Index: include/map
===================================================================
--- include/map
+++ include/map
@@ -135,6 +135,23 @@
         void insert(InputIterator first, InputIterator last);
     void insert(initializer_list<value_type> il);
 
+    template <class... Args>
+        pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);          // C++17
+    template <class... Args>
+        pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);               // C++17
+    template <class... Args>
+        iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args); // C++17
+    template <class... Args>
+        iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);      // C++17
+    template <class M>
+        pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);            // C++17
+    template <class M>
+        pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);                 // C++17
+    template <class M>
+        iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);   // C++17
+    template <class M>
+        iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);        // C++17
+
     iterator  erase(const_iterator position);
     iterator  erase(iterator position); // C++14
     size_type erase(const key_type& k);
@@ -1077,6 +1094,108 @@
 
 #endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
+#if _LIBCPP_STD_VER > 14
+#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_HAS_NO_VARIADICS
+    template <class... _Args>
+        _LIBCPP_INLINE_VISIBILITY
+        pair<iterator, bool> try_emplace(const key_type& __k, _Args&&... __args)
+    {
+        iterator __p = lower_bound(__k);
+        if ( __p != end() && !key_comp()(__k, __p->first))
+            return _VSTD::make_pair(__p, false);
+        else
+            return _VSTD::make_pair(emplace_hint(__p, __k, _VSTD::forward<_Args>(__args)...), true);
+    }
+
+    template <class... _Args>
+        _LIBCPP_INLINE_VISIBILITY
+        pair<iterator, bool> try_emplace(key_type&& __k, _Args&&... __args)
+    {
+        iterator __p = lower_bound(__k);
+        if ( __p != end() && !key_comp()(__k, __p->first))
+            return _VSTD::make_pair(__p, false);
+        else
+            return _VSTD::make_pair(emplace_hint(__p, _VSTD::forward<key_type>(__k), _VSTD::forward<_Args>(__args)...), true);
+    }
+
+    template <class... _Args>
+        _LIBCPP_INLINE_VISIBILITY
+        iterator try_emplace(const_iterator __h, const key_type& __k, _Args&&... __args)
+    {
+        iterator __p = lower_bound(__k);
+        if ( __p != end() && !key_comp()(__k, __p->first))
+            return __p;
+        else
+            return emplace_hint(__h, __k, _VSTD::forward<_Args>(__args)...);
+    }
+
+    template <class... _Args>
+        _LIBCPP_INLINE_VISIBILITY
+        iterator try_emplace(const_iterator __h, key_type&& __k, _Args&&... __args)
+    {
+        iterator __p = lower_bound(__k);
+        if ( __p != end() && !key_comp()(__k, __p->first))
+            return __p;
+        else
+            return emplace_hint(__h, _VSTD::forward<key_type>(__k), _VSTD::forward<_Args>(__args)...);
+    }
+
+    template <class _Vp>
+        _LIBCPP_INLINE_VISIBILITY
+        pair<iterator, bool> insert_or_assign(const key_type& __k, _Vp&& __v)
+    {
+        iterator __p = lower_bound(__k);
+        if ( __p != end() && !key_comp()(__k, __p->first))
+        {
+            __p->second = _VSTD::move(__v);
+            return _VSTD::make_pair(__p, false);
+        }
+        return _VSTD::make_pair(emplace_hint(__p, __k, _VSTD::forward<_Vp>(__v)), true);
+    }
+        
+    template <class _Vp>
+        _LIBCPP_INLINE_VISIBILITY
+        pair<iterator, bool> insert_or_assign(key_type&& __k, _Vp&& __v)
+    {
+        iterator __p = lower_bound(__k);
+        if ( __p != end() && !key_comp()(__k, __p->first))
+        {
+            __p->second = _VSTD::move(__v);
+            return _VSTD::make_pair(__p, false);
+        }
+        return _VSTD::make_pair(emplace_hint(__p, _VSTD::forward<key_type>(__k), _VSTD::forward<_Vp>(__v)), true);
+    }
+
+    template <class _Vp>
+        _LIBCPP_INLINE_VISIBILITY
+        iterator insert_or_assign(const_iterator __h, const key_type& __k, _Vp&& __v)
+     {
+        iterator __p = lower_bound(__k);
+        if ( __p != end() && !key_comp()(__k, __p->first))
+        {
+            __p->second = _VSTD::move(__v);
+            return __p;
+        }
+        return emplace_hint(__h, __k, _VSTD::forward<_Vp>(__v));
+     }
+
+    template <class _Vp>
+        _LIBCPP_INLINE_VISIBILITY
+        iterator insert_or_assign(const_iterator __h, key_type&& __k, _Vp&& __v)
+     {
+        iterator __p = lower_bound(__k);
+        if ( __p != end() && !key_comp()(__k, __p->first))
+        {
+            __p->second = _VSTD::move(__v);
+            return __p;
+        }
+        return emplace_hint(__h, _VSTD::forward<key_type>(__k), _VSTD::forward<_Vp>(__v));
+     }
+#endif
+#endif
+#endif
+
     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __tree_.erase(__p.__i_);}
     _LIBCPP_INLINE_VISIBILITY
Index: test/std/containers/associative/map/map.modifiers/insert_or_assign.pass.cpp
===================================================================
--- test/std/containers/associative/map/map.modifiers/insert_or_assign.pass.cpp
+++ test/std/containers/associative/map/map.modifiers/insert_or_assign.pass.cpp
@@ -0,0 +1,173 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <map>
+
+// class map
+
+// template <class M>
+//  pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);            // C++17
+// template <class M>
+//  pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);                 // C++17
+// template <class M>
+//  iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);   // C++17
+// template <class M>
+//  iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);        // C++17
+
+#include <__config>
+#include <map>
+#include <cassert>
+#include <tuple>
+
+#include <iostream>
+
+class Moveable
+{
+    Moveable(const Moveable&);
+    Moveable& operator=(const Moveable&);
+
+    int int_;
+    double double_;
+public:
+    Moveable() : int_(0), double_(0) {}
+    Moveable(int i, double d) : int_(i), double_(d) {}
+    Moveable(Moveable&& x)
+        : int_(x.int_), double_(x.double_)
+            {x.int_ = -1; x.double_ = -1;}
+    Moveable& operator=(Moveable&& x)
+        {int_ = x.int_; x.int_ = -1;
+         double_ = x.double_; x.double_ = -1;
+         return *this;
+        }
+
+    bool operator==(const Moveable& x) const
+        {return int_ == x.int_ && double_ == x.double_;}
+    bool operator<(const Moveable& x) const
+        {return int_ < x.int_ || (int_ == x.int_ && double_ < x.double_);}
+
+    int get() const {return int_;}
+    bool moved() const {return int_ == -1;}
+};
+
+
+int main()
+{
+#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_HAS_NO_VARIADICS
+
+    { // pair<iterator, bool> insert_or_assign(const key_type& k, M&& obj);
+        typedef std::map<int, Moveable> M;
+        typedef std::pair<M::iterator, bool> R;
+        M m;
+        R r;
+        for ( int i = 0; i < 20; i += 2 )
+            m.emplace ( i, Moveable(i, (double) i));
+        assert(m.size() == 10);
+
+        Moveable mv1(3, 3.0);
+        r = m.insert_or_assign(2, std::move(mv1));
+        assert(m.size() == 10);
+        assert(!r.second);                  // was not inserted
+        assert(mv1.moved());                // was moved from
+        assert(r.first->first        == 2); // key
+        assert(r.first->second.get() == 3); // value
+
+        Moveable mv2(5, 5.0);
+        r = m.insert_or_assign(3, std::move(mv2));
+        assert(m.size() == 11);
+        assert(r.second);                   // was inserted
+        assert(mv2.moved());                // was moved from
+        assert(r.first->first        == 3); // key
+        assert(r.first->second.get() == 5); // value
+    }
+    { // pair<iterator, bool> insert_or_assign(key_type&& k, M&& obj);
+        typedef std::map<Moveable, Moveable> M;
+        typedef std::pair<M::iterator, bool> R;
+        M m;
+        R r;
+        for ( int i = 0; i < 20; i += 2 )
+            m.emplace ( Moveable(i, (double) i), Moveable(i+1, (double) i+1));
+        assert(m.size() == 10);
+
+        Moveable mvkey1(2, 2.0);
+        Moveable mv1(4, 4.0);
+        r = m.insert_or_assign(std::move(mvkey1), std::move(mv1));
+        assert(m.size() == 10);
+        assert(!r.second);                  // was not inserted
+        assert(!mvkey1.moved());            // was not moved from
+        assert(mv1.moved());                // was moved from
+        assert(r.first->first == mvkey1);   // key
+        assert(r.first->second.get() == 4); // value
+
+        Moveable mvkey2(3, 3.0);
+        Moveable mv2(5, 5.0);
+        r = m.try_emplace(std::move(mvkey2), std::move(mv2));
+        assert(m.size() == 11);
+        assert(r.second);                   // was inserted
+        assert(mv2.moved());                // was moved from
+        assert(mvkey2.moved());             // was moved from
+        assert(r.first->first.get()  == 3); // key
+        assert(r.first->second.get() == 5); // value
+    }
+    { // iterator insert_or_assign(const_iterator hint, const key_type& k, M&& obj);
+        typedef std::map<int, Moveable> M;
+        M m;
+        M::iterator r;
+        for ( int i = 0; i < 20; i += 2 )
+            m.emplace ( i, Moveable(i, (double) i));
+        assert(m.size() == 10);
+        M::const_iterator it = m.find(2);
+
+        Moveable mv1(3, 3.0);
+        r = m.insert_or_assign(it, 2, std::move(mv1));
+        assert(m.size() == 10);
+        assert(mv1.moved());           // was moved from
+        assert(r->first        == 2);  // key
+        assert(r->second.get() == 3);  // value
+
+        Moveable mv2(5, 5.0);
+        r = m.insert_or_assign(it, 3, std::move(mv2));
+        assert(m.size() == 11);
+        assert(mv2.moved());           // was moved from
+        assert(r->first        == 3);  // key
+        assert(r->second.get() == 5);  // value
+    }
+    { // iterator insert_or_assign(const_iterator hint, key_type&& k, M&& obj);
+        typedef std::map<Moveable, Moveable> M;
+        M m;
+        M::iterator r;
+        for ( int i = 0; i < 20; i += 2 )
+            m.emplace ( Moveable(i, (double) i), Moveable(i+1, (double) i+1));
+        assert(m.size() == 10);
+        M::const_iterator it = std::next(m.cbegin());
+
+        Moveable mvkey1(2, 2.0);
+        Moveable mv1(4, 4.0);
+        r = m.insert_or_assign(it, std::move(mvkey1), std::move(mv1));
+        assert(m.size() == 10);
+        assert(mv1.moved());          // was moved from
+        assert(!mvkey1.moved());      // was not moved from
+        assert(r->first == mvkey1);   // key
+        assert(r->second.get() == 4); // value
+
+        Moveable mvkey2(3, 3.0);
+        Moveable mv2(5, 5.0);
+        r = m.try_emplace(it, std::move(mvkey2), std::move(mv2));
+        assert(m.size() == 11);
+        assert(mv2.moved());           // was moved from
+        assert(mvkey2.moved());        // was moved from
+        assert(r->first.get()  == 3);  // key
+        assert(r->second.get() == 5);  // value
+    }
+
+#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+}
Index: test/std/containers/associative/map/map.modifiers/try.emplace.pass.cpp
===================================================================
--- test/std/containers/associative/map/map.modifiers/try.emplace.pass.cpp
+++ test/std/containers/associative/map/map.modifiers/try.emplace.pass.cpp
@@ -0,0 +1,166 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <map>
+
+// class map
+
+// template <class... Args>
+//  pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);          // C++17
+// template <class... Args>
+//  pair<iterator, bool> try_emplace(key_type&& k, Args&&... args);               // C++17
+// template <class... Args>
+//  iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args); // C++17
+// template <class... Args>
+//  iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);      // C++17
+
+#include <__config>
+#include <map>
+#include <cassert>
+#include <tuple>
+
+class Moveable
+{
+    Moveable(const Moveable&);
+    Moveable& operator=(const Moveable&);
+
+    int int_;
+    double double_;
+public:
+    Moveable() : int_(0), double_(0) {}
+    Moveable(int i, double d) : int_(i), double_(d) {}
+    Moveable(Moveable&& x)
+        : int_(x.int_), double_(x.double_)
+            {x.int_ = -1; x.double_ = -1;}
+    Moveable& operator=(Moveable&& x)
+        {int_ = x.int_; x.int_ = -1;
+         double_ = x.double_; x.double_ = -1;
+         return *this;
+        }
+
+    bool operator==(const Moveable& x) const
+        {return int_ == x.int_ && double_ == x.double_;}
+    bool operator<(const Moveable& x) const
+        {return int_ < x.int_ || (int_ == x.int_ && double_ < x.double_);}
+
+    int get() const {return int_;}
+    bool moved() const {return int_ == -1;}
+};
+
+
+int main()
+{
+#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_HAS_NO_VARIADICS
+
+    { // pair<iterator, bool> try_emplace(const key_type& k, Args&&... args);
+        typedef std::map<int, Moveable> M;
+        typedef std::pair<M::iterator, bool> R;
+        M m;
+        R r;
+        for ( int i = 0; i < 20; i += 2 )
+            m.emplace ( i, Moveable(i, (double) i));
+        assert(m.size() == 10);
+
+        Moveable mv1(3, 3.0);
+        r = m.try_emplace(2, std::move(mv1));
+        assert(m.size() == 10);
+        assert(!r.second);                  // was not inserted
+        assert(!mv1.moved());               // was not moved from
+        assert(r.first->first == 2);        // key
+
+        r = m.try_emplace(3, std::move(mv1));
+        assert(m.size() == 11);
+        assert(r.second);                   // was inserted
+        assert(mv1.moved());                // was moved from
+        assert(r.first->first == 3);        // key
+        assert(r.first->second.get() == 3); // value
+    }
+
+    {  // pair<iterator, bool> try_emplace(key_type&& k, Args&&... args); 
+        typedef std::map<Moveable, Moveable> M;
+        typedef std::pair<M::iterator, bool> R;
+        M m;
+        R r;
+        for ( int i = 0; i < 20; i += 2 )
+            m.emplace ( Moveable(i, (double) i), Moveable(i+1, (double) i+1));
+        assert(m.size() == 10);
+
+        Moveable mvkey1(2, 2.0);
+        Moveable mv1(4, 4.0);
+        r = m.try_emplace(std::move(mvkey1), std::move(mv1));
+        assert(m.size() == 10);
+        assert(!r.second);                 // was not inserted
+        assert(!mv1.moved());              // was not moved from
+        assert(!mvkey1.moved());           // was not moved from
+        assert(r.first->first == mvkey1);  // key
+
+        Moveable mvkey2(3, 3.0);
+        r = m.try_emplace(std::move(mvkey2), std::move(mv1));
+        assert(m.size() == 11);
+        assert(r.second);                   // was inserted
+        assert(mv1.moved());                // was moved from
+        assert(mvkey2.moved());             // was moved from
+        assert(r.first->first.get()  == 3); // key
+        assert(r.first->second.get() == 4); // value
+    }
+
+    {  // iterator try_emplace(const_iterator hint, const key_type& k, Args&&... args);
+        typedef std::map<int, Moveable> M;
+        M m;
+        M::iterator r;
+        for ( int i = 0; i < 20; i += 2 )
+            m.emplace ( i, Moveable(i, (double) i));
+        assert(m.size() == 10);
+        Moveable mv1(3, 3.0);
+        M::const_iterator it = m.find(2);
+        
+        r = m.try_emplace(it, 2, std::move(mv1));
+        assert(m.size() == 10);
+        assert(!mv1.moved());         // was not moved from
+        assert(r->first == 2);        // key
+
+        r = m.try_emplace(it, 3, std::move(mv1));
+        assert(m.size() == 11);
+        assert(mv1.moved());          // was moved from
+        assert(r->first == 3);        // key
+        assert(r->second.get() == 3); // value
+    }
+
+    {  // iterator try_emplace(const_iterator hint, key_type&& k, Args&&... args);
+        typedef std::map<Moveable, Moveable> M;
+        M m;
+        M::iterator r;
+        for ( int i = 0; i < 20; i += 2 )
+            m.emplace ( Moveable(i, (double) i), Moveable(i+1, (double) i+1));
+        assert(m.size() == 10);
+        M::const_iterator it = std::next(m.cbegin());
+
+        Moveable mvkey1(2, 2.0);
+        Moveable mv1(4, 4.0);
+        r = m.try_emplace(it, std::move(mvkey1), std::move(mv1));
+        assert(m.size() == 10);
+        assert(!mv1.moved());        // was not moved from
+        assert(!mvkey1.moved());     // was not moved from
+        assert(r->first == mvkey1);  // key
+
+        Moveable mvkey2(3, 3.0);
+        r = m.try_emplace(it, std::move(mvkey2), std::move(mv1));
+        assert(m.size() == 11);
+        assert(mv1.moved());          // was moved from
+        assert(mvkey2.moved());       // was moved from
+        assert(r->first.get()  == 3); // key
+        assert(r->second.get() == 4); // value
+    }
+
+#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+}