[committed] libstdc++: Two simplifications for lexicographical_compare

Message ID 20200226152155.GA2443999@redhat.com
State New
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  • [committed] libstdc++: Two simplifications for lexicographical_compare
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Commit Message

Jonathan Wakely Feb. 26, 2020, 3:21 p.m.
* 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 <jwakely@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.

Patch

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>
     {