Index: clang/include/clang/AST/StmtIterator.h
===================================================================
--- clang/include/clang/AST/StmtIterator.h
+++ clang/include/clang/AST/StmtIterator.h
@@ -74,14 +74,17 @@
 };
 
 template <typename DERIVED, typename REFERENCE>
-class StmtIteratorImpl : public StmtIteratorBase,
-                         public std::iterator<std::forward_iterator_tag,
-                                              REFERENCE, ptrdiff_t,
-                                              REFERENCE, REFERENCE> {
+class StmtIteratorImpl : public StmtIteratorBase {
 protected:
   StmtIteratorImpl(const StmtIteratorBase& RHS) : StmtIteratorBase(RHS) {}
 
 public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = REFERENCE;
+  using difference_type = std::ptrdiff_t;
+  using pointer = REFERENCE;
+  using reference = REFERENCE;
+
   StmtIteratorImpl() = default;
   StmtIteratorImpl(Stmt **s) : StmtIteratorBase(s) {}
   StmtIteratorImpl(Decl **dgi, Decl **dge) : StmtIteratorBase(dgi, dge) {}
Index: clang/include/clang/Rewrite/Core/RewriteRope.h
===================================================================
--- clang/include/clang/Rewrite/Core/RewriteRope.h
+++ clang/include/clang/Rewrite/Core/RewriteRope.h
@@ -83,8 +83,7 @@
   /// over bytes that are in a RopePieceBTree.  This first iterates over bytes
   /// in a RopePiece, then iterates over RopePiece's in a RopePieceBTreeLeaf,
   /// then iterates over RopePieceBTreeLeaf's in a RopePieceBTree.
-  class RopePieceBTreeIterator :
-      public std::iterator<std::forward_iterator_tag, const char, ptrdiff_t> {
+  class RopePieceBTreeIterator {
     /// CurNode - The current B+Tree node that we are inspecting.
     const void /*RopePieceBTreeLeaf*/ *CurNode = nullptr;
 
@@ -96,6 +95,12 @@
     unsigned CurChar = 0;
 
   public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = const char;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     RopePieceBTreeIterator() = default;
     RopePieceBTreeIterator(const void /*RopePieceBTreeNode*/ *N);
 
Index: llvm/include/llvm/ADT/BreadthFirstIterator.h
===================================================================
--- llvm/include/llvm/ADT/BreadthFirstIterator.h
+++ llvm/include/llvm/ADT/BreadthFirstIterator.h
@@ -44,11 +44,15 @@
           class SetType =
               bf_iterator_default_set<typename GraphTraits<GraphT>::NodeRef>,
           class GT = GraphTraits<GraphT>>
-class bf_iterator
-    : public std::iterator<std::forward_iterator_tag, typename GT::NodeRef>,
-      public bf_iterator_storage<SetType> {
-  using super = std::iterator<std::forward_iterator_tag, typename GT::NodeRef>;
+class bf_iterator : public bf_iterator_storage<SetType> {
+public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = typename GT::NodeRef;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
 
+private:
   using NodeRef = typename GT::NodeRef;
   using ChildItTy = typename GT::ChildIteratorType;
 
@@ -62,7 +66,6 @@
   // Current level.
   unsigned Level;
 
-private:
   inline bf_iterator(NodeRef Node) {
     this->Visited.insert(Node);
     Level = 0;
@@ -107,8 +110,6 @@
   }
 
 public:
-  using pointer = typename super::pointer;
-
   // Provide static begin and end methods as our public "constructors"
   static bf_iterator begin(const GraphT &G) {
     return bf_iterator(GT::getEntryNode(G));
Index: llvm/include/llvm/ADT/CoalescingBitVector.h
===================================================================
--- llvm/include/llvm/ADT/CoalescingBitVector.h
+++ llvm/include/llvm/ADT/CoalescingBitVector.h
@@ -231,10 +231,17 @@
 
   bool operator!=(const ThisT &RHS) const { return !operator==(RHS); }
 
-  class const_iterator
-      : public std::iterator<std::forward_iterator_tag, IndexT> {
+  class const_iterator {
     friend class CoalescingBitVector;
 
+  public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = IndexT;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
+  private:
     // For performance reasons, make the offset at the end different than the
     // one used in \ref begin, to optimize the common `It == end()` pattern.
     static constexpr unsigned kIteratorAtTheEndOffset = ~0u;
Index: llvm/include/llvm/ADT/DepthFirstIterator.h
===================================================================
--- llvm/include/llvm/ADT/DepthFirstIterator.h
+++ llvm/include/llvm/ADT/DepthFirstIterator.h
@@ -82,10 +82,15 @@
           class SetType =
               df_iterator_default_set<typename GraphTraits<GraphT>::NodeRef>,
           bool ExtStorage = false, class GT = GraphTraits<GraphT>>
-class df_iterator
-    : public std::iterator<std::forward_iterator_tag, typename GT::NodeRef>,
-      public df_iterator_storage<SetType, ExtStorage> {
-  using super = std::iterator<std::forward_iterator_tag, typename GT::NodeRef>;
+class df_iterator : public df_iterator_storage<SetType, ExtStorage> {
+public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = typename GT::NodeRef;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
+private:
   using NodeRef = typename GT::NodeRef;
   using ChildItTy = typename GT::ChildIteratorType;
 
@@ -97,7 +102,6 @@
   // VisitStack - Used to maintain the ordering.  Top = current block
   std::vector<StackElement> VisitStack;
 
-private:
   inline df_iterator(NodeRef Node) {
     this->Visited.insert(Node);
     VisitStack.push_back(StackElement(Node, None));
@@ -144,8 +148,6 @@
   }
 
 public:
-  using pointer = typename super::pointer;
-
   // Provide static begin and end methods as our public "constructors"
   static df_iterator begin(const GraphT &G) {
     return df_iterator(GT::getEntryNode(G));
Index: llvm/include/llvm/ADT/EquivalenceClasses.h
===================================================================
--- llvm/include/llvm/ADT/EquivalenceClasses.h
+++ llvm/include/llvm/ADT/EquivalenceClasses.h
@@ -248,19 +248,18 @@
     return It != member_end() && It == findLeader(V2);
   }
 
-  class member_iterator : public std::iterator<std::forward_iterator_tag,
-                                               const ElemTy, ptrdiff_t> {
+  class member_iterator {
     friend class EquivalenceClasses;
 
-    using super = std::iterator<std::forward_iterator_tag,
-                                const ElemTy, ptrdiff_t>;
-
     const ECValue *Node;
 
   public:
-    using size_type = size_t;
-    using pointer = typename super::pointer;
-    using reference = typename super::reference;
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = const ElemTy;
+    using size_type = std::size_t;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
 
     explicit member_iterator() = default;
     explicit member_iterator(const ECValue *N) : Node(N) {}
Index: llvm/include/llvm/ADT/ImmutableSet.h
===================================================================
--- llvm/include/llvm/ADT/ImmutableSet.h
+++ llvm/include/llvm/ADT/ImmutableSet.h
@@ -652,12 +652,16 @@
 //===----------------------------------------------------------------------===//
 
 template <typename ImutInfo>
-class ImutAVLTreeGenericIterator
-    : public std::iterator<std::bidirectional_iterator_tag,
-                           ImutAVLTree<ImutInfo>> {
+class ImutAVLTreeGenericIterator {
   SmallVector<uintptr_t,20> stack;
 
 public:
+  using iterator_category = std::bidirectional_iterator_tag;
+  using value_type = ImutAVLTree<ImutInfo>;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   enum VisitFlag { VisitedNone=0x0, VisitedLeft=0x1, VisitedRight=0x3,
                    Flags=0x3 };
 
@@ -763,14 +767,18 @@
 };
 
 template <typename ImutInfo>
-class ImutAVLTreeInOrderIterator
-    : public std::iterator<std::bidirectional_iterator_tag,
-                           ImutAVLTree<ImutInfo>> {
+class ImutAVLTreeInOrderIterator {
   using InternalIteratorTy = ImutAVLTreeGenericIterator<ImutInfo>;
 
   InternalIteratorTy InternalItr;
 
 public:
+  using iterator_category = std::bidirectional_iterator_tag;
+  using value_type = ImutAVLTree<ImutInfo>;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   using TreeTy = ImutAVLTree<ImutInfo>;
 
   ImutAVLTreeInOrderIterator(const TreeTy* Root) : InternalItr(Root) {
Index: llvm/include/llvm/ADT/IntervalMap.h
===================================================================
--- llvm/include/llvm/ADT/IntervalMap.h
+++ llvm/include/llvm/ADT/IntervalMap.h
@@ -63,9 +63,14 @@
 // };
 //
 // template <typename KeyT, typename ValT, unsigned N, typename Traits>
-// class IntervalMap::const_iterator :
-//   public std::iterator<std::bidirectional_iterator_tag, ValT> {
+// class IntervalMap::const_iterator {
 // public:
+//   using iterator_category = std::bidirectional_iterator_tag;
+//   using value_type = ValT;
+//   using difference_type = std::ptrdiff_t;
+//   using pointer = value_type *;
+//   using reference = value_type &;
+//
 //   bool operator==(const const_iterator &) const;
 //   bool operator!=(const const_iterator &) const;
 //   bool valid() const;
@@ -1289,12 +1294,17 @@
 //===----------------------------------------------------------------------===//
 
 template <typename KeyT, typename ValT, unsigned N, typename Traits>
-class IntervalMap<KeyT, ValT, N, Traits>::const_iterator :
-  public std::iterator<std::bidirectional_iterator_tag, ValT> {
-
-protected:
+class IntervalMap<KeyT, ValT, N, Traits>::const_iterator {
   friend class IntervalMap;
 
+public:
+  using iterator_category = std::bidirectional_iterator_tag;
+  using value_type = ValT;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
+protected:
   // The map referred to.
   IntervalMap *map = nullptr;
 
Index: llvm/include/llvm/ADT/PostOrderIterator.h
===================================================================
--- llvm/include/llvm/ADT/PostOrderIterator.h
+++ llvm/include/llvm/ADT/PostOrderIterator.h
@@ -93,10 +93,15 @@
           class SetType =
               SmallPtrSet<typename GraphTraits<GraphT>::NodeRef, 8>,
           bool ExtStorage = false, class GT = GraphTraits<GraphT>>
-class po_iterator
-    : public std::iterator<std::forward_iterator_tag, typename GT::NodeRef>,
-      public po_iterator_storage<SetType, ExtStorage> {
-  using super = std::iterator<std::forward_iterator_tag, typename GT::NodeRef>;
+class po_iterator : public po_iterator_storage<SetType, ExtStorage> {
+public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = typename GT::NodeRef;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
+private:
   using NodeRef = typename GT::NodeRef;
   using ChildItTy = typename GT::ChildIteratorType;
 
@@ -135,8 +140,6 @@
   }
 
 public:
-  using pointer = typename super::pointer;
-
   // Provide static "constructors"...
   static po_iterator begin(GraphT G) {
     return po_iterator(GT::getEntryNode(G));
Index: llvm/include/llvm/ADT/SparseMultiSet.h
===================================================================
--- llvm/include/llvm/ADT/SparseMultiSet.h
+++ llvm/include/llvm/ADT/SparseMultiSet.h
@@ -217,10 +217,17 @@
   /// Our iterators are iterators over the collection of objects that share a
   /// key.
   template<typename SMSPtrTy>
-  class iterator_base : public std::iterator<std::bidirectional_iterator_tag,
-                                             ValueT> {
+  class iterator_base {
     friend class SparseMultiSet;
 
+  public:
+    using iterator_category = std::bidirectional_iterator_tag;
+    using value_type = ValueT;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
+  private:
     SMSPtrTy SMS;
     unsigned Idx;
     unsigned SparseIdx;
@@ -247,12 +254,6 @@
     void setNext(unsigned N) { SMS->Dense[Idx].Next = N; }
 
   public:
-    using super = std::iterator<std::bidirectional_iterator_tag, ValueT>;
-    using value_type = typename super::value_type;
-    using difference_type = typename super::difference_type;
-    using pointer = typename super::pointer;
-    using reference = typename super::reference;
-
     reference operator*() const {
       assert(isKeyed() && SMS->sparseIndex(SMS->Dense[Idx].Data) == SparseIdx &&
              "Dereferencing iterator of invalid key or index");
@@ -411,7 +412,7 @@
   RangePair equal_range(const KeyT &K) {
     iterator B = find(K);
     iterator E = iterator(this, SMSNode::INVALID, B.SparseIdx);
-    return make_pair(B, E);
+    return std::make_pair(B, E);
   }
 
   /// Insert a new element at the tail of the subset list. Returns an iterator
Index: llvm/include/llvm/ADT/iterator.h
===================================================================
--- llvm/include/llvm/ADT/iterator.h
+++ llvm/include/llvm/ADT/iterator.h
@@ -64,9 +64,14 @@
 template <typename DerivedT, typename IteratorCategoryT, typename T,
           typename DifferenceTypeT = std::ptrdiff_t, typename PointerT = T *,
           typename ReferenceT = T &>
-class iterator_facade_base
-    : public std::iterator<IteratorCategoryT, T, DifferenceTypeT, PointerT,
-                           ReferenceT> {
+class iterator_facade_base {
+public:
+  using iterator_category = IteratorCategoryT;
+  using value_type = T;
+  using difference_type = DifferenceTypeT;
+  using pointer = PointerT;
+  using reference = ReferenceT;
+
 protected:
   enum {
     IsRandomAccess = std::is_base_of<std::random_access_iterator_tag,
Index: llvm/include/llvm/Analysis/AliasSetTracker.h
===================================================================
--- llvm/include/llvm/Analysis/AliasSetTracker.h
+++ llvm/include/llvm/Analysis/AliasSetTracker.h
@@ -232,11 +232,16 @@
   void dump() const;
 
   /// Define an iterator for alias sets... this is just a forward iterator.
-  class iterator : public std::iterator<std::forward_iterator_tag,
-                                        PointerRec, ptrdiff_t> {
+  class iterator {
     PointerRec *CurNode;
 
   public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = PointerRec;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     explicit iterator(PointerRec *CN = nullptr) : CurNode(CN) {}
 
     bool operator==(const iterator& x) const {
Index: llvm/include/llvm/Analysis/MemorySSA.h
===================================================================
--- llvm/include/llvm/Analysis/MemorySSA.h
+++ llvm/include/llvm/Analysis/MemorySSA.h
@@ -1100,7 +1100,7 @@
     return MP->getIncomingBlock(ArgNo);
   }
 
-  typename BaseT::iterator::pointer operator*() const {
+  typename std::iterator_traits<BaseT>::pointer operator*() const {
     assert(Access && "Tried to access past the end of our iterator");
     // Go to the first argument for phis, and the defining access for everything
     // else.
@@ -1196,7 +1196,7 @@
     return DefIterator == Other.DefIterator;
   }
 
-  BaseT::iterator::reference operator*() const {
+  typename std::iterator_traits<BaseT>::reference operator*() const {
     assert(DefIterator != OriginalAccess->defs_end() &&
            "Tried to access past the end of our iterator");
     return CurrentPair;
Index: llvm/include/llvm/Analysis/RegionIterator.h
===================================================================
--- llvm/include/llvm/Analysis/RegionIterator.h
+++ llvm/include/llvm/Analysis/RegionIterator.h
@@ -36,9 +36,15 @@
 /// For a subregion RegionNode there is just one successor. The RegionNode
 /// representing the exit of the subregion.
 template <class NodeRef, class BlockT, class RegionT>
-class RNSuccIterator
-    : public std::iterator<std::forward_iterator_tag, NodeRef> {
-  using super = std::iterator<std::forward_iterator_tag, NodeRef>;
+class RNSuccIterator {
+public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = NodeRef;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
+private:
   using BlockTraits = GraphTraits<BlockT *>;
   using SuccIterTy = typename BlockTraits::ChildIteratorType;
 
@@ -99,7 +105,6 @@
 
 public:
   using Self = RNSuccIterator<NodeRef, BlockT, RegionT>;
-  using value_type = typename super::value_type;
 
   /// Create begin iterator of a RegionNode.
   inline RNSuccIterator(NodeRef node)
@@ -163,9 +168,7 @@
 /// are contained in the Region and its subregions. This is close to a virtual
 /// control flow graph of the Region.
 template <class NodeRef, class BlockT, class RegionT>
-class RNSuccIterator<FlatIt<NodeRef>, BlockT, RegionT>
-    : public std::iterator<std::forward_iterator_tag, NodeRef> {
-  using super = std::iterator<std::forward_iterator_tag, NodeRef>;
+class RNSuccIterator<FlatIt<NodeRef>, BlockT, RegionT> {
   using BlockTraits = GraphTraits<BlockT *>;
   using SuccIterTy = typename BlockTraits::ChildIteratorType;
 
@@ -173,8 +176,13 @@
   SuccIterTy Itor;
 
 public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = NodeRef;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   using Self = RNSuccIterator<FlatIt<NodeRef>, BlockT, RegionT>;
-  using value_type = typename super::value_type;
 
   /// Create the iterator from a RegionNode.
   ///
Index: llvm/include/llvm/CodeGen/MachineRegisterInfo.h
===================================================================
--- llvm/include/llvm/CodeGen/MachineRegisterInfo.h
+++ llvm/include/llvm/CodeGen/MachineRegisterInfo.h
@@ -970,10 +970,17 @@
   /// when incrementing.
   template <bool ReturnUses, bool ReturnDefs, bool SkipDebug, bool ByOperand,
             bool ByInstr, bool ByBundle>
-  class defusechain_iterator : public std::iterator<std::forward_iterator_tag,
-                                                    MachineOperand, ptrdiff_t> {
+  class defusechain_iterator {
     friend class MachineRegisterInfo;
 
+  public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = MachineOperand;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
+  private:
     MachineOperand *Op = nullptr;
 
     explicit defusechain_iterator(MachineOperand *op) : Op(op) {
@@ -1008,11 +1015,6 @@
     }
 
   public:
-    using reference = std::iterator<std::forward_iterator_tag, MachineOperand,
-                                    ptrdiff_t>::reference;
-    using pointer = std::iterator<std::forward_iterator_tag, MachineOperand,
-                                  ptrdiff_t>::pointer;
-
     defusechain_iterator() = default;
 
     bool operator==(const defusechain_iterator &x) const {
@@ -1076,10 +1078,17 @@
   /// when incrementing.
   template<bool ReturnUses, bool ReturnDefs, bool SkipDebug,
            bool ByOperand, bool ByInstr, bool ByBundle>
-  class defusechain_instr_iterator
-    : public std::iterator<std::forward_iterator_tag, MachineInstr, ptrdiff_t> {
+  class defusechain_instr_iterator {
     friend class MachineRegisterInfo;
 
+  public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = MachineInstr;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
+  private:
     MachineOperand *Op = nullptr;
 
     explicit defusechain_instr_iterator(MachineOperand *op) : Op(op) {
@@ -1114,11 +1123,6 @@
     }
 
   public:
-    using reference = std::iterator<std::forward_iterator_tag,
-                                    MachineInstr, ptrdiff_t>::reference;
-    using pointer = std::iterator<std::forward_iterator_tag,
-                                  MachineInstr, ptrdiff_t>::pointer;
-
     defusechain_instr_iterator() = default;
 
     bool operator==(const defusechain_instr_iterator &x) const {
Index: llvm/include/llvm/CodeGen/ScheduleDAG.h
===================================================================
--- llvm/include/llvm/CodeGen/ScheduleDAG.h
+++ llvm/include/llvm/CodeGen/ScheduleDAG.h
@@ -614,14 +614,19 @@
     const MCInstrDesc *getNodeDesc(const SDNode *Node) const;
   };
 
-  class SUnitIterator : public std::iterator<std::forward_iterator_tag,
-                                             SUnit, ptrdiff_t> {
+  class SUnitIterator {
     SUnit *Node;
     unsigned Operand;
 
     SUnitIterator(SUnit *N, unsigned Op) : Node(N), Operand(Op) {}
 
   public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = SUnit;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     bool operator==(const SUnitIterator& x) const {
       return Operand == x.Operand;
     }
Index: llvm/include/llvm/CodeGen/SelectionDAGNodes.h
===================================================================
--- llvm/include/llvm/CodeGen/SelectionDAGNodes.h
+++ llvm/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -716,8 +716,7 @@
 
   /// This class provides iterator support for SDUse
   /// operands that use a specific SDNode.
-  class use_iterator
-    : public std::iterator<std::forward_iterator_tag, SDUse, ptrdiff_t> {
+  class use_iterator {
     friend class SDNode;
 
     SDUse *Op = nullptr;
@@ -725,10 +724,11 @@
     explicit use_iterator(SDUse *op) : Op(op) {}
 
   public:
-    using reference = std::iterator<std::forward_iterator_tag,
-                                    SDUse, ptrdiff_t>::reference;
-    using pointer = std::iterator<std::forward_iterator_tag,
-                                  SDUse, ptrdiff_t>::pointer;
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = SDUse;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
 
     use_iterator() = default;
     use_iterator(const use_iterator &I) : Op(I.Op) {}
@@ -2592,14 +2592,19 @@
   }
 };
 
-class SDNodeIterator : public std::iterator<std::forward_iterator_tag,
-                                            SDNode, ptrdiff_t> {
+class SDNodeIterator {
   const SDNode *Node;
   unsigned Operand;
 
   SDNodeIterator(const SDNode *N, unsigned Op) : Node(N), Operand(Op) {}
 
 public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = SDNode;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   bool operator==(const SDNodeIterator& x) const {
     return Operand == x.Operand;
   }
Index: llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
===================================================================
--- llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
+++ llvm/include/llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h
@@ -140,7 +140,7 @@
     friend class ValueIterator;
   };
 
-  class ValueIterator : public std::iterator<std::input_iterator_tag, Entry> {
+  class ValueIterator {
     const AppleAcceleratorTable *AccelTable = nullptr;
     Entry Current;           ///< The current entry.
     uint64_t DataOffset = 0; ///< Offset into the section.
@@ -149,7 +149,14 @@
 
     /// Advance the iterator.
     void Next();
+
   public:
+    using iterator_category = std::input_iterator_tag;
+    using value_type = Entry;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     /// Construct a new iterator for the entries at \p DataOffset.
     ValueIterator(const AppleAcceleratorTable &AccelTable, uint64_t DataOffset);
     /// End marker.
@@ -466,8 +473,15 @@
     friend class DWARFDebugNames;
   };
 
-  class ValueIterator : public std::iterator<std::input_iterator_tag, Entry> {
+  class ValueIterator {
+  public:
+    using iterator_category = std::input_iterator_tag;
+    using value_type = Entry;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
 
+  private:
     /// The Name Index we are currently iterating through. The implementation
     /// relies on the fact that this can also be used as an iterator into the
     /// "NameIndices" vector in the Accelerator section.
Index: llvm/include/llvm/IR/CFG.h
===================================================================
--- llvm/include/llvm/IR/CFG.h
+++ llvm/include/llvm/IR/CFG.h
@@ -40,10 +40,15 @@
 //===----------------------------------------------------------------------===//
 
 template <class Ptr, class USE_iterator> // Predecessor Iterator
-class PredIterator : public std::iterator<std::forward_iterator_tag,
-                                          Ptr, ptrdiff_t, Ptr*, Ptr*> {
-  using super =
-      std::iterator<std::forward_iterator_tag, Ptr, ptrdiff_t, Ptr*, Ptr*>;
+class PredIterator {
+public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = Ptr;
+  using difference_type = std::ptrdiff_t;
+  using pointer = Ptr *;
+  using reference = Ptr *;
+
+private:
   using Self = PredIterator<Ptr, USE_iterator>;
   USE_iterator It;
 
@@ -59,9 +64,6 @@
   }
 
 public:
-  using pointer = typename super::pointer;
-  using reference = typename super::reference;
-
   PredIterator() = default;
   explicit inline PredIterator(Ptr *bb) : It(bb->user_begin()) {
     advancePastNonTerminators();
Index: llvm/include/llvm/IR/DebugInfoMetadata.h
===================================================================
--- llvm/include/llvm/IR/DebugInfoMetadata.h
+++ llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -80,11 +80,16 @@
     return cast_or_null<DIType>(N->getOperand(I));
   }
 
-  class iterator : std::iterator<std::input_iterator_tag, DIType *,
-                                 std::ptrdiff_t, void, DIType *> {
+  class iterator {
     MDNode::op_iterator I = nullptr;
 
   public:
+    using iterator_category = std::input_iterator_tag;
+    using value_type = DIType *;
+    using difference_type = std::ptrdiff_t;
+    using pointer = void;
+    using reference = DIType *;
+
     iterator() = default;
     explicit iterator(MDNode::op_iterator I) : I(I) {}
 
@@ -2629,11 +2634,16 @@
   };
 
   /// An iterator for expression operands.
-  class expr_op_iterator
-      : public std::iterator<std::input_iterator_tag, ExprOperand> {
+  class expr_op_iterator {
     ExprOperand Op;
 
   public:
+    using iterator_category = std::input_iterator_tag;
+    using value_type = ExprOperand;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     expr_op_iterator() = default;
     explicit expr_op_iterator(element_iterator I) : Op(I) {}
 
Index: llvm/include/llvm/IR/GetElementPtrTypeIterator.h
===================================================================
--- llvm/include/llvm/IR/GetElementPtrTypeIterator.h
+++ llvm/include/llvm/IR/GetElementPtrTypeIterator.h
@@ -28,9 +28,7 @@
 namespace llvm {
 
   template<typename ItTy = User::const_op_iterator>
-  class generic_gep_type_iterator
-    : public std::iterator<std::forward_iterator_tag, Type *, ptrdiff_t> {
-    using super = std::iterator<std::forward_iterator_tag, Type *, ptrdiff_t>;
+  class generic_gep_type_iterator {
 
     ItTy OpIt;
     PointerUnion<StructType *, Type *> CurTy;
@@ -40,6 +38,12 @@
     generic_gep_type_iterator() = default;
 
   public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = Type *;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     static generic_gep_type_iterator begin(Type *Ty, ItTy It) {
       generic_gep_type_iterator I;
       I.CurTy = Ty;
Index: llvm/include/llvm/IR/Metadata.h
===================================================================
--- llvm/include/llvm/IR/Metadata.h
+++ llvm/include/llvm/IR/Metadata.h
@@ -1248,12 +1248,16 @@
 /// An iterator that transforms an \a MDNode::iterator into an iterator over a
 /// particular Metadata subclass.
 template <class T>
-class TypedMDOperandIterator
-    : public std::iterator<std::input_iterator_tag, T *, std::ptrdiff_t, void,
-                           T *> {
+class TypedMDOperandIterator {
   MDNode::op_iterator I = nullptr;
 
 public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = T *;
+  using difference_type = std::ptrdiff_t;
+  using pointer = void;
+  using reference = T *;
+
   TypedMDOperandIterator() = default;
   explicit TypedMDOperandIterator(MDNode::op_iterator I) : I(I) {}
 
@@ -1393,8 +1397,7 @@
   explicit NamedMDNode(const Twine &N);
 
   template<class T1, class T2>
-  class op_iterator_impl :
-      public std::iterator<std::bidirectional_iterator_tag, T2> {
+  class op_iterator_impl {
     friend class NamedMDNode;
 
     const NamedMDNode *Node = nullptr;
@@ -1403,6 +1406,12 @@
     op_iterator_impl(const NamedMDNode *N, unsigned i) : Node(N), Idx(i) {}
 
   public:
+    using iterator_category = std::bidirectional_iterator_tag;
+    using value_type = T2;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     op_iterator_impl() = default;
 
     bool operator==(const op_iterator_impl &o) const { return Idx == o.Idx; }
Index: llvm/include/llvm/IR/Module.h
===================================================================
--- llvm/include/llvm/IR/Module.h
+++ llvm/include/llvm/IR/Module.h
@@ -718,14 +718,19 @@
   }
 
   /// An iterator for DICompileUnits that skips those marked NoDebug.
-  class debug_compile_units_iterator
-      : public std::iterator<std::input_iterator_tag, DICompileUnit *> {
+  class debug_compile_units_iterator {
     NamedMDNode *CUs;
     unsigned Idx;
 
     void SkipNoDebugCUs();
 
   public:
+    using iterator_category = std::input_iterator_tag;
+    using value_type = DICompileUnit *;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     explicit debug_compile_units_iterator(NamedMDNode *CUs, unsigned Idx)
         : CUs(CUs), Idx(Idx) {
       SkipNoDebugCUs();
Index: llvm/include/llvm/IR/Value.h
===================================================================
--- llvm/include/llvm/IR/Value.h
+++ llvm/include/llvm/IR/Value.h
@@ -123,8 +123,7 @@
 
 private:
   template <typename UseT> // UseT == 'Use' or 'const Use'
-  class use_iterator_impl
-      : public std::iterator<std::forward_iterator_tag, UseT *> {
+  class use_iterator_impl {
     friend class Value;
 
     UseT *U;
@@ -132,6 +131,12 @@
     explicit use_iterator_impl(UseT *u) : U(u) {}
 
   public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = UseT *;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     use_iterator_impl() : U() {}
 
     bool operator==(const use_iterator_impl &x) const { return U == x.U; }
@@ -162,13 +167,18 @@
   };
 
   template <typename UserTy> // UserTy == 'User' or 'const User'
-  class user_iterator_impl
-      : public std::iterator<std::forward_iterator_tag, UserTy *> {
+  class user_iterator_impl {
     use_iterator_impl<Use> UI;
     explicit user_iterator_impl(Use *U) : UI(U) {}
     friend class Value;
 
   public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = UserTy *;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     user_iterator_impl() = default;
 
     bool operator==(const user_iterator_impl &x) const { return UI == x.UI; }
Index: llvm/include/llvm/IR/ValueMap.h
===================================================================
--- llvm/include/llvm/IR/ValueMap.h
+++ llvm/include/llvm/IR/ValueMap.h
@@ -324,16 +324,19 @@
 };
 
 template<typename DenseMapT, typename KeyT>
-class ValueMapIterator :
-    public std::iterator<std::forward_iterator_tag,
-                         std::pair<KeyT, typename DenseMapT::mapped_type>,
-                         ptrdiff_t> {
+class ValueMapIterator {
   using BaseT = typename DenseMapT::iterator;
   using ValueT = typename DenseMapT::mapped_type;
 
   BaseT I;
 
 public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = std::pair<KeyT, typename DenseMapT::mapped_type>;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   ValueMapIterator() : I() {}
   ValueMapIterator(BaseT I) : I(I) {}
 
@@ -376,16 +379,19 @@
 };
 
 template<typename DenseMapT, typename KeyT>
-class ValueMapConstIterator :
-    public std::iterator<std::forward_iterator_tag,
-                         std::pair<KeyT, typename DenseMapT::mapped_type>,
-                         ptrdiff_t> {
+class ValueMapConstIterator {
   using BaseT = typename DenseMapT::const_iterator;
   using ValueT = typename DenseMapT::mapped_type;
 
   BaseT I;
 
 public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = std::pair<KeyT, typename DenseMapT::mapped_type>;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   ValueMapConstIterator() : I() {}
   ValueMapConstIterator(BaseT I) : I(I) {}
   ValueMapConstIterator(ValueMapIterator<DenseMapT, KeyT> Other)
Index: llvm/include/llvm/Object/ELFTypes.h
===================================================================
--- llvm/include/llvm/Object/ELFTypes.h
+++ llvm/include/llvm/Object/ELFTypes.h
@@ -656,8 +656,15 @@
 };
 
 template <class ELFT>
-class Elf_Note_Iterator_Impl
-    : std::iterator<std::forward_iterator_tag, Elf_Note_Impl<ELFT>> {
+class Elf_Note_Iterator_Impl {
+public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = Elf_Note_Impl<ELFT>;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
+private:
   // Nhdr being a nullptr marks the end of iteration.
   const Elf_Nhdr_Impl<ELFT> *Nhdr = nullptr;
   size_t RemainingSize = 0u;
Index: llvm/include/llvm/Object/SymbolicFile.h
===================================================================
--- llvm/include/llvm/Object/SymbolicFile.h
+++ llvm/include/llvm/Object/SymbolicFile.h
@@ -65,11 +65,16 @@
 }
 
 template <class content_type>
-class content_iterator
-    : public std::iterator<std::forward_iterator_tag, content_type> {
+class content_iterator {
   content_type Current;
 
 public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = content_type;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   content_iterator(content_type symb) : Current(std::move(symb)) {}
 
   const content_type *operator->() const { return &Current; }
Index: llvm/include/llvm/ProfileData/Coverage/CoverageMappingReader.h
===================================================================
--- llvm/include/llvm/ProfileData/Coverage/CoverageMappingReader.h
+++ llvm/include/llvm/ProfileData/Coverage/CoverageMappingReader.h
@@ -41,8 +41,7 @@
 };
 
 /// A file format agnostic iterator over coverage mapping data.
-class CoverageMappingIterator
-    : public std::iterator<std::input_iterator_tag, CoverageMappingRecord> {
+class CoverageMappingIterator {
   CoverageMappingReader *Reader;
   CoverageMappingRecord Record;
   coveragemap_error ReadErr;
@@ -50,6 +49,12 @@
   void increment();
 
 public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = CoverageMappingRecord;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   CoverageMappingIterator()
       : Reader(nullptr), Record(), ReadErr(coveragemap_error::success) {}
 
Index: llvm/include/llvm/ProfileData/InstrProfReader.h
===================================================================
--- llvm/include/llvm/ProfileData/InstrProfReader.h
+++ llvm/include/llvm/ProfileData/InstrProfReader.h
@@ -38,8 +38,15 @@
 class InstrProfReader;
 
 /// A file format agnostic iterator over profiling data.
-class InstrProfIterator : public std::iterator<std::input_iterator_tag,
-                                               NamedInstrProfRecord> {
+class InstrProfIterator {
+public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = NamedInstrProfRecord;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
+private:
   InstrProfReader *Reader = nullptr;
   value_type Record;
 
Index: llvm/include/llvm/Support/LineIterator.h
===================================================================
--- llvm/include/llvm/Support/LineIterator.h
+++ llvm/include/llvm/Support/LineIterator.h
@@ -30,8 +30,7 @@
 /// character.
 ///
 /// Note that this iterator requires the buffer to be nul terminated.
-class line_iterator
-    : public std::iterator<std::forward_iterator_tag, StringRef> {
+class line_iterator {
   Optional<MemoryBufferRef> Buffer;
   char CommentMarker = '\0';
   bool SkipBlanks = true;
@@ -40,6 +39,12 @@
   StringRef CurrentLine;
 
 public:
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = StringRef;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   /// Default construct an "end" iterator.
   line_iterator() = default;
 
Index: llvm/include/llvm/Support/TargetRegistry.h
===================================================================
--- llvm/include/llvm/Support/TargetRegistry.h
+++ llvm/include/llvm/Support/TargetRegistry.h
@@ -603,8 +603,7 @@
   // function).
   TargetRegistry() = delete;
 
-  class iterator
-      : public std::iterator<std::forward_iterator_tag, Target, ptrdiff_t> {
+  class iterator {
     friend struct TargetRegistry;
 
     const Target *Current = nullptr;
@@ -612,6 +611,12 @@
     explicit iterator(Target *T) : Current(T) {}
 
   public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = Target;
+    using difference_type = std::ptrdiff_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
     iterator() = default;
 
     bool operator==(const iterator &x) const { return Current == x.Current; }
Index: llvm/include/llvm/Support/YAMLParser.h
===================================================================
--- llvm/include/llvm/Support/YAMLParser.h
+++ llvm/include/llvm/Support/YAMLParser.h
@@ -326,9 +326,14 @@
 /// BaseT must have a ValueT* member named CurrentEntry and a member function
 /// increment() which must set CurrentEntry to 0 to create an end iterator.
 template <class BaseT, class ValueT>
-class basic_collection_iterator
-    : public std::iterator<std::input_iterator_tag, ValueT> {
+class basic_collection_iterator {
 public:
+  using iterator_category = std::input_iterator_tag;
+  using value_type = ValueT;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
   basic_collection_iterator() = default;
   basic_collection_iterator(BaseT *B) : Base(B) {}
 
Index: llvm/include/llvm/TextAPI/ArchitectureSet.h
===================================================================
--- llvm/include/llvm/TextAPI/ArchitectureSet.h
+++ llvm/include/llvm/TextAPI/ArchitectureSet.h
@@ -67,8 +67,14 @@
   }
 
   template <typename Ty>
-  class arch_iterator
-      : public std::iterator<std::forward_iterator_tag, Architecture, size_t> {
+  class arch_iterator {
+  public:
+    using iterator_category = std::forward_iterator_tag;
+    using value_type = Architecture;
+    using difference_type = std::size_t;
+    using pointer = value_type *;
+    using reference = value_type &;
+
   private:
     ArchSetType Index;
     Ty *ArchSet;
Index: llvm/include/llvm/Transforms/Scalar/GVNExpression.h
===================================================================
--- llvm/include/llvm/Transforms/Scalar/GVNExpression.h
+++ llvm/include/llvm/Transforms/Scalar/GVNExpression.h
@@ -240,14 +240,19 @@
   }
 };
 
-class op_inserter
-    : public std::iterator<std::output_iterator_tag, void, void, void, void> {
+class op_inserter {
 private:
   using Container = BasicExpression;
 
   Container *BE;
 
 public:
+  using iterator_category = std::output_iterator_tag;
+  using value_type = void;
+  using difference_type = void;
+  using pointer = void;
+  using reference = void;
+
   explicit op_inserter(BasicExpression &E) : BE(&E) {}
   explicit op_inserter(BasicExpression *E) : BE(E) {}
 
@@ -472,14 +477,19 @@
   }
 };
 
-class int_op_inserter
-    : public std::iterator<std::output_iterator_tag, void, void, void, void> {
+class int_op_inserter {
 private:
   using Container = AggregateValueExpression;
 
   Container *AVE;
 
 public:
+  using iterator_category = std::output_iterator_tag;
+  using value_type = void;
+  using difference_type = void;
+  using pointer = void;
+  using reference = void;
+
   explicit int_op_inserter(AggregateValueExpression &E) : AVE(&E) {}
   explicit int_op_inserter(AggregateValueExpression *E) : AVE(E) {}
 
Index: llvm/lib/Analysis/CFGPrinter.cpp
===================================================================
--- llvm/lib/Analysis/CFGPrinter.cpp
+++ llvm/lib/Analysis/CFGPrinter.cpp
@@ -286,8 +286,7 @@
   };
   /// The post order traversal iteration is done to know the status of
   /// isHiddenBasicBlock for all the successors on the current BB.
-  for_each(po_begin(&F->getEntryBlock()), po_end(&F->getEntryBlock()),
-           evaluateBB);
+  llvm::for_each(post_order(&F->getEntryBlock()), evaluateBB);
 }
 
 bool DOTGraphTraits<DOTFuncInfo *>::isNodeHidden(const BasicBlock *Node,
Index: llvm/tools/llvm-objdump/MachODump.cpp
===================================================================
--- llvm/tools/llvm-objdump/MachODump.cpp
+++ llvm/tools/llvm-objdump/MachODump.cpp
@@ -466,7 +466,7 @@
 
   if (isExtern) {
     symbol_iterator SI = O->symbol_begin();
-    advance(SI, Val);
+    std::advance(SI, Val);
     S = unwrapOrError(SI->getName(), FileName);
   } else {
     section_iterator SI = O->section_begin();
@@ -478,7 +478,7 @@
     uint32_t I = Val - 1;
     while (I != 0 && SI != O->section_end()) {
       --I;
-      advance(SI, 1);
+      std::advance(SI, 1);
     }
     if (SI == O->section_end()) {
       Fmt << Val << " (?,?)";
Index: polly/include/polly/Support/VirtualInstruction.h
===================================================================
--- polly/include/polly/Support/VirtualInstruction.h
+++ polly/include/polly/Support/VirtualInstruction.h
@@ -167,12 +167,10 @@
 };
 
 /// An iterator for virtual operands.
-class VirtualOperandIterator
-    : public std::iterator<std::forward_iterator_tag, VirtualUse> {
+class VirtualOperandIterator {
   friend class VirtualInstruction;
   friend class VirtualUse;
 
-  using super = std::iterator<std::forward_iterator_tag, VirtualUse>;
   using Self = VirtualOperandIterator;
 
   ScopStmt *User;
@@ -182,8 +180,11 @@
       : User(User), U(U) {}
 
 public:
-  using pointer = typename super::pointer;
-  using reference = typename super::reference;
+  using iterator_category = std::forward_iterator_tag;
+  using value_type = VirtualUse;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
 
   inline bool operator==(const Self &that) const {
     assert(this->User == that.User);