libstdc++: Directly implement ranges::sort [PR100795]

As with the previous patch, this patch reimplements ranges::sort
directly instead of incorrectly forwarding to std::sort.  In addition to
the compatibility changes listed in the previous patch we also:

  - use ranges::iter_swap instead of std::iter_swap
  - use ranges::move_backward instead of std::move_backward
  - use __bit_width and __to_unsigned_like instead of __lg

	PR libstdc++/100795
	PR libstdc++/118209

libstdc++-v3/ChangeLog:

	* include/bits/max_size_type.h (__bit_width): New explicit
	specialization for __max_size_type.
	* include/bits/ranges_algo.h (__detail::__move_median_to_first):
	New, based on the stl_algo.h implementation.
	(__detail::__unguarded_liner_insert): Likewise.
	(__detail::__insertion_sort): Likewise.
	(__detail::__sort_threshold): Likewise.
	(__detail::__unguarded_insertion_sort): Likewise.
	(__detail::__final_insertion_sort): Likewise.
	(__detail::__unguarded_partition): Likewise.
	(__detail::__unguarded_partition_pivot): Likewise.
	(__detail::__heap_select): Likewise.
	(__detail::__partial_sort): Likewise.
	(__detail::__introsort_loop): Likewise.
	(__sort_fn::operator()): Reimplement in terms of the above.
	* testsuite/25_algorithms/sort/118209.cc: New test.
	* testsuite/25_algorithms/sort/constrained.cc (test03): New test.

Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>

diff --git a/libstdc++-v3/include/bits/max_size_type.h b/libstdc++-v3/include/bits/max_size_type.h
index e602b1b4bee513ab605baa15887024cb63773ac7..73a6d141d5bc735a61d290633de6b96c2c17b412 100644 (file)
--- a/libstdc++-v3/include/bits/max_size_type.h
+++ b/libstdc++-v3/include/bits/max_size_type.h
@@ -36,6 +36,7 @@
 
 #if __cplusplus > 201703L && __cpp_lib_concepts
 #include <ext/numeric_traits.h>
+#include <bit> // __bit_width
 #include <numbers>
 
 // This header implements unsigned and signed integer-class types (as per
@@ -818,6 +819,16 @@ namespace ranges
       { return min(); }
     };
 
+  template<>
+  inline constexpr int
+  __bit_width(ranges::__detail::__max_size_type __x) noexcept
+  {
+    if (__x._M_msb)
+      return numeric_limits<ranges::__detail::__max_size_type>::digits;
+    else
+      return std::__bit_width(__x._M_val);
+  }
+
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 

diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h
index d13729a83f729cfc0e8188efa2193a5ccb9a8d4d..de935dde4f702881f3f88cca48a64437961758ca 100644 (file)
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -32,6 +32,7 @@
 
 #if __cplusplus > 201703L
 
+#include <bit> // __bit_width
 #if __cplusplus > 202002L
 #include <optional>
 #endif
@@ -2200,6 +2201,154 @@ namespace ranges
 
   inline constexpr __is_heap_fn is_heap{};
 
+  namespace __detail
+  {
+    template<typename _Iter, typename _Comp>
+      constexpr void
+      __move_median_to_first(_Iter __result, _Iter __a, _Iter __b, _Iter __c,
+                            _Comp __comp)
+      {
+       if (__comp(*__a, *__b))
+         {
+           if (__comp(*__b, *__c))
+             ranges::iter_swap(__result, __b);
+           else if (__comp(*__a, *__c))
+             ranges::iter_swap(__result, __c);
+           else
+             ranges::iter_swap(__result, __a);
+         }
+       else if (__comp(*__a, *__c))
+         ranges::iter_swap(__result, __a);
+       else if (__comp(*__b, *__c))
+         ranges::iter_swap(__result, __c);
+       else
+         ranges::iter_swap(__result, __b);
+      }
+
+    template<typename _Iter, typename _Comp>
+      constexpr void
+      __unguarded_linear_insert(_Iter __last, _Comp __comp)
+      {
+       iter_value_t<_Iter> __val = ranges::iter_move(__last);
+       _Iter __next = __last;
+       --__next;
+       while (__comp(__val, *__next))
+         {
+           *__last = ranges::iter_move(__next);
+           __last = __next;
+           --__next;
+         }
+       *__last = std::move(__val);
+      }
+
+    template<typename _Iter, typename _Comp>
+      constexpr void
+      __insertion_sort(_Iter __first, _Iter __last, _Comp __comp)
+      {
+       if (__first == __last)
+         return;
+
+       for (_Iter __i = __first + 1; __i != __last; ++__i)
+         {
+           if (__comp(*__i, *__first))
+             {
+               iter_value_t<_Iter> __val = ranges::iter_move(__i);
+               ranges::move_backward(__first, __i, __i + 1);
+               *__first = std::move(__val);
+             }
+           else
+             __detail::__unguarded_linear_insert(__i, __comp);
+         }
+      }
+
+    template<typename _Iter, typename _Comp>
+      constexpr void
+      __unguarded_insertion_sort(_Iter __first, _Iter __last, _Comp __comp)
+      {
+       for (_Iter __i = __first; __i != __last; ++__i)
+         __detail::__unguarded_linear_insert(__i, __comp);
+      }
+
+    inline constexpr int __sort_threshold = 16;
+
+    template<typename _Iter, typename _Comp>
+      constexpr void
+      __final_insertion_sort(_Iter __first, _Iter __last, _Comp __comp)
+      {
+       if (__last - __first > __sort_threshold)
+         {
+           __detail::__insertion_sort(__first, __first + __sort_threshold, __comp);
+           __detail::__unguarded_insertion_sort(__first + __sort_threshold, __last,
+                                                __comp);
+         }
+       else
+         __detail::__insertion_sort(__first, __last, __comp);
+      }
+
+    template<typename _Iter, typename _Comp>
+      constexpr _Iter
+      __unguarded_partition(_Iter __first, _Iter __last, _Iter __pivot, _Comp __comp)
+      {
+       while (true)
+         {
+           while (__comp(*__first, *__pivot))
+             ++__first;
+           --__last;
+           while (__comp(*__pivot, *__last))
+             --__last;
+           if (!(__first < __last))
+             return __first;
+           ranges::iter_swap(__first, __last);
+           ++__first;
+         }
+      }
+
+    template<typename _Iter, typename _Comp>
+      constexpr _Iter
+      __unguarded_partition_pivot(_Iter __first, _Iter __last, _Comp __comp)
+      {
+       _Iter __mid = __first + (__last - __first) / 2;
+       __detail::__move_median_to_first(__first, __first + 1, __mid, __last - 1, __comp);
+       return __detail::__unguarded_partition(__first + 1, __last, __first, __comp);
+      }
+
+    template<typename _Iter, typename _Comp>
+      constexpr void
+      __heap_select(_Iter __first, _Iter __middle, _Iter __last, _Comp __comp)
+      {
+       ranges::make_heap(__first, __middle, __comp);
+       for (_Iter __i = __middle; __i < __last; ++__i)
+         if (__comp(*__i, *__first))
+           __detail::__pop_heap(__first, __middle, __i, __comp);
+      }
+
+    template<typename _Iter, typename _Comp>
+      constexpr void
+      __partial_sort(_Iter __first, _Iter __middle, _Iter __last, _Comp __comp)
+      {
+       __detail::__heap_select(__first, __middle, __last, __comp);
+       ranges::sort_heap(__first, __middle, __comp);
+      }
+
+    template<typename _Iter, typename _Comp>
+      constexpr void
+      __introsort_loop(_Iter __first, _Iter __last, unsigned __depth_limit, _Comp __comp)
+      {
+       while (__last - __first > __sort_threshold)
+         {
+           if (__depth_limit == 0)
+             {
+               __detail::__partial_sort(__first, __last, __last, __comp);
+               return;
+             }
+           --__depth_limit;
+           _Iter __cut = __detail::__unguarded_partition_pivot(__first, __last, __comp);
+           __detail::__introsort_loop(__cut, __last, __depth_limit, __comp);
+           __last = __cut;
+         }
+      }
+  } // namespace __detail
+
   struct __sort_fn
   {
     template<random_access_iterator _Iter, sentinel_for<_Iter> _Sent,
@@ -2209,10 +2358,21 @@ namespace ranges
       operator()(_Iter __first, _Sent __last,
                 _Comp __comp = {}, _Proj __proj = {}) const
       {
-       auto __lasti = ranges::next(__first, __last);
-       _GLIBCXX_STD_A::sort(std::move(__first), __lasti,
-                            __detail::__make_comp_proj(__comp, __proj));
-       return __lasti;
+       if constexpr (!same_as<_Iter, _Sent>)
+         return (*this)(__first, ranges::next(__first, __last),
+                        std::move(__comp), std::move(__proj));
+       else
+         {
+           if (__first != __last)
+             {
+               auto __comp_proj = __detail::__make_comp_proj(__comp, __proj);
+               auto __n = __detail::__to_unsigned_like(__last - __first);
+               unsigned __depth_limit = (std::__bit_width(__n) - 1) * 2;
+               __detail::__introsort_loop(__first, __last, __depth_limit, __comp_proj);
+               __detail::__final_insertion_sort(__first, __last, __comp_proj);
+             }
+           return __last;
+         }
       }
 
     template<random_access_range _Range,

diff --git a/libstdc++-v3/testsuite/25_algorithms/sort/118209.cc b/libstdc++-v3/testsuite/25_algorithms/sort/118209.cc
new file mode 100644 (file)
index 0000000..6dedbde
--- /dev/null
+++ b/libstdc++-v3/testsuite/25_algorithms/sort/118209.cc
@@ -0,0 +1,23 @@
+// PR libstdc++ - ranges::sort doesn't use iter_move, cannot sort zip of move-only type
+// { dg-do compile { target c++23 } }
+
+#include <algorithm>
+#include <ranges>
+#include <vector>
+
+struct F {
+  int a = -1;
+  explicit F(int d) : a(d) { }
+  F(const F&) = delete;
+  F(F&& o) : a(o.a) { }
+  void operator=(const F&) = delete;
+  F& operator=(F&& o) { return *this; }
+  auto operator<=>(const F&) const = default;
+};
+
+int main () {
+  int a[] = {3,2,1};
+  std::vector<F> v(a, a+3);
+  std::ranges::sort(v); // OK
+  std::ranges::sort(std::views::zip(v)); // didn't compile
+}

diff --git a/libstdc++-v3/testsuite/25_algorithms/sort/constrained.cc b/libstdc++-v3/testsuite/25_algorithms/sort/constrained.cc
index 82754af964308850ce48075df661ee7af513de61..930dbd77a3766bee37c000d81720130d7932b61d 100644 (file)
--- a/libstdc++-v3/testsuite/25_algorithms/sort/constrained.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/sort/constrained.cc
@@ -20,6 +20,7 @@
 
 #include <algorithm>
 #include <random>
+#include <ranges>
 #include <vector>
 #include <testsuite_hooks.h>
 #include <testsuite_iterators.h>
@@ -72,9 +73,39 @@ test02()
          && ranges::equal(x, y, {}, &X::i, &X::i));
 }
 
+constexpr bool
+test03()
+{
+  // PR libstdc++/100795 - ranges::sort should not use std::sort directly
+#if __SIZEOF_INT128__
+  auto v = std::views::iota(__int128(0), __int128(20));
+#else
+  auto v = std::views::iota(0ll, 20ll);
+#endif
+
+  int storage[20] = {2,5,4,3,1,6,7,9,10,8,11,14,12,13,15,16,18,0,19,17};
+  auto w = v | std::views::transform([&](auto i) -> int& { return storage[i]; });
+  using type = decltype(w);
+  using cat = std::iterator_traits<std::ranges::iterator_t<type>>::iterator_category;
+  static_assert( std::same_as<cat, std::output_iterator_tag> );
+  static_assert( std::ranges::random_access_range<type> );
+
+  ranges::sort(w);
+  VERIFY( ranges::equal(w, v) );
+
+  ranges::sort(w, std::ranges::greater{});
+  VERIFY( ranges::equal(w, v | std::views::reverse) );
+
+  ranges::sort(w, std::ranges::greater{}, std::negate{});
+  VERIFY( ranges::equal(w, v) );
+
+  return true;
+}
+
 int
 main()
 {
   test01();
   static_assert(test02());
+  static_assert(test03());
 }