[libc++][P0202] Marked algorithms copy/copy_n/copy_if/copy_backward constexpr
Thanks to Michael Park for the patch.
Differential Revision: https://reviews.llvm.org/D68837
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 55ea5eb..419ec2c 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -167,20 +167,20 @@
Size count, const T& value, BinaryPredicate pred);
template <class InputIterator, class OutputIterator>
- OutputIterator
+ constexpr OutputIterator // constexpr in C++20
copy(InputIterator first, InputIterator last, OutputIterator result);
template<class InputIterator, class OutputIterator, class Predicate>
- OutputIterator
+ constexpr OutputIterator // constexpr in C++20
copy_if(InputIterator first, InputIterator last,
OutputIterator result, Predicate pred);
template<class InputIterator, class Size, class OutputIterator>
- OutputIterator
+ constexpr OutputIterator // constexpr in C++20
copy_n(InputIterator first, Size n, OutputIterator result);
template <class BidirectionalIterator1, class BidirectionalIterator2>
- BidirectionalIterator2
+ constexpr BidirectionalIterator2 // constexpr in C++20
copy_backward(BidirectionalIterator1 first, BidirectionalIterator1 last,
BidirectionalIterator2 result);
@@ -1631,7 +1631,7 @@
// copy
template <class _Iter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
_Iter
__unwrap_iter(_Iter __i)
{
@@ -1639,7 +1639,7 @@
}
template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
typename enable_if
<
is_trivially_copy_assignable<_Tp>::value,
@@ -1693,15 +1693,23 @@
#endif // _LIBCPP_DEBUG_LEVEL < 2
template <class _InputIterator, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
_OutputIterator
-__copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
+__copy_constexpr(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
{
for (; __first != __last; ++__first, (void) ++__result)
*__result = *__first;
return __result;
}
+template <class _InputIterator, class _OutputIterator>
+inline _LIBCPP_INLINE_VISIBILITY
+_OutputIterator
+__copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
+{
+ return __copy_constexpr(__first, __last, __result);
+}
+
template <class _Tp, class _Up>
inline _LIBCPP_INLINE_VISIBILITY
typename enable_if
@@ -1719,23 +1727,37 @@
}
template <class _InputIterator, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
_OutputIterator
copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
{
- return _VSTD::__copy(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+ if (__libcpp_is_constant_evaluated()) {
+ return _VSTD::__copy_constexpr(
+ __unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+ } else {
+ return _VSTD::__copy(
+ __unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+ }
}
// copy_backward
template <class _BidirectionalIterator, class _OutputIterator>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+_OutputIterator
+__copy_backward_constexpr(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
+{
+ while (__first != __last)
+ *--__result = *--__last;
+ return __result;
+}
+
+template <class _BidirectionalIterator, class _OutputIterator>
inline _LIBCPP_INLINE_VISIBILITY
_OutputIterator
__copy_backward(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
{
- while (__first != __last)
- *--__result = *--__last;
- return __result;
+ return __copy_backward_constexpr(__first, __last, __result);
}
template <class _Tp, class _Up>
@@ -1758,20 +1780,26 @@
}
template <class _BidirectionalIterator1, class _BidirectionalIterator2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
_BidirectionalIterator2
copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
_BidirectionalIterator2 __result)
{
- return _VSTD::__copy_backward(__unwrap_iter(__first),
- __unwrap_iter(__last),
- __unwrap_iter(__result));
+ if (__libcpp_is_constant_evaluated()) {
+ return _VSTD::__copy_backward_constexpr(__unwrap_iter(__first),
+ __unwrap_iter(__last),
+ __unwrap_iter(__result));
+ } else {
+ return _VSTD::__copy_backward(__unwrap_iter(__first),
+ __unwrap_iter(__last),
+ __unwrap_iter(__result));
+ }
}
// copy_if
template<class _InputIterator, class _OutputIterator, class _Predicate>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
_OutputIterator
copy_if(_InputIterator __first, _InputIterator __last,
_OutputIterator __result, _Predicate __pred)
@@ -1790,7 +1818,7 @@
// copy_n
template<class _InputIterator, class _Size, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
typename enable_if
<
__is_input_iterator<_InputIterator>::value &&
@@ -1816,7 +1844,7 @@
}
template<class _InputIterator, class _Size, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
typename enable_if
<
__is_random_access_iterator<_InputIterator>::value,
