088ed9fe94
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