbering.cpp
@@ -78,7 +78,7 @@
   ///
   struct VISIBILITY_HIDDEN BVNImpl : public InstVisitor<BVNImpl> {
     std::vector<Value*> &RetVals;
-    BVNImpl(std::vector<Value*> &RV) : RetVals(RV) {}
+    explicit BVNImpl(std::vector<Value*> &RV) : RetVals(RV) {}
 
     void visitCastInst(CastInst &I);
     void visitGetElementPtrInst(GetElementPtrInst &I);