[libc++] Add __find_end optimizations back
#171374
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philnik777
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__find_end optimizations back (#100685)"__find_end optimizations back
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This essentially reverts llvm#100685 and fixes the bidirectional and random access specializations to be actually used.
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@llvm/pr-subscribers-libcxx Author: Nikolas Klauser (philnik777) ChangesThis essentially reverts #100685 and fixes the bidirectional and random access specializations to be actually used. Full diff: https://github.com/llvm/llvm-project/pull/171374.diff 1 Files Affected:
diff --git a/libcxx/include/__algorithm/find_end.h b/libcxx/include/__algorithm/find_end.h
index 86b4a3e2e3689..84b43e31a3a59 100644
--- a/libcxx/include/__algorithm/find_end.h
+++ b/libcxx/include/__algorithm/find_end.h
@@ -76,6 +76,111 @@ _LIBCPP_HIDE_FROM_ABI inline _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter1, _Iter1>
}
}
+template <class _AlgPolicy,
+ class _Pred,
+ class _Iter1,
+ class _Sent1,
+ class _Iter2,
+ class _Sent2,
+ class _Proj1,
+ class _Proj2>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 pair<_Iter1, _Iter1> __find_end_impl(
+ _Iter1 __first1,
+ _Sent1 __sent1,
+ _Iter2 __first2,
+ _Sent2 __sent2,
+ _Pred& __pred,
+ _Proj1& __proj1,
+ _Proj2& __proj2,
+ bidirectional_iterator_tag,
+ bidirectional_iterator_tag) {
+ auto __last1 = _IterOps<_AlgPolicy>::next(__first1, __sent1);
+ auto __last2 = _IterOps<_AlgPolicy>::next(__first2, __sent2);
+ // modeled after search algorithm (in reverse)
+ if (__first2 == __last2)
+ return std::make_pair(__last1, __last1); // Everything matches an empty sequence
+ _Iter1 __l1 = __last1;
+ _Iter2 __l2 = __last2;
+ --__l2;
+ while (true) {
+ // Find last element in sequence 1 that matches *(__last2-1), with a mininum of loop checks
+ while (true) {
+ if (__first1 == __l1) // return __last1 if no element matches *__first2
+ return std::make_pair(__last1, __last1);
+ if (std::__invoke(__pred, std::__invoke(__proj1, *--__l1), std::__invoke(__proj2, *__l2)))
+ break;
+ }
+ // *__l1 matches *__l2, now match elements before here
+ _Iter1 __match_last = __l1;
+ _Iter1 __m1 = __l1;
+ _Iter2 __m2 = __l2;
+ while (true) {
+ if (__m2 == __first2) // If pattern exhausted, __m1 is the answer (works for 1 element pattern)
+ return std::make_pair(__m1, ++__match_last);
+ if (__m1 == __first1) // Otherwise if source exhaused, pattern not found
+ return std::make_pair(__last1, __last1);
+
+ // if there is a mismatch, restart with a new __l1
+ if (!std::__invoke(__pred, std::__invoke(__proj1, *--__m1), std::__invoke(__proj2, *--__m2))) {
+ break;
+ } // else there is a match, check next elements
+ }
+ }
+}
+
+template <class _AlgPolicy,
+ class _Pred,
+ class _Iter1,
+ class _Sent1,
+ class _Iter2,
+ class _Sent2,
+ class _Proj1,
+ class _Proj2>
+_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 pair<_Iter1, _Iter1> __find_end_impl(
+ _Iter1 __first1,
+ _Sent1 __sent1,
+ _Iter2 __first2,
+ _Sent2 __sent2,
+ _Pred& __pred,
+ _Proj1& __proj1,
+ _Proj2& __proj2,
+ random_access_iterator_tag,
+ random_access_iterator_tag) {
+ typedef typename iterator_traits<_Iter1>::difference_type _D1;
+ auto __last1 = _IterOps<_AlgPolicy>::next(__first1, __sent1);
+ auto __last2 = _IterOps<_AlgPolicy>::next(__first2, __sent2);
+ // Take advantage of knowing source and pattern lengths. Stop short when source is smaller than pattern
+ auto __len2 = __last2 - __first2;
+ if (__len2 == 0)
+ return std::make_pair(__last1, __last1);
+ auto __len1 = __last1 - __first1;
+ if (__len1 < __len2)
+ return std::make_pair(__last1, __last1);
+ const _Iter1 __s = __first1 + _D1(__len2 - 1); // End of pattern match can't go before here
+ _Iter1 __l1 = __last1;
+ _Iter2 __l2 = __last2;
+ --__l2;
+ while (true) {
+ while (true) {
+ if (__s == __l1)
+ return std::make_pair(__last1, __last1);
+ if (std::__invoke(__pred, std::__invoke(__proj1, *--__l1), std::__invoke(__proj2, *__l2)))
+ break;
+ }
+ _Iter1 __last_match = __l1;
+ _Iter1 __m1 = __l1;
+ _Iter2 __m2 = __l2;
+ while (true) {
+ if (__m2 == __first2)
+ return std::make_pair(__m1, ++__last_match);
+ // no need to check range on __m1 because __s guarantees we have enough source
+ if (!std::__invoke(__pred, std::__invoke(__proj1, *--__m1), std::__invoke(__proj2, *--__m2))) {
+ break;
+ }
+ }
+ }
+}
+
template <class _ForwardIterator1, class _ForwardIterator2, class _BinaryPredicate>
[[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 _ForwardIterator1 __find_end_classic(
_ForwardIterator1 __first1,
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This essentially reverts #100685 and fixes the bidirectional and random access specializations to be actually used.