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[libc++] Use __unwrap_iter_impl for both unwrapping and rewrapping 

Reviewed By: ldionne, #libc

Spies: arichardson, sstefan1, libcxx-commits

Differential Revision: https://reviews.llvm.org/D129039
This commit is contained in:
Nikolas Klauser 2022-07-12 15:29:07 +02:00
parent 041d4012e4
commit 0a92e0728c
3 changed files with 37 additions and 85 deletions
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80
libcxx/include/__algorithm/unwrap_iter.h
View File

@ -12,6 +12,7 @@
#include <__config>
#include <__iterator/iterator_traits.h>
#include <__memory/pointer_traits.h>
#include <__utility/move.h>
#include <type_traits>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@ -20,77 +21,50 @@
_LIBCPP_BEGIN_NAMESPACE_STD
// The job of __unwrap_iter is to lower contiguous iterators (such as
// vector<T>::iterator) into pointers, to reduce the number of template
// instantiations and to enable pointer-based optimizations e.g. in std::copy.
// For iterators that are not contiguous, it must be a no-op.
// TODO: Change the name of __unwrap_iter_impl to something more appropriate
// The job of __unwrap_iter is to remove iterator wrappers (like reverse_iterator or __wrap_iter),
// to reduce the number of template instantiations and to enable pointer-based optimizations e.g. in std::copy.
// In debug mode, we don't do this.
//
// __unwrap_iter is non-constexpr for user-defined iterators whose
// `to_address` and/or `operator->` is non-constexpr. This is okay; but we
// try to avoid doing __unwrap_iter in constant-evaluated contexts anyway.
//
// Some algorithms (e.g. std::copy, but not std::sort) need to convert an
// "unwrapped" result back into a contiguous iterator. Since contiguous iterators
// are random-access, we can do this portably using iterator arithmetic; this
// is the job of __rewrap_iter.
// "unwrapped" result back into the original iterator type. Doing that is the job of __rewrap_iter.
// Default case - we can't unwrap anything
template <class _Iter, bool = __is_cpp17_contiguous_iterator<_Iter>::value>
struct __unwrap_iter_impl {
static _LIBCPP_CONSTEXPR _Iter
__apply(_Iter __i) _NOEXCEPT {
return __i;
}
static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter, _Iter __iter) { return __iter; }
static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __unwrap(_Iter __i) _NOEXCEPT { return __i; }
};
#ifndef _LIBCPP_ENABLE_DEBUG_MODE
// It's a contiguous iterator, so we can use a raw pointer instead
template <class _Iter>
struct __unwrap_iter_impl<_Iter, true> {
static _LIBCPP_CONSTEXPR decltype(_VSTD::__to_address(declval<_Iter>()))
__apply(_Iter __i) _NOEXCEPT {
return _VSTD::__to_address(__i);
}
using _ToAddressT = decltype(std::__to_address(std::declval<_Iter>()));
static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Iter __rewrap(_Iter __orig_iter, _ToAddressT __unwrapped_iter) {
return __orig_iter + (__unwrapped_iter - std::__to_address(__orig_iter));
}
static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ToAddressT __unwrap(_Iter __i) _NOEXCEPT {
return std::__to_address(__i);
}
};
#endif // !_LIBCPP_ENABLE_DEBUG_MODE
template<class _Iter, class _Impl = __unwrap_iter_impl<_Iter> >
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
decltype(_Impl::__apply(declval<_Iter>()))
__unwrap_iter(_Iter __i) _NOEXCEPT
{
return _Impl::__apply(__i);
template<class _Iter,
class _Impl = __unwrap_iter_impl<_Iter>,
__enable_if_t<is_copy_constructible<_Iter>::value, int> = 0>
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_AFTER_CXX11
decltype(_Impl::__unwrap(std::declval<_Iter>())) __unwrap_iter(_Iter __i) _NOEXCEPT {
return _Impl::__unwrap(__i);
}
template <class _OrigIter, class _UnwrappedIter>
struct __rewrap_iter_impl {
static _LIBCPP_CONSTEXPR _OrigIter __apply(_OrigIter __first, _UnwrappedIter __result) {
// Precondition: __result is reachable from __first
// Precondition: _OrigIter is a contiguous iterator
return __first + (__result - std::__unwrap_iter(__first));
}
};
template <class _OrigIter>
struct __rewrap_iter_impl<_OrigIter, _OrigIter> {
static _LIBCPP_CONSTEXPR _OrigIter __apply(_OrigIter, _OrigIter __result) {
return __result;
}
};
template<class _OrigIter>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
_OrigIter __rewrap_iter(_OrigIter, _OrigIter __result)
{
return __result;
}
template<class _OrigIter, class _UnwrappedIter, class _Impl = __rewrap_iter_impl<_OrigIter, _UnwrappedIter> >
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR
_OrigIter __rewrap_iter(_OrigIter __first, _UnwrappedIter __result)
{
return _Impl::__apply(__first, __result);
template <class _OrigIter, class _Iter, class _Impl = __unwrap_iter_impl<_OrigIter> >
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _OrigIter __rewrap_iter(_OrigIter __orig_iter, _Iter __iter) _NOEXCEPT {
return _Impl::__rewrap(std::move(__orig_iter), std::move(__iter));
}
_LIBCPP_END_NAMESPACE_STD

39
libcxx/include/__iterator/reverse_iterator.h
View File

@ -332,41 +332,16 @@ using _ReverseWrapper = reverse_iterator<reverse_iterator<_Iter> >;
template <class _Iter, bool __b>
struct __unwrap_iter_impl<_ReverseWrapper<_Iter>, __b> {
static _LIBCPP_CONSTEXPR decltype(std::__unwrap_iter(std::declval<_Iter>()))
__apply(_ReverseWrapper<_Iter> __i) _NOEXCEPT {
return std::__unwrap_iter(__i.base().base());
}
};
using _UnwrappedIter = decltype(__unwrap_iter_impl<_Iter>::__unwrap(std::declval<_Iter>()));
template <class _OrigIter, class _UnwrappedIter>
struct __rewrap_iter_impl<_ReverseWrapper<_OrigIter>, _UnwrappedIter> {
template <class _Iter>
struct _ReverseWrapperCount {
static _LIBCPP_CONSTEXPR const size_t value = 1;
};
template <class _Iter>
struct _ReverseWrapperCount<_ReverseWrapper<_Iter> > {
static _LIBCPP_CONSTEXPR const size_t value = 1 + _ReverseWrapperCount<_Iter>::value;
};
template <size_t _RewrapCount, class _OIter, class _UIter, __enable_if_t<_RewrapCount != 0, int> = 0>
_LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR _ReverseWrapper<_OIter> __rewrap(_ReverseWrapper<_OIter> __iter1,
_UIter __iter2) {
return _ReverseWrapper<_OIter>(
reverse_iterator<_OIter>(__rewrap<_RewrapCount - 1>(__iter1.base().base(), __iter2)));
static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _ReverseWrapper<_Iter>
__rewrap(_ReverseWrapper<_Iter> __orig_iter, _UnwrappedIter __unwrapped_iter) {
return _ReverseWrapper<_Iter>(
reverse_iterator<_Iter>(__unwrap_iter_impl<_Iter>::__rewrap(__orig_iter.base().base(), __unwrapped_iter)));
}
template <size_t _RewrapCount, class _OIter, class _UIter, __enable_if_t<_RewrapCount == 0, int> = 0>
_LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR decltype(std::__rewrap_iter(std::declval<_OIter>(),
std::declval<_UIter>()))
__rewrap(_OIter __iter1, _UIter __iter2) {
return std::__rewrap_iter(__iter1, __iter2);
}
_LIBCPP_HIDE_FROM_ABI static _LIBCPP_CONSTEXPR _ReverseWrapper<_OrigIter> __apply(_ReverseWrapper<_OrigIter> __iter1,
_UnwrappedIter __iter2) {
return __rewrap<_ReverseWrapperCount<_OrigIter>::value>(__iter1, __iter2);
static _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _UnwrappedIter __unwrap(_ReverseWrapper<_Iter> __i) _NOEXCEPT {
return __unwrap_iter_impl<_Iter>::__unwrap(__i.base().base());
}
};

3
libcxx/utils/libcxx/test/params.py
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@ -38,6 +38,9 @@ _warningFlags = [
# TODO(mordante) investigate a solution for this issue.
'-Wno-tautological-compare',
# -Wstringop-overread seems to be a bit buggy currently
'-Wno-stringop-overread',
# These warnings should be enabled in order to support the MSVC
# team using the test suite; They enable the warnings below and
# expect the test suite to be clean.