Commit patch for integer sequences. Suggested by Richard, reworked by Howard, and annotated by me

llvm-svn: 185569

1 files changed, 46 insertions, 22 deletions

diff --git a/libcxx/include/utility b/libcxx/include/utility
index f4a86b64526..ba656493c50 100644
--- a/libcxx/include/utility
+++ b/libcxx/include/utility
@@ -602,7 +602,7 @@ get(pair<_T1, _T2>&& __p) _NOEXCEPT
 #if _LIBCPP_STD_VER > 11
 
 template<class _Tp, _Tp... _Ip>
-struct integer_sequence
+struct _LIBCPP_TYPE_VIS integer_sequence
 {
     typedef _Tp value_type;
     static_assert( is_integral<_Tp>::value,
@@ -617,26 +617,53 @@ struct integer_sequence
 template<size_t... _Ip>
     using index_sequence = integer_sequence<size_t, _Ip...>;
 
-template <class _Tp, _Tp _Sp, _Tp _Ep, class _IntSequence>
-struct __make_integer_sequence_unchecked;
-
-template <class _Tp, _Tp _Sp, _Tp _Ep, _Tp ..._Indices>
-struct __make_integer_sequence_unchecked<_Tp, _Sp, _Ep,
-                                         integer_sequence<_Tp, _Indices...>>
-{
-    typedef typename __make_integer_sequence_unchecked
-                     <
-                        _Tp, _Sp+1, _Ep,
-                        integer_sequence<_Tp, _Indices..., _Sp>
-                     >::type type;
+namespace __detail {
+
+template<typename _Tp, size_t ..._Extra> struct __repeat;
+template<typename _Tp, _Tp ..._Np, size_t ..._Extra> struct __repeat<integer_sequence<_Tp, _Np...>, _Extra...> {
+  typedef integer_sequence<_Tp,
+                           _Np...,
+                           sizeof...(_Np) + _Np...,
+                           2 * sizeof...(_Np) + _Np...,
+                           3 * sizeof...(_Np) + _Np...,
+                           4 * sizeof...(_Np) + _Np...,
+                           5 * sizeof...(_Np) + _Np...,
+                           6 * sizeof...(_Np) + _Np...,
+                           7 * sizeof...(_Np) + _Np...,
+                           _Extra...> type;
 };
 
-template <class _Tp, _Tp _Ep, _Tp ..._Indices>
-struct __make_integer_sequence_unchecked<_Tp, _Ep, _Ep,
-                                         integer_sequence<_Tp, _Indices...>>
-{
-    typedef integer_sequence<_Tp, _Indices...> type;
+template<size_t _Np> struct __parity;
+template<size_t _Np> struct __make : __parity<_Np % 8>::template __pmake<_Np> {};
+
+template<> struct __make<0> { typedef integer_sequence<size_t> type; };
+template<> struct __make<1> { typedef integer_sequence<size_t, 0> type; };
+template<> struct __make<2> { typedef integer_sequence<size_t, 0, 1> type; };
+template<> struct __make<3> { typedef integer_sequence<size_t, 0, 1, 2> type; };
+template<> struct __make<4> { typedef integer_sequence<size_t, 0, 1, 2, 3> type; };
+template<> struct __make<5> { typedef integer_sequence<size_t, 0, 1, 2, 3, 4> type; };
+template<> struct __make<6> { typedef integer_sequence<size_t, 0, 1, 2, 3, 4, 5> type; };
+template<> struct __make<7> { typedef integer_sequence<size_t, 0, 1, 2, 3, 4, 5, 6> type; };
+
+template<> struct __parity<0> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type> {}; };
+template<> struct __parity<1> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 1> {}; };
+template<> struct __parity<2> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<3> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 3, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<4> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<5> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<6> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<7> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 7, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
+
+template<typename _Tp, typename _Up> struct __convert {
+  template<typename> struct __result;
+  template<_Tp ..._Np> struct __result<integer_sequence<_Tp, _Np...> > { typedef integer_sequence<_Up, _Np...> type; };
 };
+template<typename _Tp> struct __convert<_Tp, _Tp> { template<typename _Up> struct __result { typedef _Up type; }; };
+
+}
+
+template<typename _Tp, _Tp _Np> using __make_integer_sequence_unchecked =
+  typename __detail::__convert<size_t, _Tp>::template __result<typename __detail::__make<_Np>::type>::type;
 
 template <class _Tp, _Tp _Ep>
 struct __make_integer_sequence
@@ -644,10 +671,7 @@ struct __make_integer_sequence
     static_assert(is_integral<_Tp>::value,
                   "std::make_integer_sequence can only be instantiated with an integral type" );
     static_assert(0 <= _Ep, "std::make_integer_sequence input shall not be negative");
-    typedef typename __make_integer_sequence_unchecked
-                     <
-                        _Tp, 0, _Ep, integer_sequence<_Tp>
-                     >::type type;
+    typedef __make_integer_sequence_unchecked<_Tp, _Ep> type;
 };
 
 template<class _Tp, _Tp _Np>