From: "François Dumont" <frs.dumont@gmail.com>
To: "libstdc++@gcc.gnu.org" <libstdc++@gcc.gnu.org>,
gcc-patches <gcc-patches@gcc.gnu.org>
Subject: niter_base simplification
Date: Wed, 22 Apr 2015 20:10:00 -0000 [thread overview]
Message-ID: <5538003D.30905@gmail.com> (raw)
[-- Attachment #1: Type: text/plain, Size: 1023 bytes --]
Hello
I don't know if I am missing something but I think __niter_base
could be simplified to remove usage of _Iter_base. Additionally I
overload it to also remove __normal_iterator layer even if behind a
reverse_iterator or move_iterator, might help compiler to optimize code,
no ? If not, might allow other algo optimization in the future...
I prefered to provide a __make_reverse_iterator to allow the latter
in C++11 and not only in C++14. Is it fine to do it this way or do you
prefer to simply get rid of all this part ?
* include/bits/cpp_type_traits.h (__gnu_cxx::__normal_iterator):
Delete.
* include/bits/stl_algobase.h (std::__niter_base): Adapt.
* include/bits/stl_iterator.h (__make_reverse_iterator): New in C++11.
(std::__niter_base): Overloads for std::reverse_iterator,
__gnu_cxx::__normal_iterator and std::move_iterator.
Tested under Linux x86_64. I checked that std::copy still ends up
calling __builtin_memmove when used on vector iterators.
François
[-- Attachment #2: niter.patch --]
[-- Type: text/x-patch, Size: 4438 bytes --]
diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h
index 8c6bb7f..2142917 100644
--- a/libstdc++-v3/include/bits/cpp_type_traits.h
+++ b/libstdc++-v3/include/bits/cpp_type_traits.h
@@ -64,17 +64,6 @@
// removed.
//
-// Forward declaration hack, should really include this from somewhere.
-namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
-{
-_GLIBCXX_BEGIN_NAMESPACE_VERSION
-
- template<typename _Iterator, typename _Container>
- class __normal_iterator;
-
-_GLIBCXX_END_NAMESPACE_VERSION
-} // namespace
-
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -331,24 +320,6 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
};
//
- // Normal iterator type
- //
- template<typename _Tp>
- struct __is_normal_iterator
- {
- enum { __value = 0 };
- typedef __false_type __type;
- };
-
- template<typename _Iterator, typename _Container>
- struct __is_normal_iterator< __gnu_cxx::__normal_iterator<_Iterator,
- _Container> >
- {
- enum { __value = 1 };
- typedef __true_type __type;
- };
-
- //
// An arithmetic type is an integer type or a floating point type
//
template<typename _Tp>
diff --git a/libstdc++-v3/include/bits/stl_algobase.h b/libstdc++-v3/include/bits/stl_algobase.h
index 0bcb133..73eea6b 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -270,17 +270,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return __a;
}
- // If _Iterator is a __normal_iterator return its base (a plain pointer,
- // normally) otherwise return it untouched. See copy, fill, ...
+ // Fallback implementation of the function used to remove the
+ // __normal_iterator wrapper. See copy, fill, ...
template<typename _Iterator>
- struct _Niter_base
- : _Iter_base<_Iterator, __is_normal_iterator<_Iterator>::__value>
- { };
-
- template<typename _Iterator>
- inline typename _Niter_base<_Iterator>::iterator_type
+ inline _Iterator
__niter_base(_Iterator __it)
- { return std::_Niter_base<_Iterator>::_S_base(__it); }
+ { return __it; }
// Likewise, for move_iterator.
template<typename _Iterator>
diff --git a/libstdc++-v3/include/bits/stl_iterator.h b/libstdc++-v3/include/bits/stl_iterator.h
index 4a9189e..3aad9f3 100644
--- a/libstdc++-v3/include/bits/stl_iterator.h
+++ b/libstdc++-v3/include/bits/stl_iterator.h
@@ -390,7 +390,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return __y.base() - __x.base(); }
//@}
-#if __cplusplus > 201103L
+#if __cplusplus == 201103L
+ template<typename _Iterator>
+ inline reverse_iterator<_Iterator>
+ __make_reverse_iterator(_Iterator __i)
+ { return reverse_iterator<_Iterator>(__i); }
+
+# define _GLIBCXX_MAKE_REVERSE_ITERATOR(_Iter) \
+ std::__make_reverse_iterator(_Iter)
+#elif __cplusplus > 201103L
#define __cpp_lib_make_reverse_iterator 201402
// _GLIBCXX_RESOLVE_LIB_DEFECTS
@@ -400,6 +408,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
inline reverse_iterator<_Iterator>
make_reverse_iterator(_Iterator __i)
{ return reverse_iterator<_Iterator>(__i); }
+
+# define _GLIBCXX_MAKE_REVERSE_ITERATOR(_Iter) \
+ std::make_reverse_iterator(_Iter)
+#endif
+
+#if __cplusplus >= 201103L
+ template<typename _Iterator>
+ auto
+ __niter_base(reverse_iterator<_Iterator> __it)
+ -> decltype(_GLIBCXX_MAKE_REVERSE_ITERATOR(__niter_base(__it.base())))
+ { return _GLIBCXX_MAKE_REVERSE_ITERATOR(__niter_base(__it.base())); }
#endif
// 24.4.2.2.1 back_insert_iterator
@@ -979,6 +998,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+ template<typename _Iterator, typename _Container>
+ _Iterator
+ __niter_base(__gnu_cxx::__normal_iterator<_Iterator, _Container> __it)
+ { return __it.base(); }
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace
+
#if __cplusplus >= 201103L
namespace std _GLIBCXX_VISIBILITY(default)
@@ -1212,6 +1243,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// @} group iterators
+ template<typename _Iterator>
+ auto
+ __niter_base(move_iterator<_Iterator> __it)
+ -> decltype(make_move_iterator(__niter_base(__it.base())))
+ { return make_move_iterator(__niter_base(__it.base())); }
+
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
next reply other threads:[~2015-04-22 20:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-22 20:10 François Dumont [this message]
2015-04-27 11:55 ` Jonathan Wakely
2015-04-30 9:00 ` François Dumont
2015-04-30 11:29 ` Jonathan Wakely
2015-05-03 20:19 ` miter_base simplification François Dumont
2015-05-19 20:47 ` François Dumont
2015-05-20 10:04 ` Jonathan Wakely
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