diff --git a/lld/MachO/UnwindInfoSection.cpp b/lld/MachO/UnwindInfoSection.cpp
--- a/lld/MachO/UnwindInfoSection.cpp
+++ b/lld/MachO/UnwindInfoSection.cpp
@@ -146,7 +146,7 @@
   Symbol *canonicalizePersonality(Symbol *);
 
   uint64_t unwindInfoSize = 0;
-  std::vector<decltype(symbols)::value_type> symbolsVec;
+  SmallVector<decltype(symbols)::value_type, 0> symbolsVec;
   CompactUnwindLayout cuLayout;
   std::vector<std::pair<compact_unwind_encoding_t, size_t>> commonEncodings;
   EncodingMap commonEncodingIndexes;
diff --git a/llvm/include/llvm/ADT/MapVector.h b/llvm/include/llvm/ADT/MapVector.h
--- a/llvm/include/llvm/ADT/MapVector.h
+++ b/llvm/include/llvm/ADT/MapVector.h
@@ -10,7 +10,7 @@
 /// This file implements a map that provides insertion order iteration. The
 /// interface is purposefully minimal. The key is assumed to be cheap to copy
 /// and 2 copies are kept, one for indexing in a DenseMap, one for iteration in
-/// a std::vector.
+/// a SmallVector.
 ///
 //===----------------------------------------------------------------------===//
 
@@ -24,16 +24,15 @@
 #include <iterator>
 #include <type_traits>
 #include <utility>
-#include <vector>
 
 namespace llvm {
 
 /// This class implements a map that also provides access to all stored values
-/// in a deterministic order. The values are kept in a std::vector and the
+/// in a deterministic order. The values are kept in a SmallVector<*, 0> and the
 /// mapping is done with DenseMap from Keys to indexes in that vector.
-template<typename KeyT, typename ValueT,
-         typename MapType = DenseMap<KeyT, unsigned>,
-         typename VectorType = std::vector<std::pair<KeyT, ValueT>>>
+template <typename KeyT, typename ValueT,
+          typename MapType = DenseMap<KeyT, unsigned>,
+          typename VectorType = SmallVector<std::pair<KeyT, ValueT>, 0>>
 class MapVector {
   MapType Map;
   VectorType Vector;
diff --git a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
--- a/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
+++ b/llvm/lib/Analysis/ModuleSummaryAnalysis.cpp
@@ -266,7 +266,9 @@
   unsigned NumInsts = 0;
   // Map from callee ValueId to profile count. Used to accumulate profile
   // counts for all static calls to a given callee.
-  MapVector<ValueInfo, CalleeInfo> CallGraphEdges;
+  MapVector<ValueInfo, CalleeInfo, DenseMap<ValueInfo, unsigned>,
+            std::vector<std::pair<ValueInfo, CalleeInfo>>>
+      CallGraphEdges;
   SetVector<ValueInfo> RefEdges, LoadRefEdges, StoreRefEdges;
   SetVector<GlobalValue::GUID> TypeTests;
   SetVector<FunctionSummary::VFuncId> TypeTestAssumeVCalls,