[libcxx] Optimize vectors construction of trivial types from an iterator range with const-ness mismatch.
We already have a specialization that will use memcpy for construction
of trivial types from an iterator range like
std::vector<int>(int *, int *);
But if we have const-ness mismatch like
std::vector<int>(const int *, const int *);
we would use a slow path that copies each element individually. This change
enables the optimal specialization for const-ness mismatch. Fixes PR37574.
Contributions to the patch are made by Arthur O'Dwyer, Louis Dionne.
rdar://problem/40485845
Reviewers: mclow.lists, EricWF, ldionne, scanon
Reviewed By: ldionne
Subscribers: christof, ldionne, howard.hinnant, cfe-commits
Differential Revision: https://reviews.llvm.org/D48342
llvm-svn: 350583
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: fb0e1908d4e94d83da2996a6f3fe188cc72c00c2
diff --git a/include/memory b/include/memory
index b012f5b..93f04c6 100644
--- a/include/memory
+++ b/include/memory
@@ -1502,6 +1502,12 @@
typedef typename _Alloc::difference_type type;
};
+template <class _Tp>
+struct __is_default_allocator : false_type {};
+
+template <class _Tp>
+struct __is_default_allocator<_VSTD::allocator<_Tp> > : true_type {};
+
template <class _Alloc>
struct _LIBCPP_TEMPLATE_VIS allocator_traits
{
@@ -1615,7 +1621,7 @@
static
typename enable_if
<
- (is_same<allocator_type, allocator<_Tp> >::value
+ (__is_default_allocator<allocator_type>::value
|| !__has_construct<allocator_type, _Tp*, _Tp>::value) &&
is_trivially_move_constructible<_Tp>::value,
void
@@ -1640,23 +1646,25 @@
construct(__a, _VSTD::__to_raw_pointer(__begin2), *__begin1);
}
- template <class _Tp>
+ template <class _SourceTp, class _DestTp,
+ class _RawSourceTp = typename remove_const<_SourceTp>::type,
+ class _RawDestTp = typename remove_const<_DestTp>::type>
_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,
+ is_trivially_move_constructible<_DestTp>::value &&
+ is_same<_RawSourceTp, _RawDestTp>::value &&
+ (__is_default_allocator<allocator_type>::value ||
+ !__has_construct<allocator_type, _DestTp*, _SourceTp&>::value),
void
>::type
- __construct_range_forward(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
+ __construct_range_forward(allocator_type&, _SourceTp* __begin1, _SourceTp* __end1, _DestTp*& __begin2)
{
- typedef typename remove_const<_Tp>::type _Vp;
ptrdiff_t _Np = __end1 - __begin1;
if (_Np > 0)
{
- _VSTD::memcpy(const_cast<_Vp*>(__begin2), __begin1, _Np * sizeof(_Tp));
+ _VSTD::memcpy(const_cast<_RawDestTp*>(__begin2), __begin1, _Np * sizeof(_DestTp));
__begin2 += _Np;
}
}
@@ -1679,7 +1687,7 @@
static
typename enable_if
<
- (is_same<allocator_type, allocator<_Tp> >::value
+ (__is_default_allocator<allocator_type>::value
|| !__has_construct<allocator_type, _Tp*, _Tp>::value) &&
is_trivially_move_constructible<_Tp>::value,
void