[committed] libstdc++: Remove unnecessary tag dispatching in std::vector

[Jonathan Wakely via Gcc-patches]

Tested x86_64-linux. Pushed to trunk.

-- >8 --

There's no need to call a _M_xxx_dispatch function with a
statically-known __false_type tag, we can just directly call the
function that should be dispatched to. This will compile a tiny bit
faster and save a function call with optimization or inlining turned
off.

Also add the always_inline attribute to the __iterator_category helper
used for dispatching on the iterator category.

libstdc++-v3/ChangeLog:

        * include/bits/stl_iterator_base_types.h (__iterator_category):
        Add always_inline attribute.
        * include/bits/stl_vector.h (assign(Iter, Iter)): Call
        _M_assign_aux directly, instead of _M_assign_dispatch.
        (insert(const_iterator, Iter, Iter)): Call _M_range_insert
        directly instead of _M_insert_dispatch.
---
 libstdc++-v3/include/bits/stl_iterator_base_types.h | 1 +
 libstdc++-v3/include/bits/stl_vector.h              | 6 +++---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/libstdc++-v3/include/bits/stl_iterator_base_types.h 
b/libstdc++-v3/include/bits/stl_iterator_base_types.h
index 9eecd1dd855..5d90c0d8ea7 100644
--- a/libstdc++-v3/include/bits/stl_iterator_base_types.h
+++ b/libstdc++-v3/include/bits/stl_iterator_base_types.h
@@ -233,6 +233,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  sugar for internal library use only.
   */
   template<typename _Iter>
+    __attribute__((__always_inline__))
     inline _GLIBCXX_CONSTEXPR
     typename iterator_traits<_Iter>::iterator_category
     __iterator_category(const _Iter&)
diff --git a/libstdc++-v3/include/bits/stl_vector.h 
b/libstdc++-v3/include/bits/stl_vector.h
index b4ff3989a5d..e87fab0e51c 100644
--- a/libstdc++-v3/include/bits/stl_vector.h
+++ b/libstdc++-v3/include/bits/stl_vector.h
@@ -821,7 +821,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
        _GLIBCXX20_CONSTEXPR
        void
        assign(_InputIterator __first, _InputIterator __last)
-       { _M_assign_dispatch(__first, __last, __false_type()); }
+       { _M_assign_aux(__first, __last, std::__iterator_category(__first)); }
 #else
       template<typename _InputIterator>
        void
@@ -1478,8 +1478,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
               _InputIterator __last)
        {
          difference_type __offset = __position - cbegin();
-         _M_insert_dispatch(begin() + __offset,
-                            __first, __last, __false_type());
+         _M_range_insert(begin() + __offset, __first, __last,
+                         std::__iterator_category(__first));
          return begin() + __offset;
        }
 #else
-- 
2.38.1