[libc++][ranges] add benchmark for 'ranges::shift_left'

Author: xiaoyang-sde

libcxx/benchmarks/CMakeLists.txt

@@ -191,6 +191,7 @@ set(BENCHMARK_TESTS
     algorithms/ranges_make_heap_then_sort_heap.bench.cpp
     algorithms/ranges_pop_heap.bench.cpp
     algorithms/ranges_push_heap.bench.cpp
+    algorithms/ranges_shift_left.bench.cpp
     algorithms/ranges_sort.bench.cpp
     algorithms/ranges_sort_heap.bench.cpp
     algorithms/ranges_stable_sort.bench.cpp

libcxx/benchmarks/algorithms/ranges_shift_left.bench.cpp

@@ -0,0 +1,67 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <algorithm>
+#include <benchmark/benchmark.h>
+#include <iterator>
+#include <vector>
+
+#include "test_iterators.h"
+
+static void bm_shift_left_random_access_range_with_sized_sentinel(benchmark::State& state) {
+  std::vector<int> a(state.range(), 1);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(a);
+
+    auto begin = random_access_iterator(a.data());
+    auto end   = random_access_iterator(a.data() + a.size());
+
+    static_assert(std::sized_sentinel_for<decltype(end), decltype(begin)>);
+    static_assert(std::random_access_iterator<decltype(begin)>);
+
+    benchmark::DoNotOptimize(std::ranges::shift_left(begin, end, a.size() / 2));
+  }
+}
+BENCHMARK(bm_shift_left_random_access_range_with_sized_sentinel)->RangeMultiplier(16)->Range(16, 16 << 20);
+
+static void bm_shift_left_forward_range_with_sized_sentinel(benchmark::State& state) {
+  std::vector<int> a(state.range(), 1);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(a);
+
+    auto begin = forward_iterator(a.data());
+    auto end   = sized_sentinel(forward_iterator(a.data() + a.size()));
+
+    static_assert(std::sized_sentinel_for<decltype(end), decltype(begin)>);
+    static_assert(!std::random_access_iterator<decltype(begin)>);
+
+    benchmark::DoNotOptimize(std::ranges::shift_left(begin, end, a.size() / 2));
+  }
+}
+BENCHMARK(bm_shift_left_forward_range_with_sized_sentinel)->RangeMultiplier(16)->Range(16, 16 << 20);
+
+static void bm_shift_left_forward_range(benchmark::State& state) {
+  std::vector<int> a(state.range(), 1);
+
+  for (auto _ : state) {
+    benchmark::DoNotOptimize(a);
+
+    auto begin = forward_iterator(a.data());
+    auto end   = forward_iterator(a.data() + a.size());
+
+    static_assert(!std::sized_sentinel_for<decltype(end), decltype(begin)>);
+    static_assert(!std::random_access_iterator<decltype(begin)>);
+
+    benchmark::DoNotOptimize(std::ranges::shift_left(begin, end, a.size() / 2));
+  }
+}
+BENCHMARK(bm_shift_left_forward_range)->RangeMultiplier(16)->Range(16, 16 << 20);
+
+BENCHMARK_MAIN();