Minor fixes

Author: ldionne

libcxx/include/__iterator/distance.h

@@ -59,7 +59,7 @@ __distance(_RandIter __first, _RandIter __last) {
 #if _LIBCPP_STD_VER >= 20
 template <class _SegmentedIter,
           __enable_if_t<!__has_random_access_iterator_category<_SegmentedIter>::value &&
-                            __is_segmented_iterator<_SegmentedIter>::value,
+                            __is_segmented_iterator_v<_SegmentedIter>,
                         int> = 0>
 inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX17 __iter_distance_t<_SegmentedIter>
 __distance(_SegmentedIter __first, _SegmentedIter __last) {

libcxx/test/benchmarks/iterators/distance.bench.cpp

@@ -8,6 +8,7 @@
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 
+#include <algorithm>
 #include <cstddef>
 #include <deque>
 #include <iterator>
@@ -19,7 +20,31 @@
 int main(int argc, char** argv) {
   auto std_distance = [](auto first, auto last) { return std::distance(first, last); };
 
-  // {std,ranges}::distance
+  // {std,ranges}::distance(std::deque)
+  {
+    auto bm = [](std::string name, auto distance) {
+      benchmark::RegisterBenchmark(
+          name,
+          [distance](auto& st) {
+            std::size_t const size = st.range(0);
+            std::deque<int> c(size, 1);
+
+            for ([[maybe_unused]] auto _ : st) {
+              benchmark::DoNotOptimize(c);
+              auto result = distance(c.begin(), c.end());
+              benchmark::DoNotOptimize(result);
+            }
+          })
+          ->Arg(50) // non power-of-two
+          ->Arg(1024)
+          ->Arg(4096)
+          ->Arg(8192);
+    };
+    bm.operator()("std::distance(deque<int>)", std_distance);
+    bm.operator()("rng::distance(deque<int>)", std::ranges::distance);
+  }
+
+  // {std,ranges}::distance(std::join_view)
   {
     auto bm = []<class Container>(std::string name, auto distance, std::size_t seg_size) {
       benchmark::RegisterBenchmark(
@@ -48,18 +73,8 @@ int main(int argc, char** argv) {
           ->Arg(8192);
     };
     bm.operator()<std::vector<std::vector<int>>>("std::distance(join_view(vector<vector<int>>))", std_distance, 256);
-    bm.operator()<std::deque<std::deque<int>>>("std::distance(join_view(deque<deque<int>>))", std_distance, 256);
     bm.operator()<std::vector<std::vector<int>>>(
         "rng::distance(join_view(vector<vector<int>>)", std::ranges::distance, 256);
-    bm.operator()<std::deque<std::deque<int>>>(
-        "rng::distance(join_view(deque<deque<int>>)", std::ranges::distance, 256);
-
-    bm.operator()<std::vector<std::vector<int>>>("std::distance(join_view(vector<vector<int>>))", std_distance, 1024);
-    bm.operator()<std::deque<std::deque<int>>>("std::distance(join_view(deque<deque<int>>))", std_distance, 1024);
-    bm.operator()<std::vector<std::vector<int>>>(
-        "rng::distance(join_view(vector<vector<int>>)", std::ranges::distance, 1024);
-    bm.operator()<std::deque<std::deque<int>>>(
-        "rng::distance(join_view(deque<deque<int>>)", std::ranges::distance, 1024);
   }
 
   benchmark::Initialize(&argc, argv);