Tweak vector::_M_realloc_insert for code size

2017-11-17  Marc Glisse  <marc.glisse@inria.fr>

	* include/bits/vector.tcc (vector::_M_realloc_insert): Cache old
	values before the allocation.

From-SVN: r254849

libstdc++-v3/ChangeLog

+2017-11-17  Marc Glisse  <marc.glisse@inria.fr>
+
+	* include/bits/vector.tcc (vector::_M_realloc_insert): Cache old
+	values before the allocation.
+
 2017-11-16  Jonathan Wakely  <jwakely@redhat.com>
 
 	* include/std/future (shared_future): Add noexcept to copy constructor

libstdc++-v3/include/bits/vector.tcc

@@ -421,6 +421,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
     {
       const size_type __len =
 	_M_check_len(size_type(1), "vector::_M_realloc_insert");
+      pointer __old_start = this->_M_impl._M_start;
+      pointer __old_finish = this->_M_impl._M_finish;
       const size_type __elems_before = __position - begin();
       pointer __new_start(this->_M_allocate(__len));
       pointer __new_finish(__new_start);
@@ -442,14 +444,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 
 	  __new_finish
 	    = std::__uninitialized_move_if_noexcept_a
-	    (this->_M_impl._M_start, __position.base(),
+	    (__old_start, __position.base(),
 	     __new_start, _M_get_Tp_allocator());
 
 	  ++__new_finish;
 
 	  __new_finish
 	    = std::__uninitialized_move_if_noexcept_a
-	    (__position.base(), this->_M_impl._M_finish,
+	    (__position.base(), __old_finish,
 	     __new_finish, _M_get_Tp_allocator());
 	}
       __catch(...)
@@ -463,10 +465,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 	  __throw_exception_again;
 	}
       _GLIBCXX_ASAN_ANNOTATE_REINIT;
-      std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
-		    _M_get_Tp_allocator());
-      _M_deallocate(this->_M_impl._M_start,
-		    this->_M_impl._M_end_of_storage - this->_M_impl._M_start);
+      std::_Destroy(__old_start, __old_finish, _M_get_Tp_allocator());
+      _M_deallocate(__old_start,
+		    this->_M_impl._M_end_of_storage - __old_start);
       this->_M_impl._M_start = __new_start;
       this->_M_impl._M_finish = __new_finish;
       this->_M_impl._M_end_of_storage = __new_start + __len;