libstdc++: Fix code size regressions in std::vector [PR110060]

My r14-1452-gfb409a15d9babc change to add optimization hints to
std::vector causes regressions because it makes std::vector::size() and
std::vector::capacity() too big to inline. That's the opposite of what
I wanted, so revert the changes to those functions.

To achieve the original aim of optimizing vec.assign(vec.size(), x) we
can add a local optimization hint to _M_fill_assign, so that it doesn't
affect all other uses of size() and capacity().

Additionally, add the same hint to the _M_assign_aux overload for
forward iterators and add that to the testcase.

It would be nice to similarly optimize:
  if (vec1.size() == vec2.size()) vec1 = vec2;
but adding hints to operator=(const vector&) doesn't help. Presumably
the relationships between the two sizes and two capacities are too
complex to track effectively.

libstdc++-v3/ChangeLog:

	PR libstdc++/110060
	* include/bits/stl_vector.h (_Vector_base::_M_invariant):
	Remove.
	(vector::size, vector::capacity): Remove calls to _M_invariant.
	* include/bits/vector.tcc (vector::_M_fill_assign): Add
	optimization hint to reallocating path.
	(vector::_M_assign_aux(FwdIter, FwdIter, forward_iterator_tag)):
	Likewise.
	* testsuite/23_containers/vector/capacity/invariant.cc: Moved
	to...
	* testsuite/23_containers/vector/modifiers/assign/no_realloc.cc:
	...here. Check assign(FwdIter, FwdIter) too.
	* testsuite/23_containers/vector/types/1.cc: Revert addition
	of -Wno-stringop-overread option.

diff --git a/libstdc++-v3/include/bits/stl_vector.h b/libstdc++-v3/include/bits/stl_vector.h
index e593be443bc2a0a941b1aad8ce1bb7ed9f120c15..70ced3d101fbecd2d1a0933a7e482ebb521259b4 100644 (file)
--- a/libstdc++-v3/include/bits/stl_vector.h
+++ b/libstdc++-v3/include/bits/stl_vector.h
@@ -389,23 +389,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 
     protected:
 
-      __attribute__((__always_inline__))
-      _GLIBCXX20_CONSTEXPR void
-      _M_invariant() const
-      {
-#if __OPTIMIZE__
-       if (this->_M_impl._M_finish < this->_M_impl._M_start)
-         __builtin_unreachable();
-       if (this->_M_impl._M_finish > this->_M_impl._M_end_of_storage)
-         __builtin_unreachable();
-
-       size_t __sz = this->_M_impl._M_finish - this->_M_impl._M_start;
-       size_t __cap = this->_M_impl._M_end_of_storage - this->_M_impl._M_start;
-       if (__sz > __cap)
-         __builtin_unreachable();
-#endif
-      }
-
       _GLIBCXX20_CONSTEXPR
       void
       _M_create_storage(size_t __n)
@@ -1005,10 +988,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
       size_type
       size() const _GLIBCXX_NOEXCEPT
-      {
-       _Base::_M_invariant();
-       return size_type(this->_M_impl._M_finish - this->_M_impl._M_start);
-      }
+      { return size_type(this->_M_impl._M_finish - this->_M_impl._M_start); }
 
       /**  Returns the size() of the largest possible %vector.  */
       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
@@ -1095,7 +1075,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       size_type
       capacity() const _GLIBCXX_NOEXCEPT
       {
-       _Base::_M_invariant();
        return size_type(this->_M_impl._M_end_of_storage
                           - this->_M_impl._M_start);
       }

diff --git a/libstdc++-v3/include/bits/vector.tcc b/libstdc++-v3/include/bits/vector.tcc
index d6fdea2dd01b2859a47679634f901349995e78e9..acd11e2dc68e73b29a8b8672647aaae8c24fe007 100644 (file)
--- a/libstdc++-v3/include/bits/vector.tcc
+++ b/libstdc++-v3/include/bits/vector.tcc
@@ -270,15 +270,18 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
     vector<_Tp, _Alloc>::
     _M_fill_assign(size_t __n, const value_type& __val)
     {
+      const size_type __sz = size();
       if (__n > capacity())
        {
+         if (__n <= __sz)
+           __builtin_unreachable();
          vector __tmp(__n, __val, _M_get_Tp_allocator());
          __tmp._M_impl._M_swap_data(this->_M_impl);
        }
-      else if (__n > size())
+      else if (__n > __sz)
        {
          std::fill(begin(), end(), __val);
-         const size_type __add = __n - size();
+         const size_type __add = __n - __sz;
          _GLIBCXX_ASAN_ANNOTATE_GROW(__add);
          this->_M_impl._M_finish =
            std::__uninitialized_fill_n_a(this->_M_impl._M_finish,
@@ -316,10 +319,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
       _M_assign_aux(_ForwardIterator __first, _ForwardIterator __last,
                    std::forward_iterator_tag)
       {
+       const size_type __sz = size();
        const size_type __len = std::distance(__first, __last);
 
        if (__len > capacity())
          {
+           if (__len <= __sz)
+             __builtin_unreachable();
+
            _S_check_init_len(__len, _M_get_Tp_allocator());
            pointer __tmp(_M_allocate_and_copy(__len, __first, __last));
            std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
@@ -332,14 +339,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
            this->_M_impl._M_finish = this->_M_impl._M_start + __len;
            this->_M_impl._M_end_of_storage = this->_M_impl._M_finish;
          }
-       else if (size() >= __len)
+       else if (__sz >= __len)
          _M_erase_at_end(std::copy(__first, __last, this->_M_impl._M_start));
        else
          {
            _ForwardIterator __mid = __first;
-           std::advance(__mid, size());
+           std::advance(__mid, __sz);
            std::copy(__first, __mid, this->_M_impl._M_start);
-           const size_type __attribute__((__unused__)) __n = __len - size();
+           const size_type __attribute__((__unused__)) __n = __len - __sz;
            _GLIBCXX_ASAN_ANNOTATE_GROW(__n);
            this->_M_impl._M_finish =
              std::__uninitialized_copy_a(__mid, __last,

diff --git a/libstdc++-v3/testsuite/23_containers/vector/capacity/invariant.cc b/libstdc++-v3/testsuite/23_containers/vector/modifiers/assign/no_realloc.cc
similarity index 70%
rename from libstdc++-v3/testsuite/23_containers/vector/capacity/invariant.cc
rename to libstdc++-v3/testsuite/23_containers/vector/modifiers/assign/no_realloc.cc
index d68db694add8b6f1bce0e247a0ed2066ec6b5cb4..659f18dba566869d8f34546128199d0506e86bb6 100644 (file)
--- a/libstdc++-v3/testsuite/23_containers/vector/capacity/invariant.cc
+++ b/libstdc++-v3/testsuite/23_containers/vector/modifiers/assign/no_realloc.cc
@@ -1,5 +1,6 @@
 // { dg-do compile }
 // { dg-options "-O3 -g0" }
+// { dg-require-normal-mode "" }
 // { dg-final { scan-assembler-not "_Znw" } }
 // GCC should be able to optimize away the paths involving reallocation.
 
@@ -14,3 +15,8 @@ void fill_val(std::vector<int>& vec, int i)
 {
   vec.assign(vec.size(), i);
 }
+
+void fill_range(std::vector<int>& vec, const int* first)
+{
+  vec.assign(first, first + vec.size());
+}

diff --git a/libstdc++-v3/testsuite/23_containers/vector/types/1.cc b/libstdc++-v3/testsuite/23_containers/vector/types/1.cc
index 9be07d9fd5c60958ff093ae15c31e350b590312b..079e5af95567792ee5e6e4290d640ad76bf5d6dc 100644 (file)
--- a/libstdc++-v3/testsuite/23_containers/vector/types/1.cc
+++ b/libstdc++-v3/testsuite/23_containers/vector/types/1.cc
@@ -18,7 +18,7 @@
 // <http://www.gnu.org/licenses/>.
 
 // { dg-do compile }
-// { dg-options "-Wno-unused-result -Wno-stringop-overread" }
+// { dg-options "-Wno-unused-result" }
 
 #include <vector>
 #include <testsuite_greedy_ops.h>