mirror of
https://github.com/llvm/llvm-project.git
synced 2025-04-25 21:06:06 +00:00
005916de58
Instead of using `reverse_iterator`, share the optimization between the 4 algorithms. The key observation here that `memmove` applies to both `copy` and `move` identically, and to their `_backward` versions very similarly. All algorithms now follow the same pattern along the lines of:
```
if constexpr (can_memmove<InIter, OutIter>) {
memmove(first, last, out);
} else {
naive_implementation(first, last, out);
}
```
A follow-up will delete `unconstrained_reverse_iterator`.
This patch removes duplication and divergence between `std::copy`, `std::move` and `std::move_backward`. It also improves testing:
- the test for whether the optimization is used only applied to `std::copy` and, more importantly, was essentially a no-op because it would still pass if the optimization was not used;
- there were no tests to make sure the optimization is not used when the effect would be visible.
Differential Revision: https://reviews.llvm.org/D130695
138 lines
5.4 KiB
C++
138 lines
5.4 KiB
C++
//===----------------------------------------------------------------------===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
|
|
#define _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
|
|
|
|
#include <__algorithm/iterator_operations.h>
|
|
#include <__algorithm/unwrap_iter.h>
|
|
#include <__algorithm/unwrap_range.h>
|
|
#include <__config>
|
|
#include <__iterator/iterator_traits.h>
|
|
#include <__memory/pointer_traits.h>
|
|
#include <__type_traits/enable_if.h>
|
|
#include <__type_traits/integral_constant.h>
|
|
#include <__type_traits/is_constant_evaluated.h>
|
|
#include <__type_traits/is_copy_constructible.h>
|
|
#include <__type_traits/is_trivially_assignable.h>
|
|
#include <__utility/move.h>
|
|
#include <__utility/pair.h>
|
|
|
|
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
|
|
# pragma GCC system_header
|
|
#endif
|
|
|
|
_LIBCPP_BEGIN_NAMESPACE_STD
|
|
|
|
// `memmove` algorithms implementation.
|
|
|
|
template <class _In, class _Out>
|
|
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
|
|
__copy_trivial_impl(_In* __first, _In* __last, _Out* __result) {
|
|
const size_t __n = static_cast<size_t>(__last - __first);
|
|
::__builtin_memmove(__result, __first, __n * sizeof(_Out));
|
|
|
|
return std::make_pair(__last, __result + __n);
|
|
}
|
|
|
|
template <class _In, class _Out>
|
|
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
|
|
__copy_backward_trivial_impl(_In* __first, _In* __last, _Out* __result) {
|
|
const size_t __n = static_cast<size_t>(__last - __first);
|
|
__result -= __n;
|
|
|
|
::__builtin_memmove(__result, __first, __n * sizeof(_Out));
|
|
|
|
return std::make_pair(__last, __result);
|
|
}
|
|
|
|
// Iterator unwrapping and dispatching to the correct overload.
|
|
|
|
template <class _F1, class _F2>
|
|
struct __overload : _F1, _F2 {
|
|
using _F1::operator();
|
|
using _F2::operator();
|
|
};
|
|
|
|
template <class _InIter, class _Sent, class _OutIter, class = void>
|
|
struct __can_rewrap : false_type {};
|
|
|
|
template <class _InIter, class _Sent, class _OutIter>
|
|
struct __can_rewrap<_InIter,
|
|
_Sent,
|
|
_OutIter,
|
|
// Note that sentinels are always copy-constructible.
|
|
__enable_if_t< is_copy_constructible<_InIter>::value &&
|
|
is_copy_constructible<_OutIter>::value > > : true_type {};
|
|
|
|
template <class _Algorithm,
|
|
class _InIter,
|
|
class _Sent,
|
|
class _OutIter,
|
|
__enable_if_t<__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
|
|
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
|
|
__unwrap_and_dispatch(_InIter __first, _Sent __last, _OutIter __out_first) {
|
|
auto __range = std::__unwrap_range(__first, std::move(__last));
|
|
auto __result = _Algorithm()(std::move(__range.first), std::move(__range.second), std::__unwrap_iter(__out_first));
|
|
return std::make_pair(std::__rewrap_range<_Sent>(std::move(__first), std::move(__result.first)),
|
|
std::__rewrap_iter(std::move(__out_first), std::move(__result.second)));
|
|
}
|
|
|
|
template <class _Algorithm,
|
|
class _InIter,
|
|
class _Sent,
|
|
class _OutIter,
|
|
__enable_if_t<!__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
|
|
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
|
|
__unwrap_and_dispatch(_InIter __first, _Sent __last, _OutIter __out_first) {
|
|
return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first));
|
|
}
|
|
|
|
template <class _IterOps, class _InValue, class _OutIter, class = void>
|
|
struct __can_copy_without_conversion : false_type {};
|
|
|
|
template <class _IterOps, class _InValue, class _OutIter>
|
|
struct __can_copy_without_conversion<
|
|
_IterOps,
|
|
_InValue,
|
|
_OutIter,
|
|
__enable_if_t<is_same<_InValue, typename _IterOps::template __value_type<_OutIter> >::value> > : true_type {};
|
|
|
|
template <class _AlgPolicy,
|
|
class _NaiveAlgorithm,
|
|
class _OptimizedAlgorithm,
|
|
class _InIter,
|
|
class _Sent,
|
|
class _OutIter>
|
|
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 pair<_InIter, _OutIter>
|
|
__dispatch_copy_or_move(_InIter __first, _Sent __last, _OutIter __out_first) {
|
|
#ifdef _LIBCPP_COMPILER_GCC
|
|
// GCC doesn't support `__builtin_memmove` during constant evaluation.
|
|
if (__libcpp_is_constant_evaluated()) {
|
|
return std::__unwrap_and_dispatch<_NaiveAlgorithm>(std::move(__first), std::move(__last), std::move(__out_first));
|
|
}
|
|
#else
|
|
// In Clang, `__builtin_memmove` only supports fully trivially copyable types (just having trivial copy assignment is
|
|
// insufficient). Also, conversions are not supported.
|
|
if (__libcpp_is_constant_evaluated()) {
|
|
using _InValue = typename _IterOps<_AlgPolicy>::template __value_type<_InIter>;
|
|
if (!is_trivially_copyable<_InValue>::value ||
|
|
!__can_copy_without_conversion<_IterOps<_AlgPolicy>, _InValue, _OutIter>::value) {
|
|
return std::__unwrap_and_dispatch<_NaiveAlgorithm>(std::move(__first), std::move(__last), std::move(__out_first));
|
|
}
|
|
}
|
|
#endif // _LIBCPP_COMPILER_GCC
|
|
|
|
using _Algorithm = __overload<_NaiveAlgorithm, _OptimizedAlgorithm>;
|
|
return std::__unwrap_and_dispatch<_Algorithm>(std::move(__first), std::move(__last), std::move(__out_first));
|
|
}
|
|
|
|
_LIBCPP_END_NAMESPACE_STD
|
|
|
|
#endif // _LIBCPP___ALGORITHM_COPY_MOVE_COMMON_H
|