diff options
| author | Eric Fiselier <eric@efcs.ca> | 2015-03-31 16:54:19 +0000 |
|---|---|---|
| committer | Eric Fiselier <eric@efcs.ca> | 2015-03-31 16:54:19 +0000 |
| commit | 088ed9fe946997f94682ee53d586b8c3d118e211 (patch) | |
| tree | 6038b79fb1f25f58e5827930561e7d3b6ffc4f2b /include/memory | |
| parent | bf9653d85f05b945ed5e2a79f1c93b16e064e054 (diff) | |
[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
Diffstat (limited to 'include/memory')
| -rw-r--r-- | include/memory | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/include/memory b/include/memory index 7085cedad..43f8dbada 100644 --- a/include/memory +++ b/include/memory @@ -1525,6 +1525,34 @@ struct _LIBCPP_TYPE_VIS_ONLY allocator_traits __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 |