diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -1812,6 +1812,14 @@
   C.insert(C.end(), R.begin(), R.end());
 }
 
+/// Wrapper function to insert a range in an associative container.
+///
+/// C.insert(R.begin(), R.end());
+template <typename Container, typename Range>
+inline void insert_range(Container &C, Range &&R) {
+  C.insert(R.begin(), R.end());
+}
+
 /// Given a sequence container Cont, replace the range [ContIt, ContEnd) with
 /// the range [ValIt, ValEnd) (which is not from the same container).
 template<typename Container, typename RandomAccessIterator>
diff --git a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
--- a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
+++ b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
@@ -34,6 +34,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/ScopeExit.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
@@ -186,7 +187,7 @@
       // Simple byval argument? Just add all the struct element types.
       Type *AgTy = I->getParamByValType();
       StructType *STy = cast<StructType>(AgTy);
-      llvm::append_range(Params, STy->elements());
+      append_range(Params, STy->elements());
       ArgAttrVec.insert(ArgAttrVec.end(), STy->getNumElements(),
                         AttributeSet());
       ++NumByValArgsPromoted;
@@ -573,26 +574,21 @@
 
   // Now look at all loads of the argument. Remember the load instructions
   // for the aliasing check below.
-  SmallVector<Value *, 16> Worklist;
-  SmallPtrSet<Value *, 16> Visited;
+  SmallSetVector<Value *, 16> Worklist;
   SmallVector<LoadInst *, 16> Loads;
-  auto AppendUsers = [&](Value *V) {
-    for (User *U : V->users())
-      if (Visited.insert(U).second)
-        Worklist.push_back(U);
-  };
-  AppendUsers(Arg);
+
+  insert_range(Worklist, Arg->users());
   while (!Worklist.empty()) {
     Value *V = Worklist.pop_back_val();
     if (isa<BitCastInst>(V)) {
-      AppendUsers(V);
+      insert_range(Worklist, V->users());
       continue;
     }
 
     if (auto *GEP = dyn_cast<GetElementPtrInst>(V)) {
       if (!GEP->hasAllConstantIndices())
         return false;
-      AppendUsers(V);
+      insert_range(Worklist, V->users());
       continue;
     }
 
diff --git a/llvm/unittests/ADT/STLExtrasTest.cpp b/llvm/unittests/ADT/STLExtrasTest.cpp
--- a/llvm/unittests/ADT/STLExtrasTest.cpp
+++ b/llvm/unittests/ADT/STLExtrasTest.cpp
@@ -11,6 +11,7 @@
 
 #include <climits>
 #include <list>
+#include <unordered_set>
 #include <vector>
 
 using namespace llvm;
@@ -379,6 +380,16 @@
   EXPECT_EQ(3, V[2]);
 }
 
+TEST(STLExtrasTest, InsertRange) {
+  auto InsertVals = {3, 4, 5};
+  std::unordered_set<int> S = {1, 2, 6};
+  insert_range(S, InsertVals);
+  EXPECT_EQ(S.size(), 6u);
+  for (int I = 1; I <= 6; I++) {
+    EXPECT_NE(S.find(I), S.end());
+  }
+}
+
 namespace some_namespace {
 struct some_struct {
   std::vector<int> data;