[Take 2] [libc++] Make rotate a constexpr.
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 ed653184ac63 because it was missing
some UNSUPPORTED markup for older compilers. This commit adds it.
Differential Revision: https://reviews.llvm.org/D65721
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 8c8bc74..5d09b6c 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -1631,7 +1631,7 @@
// copy
template <class _Iter>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
_Iter
__unwrap_iter(_Iter __i)
{
@@ -1639,7 +1639,7 @@
}
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,
@@ -1653,7 +1653,7 @@
#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,
@@ -1665,7 +1665,7 @@
}
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,
@@ -1679,7 +1679,7 @@
#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,
@@ -1859,18 +1859,28 @@
// 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 &&
@@ -1879,6 +1889,8 @@
>::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));
@@ -1886,7 +1898,7 @@
}
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)
{
@@ -1895,18 +1907,28 @@
// 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 &&
@@ -1915,6 +1937,8 @@
>::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)
{
@@ -1925,7 +1949,7 @@
}
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)
@@ -2333,7 +2357,7 @@
// 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;
@@ -2344,7 +2368,7 @@
}
template <class _BidirectionalIterator>
-_BidirectionalIterator
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _BidirectionalIterator
__rotate_right(_BidirectionalIterator __first, _BidirectionalIterator __last)
{
typedef typename iterator_traits<_BidirectionalIterator>::value_type value_type;
@@ -2356,7 +2380,7 @@
}
template <class _ForwardIterator>
-_ForwardIterator
+_LIBCPP_CONSTEXPR_AFTER_CXX14 _ForwardIterator
__rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
{
_ForwardIterator __i = __middle;
@@ -2392,7 +2416,7 @@
template<typename _Integral>
inline _LIBCPP_INLINE_VISIBILITY
-_Integral
+_LIBCPP_CONSTEXPR_AFTER_CXX14 _Integral
__algo_gcd(_Integral __x, _Integral __y)
{
do
@@ -2405,7 +2429,7 @@
}
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;
@@ -2441,7 +2465,7 @@
template <class _ForwardIterator>
inline _LIBCPP_INLINE_VISIBILITY
-_ForwardIterator
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _ForwardIterator
__rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last,
_VSTD::forward_iterator_tag)
{
@@ -2456,7 +2480,7 @@
template <class _BidirectionalIterator>
inline _LIBCPP_INLINE_VISIBILITY
-_BidirectionalIterator
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _BidirectionalIterator
__rotate(_BidirectionalIterator __first, _BidirectionalIterator __middle, _BidirectionalIterator __last,
_VSTD::bidirectional_iterator_tag)
{
@@ -2473,7 +2497,7 @@
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)
{
@@ -2491,7 +2515,7 @@
template <class _ForwardIterator>
inline _LIBCPP_INLINE_VISIBILITY
-_ForwardIterator
+_LIBCPP_CONSTEXPR_AFTER_CXX17 _ForwardIterator
rotate(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIterator __last)
{
if (__first == __middle)
