[libcxx] Optimize vectors uninitialized construction of trivial types from an iterator range. Summary: In certain cases vector can use memcpy to construct a range of elements at the back of the vector. We currently don't do this resulting in terrible code gen in non-optimized mode and a very large slowdown compared to libstdc++. This patch adds a `__construct_forward_range(Allocator, Iter, Iter, _Ptr&)` and `__construct_forward_range(Allocator, Tp*, Tp*, Tp*&)` functions to `allocator_traits` which act similarly to the existing `__construct_forward(...)` functions. This patch also changes vectors `__construct_at_end(Iter, Iter)` to be `__construct_at_end(Iter, Iter, SizeType)` where SizeType is the size of the range. `__construct_at_end(Iter, Iter, SizeType)` now calls `allocator_traits<Tp>::__construct_forward_range(...)`. This patch is based off the design of `__swap_out_circular_buffer(...)` which uses `allocator_traits<Tp>::__construct_forward(...)`. On my machine this code performs 4x better than the current implementation when tested against `std::vector<int>`. Reviewers: howard.hinnant, titus, kcc, mclow.lists Reviewed By: mclow.lists Subscribers: cfe-commits Differential Revision: http://reviews.llvm.org/D8109 git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@233711 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/memory b/include/memory index 7085ced..43f8dba 100644 --- a/include/memory +++ b/include/memory
@@ -1525,6 +1525,34 @@ __begin2 += _Np; } + template <class _Iter, class _Ptr> + _LIBCPP_INLINE_VISIBILITY + static + void + __construct_range_forward(allocator_type& __a, _Iter __begin1, _Iter __end1, _Ptr& __begin2) + { + for (; __begin1 != __end1; ++__begin1, (void) ++__begin2) + construct(__a, _VSTD::__to_raw_pointer(__begin2), *__begin1); + } + + template <class _Tp> + _LIBCPP_INLINE_VISIBILITY + static + typename enable_if + < + (is_same<allocator_type, allocator<_Tp> >::value + || !__has_construct<allocator_type, _Tp*, _Tp>::value) && + is_trivially_move_constructible<_Tp>::value, + void + >::type + __construct_range_forward(allocator_type& __a, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2) + { + typedef typename remove_const<_Tp>::type _Vp; + ptrdiff_t _Np = __end1 - __begin1; + _VSTD::memcpy(const_cast<_Vp*>(__begin2), __begin1, _Np * sizeof(_Tp)); + __begin2 += _Np; + } + template <class _Ptr> _LIBCPP_INLINE_VISIBILITY static 