Benchmark count for vector<bool> (#5684)

Co-authored-by: Stephan T. Lavavej <stl@microsoft.com>

Author: AlexGuteniev

benchmarks/CMakeLists.txt

@@ -135,4 +135,5 @@ add_benchmark(swap_ranges src/swap_ranges.cpp)
 add_benchmark(unique src/unique.cpp)
 add_benchmark(vector_bool_copy src/vector_bool_copy.cpp)
 add_benchmark(vector_bool_copy_n src/vector_bool_copy_n.cpp)
+add_benchmark(vector_bool_count src/vector_bool_count.cpp)
 add_benchmark(vector_bool_move src/vector_bool_move.cpp)

benchmarks/src/vector_bool_count.cpp

@@ -0,0 +1,39 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <benchmark/benchmark.h>
+//
+#include <algorithm>
+#include <cstddef>
+#include <random>
+#include <vector>
+
+using namespace std;
+
+vector<bool> createRandomVector(const size_t size) {
+    mt19937 gen;
+    bernoulli_distribution dist{0.5};
+    vector<bool> result(size);
+    generate(result.begin(), result.end(), [&] { return dist(gen); });
+    return result;
+}
+
+void count_aligned(benchmark::State& state) {
+    const auto size = static_cast<size_t>(state.range(0));
+    vector<bool> v  = createRandomVector(size);
+
+    bool b = false;
+
+    for (auto _ : state) {
+        benchmark::DoNotOptimize(b);
+        benchmark::DoNotOptimize(v);
+        auto r = count(v.cbegin(), v.cend(), b);
+        benchmark::DoNotOptimize(r);
+        b = !b;
+    }
+}
+
+
+BENCHMARK(count_aligned)->RangeMultiplier(64)->Range(64, 64 << 10);
+
+BENCHMARK_MAIN();