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[libc++][NFC] Simplify copy and move lowering to memmove a bit (llvm#…
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…83574)

We've introduced `__constexpr_memmove` a while ago, which simplified the
implementation of the copy and move lowering a bit. This allows us to
remove some of the boilerplate.
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@philnik777
philnik777 authored Mar 27, 2024
1 parent 009f88f commit c388690
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Showing 5 changed files with 15 additions and 48 deletions.
6 changes: 2 additions & 4 deletions libcxx/include/__algorithm/copy.h
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,7 @@ template <class, class _InIter, class _Sent, class _OutIter>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter> __copy(_InIter, _Sent, _OutIter);

template <class _AlgPolicy>
struct __copy_loop {
struct __copy_impl {
template <class _InIter, class _Sent, class _OutIter>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
operator()(_InIter __first, _Sent __last, _OutIter __result) const {
Expand Down Expand Up @@ -94,9 +94,7 @@ struct __copy_loop {
__local_first = _Traits::__begin(++__segment_iterator);
}
}
};

struct __copy_trivial {
// At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
template <class _In, class _Out, __enable_if_t<__can_lower_copy_assignment_to_memmove<_In, _Out>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
Expand All @@ -108,7 +106,7 @@ struct __copy_trivial {
template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
pair<_InIter, _OutIter> inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14
__copy(_InIter __first, _Sent __last, _OutIter __result) {
return std::__dispatch_copy_or_move<_AlgPolicy, __copy_loop<_AlgPolicy>, __copy_trivial>(
return std::__copy_move_unwrap_iters<__copy_impl<_AlgPolicy> >(
std::move(__first), std::move(__last), std::move(__result));
}

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6 changes: 2 additions & 4 deletions libcxx/include/__algorithm/copy_backward.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_InIter, _OutIter>
__copy_backward(_InIter __first, _Sent __last, _OutIter __result);

template <class _AlgPolicy>
struct __copy_backward_loop {
struct __copy_backward_impl {
template <class _InIter, class _Sent, class _OutIter>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
operator()(_InIter __first, _Sent __last, _OutIter __result) const {
Expand Down Expand Up @@ -104,9 +104,7 @@ struct __copy_backward_loop {
__local_last = _Traits::__end(__segment_iterator);
}
}
};

struct __copy_backward_trivial {
// At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
template <class _In, class _Out, __enable_if_t<__can_lower_copy_assignment_to_memmove<_In, _Out>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
Expand All @@ -118,7 +116,7 @@ struct __copy_backward_trivial {
template <class _AlgPolicy, class _BidirectionalIterator1, class _Sentinel, class _BidirectionalIterator2>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1, _BidirectionalIterator2>
__copy_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result) {
return std::__dispatch_copy_or_move<_AlgPolicy, __copy_backward_loop<_AlgPolicy>, __copy_backward_trivial>(
return std::__copy_move_unwrap_iters<__copy_backward_impl<_AlgPolicy> >(
std::move(__first), std::move(__last), std::move(__result));
}

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39 changes: 7 additions & 32 deletions libcxx/include/__algorithm/copy_move_common.h
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Original file line number Diff line number Diff line change
Expand Up @@ -81,30 +81,17 @@ __copy_backward_trivial_impl(_In* __first, _In* __last, _Out* __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 _InIter, class _OutIter>
struct __can_rewrap
: integral_constant<bool, is_copy_constructible<_InIter>::value && is_copy_constructible<_OutIter>::value> {};

template <class _Algorithm,
class _InIter,
class _Sent,
class _OutIter,
__enable_if_t<__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
__enable_if_t<__can_rewrap<_InIter, _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) {
__copy_move_unwrap_iters(_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)),
Expand All @@ -115,24 +102,12 @@ template <class _Algorithm,
class _InIter,
class _Sent,
class _OutIter,
__enable_if_t<!__can_rewrap<_InIter, _Sent, _OutIter>::value, int> = 0>
__enable_if_t<!__can_rewrap<_InIter, _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) {
__copy_move_unwrap_iters(_InIter __first, _Sent __last, _OutIter __out_first) {
return _Algorithm()(std::move(__first), std::move(__last), std::move(__out_first));
}

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) {
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

_LIBCPP_POP_MACROS
Expand Down
6 changes: 2 additions & 4 deletions libcxx/include/__algorithm/move.h
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIte
__move(_InIter __first, _Sent __last, _OutIter __result);

template <class _AlgPolicy>
struct __move_loop {
struct __move_impl {
template <class _InIter, class _Sent, class _OutIter>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
operator()(_InIter __first, _Sent __last, _OutIter __result) const {
Expand Down Expand Up @@ -95,9 +95,7 @@ struct __move_loop {
__local_first = _Traits::__begin(++__segment_iterator);
}
}
};

struct __move_trivial {
// At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
template <class _In, class _Out, __enable_if_t<__can_lower_move_assignment_to_memmove<_In, _Out>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
Expand All @@ -109,7 +107,7 @@ struct __move_trivial {
template <class _AlgPolicy, class _InIter, class _Sent, class _OutIter>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
__move(_InIter __first, _Sent __last, _OutIter __result) {
return std::__dispatch_copy_or_move<_AlgPolicy, __move_loop<_AlgPolicy>, __move_trivial>(
return std::__copy_move_unwrap_iters<__move_impl<_AlgPolicy> >(
std::move(__first), std::move(__last), std::move(__result));
}

Expand Down
6 changes: 2 additions & 4 deletions libcxx/include/__algorithm/move_backward.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_BidirectionalIterator1
__move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _BidirectionalIterator2 __result);

template <class _AlgPolicy>
struct __move_backward_loop {
struct __move_backward_impl {
template <class _InIter, class _Sent, class _OutIter>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_InIter, _OutIter>
operator()(_InIter __first, _Sent __last, _OutIter __result) const {
Expand Down Expand Up @@ -104,9 +104,7 @@ struct __move_backward_loop {
__local_last = _Traits::__end(--__segment_iterator);
}
}
};

struct __move_backward_trivial {
// At this point, the iterators have been unwrapped so any `contiguous_iterator` has been unwrapped to a pointer.
template <class _In, class _Out, __enable_if_t<__can_lower_move_assignment_to_memmove<_In, _Out>::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_In*, _Out*>
Expand All @@ -122,7 +120,7 @@ __move_backward(_BidirectionalIterator1 __first, _Sentinel __last, _Bidirectiona
std::is_copy_constructible<_BidirectionalIterator1>::value,
"Iterators must be copy constructible.");

return std::__dispatch_copy_or_move<_AlgPolicy, __move_backward_loop<_AlgPolicy>, __move_backward_trivial>(
return std::__copy_move_unwrap_iters<__move_backward_impl<_AlgPolicy> >(
std::move(__first), std::move(__last), std::move(__result));
}

Expand Down

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