diff --git a/llvm/include/llvm/ADT/SmallVector.h b/llvm/include/llvm/ADT/SmallVector.h
--- a/llvm/include/llvm/ADT/SmallVector.h
+++ b/llvm/include/llvm/ADT/SmallVector.h
@@ -32,6 +32,8 @@
 
 namespace llvm {
 
+template <typename T> class ArrayRef;
+
 template <typename IteratorT> class iterator_range;
 
 template <class Iterator>
@@ -1208,6 +1210,12 @@
     this->append(IL);
   }
 
+  template <typename U,
+            typename = std::enable_if_t<std::is_convertible<U, T>::value>>
+  explicit SmallVector(ArrayRef<U> A) : SmallVectorImpl<T>(N) {
+    this->append(A.begin(), A.end());
+  }
+
   SmallVector(const SmallVector &RHS) : SmallVectorImpl<T>(N) {
     if (!RHS.empty())
       SmallVectorImpl<T>::operator=(RHS);
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -19421,7 +19421,7 @@
     }
 
     if (ElementOffset != -1) {
-      SmallVector<int, 16> NewMask(Mask.begin(), Mask.end());
+      SmallVector<int, 16> NewMask(Mask);
 
       auto *ExtrIndex = cast<ConstantSDNode>(InsertVal.getOperand(1));
       NewMask[InsIndex] = ElementOffset + ExtrIndex->getZExtValue();
@@ -22401,7 +22401,7 @@
   // First, check if we are taking one element of a vector and shuffling that
   // element into another vector.
   ArrayRef<int> Mask = Shuf->getMask();
-  SmallVector<int, 16> CommutedMask(Mask.begin(), Mask.end());
+  SmallVector<int, 16> CommutedMask(Mask);
   SDValue Op0 = Shuf->getOperand(0);
   SDValue Op1 = Shuf->getOperand(1);
   int ShufOp0Index = getShuffleMaskIndexOfOneElementFromOp0IntoOp1(Mask);
@@ -22712,7 +22712,7 @@
       if (SDValue InsertN1 = ShuffleToInsert(N0, N1, Mask))
         return InsertN1;
     if (N0.getOpcode() == ISD::CONCAT_VECTORS) {
-      SmallVector<int> CommuteMask(Mask.begin(), Mask.end());
+      SmallVector<int> CommuteMask(Mask);
       ShuffleVectorSDNode::commuteMask(CommuteMask);
       if (SDValue InsertN0 = ShuffleToInsert(N1, N0, CommuteMask))
         return InsertN0;
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -2286,7 +2286,7 @@
   // If Lo or Hi uses elements from at most two of the four input vectors, then
   // express it as a vector shuffle of those two inputs.  Otherwise extract the
   // input elements by hand and construct the Lo/Hi output using a BUILD_VECTOR.
-  SmallVector<int> OrigMask(N->getMask().begin(), N->getMask().end());
+  SmallVector<int> OrigMask(N->getMask());
   // Try to pack incoming shuffles/inputs.
   auto &&TryPeekThroughShufflesInputs = [&Inputs, &NewVT, this, NewElts,
                                          &DL](SmallVectorImpl<int> &Mask) {
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1895,7 +1895,7 @@
          "Index out of range");
 
   // Copy the mask so we can do any needed cleanup.
-  SmallVector<int, 8> MaskVec(Mask.begin(), Mask.end());
+  SmallVector<int, 8> MaskVec(Mask);
 
   // Canonicalize shuffle v, v -> v, undef
   if (N1 == N2) {
@@ -2051,7 +2051,7 @@
 
 SDValue SelectionDAG::getCommutedVectorShuffle(const ShuffleVectorSDNode &SV) {
   EVT VT = SV.getValueType(0);
-  SmallVector<int, 8> MaskVec(SV.getMask().begin(), SV.getMask().end());
+  SmallVector<int, 8> MaskVec(SV.getMask());
   ShuffleVectorSDNode::commuteMask(MaskVec);
 
   SDValue Op0 = SV.getOperand(0);
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3723,7 +3723,7 @@
       }
 
       // Calculate new mask.
-      SmallVector<int, 8> MappedOps(Mask.begin(), Mask.end());
+      SmallVector<int, 8> MappedOps(Mask);
       for (int &Idx : MappedOps) {
         if (Idx >= (int)SrcNumElts)
           Idx -= SrcNumElts + StartIdx[1] - MaskNumElts;
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -3220,7 +3220,7 @@
     // Simplify mask using undef elements from LHS/RHS.
     bool Updated = false;
     bool IdentityLHS = true, IdentityRHS = true;
-    SmallVector<int, 32> NewMask(ShuffleMask.begin(), ShuffleMask.end());
+    SmallVector<int, 32> NewMask(ShuffleMask);
     for (unsigned i = 0; i != NumElts; ++i) {
       int &M = NewMask[i];
       if (M < 0)
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -18334,7 +18334,7 @@
     if (S0->getOperand(0) == S1->getOperand(0) &&
         S0->getOperand(1) == S1->getOperand(1)) {
       // Construct complete shuffle mask
-      SmallVector<int, 8> Mask(S0->getMask().begin(), S0->getMask().end());
+      SmallVector<int, 8> Mask(S0->getMask());
       Mask.append(S1->getMask().begin(), S1->getMask().end());
 
       if (isVMOVNTruncMask(Mask, VT, false))
diff --git a/llvm/lib/Target/Hexagon/HexagonISelDAGToDAGHVX.cpp b/llvm/lib/Target/Hexagon/HexagonISelDAGToDAGHVX.cpp
--- a/llvm/lib/Target/Hexagon/HexagonISelDAGToDAGHVX.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonISelDAGToDAGHVX.cpp
@@ -1149,7 +1149,7 @@
 
   // Check if we can shuffle vector halves around to get the used elements
   // into a single vector.
-  SmallVector<int,128> MaskH(SM.Mask.begin(), SM.Mask.end());
+  SmallVector<int, 128> MaskH(SM.Mask);
   SmallVector<unsigned, 4> SegList = getInputSegmentList(SM.Mask, SegLen);
   unsigned SegCount = SegList.size();
   SmallVector<unsigned, 4> SegMap = getOutputSegmentMap(SM.Mask, SegLen);
@@ -1271,11 +1271,11 @@
 
   ShuffleMask SMH(MaskH);
   assert(SMH.Mask.size() == VecLen);
-  SmallVector<int,128> MaskA(SMH.Mask.begin(), SMH.Mask.end());
+  SmallVector<int, 128> MaskA(SMH.Mask);
 
   if (SMH.MaxSrc - SMH.MinSrc >= static_cast<int>(HwLen)) {
     // valign(Lo=Va,Hi=Vb) won't work. Try swapping Va/Vb.
-    SmallVector<int,128> Swapped(SMH.Mask.begin(), SMH.Mask.end());
+    SmallVector<int, 128> Swapped(SMH.Mask);
     ShuffleVectorSDNode::commuteMask(Swapped);
     ShuffleMask SW(Swapped);
     if (SW.MaxSrc - SW.MinSrc < static_cast<int>(HwLen)) {
@@ -1998,7 +1998,7 @@
   // a vector pair, but the two vectors in the pair are swapped.
   // The code below that identifies perfect shuffles will reject
   // it, unless the order is reversed.
-  SmallVector<int,128> MaskStorage(SM.Mask.begin(), SM.Mask.end());
+  SmallVector<int, 128> MaskStorage(SM.Mask);
   bool InvertedPair = false;
   if (HavePairs && SM.Mask[0] >= int(HwLen)) {
     for (int i = 0, e = SM.Mask.size(); i != e; ++i) {
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -14885,7 +14885,7 @@
   // Adjust the shuffle mask if either input vector comes from a
   // SCALAR_TO_VECTOR and keep the respective input vector in permuted
   // form (to prevent the need for a swap).
-  SmallVector<int, 16> ShuffV(Mask.begin(), Mask.end());
+  SmallVector<int, 16> ShuffV(Mask);
   SDValue SToVLHS = isScalarToVec(LHS);
   SDValue SToVRHS = isScalarToVec(RHS);
   if (SToVLHS || SToVRHS) {
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -6158,7 +6158,7 @@
                                     SmallVectorImpl<int> &WidenedMask) {
   // Create an alternative mask with info about zeroable elements.
   // Here we do not set undef elements as zeroable.
-  SmallVector<int, 64> ZeroableMask(Mask.begin(), Mask.end());
+  SmallVector<int, 64> ZeroableMask(Mask);
   if (V2IsZero) {
     assert(!Zeroable.isZero() && "V2's non-undef elements are used?!");
     for (int i = 0, Size = Mask.size(); i != Size; ++i)
@@ -11927,7 +11927,7 @@
   MVT VT = MVT::getVectorVT(EltVT, Mask.size());
 
   // We can't assume a canonical shuffle mask, so try the commuted version too.
-  SmallVector<int, 4> CommutedMask(Mask.begin(), Mask.end());
+  SmallVector<int, 4> CommutedMask(Mask);
   ShuffleVectorSDNode::commuteMask(CommutedMask);
 
   // Match any of unary/binary or low/high.
@@ -12786,7 +12786,7 @@
                                    SelectionDAG &DAG) {
   uint64_t BlendMask = 0;
   bool ForceV1Zero = false, ForceV2Zero = false;
-  SmallVector<int, 64> Mask(Original.begin(), Original.end());
+  SmallVector<int, 64> Mask(Original);
   if (!matchShuffleAsBlend(V1, V2, Mask, Zeroable, ForceV1Zero, ForceV2Zero,
                            BlendMask))
     return SDValue();
@@ -14242,7 +14242,7 @@
     assert(VT == ExtVT && "Cannot change extended type when non-zeroable!");
     if (!VT.isFloatingPoint() || V2Index != 0)
       return SDValue();
-    SmallVector<int, 8> V1Mask(Mask.begin(), Mask.end());
+    SmallVector<int, 8> V1Mask(Mask);
     V1Mask[V2Index] = -1;
     if (!isNoopShuffleMask(V1Mask))
       return SDValue();
@@ -14391,7 +14391,7 @@
   // Match extracts of each half of the wide source vector. Commute the shuffle
   // if the extract of the low half is N1.
   unsigned NumElts = VT.getVectorNumElements();
-  SmallVector<int, 4> NewMask(Mask.begin(), Mask.end());
+  SmallVector<int, 4> NewMask(Mask);
   const APInt &ExtIndex0 = N0.getConstantOperandAPInt(1);
   const APInt &ExtIndex1 = N1.getConstantOperandAPInt(1);
   if (ExtIndex1 == 0 && ExtIndex0 == NumElts)
@@ -14695,7 +14695,7 @@
     return true;
 
   // Commute and try again.
-  SmallVector<int, 4> CommutedMask(Mask.begin(), Mask.end());
+  SmallVector<int, 4> CommutedMask(Mask);
   ShuffleVectorSDNode::commuteMask(CommutedMask);
   if (matchAsInsertPS(V2, V1, CommutedMask))
     return true;
@@ -15030,7 +15030,7 @@
                                       ArrayRef<int> Mask, SDValue V1,
                                       SDValue V2, SelectionDAG &DAG) {
   SDValue LowV = V1, HighV = V2;
-  SmallVector<int, 4> NewMask(Mask.begin(), Mask.end());
+  SmallVector<int, 4> NewMask(Mask);
   int NumV2Elements = count_if(Mask, [](int M) { return M >= 4; });
 
   if (NumV2Elements == 1) {
@@ -15951,7 +15951,7 @@
       return Rotate;
 
     // Make a copy of the mask so it can be modified.
-    SmallVector<int, 8> MutableMask(Mask.begin(), Mask.end());
+    SmallVector<int, 8> MutableMask(Mask);
     return lowerV8I16GeneralSingleInputShuffle(DL, MVT::v8i16, V1, MutableMask,
                                                Subtarget, DAG);
   }
@@ -16135,7 +16135,7 @@
     // Adjust mask to correct indices for the second input.
     int NumElts = VT.getVectorNumElements();
     unsigned Scale = 512 / VT.getSizeInBits();
-    SmallVector<int, 32> AdjustedMask(Mask.begin(), Mask.end());
+    SmallVector<int, 32> AdjustedMask(Mask);
     for (int &M : AdjustedMask)
       if (NumElts <= M)
         M += (Scale - 1) * NumElts;
@@ -16881,7 +16881,7 @@
   assert(V2.isUndef() &&
          "This last part of this routine only works on single input shuffles");
 
-  SmallVector<int, 32> InLaneMask(Mask.begin(), Mask.end());
+  SmallVector<int, 32> InLaneMask(Mask);
   for (int i = 0; i < Size; ++i) {
     int &M = InLaneMask[i];
     if (M < 0)
@@ -19369,7 +19369,7 @@
   // the mask.
   if (V2IsUndef &&
       any_of(OrigMask, [NumElements](int M) { return M >= NumElements; })) {
-    SmallVector<int, 8> NewMask(OrigMask.begin(), OrigMask.end());
+    SmallVector<int, 8> NewMask(OrigMask);
     for (int &M : NewMask)
       if (M >= NumElements)
         M = -1;
@@ -19442,7 +19442,7 @@
   }
 
   SmallVector<SDValue> Ops = {V1, V2};
-  SmallVector<int> Mask(OrigMask.begin(), OrigMask.end());
+  SmallVector<int> Mask(OrigMask);
 
   // Canonicalize the shuffle with any horizontal ops inputs.
   // NOTE: This may update Ops and Mask.
@@ -37692,7 +37692,7 @@
       (MaskVT == MVT::v16i16 && Subtarget.hasAVX2())) {
     uint64_t BlendMask = 0;
     bool ForceV1Zero = false, ForceV2Zero = false;
-    SmallVector<int, 8> TargetMask(Mask.begin(), Mask.end());
+    SmallVector<int, 8> TargetMask(Mask);
     if (matchShuffleAsBlend(V1, V2, TargetMask, Zeroable, ForceV1Zero,
                             ForceV2Zero, BlendMask)) {
       if (MaskVT == MVT::v16i16) {
@@ -37895,7 +37895,7 @@
     return CanonicalizeShuffleInput(RootVT, V1);
   }
 
-  SmallVector<int, 64> Mask(BaseMask.begin(), BaseMask.end());
+  SmallVector<int, 64> Mask(BaseMask);
 
   // See if the shuffle is a hidden identity shuffle - repeated args in HOPs
   // etc. can be simplified.
@@ -38638,7 +38638,7 @@
   for (unsigned i = 1; i != NumInputs; ++i)
     Offsets[i] += i * Scale * NumMaskElts;
 
-  SmallVector<int, 64> WideMask(BaseMask.begin(), BaseMask.end());
+  SmallVector<int, 64> WideMask(BaseMask);
   for (int &M : WideMask) {
     if (M < 0)
       continue;
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1856,7 +1856,7 @@
       SrcOp2.isReg() ? GetRegisterName(SrcOp2.getReg()) : "mem";
 
   // One source operand, fix the mask to print all elements in one span.
-  SmallVector<int, 8> ShuffleMask(Mask.begin(), Mask.end());
+  SmallVector<int, 8> ShuffleMask(Mask);
   if (Src1Name == Src2Name)
     for (int i = 0, e = ShuffleMask.size(); i != e; ++i)
       if (ShuffleMask[i] >= e)
diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -7662,7 +7662,7 @@
 
   /// Functions adds masks, merging them into  single one.
   void addMask(ArrayRef<unsigned> SubMask) {
-    SmallVector<int, 4> NewMask(SubMask.begin(), SubMask.end());
+    SmallVector<int, 4> NewMask(SubMask);
     addMask(NewMask);
   }
 
@@ -8758,7 +8758,7 @@
       return PoisonValue::get(FixedVectorType::get(
           cast<VectorType>(V1->getType())->getElementType(), Mask.size()));
     Value *Op = V1;
-    SmallVector<int> CombinedMask(Mask.begin(), Mask.end());
+    SmallVector<int> CombinedMask(Mask);
     PeekThroughShuffles(Op, CombinedMask);
     if (!isa<FixedVectorType>(Op->getType()) ||
         !IsIdentityMask(CombinedMask, cast<FixedVectorType>(Op->getType()))) {
diff --git a/llvm/unittests/ADT/SmallVectorTest.cpp b/llvm/unittests/ADT/SmallVectorTest.cpp
--- a/llvm/unittests/ADT/SmallVectorTest.cpp
+++ b/llvm/unittests/ADT/SmallVectorTest.cpp
@@ -246,6 +246,18 @@
   assertValuesInOrder(V, 3u, 1, 2, 3);
 }
 
+// Constructor test.
+TYPED_TEST(SmallVectorTest, ConstructorFromArrayRefSimpleTest) {
+  SCOPED_TRACE("ConstructorFromArrayRefSimpleTest");
+  std::array<Constructable, 3> StdArray = {Constructable(1), Constructable(2),
+                                           Constructable(3)};
+  ArrayRef<Constructable> Array = StdArray;
+  auto &V = this->theVector;
+  V = SmallVector<Constructable, 4>(Array);
+  assertValuesInOrder(V, 3u, 1, 2, 3);
+  ASSERT_EQ(NumBuiltinElts(TypeParam{}), NumBuiltinElts(V));
+}
+
 // New vector test.
 TYPED_TEST(SmallVectorTest, EmptyVectorTest) {
   SCOPED_TRACE("EmptyVectorTest");
@@ -1130,6 +1142,44 @@
   EXPECT_TRUE(makeArrayRef(V2).equals({4, 5, 3, 2}));
 }
 
+struct To {
+  int Content;
+  friend bool operator==(const To &LHS, const To &RHS) {
+    return LHS.Content == RHS.Content;
+  }
+};
+
+class From {
+public:
+  From() = default;
+  From(To M) { T = M; }
+  operator To() const { return T; }
+
+private:
+  To T;
+};
+
+TEST(SmallVectorTest, ConstructFromArrayRefOfConvertibleType) {
+  To to1{1}, to2{2}, to3{3};
+  std::vector<From> StdVector = {From(to1), From(to2), From(to3)};
+  ArrayRef<From> Array = StdVector;
+  {
+    llvm::SmallVector<To> Vector(Array);
+
+    ASSERT_EQ(Array.size(), Vector.size());
+    for (size_t I = 0; I < Array.size(); ++I)
+      EXPECT_EQ(Array[I], Vector[I]);
+  }
+  {
+    llvm::SmallVector<To, 4> Vector(Array);
+
+    ASSERT_EQ(Array.size(), Vector.size());
+    ASSERT_EQ(4u, NumBuiltinElts(Vector));
+    for (size_t I = 0; I < Array.size(); ++I)
+      EXPECT_EQ(Array[I], Vector[I]);
+  }
+}
+
 template <class VectorT>
 class SmallVectorReferenceInvalidationTest : public SmallVectorTestBase {
 protected: