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[libcxx] Optimize vectors uninitialized construction of trivial types from an iterator range.

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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
This commit is contained in:
Eric Fiselier 2015-03-31 16:54:19 +00:00
parent bf9653d85f
commit 088ed9fe94
2 changed files with 48 additions and 23 deletions
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28
include/memory
View File

@ -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

41
include/vector
View File

@ -783,7 +783,7 @@ private:
__is_forward_iterator<_ForwardIterator>::value,
void
>::type
__construct_at_end(_ForwardIterator __first, _ForwardIterator __last);
__construct_at_end(_ForwardIterator __first, _ForwardIterator __last, size_type __n);
void __append(size_type __n);
void __append(size_type __n, const_reference __x);
_LIBCPP_INLINE_VISIBILITY
@ -1021,16 +1021,12 @@ typename enable_if
__is_forward_iterator<_ForwardIterator>::value,
void
>::type
vector<_Tp, _Allocator>::__construct_at_end(_ForwardIterator __first, _ForwardIterator __last)
vector<_Tp, _Allocator>::__construct_at_end(_ForwardIterator __first, _ForwardIterator __last, size_type __n)
{
allocator_type& __a = this->__alloc();
for (; __first != __last; ++__first)
{
__RAII_IncreaseAnnotator __annotator(*this);
__alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_), *__first);
__RAII_IncreaseAnnotator __annotator(*this, __n);
__alloc_traits::__construct_range_forward(__a, __first, __last, this->__end_);
__annotator.__done();
++this->__end_;
}
}
// Default constructs __n objects starting at __end_
@ -1177,7 +1173,7 @@ vector<_Tp, _Allocator>::vector(_ForwardIterator __first,
if (__n > 0)
{
allocate(__n);
__construct_at_end(__first, __last);
__construct_at_end(__first, __last, __n);
}
}
@ -1197,7 +1193,7 @@ vector<_Tp, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __las
if (__n > 0)
{
allocate(__n);
__construct_at_end(__first, __last);
__construct_at_end(__first, __last, __n);
}
}
@ -1212,7 +1208,7 @@ vector<_Tp, _Allocator>::vector(const vector& __x)
if (__n > 0)
{
allocate(__n);
__construct_at_end(__x.__begin_, __x.__end_);
__construct_at_end(__x.__begin_, __x.__end_, __n);
}
}
@ -1227,7 +1223,7 @@ vector<_Tp, _Allocator>::vector(const vector& __x, const allocator_type& __a)
if (__n > 0)
{
allocate(__n);
__construct_at_end(__x.__begin_, __x.__end_);
__construct_at_end(__x.__begin_, __x.__end_, __n);
}
}
@ -1286,7 +1282,7 @@ vector<_Tp, _Allocator>::vector(initializer_list<value_type> __il)
if (__il.size() > 0)
{
allocate(__il.size());
__construct_at_end(__il.begin(), __il.end());
__construct_at_end(__il.begin(), __il.end(), __il.size());
}
}
@ -1301,7 +1297,7 @@ vector<_Tp, _Allocator>::vector(initializer_list<value_type> __il, const allocat
if (__il.size() > 0)
{
allocate(__il.size());
__construct_at_end(__il.begin(), __il.end());
__construct_at_end(__il.begin(), __il.end(), __il.size());
}
}
@ -1394,12 +1390,12 @@ typename enable_if
>::type
vector<_Tp, _Allocator>::assign(_ForwardIterator __first, _ForwardIterator __last)
{
typename iterator_traits<_ForwardIterator>::difference_type __new_size = _VSTD::distance(__first, __last);
if (static_cast<size_type>(__new_size) <= capacity())
size_type __new_size = static_cast<size_type>(_VSTD::distance(__first, __last));
if (__new_size <= capacity())
{
_ForwardIterator __mid = __last;
bool __growing = false;
if (static_cast<size_type>(__new_size) > size())
if (__new_size > size())
{
__growing = true;
__mid = __first;
@ -1407,15 +1403,15 @@ vector<_Tp, _Allocator>::assign(_ForwardIterator __first, _ForwardIterator __las
}
pointer __m = _VSTD::copy(__first, __mid, this->__begin_);
if (__growing)
__construct_at_end(__mid, __last);
__construct_at_end(__mid, __last, __new_size - size());
else
this->__destruct_at_end(__m);
}
else
{
deallocate();
allocate(__recommend(static_cast<size_type>(__new_size)));
__construct_at_end(__first, __last);
allocate(__recommend(__new_size));
__construct_at_end(__first, __last, __new_size);
}
}
@ -1967,8 +1963,9 @@ vector<_Tp, _Allocator>::insert(const_iterator __position, _ForwardIterator __fi
if (__n > __dx)
{
__m = __first;
_VSTD::advance(__m, this->__end_ - __p);
__construct_at_end(__m, __last);
difference_type __diff = this->__end_ - __p;
_VSTD::advance(__m, __diff);
__construct_at_end(__m, __last, __n - __diff);
__n = __dx;
}
if (__n > 0)