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Re: std::vector<bool> fix & enhancements

On 30/10/18 07:28 +0100, François Dumont wrote:
Following Marc Glisse change to ignore _M_start offset I wanted to go a little step further and just remove it in _GLIBCXX_INLINE_VERSION mode.

I also fix a regression we already fixed on mainstream std::vector regarding noexcept qualification of move constructor with allocator.

And I implemented the same optimizations than in std::vector for allocators always comparing equals and for the std::swap operation.

I also avoid re-implementing in vector::operator[] the same code already implemented in iterator::operator[] but this one should perhaps go in a different commit.

    * include/bits/stl_bvector.h
    [_GLIBCXX_INLINE_VERSION](_Bvector_impl_data::_M_start): Define as
    (_Bvector_impl_data(const _Bvector_impl_data&)): New.
    (_Bvector_impl_data(_Bvector_impl_data&&)): Delegate to latter.
    (_Bvector_impl_data::operator=(const _Bvector_impl_data&)): New.
(_Bvector_impl_data::_M_move_data(_Bvector_impl_data&&)): Use latter.
    (_Bvector_impl_data::_M_reset()): Likewise.
    (_Bvector_impl_data::_M_begin()): New.
    (_Bvector_impl_data::_M_cbegin()): New.
    (_Bvector_impl_data::_M_start_p()): New.
    (_Bvector_impl_data::_M_set_start(_Bit_type*)): New.
    (_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&)):
    (_Bvector_base::_M_deallocate()): Adapt.
    (vector::vector(const vector&, const allocator_type&)): Adapt.
    (vector::vector(vector&&, const allocator_type&, true_type)): New.
    (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.
    (vector::begin()): Adapt.
    (vector::cbegin()): Adapt.
    (vector::operator[](size_type)): Use iterator operator[].
    (vector::swap(vector&)): Adapt.
    (vector::flip()): Adapt.
    (vector::_M_initialize(size_type)): Adapt.
    (vector::_M_initialize_value(bool)): Adapt.
    * include/bits/vector.tcc:
    (vector<bool>::_M_reallocate(size_type)): Adapt.
    (vector<bool>::_M_fill_insert(iterator, size_type, bool)): Adapt.
    (vector<bool>::_M_insert_range<_FwdIter>(iterator, _FwdIter, _FwdIter
    std::forward_iterator_tag)): Adapt.
    (vector<bool>::_M_insert_aux(iterator, bool)): Adapt.
    (std::hash<std::vector<bool>>::operator()): Adapt.
    * testsuite/23_containers/vector/bool/cons/
    Add check.

Tested under Linux x86_64.

Ok to commit ?


diff --git a/libstdc++-v3/include/bits/stl_bvector.h b/libstdc++-v3/include/bits/stl_bvector.h
index 8fbef7a1a3a..81b4a75236d 100644
--- a/libstdc++-v3/include/bits/stl_bvector.h
+++ b/libstdc++-v3/include/bits/stl_bvector.h

      struct _Bvector_impl_data
	_Bit_iterator	_M_start;
+	_Bit_type*	_M_start;

An alternative that would require fewer changes elsewhere in the file
would be:

	_Bit_iterator	_M_start;
       // We don't need the offset field for the start pointer,
       // 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;

Now the rest of the file doesn't need any checks for
_GLIBCXX_INLINE_VERSION (which I'd prefer to avoid, because it
clutters the code up with extra conditionals for a mode that
**nobody** uses in practice).

	_Bit_iterator	_M_finish;
	_Bit_pointer	_M_end_of_storage;


#if __cplusplus >= 201103L
	_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(); }

+	_Bvector_impl_data(const _Bvector_impl_data&) = default;
+	_Bvector_impl_data&
+	operator=(const _Bvector_impl_data&) = default;
	_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;
+	_Bvector_impl_data(const _Bvector_impl_data& __x)
+	  : _M_start(__x._M_start), _M_finish(__x._M_finish)
+	  , _M_end_of_storage(__x._M_end_of_storage)
+	{ }

Do we need this definition? Won't the compiler generate the same thing
for us anyway?

+	_Bvector_impl_data&
+	operator=(const _Bvector_impl_data& __x)
+	{
+	  _M_start = __x._M_start;
+	  _M_finish = __x._M_finish;
+	  _M_end_of_storage = __x._M_end_of_storage;
+	}

Same here.

+	_Bit_iterator
+	_M_begin() const _GLIBCXX_NOEXCEPT
+	{ return _Bit_iterator(_M_start_p(), 0); }
+	_Bit_const_iterator
+	_M_cbegin() const _GLIBCXX_NOEXCEPT
+	{ return _Bit_const_iterator(_M_start_p(), 0); }
+	_Bit_type*
+	_M_start_p() const _GLIBCXX_NOEXCEPT

We already have _M_end_addr() so would _M_begin_addr be a better name
for this new function?

+	{ return _M_start._M_p; }
+	{ return _M_start; }

Using the suggestion above you wouldn't need #if because return
_M_start._M_p would always be right. But you wouldn't even need this
function at all, the code that uses _M_start._M_p would Just Work™.

+	void
+	_M_set_start(_Bit_type* __p) _GLIBCXX_NOEXCEPT
+	{ _M_start._M_p = __p; }
+	{ _M_start = __p; }

You wouldn't need this function.

etc. etc.

+	{ *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:
	  _GLIBCXX_NOEXCEPT_IF( noexcept(_Bit_alloc_type()) )

You'll need to rebase the patch, because I just fixed a bug in this
exception specification (r265626).

	: _Bit_alloc_type()

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