[committed] libstdc++: Two simplifications for lexicographical_compare

[Jonathan Wakely]

        * include/bits/ranges_algo.h (__lexicographical_compare_fn): Declare
        variables in smaller scope and avoid calling ranges::distance when we
        know they are pointers. Remove statically-unreachable use of
        __builtin_unreachable().
        * include/bits/stl_algobase.h (__lexicographical_compare::__lc):
        Define inline.

Tested powerpc64le-linux, committed to master.



commit 113f0a639dbdd78048373a253ec64145ead7d29d
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Wed Feb 26 15:19:44 2020 +0000

    libstdc++ Two simplifications for lexicographical_compare
    
            * include/bits/ranges_algo.h (__lexicographical_compare_fn): Declare
            variables in smaller scope and avoid calling ranges::distance when 
we
            know they are pointers. Remove statically-unreachable use of
            __builtin_unreachable().
            * include/bits/stl_algobase.h (__lexicographical_compare::__lc):
            Define inline.

diff --git a/libstdc++-v3/include/bits/ranges_algo.h 
b/libstdc++-v3/include/bits/ranges_algo.h
index 7d7dbf04103..05c0851d411 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -3464,9 +3464,6 @@ namespace ranges
                 && sized_sentinel_for<_Sent2, _Iter2>);
            if constexpr (__sized_iters)
              {
-               auto __d1 = ranges::distance(__first1, __last1);
-               auto __d2 = ranges::distance(__first2, __last2);
-
                using _ValueType1 = iter_value_t<_Iter1>;
                using _ValueType2 = iter_value_t<_Iter2>;
                constexpr bool __use_memcmp
@@ -3480,6 +3477,9 @@ namespace ranges
                     && is_same_v<_Proj2, identity>);
                if constexpr (__use_memcmp)
                  {
+                   const auto __d1 = __last1 - __first1;
+                   const auto __d2 = __last2 - __first2;
+
                    if (const auto __len = std::min(__d1, __d2))
                      {
                        const auto __c
@@ -3498,10 +3498,8 @@ namespace ranges
                            if (__c < 0)
                              return false;
                          }
-                       else
-                         __builtin_unreachable();
                      }
-                   return (__last1 - __first1 < __last2 - __first2);
+                   return __d1 < __d2;
                  }
              }
 
diff --git a/libstdc++-v3/include/bits/stl_algobase.h 
b/libstdc++-v3/include/bits/stl_algobase.h
index 268569336b0..e4f7fa417ed 100644
--- a/libstdc++-v3/include/bits/stl_algobase.h
+++ b/libstdc++-v3/include/bits/stl_algobase.h
@@ -1254,21 +1254,16 @@ _GLIBCXX_END_NAMESPACE_CONTAINER
     {
       template<typename _II1, typename _II2>
        _GLIBCXX20_CONSTEXPR
-       static bool __lc(_II1, _II1, _II2, _II2);
+       static bool
+       __lc(_II1 __first1, _II1 __last1, _II2 __first2, _II2 __last2)
+       {
+         using __gnu_cxx::__ops::__iter_less_iter;
+         return std::__lexicographical_compare_impl(__first1, __last1,
+                                                    __first2, __last2,
+                                                    __iter_less_iter());
+       }
     };
 
-  template<bool _BoolType>
-    template<typename _II1, typename _II2>
-      _GLIBCXX20_CONSTEXPR
-      bool
-      __lexicographical_compare<_BoolType>::
-      __lc(_II1 __first1, _II1 __last1, _II2 __first2, _II2 __last2)
-      {
-       return std::__lexicographical_compare_impl(__first1, __last1,
-                                                  __first2, __last2,
-                                       __gnu_cxx::__ops::__iter_less_iter());
-      }
-
   template<>
     struct __lexicographical_compare<true>
     {