re PR libstdc++/61347 (std::distance(list.first(),list.end()) in O(1))

2015-04-14  Marc Glisse  <marc.glisse@inria.fr>

	PR libstdc++/61347
	* include/bits/stl_iterator_base_funcs.h (_List_iterator,
	_List_const_iterator): Declare.
	(__distance): Declare new overloads for _List_iterator and
	_List_const_iterator.
	* include/bits/stl_list.h (__distance): New overloads for
	_List_iterator and _List_const_iterator.
	* testsuite/23_containers/list/61347.cc: New testcase.

From-SVN: r222082

libstdc++-v3/ChangeLog

@@ -1,3 +1,14 @@
+2015-04-14  Marc Glisse  <marc.glisse@inria.fr>
+
+	PR libstdc++/61347
+	* include/bits/stl_iterator_base_funcs.h (_List_iterator,
+	_List_const_iterator): Declare.
+	(__distance): Declare new overloads for _List_iterator and
+	_List_const_iterator.
+	* include/bits/stl_list.h (__distance): New overloads for
+	_List_iterator and _List_const_iterator.
+	* testsuite/23_containers/list/61347.cc: New testcase.
+
 2015-04-14  Jonathan Wakely  <jwakely@redhat.com>
 
 	* doc/xml/manual/evolution.xml: Fix typos.

libstdc++-v3/include/bits/stl_iterator_base_funcs.h

@@ -66,6 +66,12 @@
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
+_GLIBCXX_BEGIN_NAMESPACE_CONTAINER
+  // Forward declaration for the overloads of __distance.
+  template <typename> struct _List_iterator;
+  template <typename> struct _List_const_iterator;
+_GLIBCXX_END_NAMESPACE_CONTAINER
+
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
   template<typename _InputIterator>
@@ -96,6 +102,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       return __last - __first;
     }
 
+#if _GLIBCXX_USE_CXX11_ABI
+  // Forward declaration because of the qualified call in distance.
+  template<typename _Tp>
+    ptrdiff_t
+    __distance(_GLIBCXX_STD_C::_List_iterator<_Tp>,
+	       _GLIBCXX_STD_C::_List_iterator<_Tp>,
+	       input_iterator_tag);
+
+  template<typename _Tp>
+    ptrdiff_t
+    __distance(_GLIBCXX_STD_C::_List_const_iterator<_Tp>,
+	       _GLIBCXX_STD_C::_List_const_iterator<_Tp>,
+	       input_iterator_tag);
+#endif
+
   /**
    *  @brief A generalization of pointer arithmetic.
    *  @param  __first  An input iterator.

libstdc++-v3/include/bits/stl_list.h

@@ -1868,6 +1868,45 @@ _GLIBCXX_END_NAMESPACE_CXX11
     { __x.swap(__y); }
 
 _GLIBCXX_END_NAMESPACE_CONTAINER
+
+#if _GLIBCXX_USE_CXX11_ABI
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+  // Detect when distance is used to compute the size of the whole list.
+  template<typename _Tp>
+    inline ptrdiff_t
+    __distance(_GLIBCXX_STD_C::_List_iterator<_Tp> __first,
+	       _GLIBCXX_STD_C::_List_iterator<_Tp> __last,
+	       input_iterator_tag __tag)
+    {
+      typedef _GLIBCXX_STD_C::_List_const_iterator<_Tp> _CIter;
+      return std::__distance(_CIter(__first), _CIter(__last), __tag);
+    }
+
+  template<typename _Tp>
+    inline ptrdiff_t
+    __distance(_GLIBCXX_STD_C::_List_const_iterator<_Tp> __first,
+	       _GLIBCXX_STD_C::_List_const_iterator<_Tp> __last,
+	       input_iterator_tag)
+    {
+      typedef _GLIBCXX_STD_C::_List_node<size_t> _Sentinel;
+      _GLIBCXX_STD_C::_List_const_iterator<_Tp> __beyond = __last;
+      ++__beyond;
+      bool __whole = __first == __beyond;
+      if (__builtin_constant_p (__whole) && __whole)
+	return static_cast<const _Sentinel*>(__last._M_node)->_M_data;
+
+      ptrdiff_t __n = 0;
+      while (__first != __last)
+	{
+	  ++__first;
+	  ++__n;
+	}
+      return __n;
+    }
+
+_GLIBCXX_END_NAMESPACE_VERSION
+#endif
 } // namespace std
 
 #endif /* _STL_LIST_H */

libstdc++-v3/testsuite/23_containers/list/61347.cc

@@ -0,0 +1,49 @@
+// { dg-options "-std=gnu++11 -O2 -D_GLIBCXX_USE_CXX11_ABI" }
+
+// Copyright (C) 2015 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <list>
+#include <iterator>
+#include <testsuite_hooks.h>
+
+__attribute__((__noinline__, __noclone__))
+void testm(std::list<short>& l)
+{
+  bool b = std::distance(l.begin(), l.end()) == l.size();
+  VERIFY( __builtin_constant_p(b) );
+  VERIFY( b );
+}
+
+__attribute__((__noinline__, __noclone__))
+void testc(const std::list<short>& l)
+{
+  bool b = std::distance(l.begin(), l.end()) == l.size();
+  VERIFY( __builtin_constant_p(b) );
+  VERIFY( b );
+}
+
+int main()
+{
+  bool test __attribute__((unused)) = true;
+
+#if _GLIBCXX_USE_DUAL_ABI
+  std::list<short> l;
+  testm(l);
+  testc(l);
+#endif
+}