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[Take 2] [libc++] Make rotate a constexpr.
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This patch makes `std::rotate` a constexpr. In doing so, this patch also
updates the internal `__move` and `__move_backward` funtions to be
constexpr.

This patch was previously reverted in ed65318 because it was missing
some UNSUPPORTED markup for older compilers. This commit adds it.

Differential Revision: https://reviews.llvm.org/D65721
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@zoecarver @ldionne
zoecarver authored and ldionne committed Sep 14, 2020
1 parent ed65318 commit 3ed89b5
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Showing 9 changed files with 145 additions and 36 deletions.
68 changes: 46 additions & 22 deletions libcxx/include/algorithm
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1631,15 +1631,15 @@ search_n(_ForwardIterator __first, _ForwardIterator __last, _Size __count, const

// copy
template <class _Iter>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
_Iter
__unwrap_iter(_Iter __i)
{
return __i;
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
Expand All @@ -1653,7 +1653,7 @@ __unwrap_iter(move_iterator<_Tp*> __i)
#if _LIBCPP_DEBUG_LEVEL < 2

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
Expand All @@ -1665,7 +1665,7 @@ __unwrap_iter(__wrap_iter<_Tp*> __i)
}

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
Expand All @@ -1679,7 +1679,7 @@ __unwrap_iter(__wrap_iter<const _Tp*> __i)
#else

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
Expand Down Expand Up @@ -1859,18 +1859,28 @@ copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)

// move

// __move_constexpr exists so that __move doesn't call itself when delegating to the constexpr
// version of __move.
template <class _InputIterator, class _OutputIterator>
inline _LIBCPP_INLINE_VISIBILITY
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
_OutputIterator
__move(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
__move_constexpr(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
{
for (; __first != __last; ++__first, (void) ++__result)
*__result = _VSTD::move(*__first);
return __result;
}

template <class _InputIterator, class _OutputIterator>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
_OutputIterator
__move(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
{
return __move_constexpr(__first, __last, __result);
}

template <class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
typename enable_if
<
is_same<typename remove_const<_Tp>::type, _Up>::value &&
Expand All @@ -1879,14 +1889,16 @@ typename enable_if
>::type
__move(_Tp* __first, _Tp* __last, _Up* __result)
{
if (__libcpp_is_constant_evaluated())
return __move_constexpr(__first, __last, __result);
const size_t __n = static_cast<size_t>(__last - __first);
if (__n > 0)
_VSTD::memmove(__result, __first, __n * sizeof(_Up));
return __result + __n;
}

template <class _InputIterator, class _OutputIterator>
inline _LIBCPP_INLINE_VISIBILITY
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
_OutputIterator
move(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
{
Expand All @@ -1895,18 +1907,28 @@ move(_InputIterator __first, _InputIterator __last, _OutputIterator __result)

// move_backward

// __move_backward_constexpr exists so that __move_backward doesn't call itself when delegating to
// the constexpr version of __move_backward.
template <class _InputIterator, class _OutputIterator>
inline _LIBCPP_INLINE_VISIBILITY
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
_OutputIterator
__move_backward(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
__move_backward_constexpr(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
{
while (__first != __last)
*--__result = _VSTD::move(*--__last);
return __result;
}

template <class _InputIterator, class _OutputIterator>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
_OutputIterator
__move_backward(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
{
return __move_backward_constexpr(__first, __last, __result);
}

template <class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
typename enable_if
<
is_same<typename remove_const<_Tp>::type, _Up>::value &&
Expand All @@ -1915,6 +1937,8 @@ typename enable_if
>::type
__move_backward(_Tp* __first, _Tp* __last, _Up* __result)
{
if (__libcpp_is_constant_evaluated())
return __move_backward_constexpr(__first, __last, __result);
const size_t __n = static_cast<size_t>(__last - __first);
if (__n > 0)
{
Expand All @@ -1925,7 +1949,7 @@ __move_backward(_Tp* __first, _Tp* __last, _Up* __result)
}

template <class _BidirectionalIterator1, class _BidirectionalIterator2>
inline _LIBCPP_INLINE_VISIBILITY
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
_BidirectionalIterator2
move_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
_BidirectionalIterator2 __result)
Expand Down Expand Up @@ -2333,7 +2357,7 @@ reverse_copy(_BidirectionalIterator __first, _BidirectionalIterator __last, _Out
// rotate

template <class _ForwardIterator>
_ForwardIterator
_LIBCPP_CONSTEXPR_AFTER_CXX11 _ForwardIterator
__rotate_left(_ForwardIterator __first, _ForwardIterator __last)
{
typedef typename iterator_traits<_ForwardIterator>::value_type value_type;
Expand All @@ -2344,7 +2368,7 @@ __rotate_left(_ForwardIterator __first, _ForwardIterator __last)
}

template <class _BidirectionalIterator>
_BidirectionalIterator
_LIBCPP_CONSTEXPR_AFTER_CXX11 _BidirectionalIterator
__rotate_right(_BidirectionalIterator __first, _BidirectionalIterator __last)
{
typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
Expand All @@ -2356,7 +2380,7 @@ __rotate_right(_BidirectionalIterator __first, _BidirectionalIterator __last)
}

template <class _ForwardIterator>
_ForwardIterator
_LIBCPP_CONSTEXPR_AFTER_CXX14 _ForwardIterator
__rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
{
_ForwardIterator __i = __middle;
Expand Down Expand Up @@ -2392,7 +2416,7 @@ __rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIt

template<typename _Integral>
inline _LIBCPP_INLINE_VISIBILITY
_Integral
_LIBCPP_CONSTEXPR_AFTER_CXX14 _Integral
__algo_gcd(_Integral __x, _Integral __y)
{
do
Expand All @@ -2405,7 +2429,7 @@ __algo_gcd(_Integral __x, _Integral __y)
}

template<typename _RandomAccessIterator>
_RandomAccessIterator
_LIBCPP_CONSTEXPR_AFTER_CXX14 _RandomAccessIterator
__rotate_gcd(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last)
{
typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
Expand Down Expand Up @@ -2441,7 +2465,7 @@ __rotate_gcd(_RandomAccessIterator __first, _RandomAccessIterator __middle, _Ran

template <class _ForwardIterator>
inline _LIBCPP_INLINE_VISIBILITY
_ForwardIterator
_LIBCPP_CONSTEXPR_AFTER_CXX11 _ForwardIterator
__rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last,
_VSTD::forward_iterator_tag)
{
Expand All @@ -2456,7 +2480,7 @@ __rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator _

template <class _BidirectionalIterator>
inline _LIBCPP_INLINE_VISIBILITY
_BidirectionalIterator
_LIBCPP_CONSTEXPR_AFTER_CXX11 _BidirectionalIterator
__rotate(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
_VSTD::bidirectional_iterator_tag)
{
Expand All @@ -2473,7 +2497,7 @@ __rotate(_BidirectionalIterator __first, _BidirectionalIterator __middle, _Bidir

template <class _RandomAccessIterator>
inline _LIBCPP_INLINE_VISIBILITY
_RandomAccessIterator
_LIBCPP_CONSTEXPR_AFTER_CXX11 _RandomAccessIterator
__rotate(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomAccessIterator __last,
_VSTD::random_access_iterator_tag)
{
Expand All @@ -2491,7 +2515,7 @@ __rotate(_RandomAccessIterator __first, _RandomAccessIterator __middle, _RandomA

template <class _ForwardIterator>
inline _LIBCPP_INLINE_VISIBILITY
_ForwardIterator
_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
{
if (__first == __middle)
Expand Down
16 changes: 8 additions & 8 deletions libcxx/include/iterator
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1393,13 +1393,13 @@ operator+(typename __wrap_iter<_Iter>::difference_type, __wrap_iter<_Iter>) _NOE

template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 copy(_Ip, _Ip, _Op);
template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 copy_backward(_B1, _B1, _B2);
template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY move(_Ip, _Ip, _Op);
template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY move_backward(_B1, _B1, _B2);
template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 move(_Ip, _Ip, _Op);
template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 move_backward(_B1, _B1, _B2);

#if _LIBCPP_DEBUG_LEVEL < 2

template <class _Tp>
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
Expand All @@ -1410,7 +1410,7 @@ __unwrap_iter(__wrap_iter<_Tp*>);
#else

template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
Expand Down Expand Up @@ -1604,12 +1604,12 @@ private:

template <class _Ip, class _Op> friend _LIBCPP_CONSTEXPR_AFTER_CXX17 _Op copy(_Ip, _Ip, _Op);
template <class _B1, class _B2> friend _LIBCPP_CONSTEXPR_AFTER_CXX17 _B2 copy_backward(_B1, _B1, _B2);
template <class _Ip, class _Op> friend _Op move(_Ip, _Ip, _Op);
template <class _B1, class _B2> friend _B2 move_backward(_B1, _B1, _B2);
template <class _Ip, class _Op> friend _LIBCPP_CONSTEXPR_AFTER_CXX17 _Op move(_Ip, _Ip, _Op);
template <class _B1, class _B2> friend _LIBCPP_CONSTEXPR_AFTER_CXX17 _B2 move_backward(_B1, _B1, _B2);

#if _LIBCPP_DEBUG_LEVEL < 2
template <class _Tp>
_LIBCPP_CONSTEXPR_IF_NODEBUG friend
_LIBCPP_CONSTEXPR friend
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
Expand All @@ -1618,7 +1618,7 @@ private:
__unwrap_iter(__wrap_iter<_Tp*>);
#else
template <class _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
Expand Down
43 changes: 41 additions & 2 deletions libcxx/test/std/algorithms/alg.modifying.operations/alg.move/move.pass.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,11 @@
// OutIter
// move(InIter first, InIter last, OutIter result);

// Older compilers don't support std::is_constant_evaluated
// UNSUPPORTED: clang-4, clang-5, clang-6, clang-7, clang-8
// UNSUPPORTED: apple-clang-9, apple-clang-10, apple-clang-11
// UNSUPPORTED: gcc-5, gcc-6, gcc-7, gcc-8

#include <algorithm>
#include <cassert>
#include <memory>
Expand All @@ -21,11 +26,11 @@
#include "test_iterators.h"

template <class InIter, class OutIter>
void
_LIBCPP_CONSTEXPR_AFTER_CXX17 bool
test()
{
const unsigned N = 1000;
int ia[N];
int ia[N] = {};
for (unsigned i = 0; i < N; ++i)
ia[i] = i;
int ib[N] = {0};
Expand All @@ -34,6 +39,8 @@ test()
assert(base(r) == ib+N);
for (unsigned i = 0; i < N; ++i)
assert(ia[i] == ib[i]);

return true;
}

#if TEST_STD_VER >= 11
Expand Down Expand Up @@ -128,5 +135,37 @@ int main(int, char**)
test1<std::unique_ptr<int>*, std::unique_ptr<int>*>();
#endif // TEST_STD_VER >= 11

#if TEST_STD_VER > 17
static_assert(test<input_iterator<const int*>, input_iterator<int*> >());
static_assert(test<input_iterator<const int*>, forward_iterator<int*> >());
static_assert(test<input_iterator<const int*>, bidirectional_iterator<int*> >());
static_assert(test<input_iterator<const int*>, random_access_iterator<int*> >());
static_assert(test<input_iterator<const int*>, int*>());

static_assert(test<forward_iterator<const int*>, input_iterator<int*> >());
static_assert(test<forward_iterator<const int*>, forward_iterator<int*> >());
static_assert(test<forward_iterator<const int*>, bidirectional_iterator<int*> >());
static_assert(test<forward_iterator<const int*>, random_access_iterator<int*> >());
static_assert(test<forward_iterator<const int*>, int*>());

static_assert(test<bidirectional_iterator<const int*>, input_iterator<int*> >());
static_assert(test<bidirectional_iterator<const int*>, forward_iterator<int*> >());
static_assert(test<bidirectional_iterator<const int*>, bidirectional_iterator<int*> >());
static_assert(test<bidirectional_iterator<const int*>, random_access_iterator<int*> >());
static_assert(test<bidirectional_iterator<const int*>, int*>());

static_assert(test<random_access_iterator<const int*>, input_iterator<int*> >());
static_assert(test<random_access_iterator<const int*>, forward_iterator<int*> >());
static_assert(test<random_access_iterator<const int*>, bidirectional_iterator<int*> >());
static_assert(test<random_access_iterator<const int*>, random_access_iterator<int*> >());
static_assert(test<random_access_iterator<const int*>, int*>());

static_assert(test<const int*, input_iterator<int*> >());
static_assert(test<const int*, forward_iterator<int*> >());
static_assert(test<const int*, bidirectional_iterator<int*> >());
static_assert(test<const int*, random_access_iterator<int*> >());
static_assert(test<const int*, int*>());
#endif // TEST_STD_VER > 17

return 0;
}
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