std::vector<bool> code cleanup fixes optimizations

Message ID c48dfa67-2040-7df6-10d3-c07460573b3d@gmail.com
State New
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  • std::vector<bool> code cleanup fixes optimizations
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Commit Message

François Dumont May 14, 2019, 5:46 a.m.
Hi

     This is the patch on vector<bool> to:

- Optimize sizeof in Versioned namespace mode. We could go one step 
further by removing _M_p from _M_finish and just transform it into an 
offset but it is a little bit more impacting for the code.

- Implement the swap optimization already done on main std::vector 
template class.

- Fix move constructor so that it is noexcept no matter allocator move 
constructor noexcept qualification

- Optimize move constructor with allocator when allocator type is always 
equal.

- Use shortcuts in C++11 by skipping the _M_XXX_dispatch methods. Those 
are now defined only in pre-C++11 mode, I can't see any abi issue in 
doing so.

     * include/bits/stl_bvector.h
     [_GLIBCXX_INLINE_VERSION](_Bvector_impl_data::_M_start): Define as
     _Bit_type*.
     (_Bvector_impl_data(const _Bvector_impl_data&)): Default.
     (_Bvector_impl_data(_Bvector_impl_data&&)): Delegate to latter.
     (_Bvector_impl_data::operator=(const _Bvector_impl_data&)): Default.
(_Bvector_impl_data::_M_move_data(_Bvector_impl_data&&)): Use latter.
     (_Bvector_impl_data::_M_reset()): Likewise.
     (_Bvector_impl_data::_M_swap_data): New.
     (_Bvector_impl::_Bvector_impl(_Bvector_impl&&)): Implement explicitely.
     (_Bvector_impl::_Bvector_impl(_Bit_alloc_type&&, _Bvector_impl&&)): 
New.
     (_Bvector_base::_Bvector_base(_Bvector_base&&, const allocator_type&)):
     New, use latter.
     (vector::vector(vector&&, const allocator_type&, true_type)): New, use
     latter.
     (vector::vector(vector&&, const allocator_type&, false_type)): New.
     (vector::vector(vector&&, const allocator_type&)): Use latters.
     (vector::vector(const vector&, const allocator_type&)): Adapt.
     [__cplusplus >= 201103](vector::vector(_InputIt, _InputIt,
     const allocator_type&)): Use _M_initialize_range.
     (vector::operator[](size_type)): Use iterator operator[].
     (vector::operator[](size_type) const): Use const_iterator operator[].
     (vector::swap(vector&)): Adapt.
     (vector::_M_initialize(size_type)): Add assertions on allocators.
     Use _M_swap_data.
     [__cplusplus >= 201103](vector::insert(const_iterator, _InputIt,
     _InputIt)): Use _M_insert_range.
     [__cplusplus >= 201103](vector::_M_initialize_dispatch): Remove.
     [__cplusplus >= 201103](vector::_M_insert_dispatch): Remove.
     * testsuite/23_containers/vector/bool/allocator/swap.cc: Adapt.
     * testsuite/23_containers/vector/bool/cons/noexcept_move_construct.cc:
     Add check.

Tested under Linux x86_64, normal and debug modes.

Ok to commit ?

François

Comments

François Dumont June 24, 2019, 7:31 p.m. | #1
Hi

     Any feedback regarding this patch ?

Thanks

On 5/14/19 7:46 AM, François Dumont wrote:
> Hi

>

>     This is the patch on vector<bool> to:

>

> - Optimize sizeof in Versioned namespace mode. We could go one step 

> further by removing _M_p from _M_finish and just transform it into an 

> offset but it is a little bit more impacting for the code.

>

> - Implement the swap optimization already done on main std::vector 

> template class.

>

> - Fix move constructor so that it is noexcept no matter allocator move 

> constructor noexcept qualification

>

> - Optimize move constructor with allocator when allocator type is 

> always equal.

>

> - Use shortcuts in C++11 by skipping the _M_XXX_dispatch methods. 

> Those are now defined only in pre-C++11 mode, I can't see any abi 

> issue in doing so.

>

>     * include/bits/stl_bvector.h

>     [_GLIBCXX_INLINE_VERSION](_Bvector_impl_data::_M_start): Define as

>     _Bit_type*.

>     (_Bvector_impl_data(const _Bvector_impl_data&)): Default.

>     (_Bvector_impl_data(_Bvector_impl_data&&)): Delegate to latter.

>     (_Bvector_impl_data::operator=(const _Bvector_impl_data&)): Default.

> (_Bvector_impl_data::_M_move_data(_Bvector_impl_data&&)): Use latter.

>     (_Bvector_impl_data::_M_reset()): Likewise.

>     (_Bvector_impl_data::_M_swap_data): New.

>     (_Bvector_impl::_Bvector_impl(_Bvector_impl&&)): Implement 

> explicitely.

>     (_Bvector_impl::_Bvector_impl(_Bit_alloc_type&&, 

> _Bvector_impl&&)): New.

>     (_Bvector_base::_Bvector_base(_Bvector_base&&, const 

> allocator_type&)):

>     New, use latter.

>     (vector::vector(vector&&, const allocator_type&, true_type)): New, 

> use

>     latter.

>     (vector::vector(vector&&, const allocator_type&, false_type)): New.

>     (vector::vector(vector&&, const allocator_type&)): Use latters.

>     (vector::vector(const vector&, const allocator_type&)): Adapt.

>     [__cplusplus >= 201103](vector::vector(_InputIt, _InputIt,

>     const allocator_type&)): Use _M_initialize_range.

>     (vector::operator[](size_type)): Use iterator operator[].

>     (vector::operator[](size_type) const): Use const_iterator operator[].

>     (vector::swap(vector&)): Adapt.

>     (vector::_M_initialize(size_type)): Add assertions on allocators.

>     Use _M_swap_data.

>     [__cplusplus >= 201103](vector::insert(const_iterator, _InputIt,

>     _InputIt)): Use _M_insert_range.

>     [__cplusplus >= 201103](vector::_M_initialize_dispatch): Remove.

>     [__cplusplus >= 201103](vector::_M_insert_dispatch): Remove.

>     * testsuite/23_containers/vector/bool/allocator/swap.cc: Adapt.

>     * 

> testsuite/23_containers/vector/bool/cons/noexcept_move_construct.cc:

>     Add check.

>

> Tested under Linux x86_64, normal and debug modes.

>

> Ok to commit ?

>

> François

>

Patch

diff --git a/libstdc++-v3/include/bits/stl_bvector.h b/libstdc++-v3/include/bits/stl_bvector.h
index 280d40f60c5..d6fcc2d848d 100644
--- a/libstdc++-v3/include/bits/stl_bvector.h
+++ b/libstdc++-v3/include/bits/stl_bvector.h
@@ -441,7 +441,16 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 
       struct _Bvector_impl_data
       {
+#if !_GLIBCXX_INLINE_VERSION
 	_Bit_iterator	_M_start;
+#else
+	// We don't need the offset field for the start, it's always zero.
+	struct {
+	  _Bit_type* _M_p;
+	  // Allow assignment from iterators (assume offset is zero):
+	  void operator=(_Bit_iterator __it) { _M_p = __it._M_p; }
+	} _M_start;
+#endif
 	_Bit_iterator	_M_finish;
 	_Bit_pointer	_M_end_of_storage;
 
@@ -450,33 +459,38 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	{ }
 
 #if __cplusplus >= 201103L
+	_Bvector_impl_data(const _Bvector_impl_data&) = default;
+	_Bvector_impl_data&
+	operator=(const _Bvector_impl_data&) = default;
+
 	_Bvector_impl_data(_Bvector_impl_data&& __x) noexcept
-	: _M_start(__x._M_start), _M_finish(__x._M_finish)
-	, _M_end_of_storage(__x._M_end_of_storage)
+	: _Bvector_impl_data(__x)
 	{ __x._M_reset(); }
 
 	void
 	_M_move_data(_Bvector_impl_data&& __x) noexcept
 	{
-	  this->_M_start = __x._M_start;
-	  this->_M_finish = __x._M_finish;
-	  this->_M_end_of_storage = __x._M_end_of_storage;
+	  *this = __x;
 	  __x._M_reset();
 	}
 #endif
 
 	void
 	_M_reset() _GLIBCXX_NOEXCEPT
+	{ *this = _Bvector_impl_data(); }
+
+	void
+	_M_swap_data(_Bvector_impl_data& __x) _GLIBCXX_NOEXCEPT
 	{
-	  _M_start = _M_finish = _Bit_iterator();
-	  _M_end_of_storage = _Bit_pointer();
+	  // Do not use std::swap(_M_start, __x._M_start), etc as it loses
+	  // information used by TBAA.
+	  std::swap(*this, __x);
 	}
       };
 
       struct _Bvector_impl
 	: public _Bit_alloc_type, public _Bvector_impl_data
       {
-	public:
 	_Bvector_impl() _GLIBCXX_NOEXCEPT_IF(
 	  is_nothrow_default_constructible<_Bit_alloc_type>::value)
 	: _Bit_alloc_type()
@@ -487,7 +501,15 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	{ }
 
 #if __cplusplus >= 201103L
-	_Bvector_impl(_Bvector_impl&&) = default;
+	// Not defaulted, to enforce noexcept(true) even when
+	// !is_nothrow_move_constructible<_Bit_alloc_type>.
+	_Bvector_impl(_Bvector_impl&& __x) noexcept
+	: _Bit_alloc_type(std::move(__x)), _Bvector_impl_data(std::move(__x))
+	{ }
+
+	_Bvector_impl(_Bit_alloc_type&& __a, _Bvector_impl&& __x) noexcept
+	: _Bit_alloc_type(std::move(__a)), _Bvector_impl_data(std::move(__x))
+	{ }
 #endif
 
 	_Bit_type*
@@ -525,6 +547,10 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 
 #if __cplusplus >= 201103L
       _Bvector_base(_Bvector_base&&) = default;
+
+      _Bvector_base(_Bvector_base&& __x, const allocator_type& __a)
+      : _M_impl(_Bit_alloc_type(__a), std::move(__x._M_impl))
+      { }
 #endif
 
       ~_Bvector_base()
@@ -661,14 +687,18 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       : _Base(_Bit_alloc_traits::_S_select_on_copy(__x._M_get_Bit_allocator()))
       {
 	_M_initialize(__x.size());
-	_M_copy_aligned(__x.begin(), __x.end(), this->_M_impl._M_start);
+	_M_copy_aligned(__x.begin(), __x.end(), begin());
       }
 
 #if __cplusplus >= 201103L
       vector(vector&&) = default;
 
-      vector(vector&& __x, const allocator_type& __a)
-      noexcept(_Bit_alloc_traits::_S_always_equal())
+    private:
+      vector(vector&& __x, const allocator_type& __a, true_type) noexcept
+      : _Base(std::move(__x), __a)
+      { }
+
+      vector(vector&& __x, const allocator_type& __a, false_type)
       : _Base(__a)
       {
 	if (__x.get_allocator() == __a)
@@ -681,11 +711,18 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	  }
       }
 
+    public:
+      vector(vector&& __x, const allocator_type& __a)
+      noexcept(_Bit_alloc_traits::_S_always_equal())
+      : vector(std::move(__x), __a,
+	       typename _Bit_alloc_traits::is_always_equal{})
+      { }
+
       vector(const vector& __x, const allocator_type& __a)
       : _Base(__a)
       {
 	_M_initialize(__x.size());
-	_M_copy_aligned(__x.begin(), __x.end(), this->_M_impl._M_start);
+	_M_copy_aligned(__x.begin(), __x.end(), begin());
       }
 
       vector(initializer_list<bool> __l,
@@ -703,13 +740,17 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	vector(_InputIterator __first, _InputIterator __last,
 	       const allocator_type& __a = allocator_type())
 	: _Base(__a)
-	{ _M_initialize_dispatch(__first, __last, __false_type()); }
+	{
+	  _M_initialize_range(__first, __last,
+			      std::__iterator_category(__first));
+	}
 #else
       template<typename _InputIterator>
 	vector(_InputIterator __first, _InputIterator __last,
 	       const allocator_type& __a = allocator_type())
 	: _Base(__a)
 	{
+	  // Check whether it's an integral type. If so, it's not an iterator.
 	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
 	  _M_initialize_dispatch(__first, __last, _Integral());
 	}
@@ -800,6 +841,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	void
 	assign(_InputIterator __first, _InputIterator __last)
 	{
+	  // Check whether it's an integral type. If so, it's not an iterator.
 	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
 	  _M_assign_dispatch(__first, __last, _Integral());
 	}
@@ -888,17 +930,11 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 
       reference
       operator[](size_type __n)
-      {
-	return *iterator(this->_M_impl._M_start._M_p
-			 + __n / int(_S_word_bit), __n % int(_S_word_bit));
-      }
+      { return begin()[__n]; }
 
       const_reference
       operator[](size_type __n) const
-      {
-	return *const_iterator(this->_M_impl._M_start._M_p
-			     + __n / int(_S_word_bit), __n % int(_S_word_bit));
-      }
+      { return begin()[__n]; }
 
     protected:
       void
@@ -965,10 +1001,11 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       void
       swap(vector& __x) _GLIBCXX_NOEXCEPT
       {
-	std::swap(this->_M_impl._M_start, __x._M_impl._M_start);
-	std::swap(this->_M_impl._M_finish, __x._M_impl._M_finish);
-	std::swap(this->_M_impl._M_end_of_storage,
-		  __x._M_impl._M_end_of_storage);
+#if __cplusplus >= 201103L
+	__glibcxx_assert(_Bit_alloc_traits::propagate_on_container_swap::value
+			 || _M_get_Bit_allocator() == __x._M_get_Bit_allocator());
+#endif
+	this->_M_impl._M_swap_data(__x._M_impl);
 	_Bit_alloc_traits::_S_on_swap(_M_get_Bit_allocator(),
 				      __x._M_get_Bit_allocator());
       }
@@ -1006,8 +1043,9 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	       _InputIterator __first, _InputIterator __last)
 	{
 	  difference_type __offset = __position - cbegin();
-	  _M_insert_dispatch(__position._M_const_cast(),
-			     __first, __last, __false_type());
+	  _M_insert_range(__position._M_const_cast(),
+			  __first, __last,
+			  std::__iterator_category(__first));
 	  return begin() + __offset;
 	}
 #else
@@ -1016,6 +1054,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	insert(iterator __position,
 	       _InputIterator __first, _InputIterator __last)
 	{
+	  // Check whether it's an integral type. If so, it's not an iterator.
 	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
 	  _M_insert_dispatch(__position, __first, __last, _Integral());
 	}
@@ -1127,15 +1166,10 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	  {
 	    _Bit_pointer __q = this->_M_allocate(__n);
 	    this->_M_impl._M_end_of_storage = __q + _S_nword(__n);
-	    this->_M_impl._M_start = iterator(std::__addressof(*__q), 0);
+	    iterator __start = iterator(std::__addressof(*__q), 0);
+	    this->_M_impl._M_start = __start;
+	    this->_M_impl._M_finish = __start + difference_type(__n);
 	  }
-	else
-	  {
-	    this->_M_impl._M_end_of_storage = _Bit_pointer();
-	    this->_M_impl._M_start = iterator(0, 0);
-	  }
-	this->_M_impl._M_finish = this->_M_impl._M_start + difference_type(__n);
-
       }
 
       void
@@ -1155,8 +1189,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       _M_shrink_to_fit();
 #endif
 
-      // Check whether it's an integral type.  If so, it's not an iterator.
-
+#if __cplusplus < 201103L
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 438. Ambiguity in the "do the right thing" clause
       template<typename _Integer>
@@ -1173,6 +1206,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 			       __false_type)
 	{ _M_initialize_range(__first, __last,
 			      std::__iterator_category(__first)); }
+#endif
 
       template<typename _InputIterator>
 	void
@@ -1190,7 +1224,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	{
 	  const size_type __n = std::distance(__first, __last);
 	  _M_initialize(__n);
-	  std::copy(__first, __last, this->_M_impl._M_start);
+	  std::copy(__first, __last, begin());
 	}
 
 #if __cplusplus < 201103L
@@ -1254,8 +1288,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	    }
 	}
 
-      // Check whether it's an integral type.  If so, it's not an iterator.
-
+#if __cplusplus < 201103L
       // _GLIBCXX_RESOLVE_LIB_DEFECTS
       // 438. Ambiguity in the "do the right thing" clause
       template<typename _Integer>
@@ -1271,6 +1304,7 @@  _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 			   __false_type)
 	{ _M_insert_range(__pos, __first, __last,
 			  std::__iterator_category(__first)); }
+#endif
 
       void
       _M_fill_insert(iterator __position, size_type __n, bool __x);
diff --git a/libstdc++-v3/testsuite/23_containers/vector/bool/allocator/swap.cc b/libstdc++-v3/testsuite/23_containers/vector/bool/allocator/swap.cc
index de441426532..745fdc85cf6 100644
--- a/libstdc++-v3/testsuite/23_containers/vector/bool/allocator/swap.cc
+++ b/libstdc++-v3/testsuite/23_containers/vector/bool/allocator/swap.cc
@@ -28,19 +28,17 @@  namespace __gnu_test
   // It is undefined behaviour to swap() containers with unequal allocators
   // if the allocator doesn't propagate, so ensure the allocators compare
   // equal, while still being able to test propagation via get_personality().
+  template<typename Type>
     bool
-  operator==(const propagating_allocator<T, false>&,
-	     const propagating_allocator<T, false>&)
-  {
-    return true;
-  }
+    operator==(const propagating_allocator<Type, false>&,
+	       const propagating_allocator<Type, false>&)
+    { return true; }
 
+  template<typename Type>
     bool
-  operator!=(const propagating_allocator<T, false>&,
-	     const propagating_allocator<T, false>&)
-  {
-    return false;
-  }
+    operator!=(const propagating_allocator<Type, false>&,
+	       const propagating_allocator<Type, false>&)
+    { return false; }
 }
 
 using __gnu_test::propagating_allocator;
diff --git a/libstdc++-v3/testsuite/23_containers/vector/bool/cons/noexcept_move_construct.cc b/libstdc++-v3/testsuite/23_containers/vector/bool/cons/noexcept_move_construct.cc
index abc4114e31d..90c863d8a35 100644
--- a/libstdc++-v3/testsuite/23_containers/vector/bool/cons/noexcept_move_construct.cc
+++ b/libstdc++-v3/testsuite/23_containers/vector/bool/cons/noexcept_move_construct.cc
@@ -23,4 +23,34 @@ 
 
 typedef std::vector<bool> vbtype;
 
-static_assert(std::is_nothrow_move_constructible<vbtype>::value, "Error");
+static_assert( std::is_nothrow_move_constructible<vbtype>::value,
+	       "noexcept move constructor" );
+static_assert( std::is_nothrow_constructible<vbtype,
+	       vbtype&&, const typename vbtype::allocator_type&>::value,
+	       "noexcept move constructor with allocator" );
+
+template<typename Type>
+  class not_noexcept_move_constructor_alloc : public std::allocator<Type>
+  {
+  public:
+    not_noexcept_move_constructor_alloc() noexcept { }
+
+    not_noexcept_move_constructor_alloc(
+	const not_noexcept_move_constructor_alloc& x) noexcept
+    : std::allocator<Type>(x)
+    { }
+
+    not_noexcept_move_constructor_alloc(
+	not_noexcept_move_constructor_alloc&& x) noexcept(false)
+    : std::allocator<Type>(std::move(x))
+    { }
+
+    template<typename _Tp1>
+      struct rebind
+      { typedef not_noexcept_move_constructor_alloc<_Tp1> other; };
+  };
+
+typedef std::vector<bool, not_noexcept_move_constructor_alloc<bool>> vbtype2;
+
+static_assert( std::is_nothrow_move_constructible<vbtype2>::value,
+	       "noexcept move constructor with not noexcept alloc" );