Replace __make_tuple_indices implementation with superior implementation.
The previous __make_tuple_indices implementation caused O(N) instantiations
and was pretty inefficient. The C++14 __make_integer_sequence implementation
is much better, since it either uses a builtin to generate the sequence or
a very nice Log8(N) implementation provided by richard smith.
This patch moves the __make_integer_sequence implementation into __tuple
and uses it to implement __make_tuple_indices.
Since libc++ can't expose the name 'integer_sequence' in C++11 this patch
also introduces a dummy type '__integer_sequence' which is used when generating
the sequence. One the sequence is generated '__integer_sequence' can be
converted into the required type; either '__tuple_indices' or 'integer_sequence'.
llvm-svn: 274286
diff --git a/libcxx/include/utility b/libcxx/include/utility
index d286e43..9b8e792 100644
--- a/libcxx/include/utility
+++ b/libcxx/include/utility
@@ -741,63 +741,15 @@
#if __has_builtin(__make_integer_seq) && !defined(_LIBCPP_TESTING_FALLBACK_MAKE_INTEGER_SEQUENCE)
template <class _Tp, _Tp _Ep>
-struct __make_integer_sequence
-{
- typedef __make_integer_seq<integer_sequence, _Tp, _Ep> type;
-};
+using __make_integer_sequence = __make_integer_seq<integer_sequence, _Tp, _Ep>;
#else
-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<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;
+ typename __detail::__make<_Np>::type::template __convert<integer_sequence, _Tp>;
template <class _Tp, _Tp _Ep>
-struct __make_integer_sequence
+struct __make_integer_sequence_checked
{
static_assert(is_integral<_Tp>::value,
"std::make_integer_sequence can only be instantiated with an integral type" );
@@ -807,10 +759,13 @@
typedef __make_integer_sequence_unchecked<_Tp, 0 <= _Ep ? _Ep : 0> type;
};
+template <class _Tp, _Tp _Ep>
+using __make_integer_sequence = typename __make_integer_sequence_checked<_Tp, _Ep>::type;
+
#endif
template<class _Tp, _Tp _Np>
- using make_integer_sequence = typename __make_integer_sequence<_Tp, _Np>::type;
+ using make_integer_sequence = __make_integer_sequence<_Tp, _Np>;
template<size_t _Np>
using make_index_sequence = make_integer_sequence<size_t, _Np>;