Index: include/experimental/numeric
===================================================================
--- include/experimental/numeric
+++ include/experimental/numeric
@@ -0,0 +1,103 @@
+// -*- C++ -*-
+//===--------------------------- numeric ----------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_NUMERIC
+#define _LIBCPP_EXPERIMENTAL_NUMERIC
+/*
+    experimental/numeric synopsis
+
+// C++1z
+namespace std {
+namespace experimental {
+inline namespace fundamentals_v2 {
+
+  // 13.1.2, Greatest common divisor
+  template<class M, class N>
+  constexpr common_type_t<M,N> gcd(M m, N n);
+
+  // 13.1.3, Least common multiple
+  template<class M, class N>
+  constexpr common_type_t<M,N> lcm(M m, N n);
+
+} // namespace fundamentals_v2
+} // namespace experimental
+} // namespace std
+
+ */
+
+#include <experimental/__config>
+#include <numeric>
+#include <type_traits>              // is_integral
+#include <limits>                   // numeric_limits
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER > 11
+
+_LIBCPP_BEGIN_NAMESPACE_LFTS
+
+template <typename _Tp, bool _IsSigned = is_signed<_Tp>::value> struct __abs;
+
+template <typename _Tp>
+struct __abs<_Tp, true> {
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(_Tp __t) const noexcept { return __t >= 0 ? __t : -__t; }
+};
+
+template <typename _Tp>
+struct __abs<_Tp, false> {
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    _Tp operator()(_Tp __t) const noexcept { return __t; }
+};
+
+
+template<class _Tp>
+_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+_Tp __gcd(_Tp __m, _Tp __n)
+{
+    static_assert((!is_signed<_Tp>::value), "" );
+    return __n == 0 ? __m : __gcd<_Tp>(__n, __m % __n);
+}
+
+
+template<class _Tp, class _Up>
+_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+common_type_t<_Tp,_Up>
+gcd(_Tp __m, _Up __n)
+{
+    static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to gcd must be integer types");
+    using _Rp = common_type_t<_Tp,_Up>;
+    using _Wp = make_unsigned_t<_Rp>;
+    return static_cast<_Rp>(__gcd(static_cast<_Wp>(__abs<_Tp>()(__m)),
+                                  static_cast<_Wp>(__abs<_Up>()(__n))));
+}
+
+template<class _Tp, class _Up>
+_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+common_type_t<_Tp,_Up>
+lcm(_Tp __m, _Up __n)
+{
+    static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to lcm must be integer types");
+    if (__m == 0 || __n == 0)
+        return 0;
+
+    using _Rp = common_type_t<_Tp,_Up>;
+    _Rp __val1 = __abs<_Tp>()(__m) / gcd(__m,__n);
+    _Up __val2 = __abs<_Up>()(__n);
+    _LIBCPP_ASSERT((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm");
+    return __val1 * __val2;
+}
+
+_LIBCPP_END_NAMESPACE_LFTS
+
+#endif /* _LIBCPP_STD_VER > 11 */
+#endif /* _LIBCPP_EXPERIMENTAL_NUMERIC */
Index: test/std/experimental/numeric/numeric.ops.overview/nothing_to_do.pass.cpp
===================================================================
--- test/std/experimental/numeric/numeric.ops.overview/nothing_to_do.pass.cpp
+++ test/std/experimental/numeric/numeric.ops.overview/nothing_to_do.pass.cpp
@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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++98, c++03, c++11
+// <numeric>
+
+#include <experimental/numeric>
+
+int main () {}
Index: test/std/experimental/numeric/numeric.ops/nothing_to_do.pass.cpp
===================================================================
--- test/std/experimental/numeric/numeric.ops/nothing_to_do.pass.cpp
+++ test/std/experimental/numeric/numeric.ops/nothing_to_do.pass.cpp
@@ -0,0 +1,15 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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++98, c++03, c++11
+// <numeric>
+
+#include <experimental/numeric>
+
+int main () {}
Index: test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.not_integral1.fail.cpp
===================================================================
--- test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.not_integral1.fail.cpp
+++ test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.not_integral1.fail.cpp
@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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++98, c++03, c++11
+// <numeric>
+
+// template<class _M, class _N>
+// constexpr common_type_t<_M,_N> gcd(_M __m, _N __n)
+
+// Remarks: If either M or N is not an integer type, the program is ill-formed.
+
+#include <experimental/numeric>
+
+
+int main()
+{
+    std::experimental::gcd(2.0, 4);
+}
Index: test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.not_integral2.fail.cpp
===================================================================
--- test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.not_integral2.fail.cpp
+++ test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.not_integral2.fail.cpp
@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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++98, c++03, c++11
+// <numeric>
+
+// template<class _M, class _N>
+// constexpr common_type_t<_M,_N> gcd(_M __m, _N __n)
+
+// Remarks: If either M or N is not an integer type, the program is ill-formed.
+
+#include <experimental/numeric>
+
+
+int main()
+{
+    std::experimental::gcd(4, 6.0);
+}
Index: test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
===================================================================
--- test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
+++ test/std/experimental/numeric/numeric.ops/numeric.ops.gcd/gcd.pass.cpp
@@ -0,0 +1,132 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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++98, c++03, c++11
+// <numeric>
+
+// template<class _M, class _N>
+// constexpr common_type_t<_M,_N> gcd(_M __m, _N __n)
+
+#include <experimental/numeric>
+#include <cassert>
+#include <cstdlib>    // for rand()
+#include <iostream>
+
+constexpr struct {
+  int x;
+  int y;
+  int expect;
+} Cases[] = {
+    {0, 0, 0},
+    {1, 0, 1},
+    {0, 1, 1},
+    {1, 1, 1},
+    {2, 3, 1},
+    {2, 4, 2},
+    {36, 17, 1},
+    {36, 18, 18}
+};
+
+
+template <typename Input1, typename Input2, typename Output>
+constexpr bool test0(Input1 in1, Input2 in2, Output out)
+{
+    static_assert((std::is_same<Output, decltype(std::experimental::gcd(in1, in2))>::value), "" );
+    static_assert((std::is_same<Output, decltype(std::experimental::gcd(in2, in1))>::value), "" );
+    return out == std::experimental::gcd(in1, in2) ? true : (std::abort(), false);
+}
+
+
+template <typename Input1, typename Input2 = Input1>
+constexpr bool do_test(int dummy = 0)
+{
+    using S1 = typename std::make_signed<Input1>::type;
+    using S2 = typename std::make_signed<Input2>::type;
+    using U1 = typename std::make_unsigned<Input1>::type;
+    using U2 = typename std::make_unsigned<Input2>::type;
+    bool accumulate = true;
+    for (auto TC : Cases) {
+        { // Test with two signed types
+            using Output = std::common_type_t<S1, S2>;
+            accumulate &= test0<S1, S2, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<S1, S2, Output>(-TC.x, TC.y, TC.expect);
+            accumulate &= test0<S1, S2, Output>(TC.x, -TC.y, TC.expect);
+            accumulate &= test0<S1, S2, Output>(-TC.x, -TC.y, TC.expect);
+            accumulate &= test0<S2, S1, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<S2, S1, Output>(-TC.x, TC.y, TC.expect);
+            accumulate &= test0<S2, S1, Output>(TC.x, -TC.y, TC.expect);
+            accumulate &= test0<S2, S1, Output>(-TC.x, -TC.y, TC.expect);
+        }
+        { // test with two unsigned types
+            using Output = std::common_type_t<U1, U2>;
+            accumulate &= test0<U1, U2, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<U2, U1, Output>(TC.x, TC.y, TC.expect);
+        }
+        { // Test with mixed signs
+            using Output = std::common_type_t<S1, U2>;
+            accumulate &= test0<S1, U2, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<U2, S1, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<S1, U2, Output>(-TC.x, TC.y, TC.expect);
+            accumulate &= test0<U2, S1, Output>(TC.x, -TC.y, TC.expect);
+        }
+        { // Test with mixed signs
+            using Output = std::common_type_t<S2, U1>;
+            accumulate &= test0<S2, U1, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<U1, S2, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<S2, U1, Output>(-TC.x, TC.y, TC.expect);
+            accumulate &= test0<U1, S2, Output>(TC.x, -TC.y, TC.expect);
+        }
+    }
+    return accumulate;
+}
+
+int main()
+{
+    auto non_cce = std::rand(); // a value that can't possibly be constexpr
+
+    static_assert(do_test<signed char>(), "");
+    static_assert(do_test<short>(), "");
+    static_assert(do_test<int>(), "");
+    static_assert(do_test<long>(), "");
+    static_assert(do_test<long long>(), "");
+
+    assert(do_test<signed char>(non_cce));
+    assert(do_test<short>(non_cce));
+    assert(do_test<int>(non_cce));
+    assert(do_test<long>(non_cce));
+    assert(do_test<long long>(non_cce));
+
+    static_assert(do_test< int8_t>(), "");
+    static_assert(do_test<int16_t>(), "");
+    static_assert(do_test<int32_t>(), "");
+    static_assert(do_test<int64_t>(), "");
+
+    assert(do_test< int8_t>(non_cce));
+    assert(do_test<int16_t>(non_cce));
+    assert(do_test<int32_t>(non_cce));
+    assert(do_test<int64_t>(non_cce));
+
+    static_assert(do_test<signed char, int>(), "");
+    static_assert(do_test<int, signed char>(), "");
+    static_assert(do_test<short, int>(), "");
+    static_assert(do_test<int, short>(), "");
+    static_assert(do_test<int, long>(), "");
+    static_assert(do_test<long, int>(), "");
+    static_assert(do_test<int, long long>(), "");
+    static_assert(do_test<long long, int>(), "");
+
+    assert((do_test<signed char, int>(non_cce)));
+    assert((do_test<int, signed char>(non_cce)));
+    assert((do_test<short, int>(non_cce)));
+    assert((do_test<int, short>(non_cce)));
+    assert((do_test<int, long>(non_cce)));
+    assert((do_test<long, int>(non_cce)));
+    assert((do_test<int, long long>(non_cce)));
+    assert((do_test<long long, int>(non_cce)));
+}
Index: test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.not_integral1.fail.cpp
===================================================================
--- test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.not_integral1.fail.cpp
+++ test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.not_integral1.fail.cpp
@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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++98, c++03, c++11
+// <numeric>
+
+// template<class _M, class _N>
+// constexpr common_type_t<_M,_N> lcm(_M __m, _N __n)
+
+// Remarks: If either M or N is not an integer type, the program is ill-formed.
+
+#include <experimental/numeric>
+
+
+int main()
+{
+    std::experimental::lcm(2.0, 4);
+}
Index: test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.not_integral2.fail.cpp
===================================================================
--- test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.not_integral2.fail.cpp
+++ test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.not_integral2.fail.cpp
@@ -0,0 +1,24 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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++98, c++03, c++11
+// <numeric>
+
+// template<class _M, class _N>
+// constexpr common_type_t<_M,_N> lcm(_M __m, _N __n)
+
+// Remarks: If either M or N is not an integer type, the program is ill-formed.
+
+#include <experimental/numeric>
+
+
+int main()
+{
+    std::experimental::lcm(4, 6.0);
+}
Index: test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.pass.cpp
===================================================================
--- test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.pass.cpp
+++ test/std/experimental/numeric/numeric.ops/numeric.ops.lcm/lcm.pass.cpp
@@ -0,0 +1,131 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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++98, c++03, c++11
+// <numeric>
+
+// template<class _M, class _N>
+// constexpr common_type_t<_M,_N> gcd(_M __m, _N __n)
+
+#include <experimental/numeric>
+#include <cassert>
+#include <cstdlib>
+#include <iostream>
+
+constexpr struct {
+  int x;
+  int y;
+  int expect;
+} Cases[] = {
+    {0, 0, 0},
+    {1, 0, 0},
+    {0, 1, 0},
+    {1, 1, 1},
+    {2, 3, 6},
+    {2, 4, 4},
+    {3, 17, 51},
+    {36, 18, 36}
+};
+
+template <typename Input1, typename Input2, typename Output>
+constexpr bool test0(Input1 in1, Input2 in2, Output out)
+{
+    static_assert((std::is_same<Output, decltype(std::experimental::lcm(Input1(0), Input2(0)))>::value), "" );
+    static_assert((std::is_same<Output, decltype(std::experimental::lcm(Input2(0), Input1(0)))>::value), "" );
+    return out == std::experimental::lcm(in1, in2) ? true : (std::abort(), false);
+}
+
+
+template <typename Input1, typename Input2 = Input1>
+constexpr bool do_test(int dummy = 0)
+{
+    using S1 = typename std::make_signed<Input1>::type;
+    using S2 = typename std::make_signed<Input2>::type;
+    using U1 = typename std::make_unsigned<Input1>::type;
+    using U2 = typename std::make_unsigned<Input2>::type;
+    bool accumulate = true;
+    for (auto TC : Cases) {
+        { // Test with two signed types
+            using Output = std::common_type_t<S1, S2>;
+            accumulate &= test0<S1, S2, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<S1, S2, Output>(-TC.x, TC.y, TC.expect);
+            accumulate &= test0<S1, S2, Output>(TC.x, -TC.y, TC.expect);
+            accumulate &= test0<S1, S2, Output>(-TC.x, -TC.y, TC.expect);
+            accumulate &= test0<S2, S1, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<S2, S1, Output>(-TC.x, TC.y, TC.expect);
+            accumulate &= test0<S2, S1, Output>(TC.x, -TC.y, TC.expect);
+            accumulate &= test0<S2, S1, Output>(-TC.x, -TC.y, TC.expect);
+        }
+        { // test with two unsigned types
+            using Output = std::common_type_t<U1, U2>;
+            accumulate &= test0<U1, U2, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<U2, U1, Output>(TC.x, TC.y, TC.expect);
+        }
+        { // Test with mixed signs
+            using Output = std::common_type_t<S1, U2>;
+            accumulate &= test0<S1, U2, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<U2, S1, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<S1, U2, Output>(-TC.x, TC.y, TC.expect);
+            accumulate &= test0<U2, S1, Output>(TC.x, -TC.y, TC.expect);
+        }
+        { // Test with mixed signs
+            using Output = std::common_type_t<S2, U1>;
+            accumulate &= test0<S2, U1, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<U1, S2, Output>(TC.x, TC.y, TC.expect);
+            accumulate &= test0<S2, U1, Output>(-TC.x, TC.y, TC.expect);
+            accumulate &= test0<U1, S2, Output>(TC.x, -TC.y, TC.expect);
+        }
+    }
+    return accumulate;
+}
+
+int main()
+{
+    auto non_cce = std::rand(); // a value that can't possibly be constexpr
+
+    static_assert(do_test<signed char>(), "");
+    static_assert(do_test<short>(), "");
+    static_assert(do_test<int>(), "");
+    static_assert(do_test<long>(), "");
+    static_assert(do_test<long long>(), "");
+
+    assert(do_test<signed char>(non_cce));
+    assert(do_test<short>(non_cce));
+    assert(do_test<int>(non_cce));
+    assert(do_test<long>(non_cce));
+    assert(do_test<long long>(non_cce));
+
+    static_assert(do_test< int8_t>(), "");
+    static_assert(do_test<int16_t>(), "");
+    static_assert(do_test<int32_t>(), "");
+    static_assert(do_test<int64_t>(), "");
+
+    assert(do_test< int8_t>(non_cce));
+    assert(do_test<int16_t>(non_cce));
+    assert(do_test<int32_t>(non_cce));
+    assert(do_test<int64_t>(non_cce));
+
+    static_assert(do_test<signed char, int>(), "");
+    static_assert(do_test<int, signed char>(), "");
+    static_assert(do_test<short, int>(), "");
+    static_assert(do_test<int, short>(), "");
+    static_assert(do_test<int, long>(), "");
+    static_assert(do_test<long, int>(), "");
+    static_assert(do_test<int, long long>(), "");
+    static_assert(do_test<long long, int>(), "");
+
+    assert((do_test<signed char, int>(non_cce)));
+    assert((do_test<int, signed char>(non_cce)));
+    assert((do_test<short, int>(non_cce)));
+    assert((do_test<int, short>(non_cce)));
+    assert((do_test<int, long>(non_cce)));
+    assert((do_test<long, int>(non_cce)));
+    assert((do_test<int, long long>(non_cce)));
+    assert((do_test<long long, int>(non_cce)));
+}